From: Brad Jorsch <bjorsch@wikimedia.org>
Date: Fri, 4 Jan 2019 18:55:11 +0000 (-0500)
Subject: Mostly drop old comment schemas
X-Git-Tag: 1.34.0-rc.0~2911
X-Git-Url: http://git.cyclocoop.org/?a=commitdiff_plain;h=0abb9338f870824e258a7a138ad07efbaa6b3894;p=lhc%2Fweb%2Fwiklou.git

Mostly drop old comment schemas

This removes most of the pre-CommentStore text columns, and the
$wgCommentTableSchemaMigrationStage setting that used to determine
whether the columns were used.

rev_comment remains in the code, as on Wikimedia wikis the revision
table is too large to alter at this time. A future change will combine
that with the removal of rev_user_text, rev_content_model, and
rev_content_format (and the addition of rev_comment_id and rev_actor).

CommentStore's constructor continues to take a $stage parameter, and
continues to have the logic for handling it, for the benefit of
extensions that might need their own migration process.

Bug: T166733
Change-Id: I1479c73774e01ead1490adf6128f820c09bce9d4
---

diff --git a/RELEASE-NOTES-1.33 b/RELEASE-NOTES-1.33
index 57984f6bea..8105446e9f 100644
--- a/RELEASE-NOTES-1.33
+++ b/RELEASE-NOTES-1.33
@@ -35,6 +35,8 @@ production.
 * $wgEnableParserCache, deprecated since 1.26, was removed.
   If disabling the parser cache is still desirable,
   set `$wgParserCacheType = CACHE_NONE;` instead.
+* $wgCommentTableSchemaMigrationStage has been removed. Extension code finding
+  it unset should treat it as being MIGRATION_NEW.
 
 === New features in 1.33 ===
 * (T96041) __EXPECTUNUSEDCATEGORY__ on a category page causes the category
diff --git a/includes/CommentStore.php b/includes/CommentStore.php
index cba7a150d3..1a60bb7412 100644
--- a/includes/CommentStore.php
+++ b/includes/CommentStore.php
@@ -82,7 +82,11 @@ class CommentStore {
 	 */
 	protected $key = null;
 
-	/** @var int One of the MIGRATION_* constants */
+	/**
+	 * @var int One of the MIGRATION_* constants
+	 * @todo Deprecate and remove once extensions seem unlikely to need to use
+	 *  it for migration anymore.
+	 */
 	protected $stage;
 
 	/** @var array[] Cache for `self::getJoin()` */
@@ -94,7 +98,8 @@ class CommentStore {
 	/**
 	 * @param Language $lang Language to use for comment truncation. Defaults
 	 *  to content language.
-	 * @param int $migrationStage One of the MIGRATION_* constants
+	 * @param int $migrationStage One of the MIGRATION_* constants. Always
+	 *  MIGRATION_NEW for MediaWiki core since 1.33.
 	 */
 	public function __construct( Language $lang, $migrationStage ) {
 		$this->stage = $migrationStage;
@@ -109,10 +114,10 @@ class CommentStore {
 	 * @return CommentStore
 	 */
 	public static function newKey( $key ) {
-		global $wgCommentTableSchemaMigrationStage;
 		wfDeprecated( __METHOD__, '1.31' );
-		$store = new CommentStore( MediaWikiServices::getInstance()->getContentLanguage(),
-			$wgCommentTableSchemaMigrationStage );
+		$store = new CommentStore(
+			MediaWikiServices::getInstance()->getContentLanguage(), MIGRATION_NEW
+		);
 		$store->key = $key;
 		return $store;
 	}
diff --git a/includes/DefaultSettings.php b/includes/DefaultSettings.php
index 31b0988b69..e6b44edd66 100644
--- a/includes/DefaultSettings.php
+++ b/includes/DefaultSettings.php
@@ -8964,13 +8964,6 @@ $wgExperiencedUserMemberSince = 30; # days
  */
 $wgInterwikiPrefixDisplayTypes = [];
 
-/**
- * Comment table schema migration stage.
- * @since 1.30
- * @var int One of the MIGRATION_* constants
- */
-$wgCommentTableSchemaMigrationStage = MIGRATION_NEW;
-
 /**
  * RevisionStore table schema migration stage (content, slots, content_models & slot_roles tables).
  * Use the SCHEMA_COMPAT_XXX flags. Supported values:
diff --git a/includes/EditPage.php b/includes/EditPage.php
index 45995646da..300c5f3147 100644
--- a/includes/EditPage.php
+++ b/includes/EditPage.php
@@ -3250,15 +3250,13 @@ ERROR;
 	 * @return array
 	 */
 	private function getSummaryInputAttributes( array $inputAttrs = null ) {
-		$conf = $this->context->getConfig();
-		$oldCommentSchema = $conf->get( 'CommentTableSchemaMigrationStage' ) === MIGRATION_OLD;
 		// HTML maxlength uses "UTF-16 code units", which means that characters outside BMP
 		// (e.g. emojis) count for two each. This limit is overridden in JS to instead count
-		// Unicode codepoints (or 255 UTF-8 bytes for old schema).
+		// Unicode codepoints.
 		return ( is_array( $inputAttrs ) ? $inputAttrs : [] ) + [
 			'id' => 'wpSummary',
 			'name' => 'wpSummary',
-			'maxlength' => $oldCommentSchema ? 200 : CommentStore::COMMENT_CHARACTER_LIMIT,
+			'maxlength' => CommentStore::COMMENT_CHARACTER_LIMIT,
 			'tabindex' => 1,
 			'size' => 60,
 			'spellcheck' => 'true',
diff --git a/includes/FileDeleteForm.php b/includes/FileDeleteForm.php
index 8866a88bda..5aa6edf879 100644
--- a/includes/FileDeleteForm.php
+++ b/includes/FileDeleteForm.php
@@ -246,9 +246,6 @@ class FileDeleteForm {
 	private function showForm() {
 		global $wgOut, $wgUser, $wgRequest;
 
-		$conf = RequestContext::getMain()->getConfig();
-		$oldCommentSchema = $conf->get( 'CommentTableSchemaMigrationStage' ) === MIGRATION_OLD;
-
 		$wgOut->addModules( 'mediawiki.action.delete.file' );
 
 		$checkWatch = $wgUser->getBoolOption( 'watchdeletion' ) || $wgUser->isWatched( $this->title );
@@ -282,13 +279,13 @@ class FileDeleteForm {
 
 		// HTML maxlength uses "UTF-16 code units", which means that characters outside BMP
 		// (e.g. emojis) count for two each. This limit is overridden in JS to instead count
-		// Unicode codepoints (or 255 UTF-8 bytes for old schema).
+		// Unicode codepoints.
 		$fields[] = new OOUI\FieldLayout(
 			new OOUI\TextInputWidget( [
 				'name' => 'wpReason',
 				'inputId' => 'wpReason',
 				'tabIndex' => 2,
-				'maxLength' => $oldCommentSchema ? 255 : CommentStore::COMMENT_CHARACTER_LIMIT,
+				'maxLength' => CommentStore::COMMENT_CHARACTER_LIMIT,
 				'infusable' => true,
 				'value' => $wgRequest->getText( 'wpReason' ),
 				'autofocus' => true,
diff --git a/includes/ProtectionForm.php b/includes/ProtectionForm.php
index bb8eba125f..ac4ca773a7 100644
--- a/includes/ProtectionForm.php
+++ b/includes/ProtectionForm.php
@@ -355,7 +355,6 @@ class ProtectionForm {
 		$lang = $context->getLanguage();
 		$conf = $context->getConfig();
 		$cascadingRestrictionLevels = $conf->get( 'CascadingRestrictionLevels' );
-		$oldCommentSchema = $conf->get( 'CommentTableSchemaMigrationStage' ) === MIGRATION_OLD;
 		$out = '';
 		if ( !$this->disabled ) {
 			$output->addModules( 'mediawiki.legacy.protect' );
@@ -502,10 +501,10 @@ class ProtectionForm {
 
 			// HTML maxlength uses "UTF-16 code units", which means that characters outside BMP
 			// (e.g. emojis) count for two each. This limit is overridden in JS to instead count
-			// Unicode codepoints (or 180 UTF-8 bytes for old schema).
+			// Unicode codepoints.
 			// Subtract arbitrary 75 to leave some space for the autogenerated null edit's summary
 			// and other texts chosen by dropdown menus on this page.
-			$maxlength = $oldCommentSchema ? 180 : CommentStore::COMMENT_CHARACTER_LIMIT - 75;
+			$maxlength = CommentStore::COMMENT_CHARACTER_LIMIT - 75;
 
 			$out .= Xml::openElement( 'table', [ 'id' => 'mw-protect-table3' ] ) .
 				Xml::openElement( 'tbody' );
diff --git a/includes/ServiceWiring.php b/includes/ServiceWiring.php
index 9a94389f74..44ca5025dd 100644
--- a/includes/ServiceWiring.php
+++ b/includes/ServiceWiring.php
@@ -85,7 +85,7 @@ return [
 	'CommentStore' => function ( MediaWikiServices $services ) : CommentStore {
 		return new CommentStore(
 			$services->getContentLanguage(),
-			$services->getMainConfig()->get( 'CommentTableSchemaMigrationStage' )
+			MIGRATION_NEW
 		);
 	},
 
diff --git a/includes/actions/McrUndoAction.php b/includes/actions/McrUndoAction.php
index b60820c0c3..47bbdc0b5c 100644
--- a/includes/actions/McrUndoAction.php
+++ b/includes/actions/McrUndoAction.php
@@ -358,8 +358,6 @@ class McrUndoAction extends FormAction {
 
 	protected function getFormFields() {
 		$request = $this->getRequest();
-		$config = $this->context->getConfig();
-		$oldCommentSchema = $config->get( 'CommentTableSchemaMigrationStage' ) === MIGRATION_OLD;
 		$ret = [
 			'diff' => [
 				'type' => 'info',
@@ -375,7 +373,7 @@ class McrUndoAction extends FormAction {
 				'name' => 'wpSummary',
 				'cssclass' => 'mw-summary',
 				'label-message' => 'summary',
-				'maxlength' => $oldCommentSchema ? 200 : CommentStore::COMMENT_CHARACTER_LIMIT,
+				'maxlength' => CommentStore::COMMENT_CHARACTER_LIMIT,
 				'value' => $request->getVal( 'wpSummary', '' ),
 				'size' => 60,
 				'spellcheck' => 'true',
diff --git a/includes/filerepo/file/LocalFile.php b/includes/filerepo/file/LocalFile.php
index 878e82d032..789d7c5215 100644
--- a/includes/filerepo/file/LocalFile.php
+++ b/includes/filerepo/file/LocalFile.php
@@ -1431,7 +1431,7 @@ class LocalFile extends File {
 		$oldver, $comment, $pageText, $props = false, $timestamp = false, $user = null, $tags = [],
 		$createNullRevision = true
 	) {
-		global $wgCommentTableSchemaMigrationStage, $wgActorTableSchemaMigrationStage;
+		global $wgActorTableSchemaMigrationStage;
 
 		if ( is_null( $user ) ) {
 			global $wgUser;
@@ -1528,6 +1528,7 @@ class LocalFile extends File {
 				'oi_width' => 'img_width',
 				'oi_height' => 'img_height',
 				'oi_bits' => 'img_bits',
+				'oi_description_id' => 'img_description_id',
 				'oi_timestamp' => 'img_timestamp',
 				'oi_metadata' => 'img_metadata',
 				'oi_media_type' => 'img_media_type',
@@ -1537,39 +1538,6 @@ class LocalFile extends File {
 			];
 			$joins = [];
 
-			if ( $wgCommentTableSchemaMigrationStage <= MIGRATION_WRITE_BOTH ) {
-				$fields['oi_description'] = 'img_description';
-			}
-			if ( $wgCommentTableSchemaMigrationStage >= MIGRATION_WRITE_BOTH ) {
-				$fields['oi_description_id'] = 'img_description_id';
-			}
-
-			if ( $wgCommentTableSchemaMigrationStage !== MIGRATION_OLD &&
-				$wgCommentTableSchemaMigrationStage !== MIGRATION_NEW
-			) {
-				// Upgrade any rows that are still old-style. Otherwise an upgrade
-				// might be missed if a deletion happens while the migration script
-				// is running.
-				$res = $dbw->select(
-					[ 'image' ],
-					[ 'img_name', 'img_description' ],
-					[
-						'img_name' => $this->getName(),
-						'img_description_id' => 0,
-					],
-					__METHOD__
-				);
-				foreach ( $res as $row ) {
-					$imgFields = $commentStore->insert( $dbw, 'img_description', $row->img_description );
-					$dbw->update(
-						'image',
-						$imgFields,
-						[ 'img_name' => $row->img_name ],
-						__METHOD__
-					);
-				}
-			}
-
 			if ( $wgActorTableSchemaMigrationStage & SCHEMA_COMPAT_WRITE_OLD ) {
 				$fields['oi_user'] = 'img_user';
 				$fields['oi_user_text'] = 'img_user_text';
@@ -2470,7 +2438,7 @@ class LocalFileDeleteBatch {
 	}
 
 	protected function doDBInserts() {
-		global $wgCommentTableSchemaMigrationStage, $wgActorTableSchemaMigrationStage;
+		global $wgActorTableSchemaMigrationStage;
 
 		$now = time();
 		$dbw = $this->file->repo->getMasterDB();
@@ -2515,6 +2483,7 @@ class LocalFileDeleteBatch {
 				'fa_media_type' => 'img_media_type',
 				'fa_major_mime' => 'img_major_mime',
 				'fa_minor_mime' => 'img_minor_mime',
+				'fa_description_id' => 'img_description_id',
 				'fa_timestamp' => 'img_timestamp',
 				'fa_sha1' => 'img_sha1'
 			];
@@ -2525,39 +2494,6 @@ class LocalFileDeleteBatch {
 				$commentStore->insert( $dbw, 'fa_deleted_reason', $this->reason )
 			);
 
-			if ( $wgCommentTableSchemaMigrationStage <= MIGRATION_WRITE_BOTH ) {
-				$fields['fa_description'] = 'img_description';
-			}
-			if ( $wgCommentTableSchemaMigrationStage >= MIGRATION_WRITE_BOTH ) {
-				$fields['fa_description_id'] = 'img_description_id';
-			}
-
-			if ( $wgCommentTableSchemaMigrationStage !== MIGRATION_OLD &&
-				$wgCommentTableSchemaMigrationStage !== MIGRATION_NEW
-			) {
-				// Upgrade any rows that are still old-style. Otherwise an upgrade
-				// might be missed if a deletion happens while the migration script
-				// is running.
-				$res = $dbw->select(
-					[ 'image' ],
-					[ 'img_name', 'img_description' ],
-					[
-						'img_name' => $this->file->getName(),
-						'img_description_id' => 0,
-					],
-					__METHOD__
-				);
-				foreach ( $res as $row ) {
-					$imgFields = $commentStore->insert( $dbw, 'img_description', $row->img_description );
-					$dbw->update(
-						'image',
-						$imgFields,
-						[ 'img_name' => $row->img_name ],
-						__METHOD__
-					);
-				}
-			}
-
 			if ( $wgActorTableSchemaMigrationStage & SCHEMA_COMPAT_WRITE_OLD ) {
 				$fields['fa_user'] = 'img_user';
 				$fields['fa_user_text'] = 'img_user_text';
diff --git a/includes/installer/DatabaseUpdater.php b/includes/installer/DatabaseUpdater.php
index 43000b8b99..d64e2d7b69 100644
--- a/includes/installer/DatabaseUpdater.php
+++ b/includes/installer/DatabaseUpdater.php
@@ -1261,10 +1261,7 @@ abstract class DatabaseUpdater {
 	 * @since 1.30
 	 */
 	protected function migrateComments() {
-		global $wgCommentTableSchemaMigrationStage;
-		if ( $wgCommentTableSchemaMigrationStage >= MIGRATION_WRITE_NEW &&
-			!$this->updateRowExists( 'MigrateComments' )
-		) {
+		if ( !$this->updateRowExists( 'MigrateComments' ) ) {
 			$this->output(
 				"Migrating comments to the 'comments' table, printing progress markers. For large\n" .
 				"databases, you may want to hit Ctrl-C and do this manually with\n" .
@@ -1281,20 +1278,14 @@ abstract class DatabaseUpdater {
 	 * @since 1.32
 	 */
 	protected function migrateImageCommentTemp() {
-		global $wgCommentTableSchemaMigrationStage;
-
 		if ( $this->tableExists( 'image_comment_temp' ) ) {
-			if ( $wgCommentTableSchemaMigrationStage > MIGRATION_OLD ) {
-				$this->output( "Merging image_comment_temp into the image table\n" );
-				$task = $this->maintenance->runChild(
-					MigrateImageCommentTemp::class, 'migrateImageCommentTemp.php'
-				);
-				$task->setForce();
-				$ok = $task->execute();
-				$this->output( $ok ? "done.\n" : "errors were encountered.\n" );
-			} else {
-				$ok = true;
-			}
+			$this->output( "Merging image_comment_temp into the image table\n" );
+			$task = $this->maintenance->runChild(
+				MigrateImageCommentTemp::class, 'migrateImageCommentTemp.php'
+			);
+			$task->setForce();
+			$ok = $task->execute();
+			$this->output( $ok ? "done.\n" : "errors were encountered.\n" );
 			if ( $ok ) {
 				$this->dropTable( 'image_comment_temp' );
 			}
diff --git a/includes/installer/MssqlUpdater.php b/includes/installer/MssqlUpdater.php
index 2f1c0f3039..75f389478c 100644
--- a/includes/installer/MssqlUpdater.php
+++ b/includes/installer/MssqlUpdater.php
@@ -156,6 +156,7 @@ class MssqlUpdater extends DatabaseUpdater {
 			[ 'dropField', 'change_tag', 'ct_tag', 'patch-drop-ct_tag.sql' ],
 			[ 'dropTable', 'valid_tag' ],
 			[ 'dropTable', 'tag_summary' ],
+			[ 'dropField', 'protected_titles', 'pt_reason', 'patch-drop-comment-fields.sql' ],
 		];
 	}
 
diff --git a/includes/installer/MysqlUpdater.php b/includes/installer/MysqlUpdater.php
index f7362cbf12..2e3fdba004 100644
--- a/includes/installer/MysqlUpdater.php
+++ b/includes/installer/MysqlUpdater.php
@@ -374,6 +374,7 @@ class MysqlUpdater extends DatabaseUpdater {
 			[ 'dropField', 'change_tag', 'ct_tag', 'patch-drop-ct_tag.sql' ],
 			[ 'dropTable', 'valid_tag' ],
 			[ 'dropTable', 'tag_summary' ],
+			[ 'dropField', 'protected_titles', 'pt_reason', 'patch-drop-comment-fields.sql' ],
 		];
 	}
 
diff --git a/includes/installer/OracleUpdater.php b/includes/installer/OracleUpdater.php
index e9be744555..d3a7b132a7 100644
--- a/includes/installer/OracleUpdater.php
+++ b/includes/installer/OracleUpdater.php
@@ -167,6 +167,7 @@ class OracleUpdater extends DatabaseUpdater {
 			[ 'dropField', 'change_tag', 'ct_tag', 'patch-drop-ct_tag.sql' ],
 			[ 'dropTable', 'valid_tag' ],
 			[ 'dropTable', 'tag_summary' ],
+			[ 'dropField', 'protected_titles', 'pt_reason', 'patch-drop-comment-fields.sql' ],
 
 			// KEEP THIS AT THE BOTTOM!!
 			[ 'doRebuildDuplicateFunction' ],
diff --git a/includes/installer/PostgresUpdater.php b/includes/installer/PostgresUpdater.php
index 7c0d3e3c74..75877a1e50 100644
--- a/includes/installer/PostgresUpdater.php
+++ b/includes/installer/PostgresUpdater.php
@@ -600,6 +600,24 @@ class PostgresUpdater extends DatabaseUpdater {
 			[ 'dropField', 'change_tag', 'ct_tag', 'patch-drop-ct_tag.sql' ],
 			[ 'dropTable', 'valid_tag' ],
 			[ 'dropTable', 'tag_summary' ],
+			[ 'dropPgField', 'archive', 'ar_comment' ],
+			[ 'dropDefault', 'archive', 'ar_comment_id' ],
+			[ 'dropPgField', 'ipblocks', 'ipb_reason' ],
+			[ 'dropDefault', 'ipblocks', 'ipb_reason_id' ],
+			[ 'dropPgField', 'image', 'img_description' ],
+			[ 'dropDefault', 'image', 'img_description_id' ],
+			[ 'dropPgField', 'oldimage', 'oi_description' ],
+			[ 'dropDefault', 'oldimage', 'oi_description_id' ],
+			[ 'dropPgField', 'filearchive', 'fa_deleted_reason' ],
+			[ 'dropDefault', 'filearchive', 'fa_deleted_reason_id' ],
+			[ 'dropPgField', 'filearchive', 'fa_description' ],
+			[ 'dropDefault', 'filearchive', 'fa_description_id' ],
+			[ 'dropPgField', 'recentchanges', 'rc_comment' ],
+			[ 'dropDefault', 'recentchanges', 'rc_comment_id' ],
+			[ 'dropPgField', 'logging', 'log_comment' ],
+			[ 'dropDefault', 'logging', 'log_comment_id' ],
+			[ 'dropPgField', 'protected_titles', 'pt_reason' ],
+			[ 'dropDefault', 'protected_titles', 'pt_reason_id' ],
 		];
 	}
 
@@ -928,7 +946,7 @@ END;
 
 	protected function setDefault( $table, $field, $default ) {
 		$info = $this->db->fieldInfo( $table, $field );
-		if ( $info->defaultValue() !== $default ) {
+		if ( $info && $info->defaultValue() !== $default ) {
 			$this->output( "Changing '$table.$field' default value\n" );
 			$this->db->query( "ALTER TABLE $table ALTER $field SET DEFAULT "
 				. $this->db->addQuotes( $default ) );
diff --git a/includes/installer/SqliteUpdater.php b/includes/installer/SqliteUpdater.php
index 1d99b87096..17ced507a2 100644
--- a/includes/installer/SqliteUpdater.php
+++ b/includes/installer/SqliteUpdater.php
@@ -241,6 +241,14 @@ class SqliteUpdater extends DatabaseUpdater {
 			[ 'dropField', 'change_tag', 'ct_tag', 'patch-drop-ct_tag.sql' ],
 			[ 'dropTable', 'valid_tag' ],
 			[ 'dropTable', 'tag_summary' ],
+			[ 'dropField', 'archive', 'ar_comment', 'patch-archive-drop-ar_comment.sql' ],
+			[ 'dropField', 'ipblocks', 'ipb_reason', 'patch-ipblocks-drop-ipb_reason.sql' ],
+			[ 'dropField', 'image', 'img_description', 'patch-image-drop-img_description.sql' ],
+			[ 'dropField', 'oldimage', 'oi_description', 'patch-oldimage-drop-oi_description.sql' ],
+			[ 'dropField', 'filearchive', 'fa_description', 'patch-filearchive-drop-fa_description.sql' ],
+			[ 'dropField', 'recentchanges', 'rc_comment', 'patch-recentchanges-drop-rc_comment.sql' ],
+			[ 'dropField', 'logging', 'log_comment', 'patch-logging-drop-log_comment.sql' ],
+			[ 'dropField', 'protected_titles', 'pt_reason', 'patch-protected_titles-drop-pt_reason.sql' ],
 		];
 	}
 
diff --git a/includes/page/Article.php b/includes/page/Article.php
index 9b5e5a5366..983f06986e 100644
--- a/includes/page/Article.php
+++ b/includes/page/Article.php
@@ -1946,15 +1946,13 @@ class Article implements Page {
 
 		// HTML maxlength uses "UTF-16 code units", which means that characters outside BMP
 		// (e.g. emojis) count for two each. This limit is overridden in JS to instead count
-		// Unicode codepoints (or 255 UTF-8 bytes for old schema).
-		$conf = $this->getContext()->getConfig();
-		$oldCommentSchema = $conf->get( 'CommentTableSchemaMigrationStage' ) === MIGRATION_OLD;
+		// Unicode codepoints.
 		$fields[] = new OOUI\FieldLayout(
 			new OOUI\TextInputWidget( [
 				'name' => 'wpReason',
 				'inputId' => 'wpReason',
 				'tabIndex' => 2,
-				'maxLength' => $oldCommentSchema ? 255 : CommentStore::COMMENT_CHARACTER_LIMIT,
+				'maxLength' => CommentStore::COMMENT_CHARACTER_LIMIT,
 				'infusable' => true,
 				'value' => $reason,
 				'autofocus' => true,
diff --git a/includes/page/WikiPage.php b/includes/page/WikiPage.php
index 6217ee7e93..072c3c6385 100644
--- a/includes/page/WikiPage.php
+++ b/includes/page/WikiPage.php
@@ -2815,8 +2815,7 @@ class WikiPage implements Page, IDBAccessObject {
 	 */
 	protected function archiveRevisions( $dbw, $id, $suppress ) {
 		global $wgContentHandlerUseDB, $wgMultiContentRevisionSchemaMigrationStage,
-			$wgCommentTableSchemaMigrationStage, $wgActorTableSchemaMigrationStage,
-			$wgDeleteRevisionsBatchSize;
+			$wgActorTableSchemaMigrationStage, $wgDeleteRevisionsBatchSize;
 
 		// Given the lock above, we can be confident in the title and page ID values
 		$namespace = $this->getTitle()->getNamespace();
@@ -2942,9 +2941,7 @@ class WikiPage implements Page, IDBAccessObject {
 			$dbw->insert( 'archive', $rowsInsert, __METHOD__ );
 
 			$dbw->delete( 'revision', [ 'rev_id' => $revids ], __METHOD__ );
-			if ( $wgCommentTableSchemaMigrationStage > MIGRATION_OLD ) {
-				$dbw->delete( 'revision_comment_temp', [ 'revcomment_rev' => $revids ], __METHOD__ );
-			}
+			$dbw->delete( 'revision_comment_temp', [ 'revcomment_rev' => $revids ], __METHOD__ );
 			if ( $wgActorTableSchemaMigrationStage & SCHEMA_COMPAT_WRITE_NEW ) {
 				$dbw->delete( 'revision_actor_temp', [ 'revactor_rev' => $revids ], __METHOD__ );
 			}
diff --git a/includes/resourceloader/ResourceLoaderStartUpModule.php b/includes/resourceloader/ResourceLoaderStartUpModule.php
index b5d31efac7..334fc73261 100644
--- a/includes/resourceloader/ResourceLoaderStartUpModule.php
+++ b/includes/resourceloader/ResourceLoaderStartUpModule.php
@@ -75,7 +75,6 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 		}
 
 		$illegalFileChars = $conf->get( 'IllegalFileChars' );
-		$oldCommentSchema = $conf->get( 'CommentTableSchemaMigrationStage' ) === MIGRATION_OLD;
 
 		// Build list of variables
 		$skin = $context->getSkin();
@@ -123,8 +122,8 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 			'wgResourceLoaderStorageEnabled' => $conf->get( 'ResourceLoaderStorageEnabled' ),
 			'wgForeignUploadTargets' => $conf->get( 'ForeignUploadTargets' ),
 			'wgEnableUploads' => $conf->get( 'EnableUploads' ),
-			'wgCommentByteLimit' => $oldCommentSchema ? 255 : null,
-			'wgCommentCodePointLimit' => $oldCommentSchema ? null : CommentStore::COMMENT_CHARACTER_LIMIT,
+			'wgCommentByteLimit' => null,
+			'wgCommentCodePointLimit' => CommentStore::COMMENT_CHARACTER_LIMIT,
 		];
 
 		Hooks::run( 'ResourceLoaderGetConfigVars', [ &$vars, $skin ] );
diff --git a/includes/specials/SpecialBlock.php b/includes/specials/SpecialBlock.php
index 9c8882b820..81b82d9577 100644
--- a/includes/specials/SpecialBlock.php
+++ b/includes/specials/SpecialBlock.php
@@ -148,7 +148,6 @@ class SpecialBlock extends FormSpecialPage {
 		$suggestedDurations = self::getSuggestedDurations();
 
 		$conf = $this->getConfig();
-		$oldCommentSchema = $conf->get( 'CommentTableSchemaMigrationStage' ) === MIGRATION_OLD;
 		$enablePartialBlocks = $conf->get( 'EnablePartialBlocks' );
 
 		$a = [];
@@ -243,8 +242,8 @@ class SpecialBlock extends FormSpecialPage {
 			'type' => 'selectandother',
 			// HTML maxlength uses "UTF-16 code units", which means that characters outside BMP
 			// (e.g. emojis) count for two each. This limit is overridden in JS to instead count
-			// Unicode codepoints (or 255 UTF-8 bytes for old schema).
-			'maxlength' => $oldCommentSchema ? 255 : CommentStore::COMMENT_CHARACTER_LIMIT,
+			// Unicode codepoints.
+			'maxlength' => CommentStore::COMMENT_CHARACTER_LIMIT,
 			'maxlength-unit' => 'codepoints',
 			'options-message' => 'ipbreason-dropdown',
 			'section' => 'reason',
diff --git a/includes/specials/SpecialEditTags.php b/includes/specials/SpecialEditTags.php
index 6198a8455b..d0bfcb09bf 100644
--- a/includes/specials/SpecialEditTags.php
+++ b/includes/specials/SpecialEditTags.php
@@ -239,9 +239,6 @@ class SpecialEditTags extends UnlistedSpecialPage {
 
 		// Show form if the user can submit
 		if ( $this->isAllowed ) {
-			$conf = $this->getConfig();
-			$oldCommentSchema = $conf->get( 'CommentTableSchemaMigrationStage' ) === MIGRATION_OLD;
-
 			$form = Xml::openElement( 'form', [ 'method' => 'post',
 					'action' => $this->getPageTitle()->getLocalURL( [ 'action' => 'submit' ] ),
 					'id' => 'mw-revdel-form-revisions' ] ) .
@@ -258,9 +255,9 @@ class SpecialEditTags extends UnlistedSpecialPage {
 							'id' => 'wpReason',
 							// HTML maxlength uses "UTF-16 code units", which means that characters outside BMP
 							// (e.g. emojis) count for two each. This limit is overridden in JS to instead count
-							// Unicode codepoints (or 255 UTF-8 bytes for old schema).
+							// Unicode codepoints.
 							// "- 155" is to leave room for the auto-generated part of the log entry.
-							'maxlength' => $oldCommentSchema ? 100 : CommentStore::COMMENT_CHARACTER_LIMIT - 155,
+							'maxlength' => CommentStore::COMMENT_CHARACTER_LIMIT - 155,
 						] ) .
 					'</td>' .
 				"</tr><tr>\n" .
diff --git a/includes/specials/SpecialMovepage.php b/includes/specials/SpecialMovepage.php
index 599ab31135..0234507a13 100644
--- a/includes/specials/SpecialMovepage.php
+++ b/includes/specials/SpecialMovepage.php
@@ -333,14 +333,12 @@ class MovePageForm extends UnlistedSpecialPage {
 
 		// HTML maxlength uses "UTF-16 code units", which means that characters outside BMP
 		// (e.g. emojis) count for two each. This limit is overridden in JS to instead count
-		// Unicode codepoints (or 255 UTF-8 bytes for old schema).
-		$conf = $this->getConfig();
-		$oldCommentSchema = $conf->get( 'CommentTableSchemaMigrationStage' ) === MIGRATION_OLD;
+		// Unicode codepoints.
 		$fields[] = new OOUI\FieldLayout(
 			new OOUI\TextInputWidget( [
 				'name' => 'wpReason',
 				'id' => 'wpReason',
-				'maxLength' => $oldCommentSchema ? 200 : CommentStore::COMMENT_CHARACTER_LIMIT,
+				'maxLength' => CommentStore::COMMENT_CHARACTER_LIMIT,
 				'infusable' => true,
 				'value' => $this->reason,
 			] ),
diff --git a/includes/specials/SpecialRevisiondelete.php b/includes/specials/SpecialRevisiondelete.php
index 50f3710143..d5bb576e51 100644
--- a/includes/specials/SpecialRevisiondelete.php
+++ b/includes/specials/SpecialRevisiondelete.php
@@ -421,9 +421,6 @@ class SpecialRevisionDelete extends UnlistedSpecialPage {
 			$out->addModules( [ 'mediawiki.special.revisionDelete' ] );
 			$out->addModuleStyles( 'mediawiki.special' );
 
-			$conf = $this->getConfig();
-			$oldCommentSchema = $conf->get( 'CommentTableSchemaMigrationStage' ) === MIGRATION_OLD;
-
 			$form = Xml::openElement( 'form', [ 'method' => 'post',
 					'action' => $this->getPageTitle()->getLocalURL( [ 'action' => 'submit' ] ),
 					'id' => 'mw-revdel-form-revisions' ] ) .
@@ -450,9 +447,9 @@ class SpecialRevisionDelete extends UnlistedSpecialPage {
 							'id' => 'wpReason',
 							// HTML maxlength uses "UTF-16 code units", which means that characters outside BMP
 							// (e.g. emojis) count for two each. This limit is overridden in JS to instead count
-							// Unicode codepoints (or 255 UTF-8 bytes for old schema).
+							// Unicode codepoints.
 							// "- 155" is to leave room for the 'wpRevDeleteReasonList' value.
-							'maxlength' => $oldCommentSchema ? 100 : CommentStore::COMMENT_CHARACTER_LIMIT - 155,
+							'maxlength' => CommentStore::COMMENT_CHARACTER_LIMIT - 155,
 						] ) .
 					'</td>' .
 				"</tr><tr>\n" .
diff --git a/includes/specials/SpecialUndelete.php b/includes/specials/SpecialUndelete.php
index cd754ca03d..9654bb7093 100644
--- a/includes/specials/SpecialUndelete.php
+++ b/includes/specials/SpecialUndelete.php
@@ -769,9 +769,6 @@ class SpecialUndelete extends SpecialPage {
 				'content' => new OOUI\HtmlSnippet( $this->msg( 'undeleteextrahelp' )->parseAsBlock() )
 			] );
 
-			$conf = $this->getConfig();
-			$oldCommentSchema = $conf->get( 'CommentTableSchemaMigrationStage' ) === MIGRATION_OLD;
-
 			$fields[] = new OOUI\FieldLayout(
 				new OOUI\TextInputWidget( [
 					'name' => 'wpComment',
@@ -781,8 +778,8 @@ class SpecialUndelete extends SpecialPage {
 					'autofocus' => true,
 					// HTML maxlength uses "UTF-16 code units", which means that characters outside BMP
 					// (e.g. emojis) count for two each. This limit is overridden in JS to instead count
-					// Unicode codepoints (or 255 UTF-8 bytes for old schema).
-					'maxLength' => $oldCommentSchema ? 255 : CommentStore::COMMENT_CHARACTER_LIMIT,
+					// Unicode codepoints.
+					'maxLength' => CommentStore::COMMENT_CHARACTER_LIMIT,
 				] ),
 				[
 					'label' => $this->msg( 'undeletecomment' )->text(),
diff --git a/includes/specials/SpecialUserrights.php b/includes/specials/SpecialUserrights.php
index 3c2907b87d..6e6d90595f 100644
--- a/includes/specials/SpecialUserrights.php
+++ b/includes/specials/SpecialUserrights.php
@@ -714,8 +714,6 @@ class UserrightsPage extends SpecialPage {
 				->rawParams( $userToolLinks )->parse()
 		);
 		if ( $canChangeAny ) {
-			$conf = $this->getConfig();
-			$oldCommentSchema = $conf->get( 'CommentTableSchemaMigrationStage' ) === MIGRATION_OLD;
 			$this->getOutput()->addHTML(
 				$this->msg( 'userrights-groups-help', $user->getName() )->parse() .
 				$grouplist .
@@ -730,8 +728,8 @@ class UserrightsPage extends SpecialPage {
 								'id' => 'wpReason',
 								// HTML maxlength uses "UTF-16 code units", which means that characters outside BMP
 								// (e.g. emojis) count for two each. This limit is overridden in JS to instead count
-								// Unicode codepoints (or 255 UTF-8 bytes for old schema).
-								'maxlength' => $oldCommentSchema ? 255 : CommentStore::COMMENT_CHARACTER_LIMIT,
+								// Unicode codepoints.
+								'maxlength' => CommentStore::COMMENT_CHARACTER_LIMIT,
 							] ) .
 						"</td>
 					</tr>
diff --git a/maintenance/archives/patch-drop-comment-fields.sql b/maintenance/archives/patch-drop-comment-fields.sql
new file mode 100644
index 0000000000..a4b248d468
--- /dev/null
+++ b/maintenance/archives/patch-drop-comment-fields.sql
@@ -0,0 +1,38 @@
+--
+-- patch-drop-comment-fields.sql
+--
+-- T166732. Drop old xx_comment fields, and defaults from xx_comment_id fields.
+
+ALTER TABLE /*_*/archive
+  DROP COLUMN ar_comment,
+  ALTER COLUMN ar_comment_id DROP DEFAULT;
+
+ALTER TABLE /*_*/ipblocks
+  DROP COLUMN ipb_reason,
+  ALTER COLUMN ipb_reason_id DROP DEFAULT;
+
+ALTER TABLE /*_*/image
+  DROP COLUMN img_description,
+  ALTER COLUMN img_description_id DROP DEFAULT;
+
+ALTER TABLE /*_*/oldimage
+  DROP COLUMN oi_description,
+  ALTER COLUMN oi_description_id DROP DEFAULT;
+
+ALTER TABLE /*_*/filearchive
+  DROP COLUMN fa_deleted_reason,
+  ALTER COLUMN fa_deleted_reason_id DROP DEFAULT,
+  DROP COLUMN fa_description,
+  ALTER COLUMN fa_description_id DROP DEFAULT;
+
+ALTER TABLE /*_*/recentchanges
+  DROP COLUMN rc_comment,
+  ALTER COLUMN rc_comment_id DROP DEFAULT;
+
+ALTER TABLE /*_*/logging
+  DROP COLUMN log_comment,
+  ALTER COLUMN log_comment_id DROP DEFAULT;
+
+ALTER TABLE /*_*/protected_titles
+  DROP COLUMN pt_reason,
+  ALTER COLUMN pt_reason_id DROP DEFAULT;
diff --git a/maintenance/migrateComments.php b/maintenance/migrateComments.php
index 555f2d13f0..8025df1f67 100644
--- a/maintenance/migrateComments.php
+++ b/maintenance/migrateComments.php
@@ -47,15 +47,6 @@ class MigrateComments extends LoggedUpdateMaintenance {
 	}
 
 	protected function doDBUpdates() {
-		global $wgCommentTableSchemaMigrationStage;
-
-		if ( $wgCommentTableSchemaMigrationStage < MIGRATION_WRITE_NEW ) {
-			$this->output(
-				"...cannot update while \$wgCommentTableSchemaMigrationStage < MIGRATION_WRITE_NEW\n"
-			);
-			return false;
-		}
-
 		$this->migrateToTemp(
 			'revision', 'rev_id', 'rev_comment', 'revcomment_rev', 'revcomment_comment_id'
 		);
@@ -138,13 +129,18 @@ class MigrateComments extends LoggedUpdateMaintenance {
 	 * @param string $oldField Old comment field name
 	 */
 	protected function migrate( $table, $primaryKey, $oldField ) {
+		$dbw = $this->getDB( DB_MASTER );
+		if ( !$dbw->fieldExists( $table, $oldField, __METHOD__ ) ) {
+			$this->output( "No need to migrate $table.$oldField, field does not exist\n" );
+			return;
+		}
+
 		$newField = $oldField . '_id';
 		$primaryKey = (array)$primaryKey;
 		$pkFilter = array_flip( $primaryKey );
 		$this->output( "Beginning migration of $table.$oldField to $table.$newField\n" );
 		wfWaitForSlaves();
 
-		$dbw = $this->getDB( DB_MASTER );
 		$next = '1=1';
 		$countUpdated = 0;
 		$countComments = 0;
@@ -229,6 +225,12 @@ class MigrateComments extends LoggedUpdateMaintenance {
 	 * @param string $newField New comment field name
 	 */
 	protected function migrateToTemp( $table, $primaryKey, $oldField, $newPrimaryKey, $newField ) {
+		$dbw = $this->getDB( DB_MASTER );
+		if ( !$dbw->fieldExists( $table, $oldField, __METHOD__ ) ) {
+			$this->output( "No need to migrate $table.$oldField, field does not exist\n" );
+			return;
+		}
+
 		$newTable = $table . '_comment_temp';
 		$this->output( "Beginning migration of $table.$oldField to $newTable.$newField\n" );
 		wfWaitForSlaves();
diff --git a/maintenance/mssql/archives/patch-drop-comment-fields.sql b/maintenance/mssql/archives/patch-drop-comment-fields.sql
new file mode 100644
index 0000000000..bdc8c91e7f
--- /dev/null
+++ b/maintenance/mssql/archives/patch-drop-comment-fields.sql
@@ -0,0 +1,55 @@
+--
+-- patch-drop-comment-fields.sql
+--
+-- T166732. Drop old xx_comment fields, and defaults from xx_comment_id fields.
+
+DECLARE @sql nvarchar(max),
+	@id sysname;
+
+ALTER TABLE /*_*/archive DROP CONSTRAINT DF_ar_comment, COLUMN ar_comment;
+ALTER TABLE /*_*/archive DROP CONSTRAINT DF_ar_comment_id;
+
+ALTER TABLE /*_*/ipblocks DROP CONSTRAINT DF_ipb_reason, COLUMN ipb_reason;
+ALTER TABLE /*_*/ipblocks DROP CONSTRAINT DF_ipb_reason_id;
+
+ALTER TABLE /*_*/image DROP CONSTRAINT DF_img_description, COLUMN img_description;
+ALTER TABLE /*_*/image DROP CONSTRAINT DF_img_description_id;
+
+ALTER TABLE /*_*/oldimage DROP CONSTRAINT DF_oi_description, COLUMN oi_description;
+ALTER TABLE /*_*/oldimage DROP CONSTRAINT DF_oi_description_id;
+
+ALTER TABLE /*_*/filearchive DROP CONSTRAINT DF_fa_deleted_reason, COLUMN fa_deleted_reason;
+ALTER TABLE /*_*/filearchive DROP CONSTRAINT DF_fa_deleted_reason_id;
+ALTER TABLE /*_*/filearchive DROP CONSTRAINT DF_fa_description, COLUMN fa_description;
+ALTER TABLE /*_*/filearchive DROP CONSTRAINT DF_fa_description_id;
+
+SET @sql = 'ALTER TABLE /*_*/recentchanges DROP CONSTRAINT ';
+SELECT @id = df.name
+FROM sys.default_constraints df
+JOIN sys.columns c
+	ON c.object_id = df.parent_object_id
+	AND c.column_id = df.parent_column_id
+WHERE
+	df.parent_object_id = OBJECT_ID('/*_*/recentchanges')
+	AND c.name = 'rc_comment';
+SET @sql = @sql + @id;
+EXEC sp_executesql @sql;
+ALTER TABLE /*_*/recentchanges DROP COLUMN rc_comment;
+ALTER TABLE /*_*/recentchanges DROP CONSTRAINT DF_rc_comment_id;
+
+SET @sql = 'ALTER TABLE /*_*/logging DROP CONSTRAINT ';
+SELECT @id = df.name
+FROM sys.default_constraints df
+JOIN sys.columns c
+	ON c.object_id = df.parent_object_id
+	AND c.column_id = df.parent_column_id
+WHERE
+	df.parent_object_id = OBJECT_ID('/*_*/logging')
+	AND c.name = 'log_comment';
+SET @sql = @sql + @id;
+EXEC sp_executesql @sql;
+ALTER TABLE /*_*/logging DROP COLUMN log_comment;
+ALTER TABLE /*_*/logging DROP CONSTRAINT DF_log_comment_id;
+
+ALTER TABLE /*_*/protected_titles DROP CONSTRAINT DF_pt_reason, COLUMN pt_reason;
+ALTER TABLE /*_*/protected_titles DROP CONSTRAINT DF_pt_reason_id;
diff --git a/maintenance/mssql/tables.sql b/maintenance/mssql/tables.sql
index 4ecc6db835..72ea69d6bc 100644
--- a/maintenance/mssql/tables.sql
+++ b/maintenance/mssql/tables.sql
@@ -270,8 +270,7 @@ CREATE TABLE /*_*/archive (
    ar_id int NOT NULL PRIMARY KEY IDENTITY,
    ar_namespace SMALLINT NOT NULL DEFAULT 0,
    ar_title NVARCHAR(255) NOT NULL DEFAULT '',
-   ar_comment NVARCHAR(255) NOT NULL CONSTRAINT DF_ar_comment DEFAULT '',
-   ar_comment_id bigint NOT NULL CONSTRAINT DF_ar_comment_id DEFAULT 0 CONSTRAINT FK_ar_comment_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
+   ar_comment_id bigint NOT NULL CONSTRAINT FK_ar_comment_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
    ar_user INT CONSTRAINT ar_user__user_id__fk FOREIGN KEY REFERENCES /*_*/mwuser(user_id),
    ar_user_text NVARCHAR(255) NOT NULL CONSTRAINT DF_ar_user_text DEFAULT '',
    ar_actor bigint NOT NULL CONSTRAINT DF_ar_actor DEFAULT 0,
@@ -651,12 +650,8 @@ CREATE TABLE /*_*/ipblocks (
   -- User name of blocker
   ipb_by_text nvarchar(255) NOT NULL default '',
 
-  -- Text comment made by blocker.
-  ipb_reason nvarchar(255) NOT NULL CONSTRAINT DF_ipb_reason DEFAULT '',
-
   -- Key to comment_id. Text comment made by blocker.
-  -- ("DEFAULT 0" is temporary, signaling that ipb_reason should be used)
-  ipb_reason_id bigint NOT NULL CONSTRAINT DF_ipb_reason_id DEFAULT 0 CONSTRAINT FK_ipb_reason_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
+  ipb_reason_id bigint NOT NULL CONSTRAINT FK_ipb_reason_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
 
   -- Creation (or refresh) date in standard YMDHMS form.
   -- IP blocks expire automatically.
@@ -776,8 +771,7 @@ CREATE TABLE /*_*/image (
 
   -- Description field as entered by the uploader.
   -- This is displayed in image upload history and logs.
-  img_description nvarchar(255) NOT NULL CONSTRAINT DF_img_description DEFAULT '',
-  img_description_id bigint NOT NULL CONSTRAINT DF_img_description_id DEFAULT 0 CONSTRAINT FK_img_description_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
+  img_description_id bigint NOT NULL CONSTRAINT FK_img_description_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
 
   -- user_id and user_name of uploader.
   img_user int REFERENCES /*_*/mwuser(user_id) ON DELETE SET NULL,
@@ -825,8 +819,7 @@ CREATE TABLE /*_*/oldimage (
   oi_width int NOT NULL default 0,
   oi_height int NOT NULL default 0,
   oi_bits int NOT NULL default 0,
-  oi_description nvarchar(255) NOT NULL CONSTRAINT DF_oi_description DEFAULT '',
-  oi_description_id bigint NOT NULL CONSTRAINT DF_oi_description_id DEFAULT 0 CONSTRAINT FK_oi_description_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
+  oi_description_id bigint NOT NULL CONSTRAINT FK_oi_description_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
   oi_user int REFERENCES /*_*/mwuser(user_id),
   oi_user_text nvarchar(255) NOT NULL CONSTRAINT DF_oi_user_text DEFAULT '',
   oi_actor bigint NOT NULL CONSTRAINT DF_oi_actor DEFAULT 0,
@@ -877,8 +870,7 @@ CREATE TABLE /*_*/filearchive (
   -- Deletion information, if this file is deleted.
   fa_deleted_user int,
   fa_deleted_timestamp varchar(14) default '',
-  fa_deleted_reason nvarchar(max) CONSTRAINT DF_fa_deleted_reason DEFAULT '',
-  fa_deleted_reason_id bigint NOT NULL CONSTRAINT DF_fa_deleted_reason_id DEFAULT 0 CONSTRAINT FK_fa_deleted_reason_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
+  fa_deleted_reason_id bigint NOT NULL CONSTRAINT FK_fa_deleted_reason_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
 
   -- Duped fields from image
   fa_size int default 0,
@@ -889,8 +881,7 @@ CREATE TABLE /*_*/filearchive (
   fa_media_type varchar(16) default null,
   fa_major_mime varchar(16) not null default 'unknown',
   fa_minor_mime nvarchar(100) default 'unknown',
-  fa_description nvarchar(255) CONSTRAINT DF_fa_description DEFAULT '',
-  fa_description_id bigint NOT NULL CONSTRAINT DF_fa_description_id DEFAULT 0 CONSTRAINT FK_fa_description_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
+  fa_description_id bigint NOT NULL CONSTRAINT FK_fa_description_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
   fa_user int default 0 REFERENCES /*_*/mwuser(user_id) ON DELETE SET NULL,
   fa_user_text nvarchar(255) CONSTRAINT DF_fa_user_text DEFAULT '',
   fa_actor bigint NOT NULL CONSTRAINT DF_fa_actor DEFAULT 0,
@@ -995,8 +986,7 @@ CREATE TABLE /*_*/recentchanges (
   rc_title nvarchar(255) NOT NULL default '',
 
   -- as in revision...
-  rc_comment nvarchar(255) NOT NULL default '',
-  rc_comment_id bigint NOT NULL CONSTRAINT DF_rc_comment_id DEFAULT 0 CONSTRAINT FK_rc_comment_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
+  rc_comment_id bigint NOT NULL CONSTRAINT FK_rc_comment_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
   rc_minor bit NOT NULL default 0,
 
   -- Edits by user accounts with the 'bot' rights key are
@@ -1189,12 +1179,8 @@ CREATE TABLE /*_*/logging (
   log_title nvarchar(255) NOT NULL default '',
   log_page int NULL, -- NOT an FK, logging entries are inserted for deleted pages which still reference the deleted page ids
 
-  -- Freeform text. Interpreted as edit history comments.
-  log_comment nvarchar(255) NOT NULL default '',
-
   -- Key to comment_id. Comment summarizing the change.
-  -- ("DEFAULT 0" is temporary, signaling that log_comment should be used)
-  log_comment_id bigint NOT NULL CONSTRAINT DF_log_comment_id DEFAULT 0 CONSTRAINT FK_log_comment_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
+  log_comment_id bigint NOT NULL CONSTRAINT FK_log_comment_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
 
   -- miscellaneous parameters:
   -- LF separated list (old system) or serialized PHP array (new system)
@@ -1358,8 +1344,7 @@ CREATE TABLE /*_*/protected_titles (
   pt_namespace int NOT NULL,
   pt_title nvarchar(255) NOT NULL,
   pt_user int REFERENCES /*_*/mwuser(user_id) ON DELETE SET NULL,
-  pt_reason nvarchar(255) CONSTRAINT DF_pt_reason DEFAULT '',
-  pt_reason_id bigint NOT NULL CONSTRAINT DF_pt_reason_id DEFAULT 0 CONSTRAINT FK_pt_reason_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
+  pt_reason_id bigint NOT NULL CONSTRAINT FK_pt_reason_id FOREIGN KEY REFERENCES /*_*/comment(comment_id),
   pt_timestamp varchar(14) NOT NULL,
   pt_expiry varchar(14) NOT NULL,
   pt_create_perm nvarchar(60) NOT NULL,
diff --git a/maintenance/oracle/archives/patch-drop-comment-fields.sql b/maintenance/oracle/archives/patch-drop-comment-fields.sql
new file mode 100644
index 0000000000..ea3c6410ba
--- /dev/null
+++ b/maintenance/oracle/archives/patch-drop-comment-fields.sql
@@ -0,0 +1,30 @@
+--
+-- patch-drop-comment-fields.sql
+--
+-- T166732. Drop old xx_comment fields, and defaults from xx_comment_id fields.
+
+ALTER TABLE &mw_prefix.archive DROP COLUMN ar_comment;
+ALTER TABLE &mw_prefix.archive MODIFY ar_comment_id DEFAULT NULL;
+
+ALTER TABLE &mw_prefix.ipblocks DROP COLUMN ipb_reason;
+ALTER TABLE &mw_prefix.ipblocks MODIFY ipb_reason_id DEFAULT NULL;
+
+ALTER TABLE &mw_prefix.image DROP COLUMN img_description;
+ALTER TABLE &mw_prefix.image MODIFY img_description_id DEFAULT NULL;
+
+ALTER TABLE &mw_prefix.oldimage DROP COLUMN oi_description;
+ALTER TABLE &mw_prefix.oldimage MODIFY oi_description_id DEFAULT NULL;
+
+ALTER TABLE &mw_prefix.filearchive DROP COLUMN fa_deleted_reason;
+ALTER TABLE &mw_prefix.filearchive MODIFY fa_deleted_reason_id DEFAULT NULL,
+ALTER TABLE &mw_prefix.filearchive DROP COLUMN fa_description;
+ALTER TABLE &mw_prefix.filearchive MODIFY fa_description_id DEFAULT NULL;
+
+ALTER TABLE &mw_prefix.recentchanges DROP COLUMN rc_comment;
+ALTER TABLE &mw_prefix.recentchanges MODIFY rc_comment_id DEFAULT NULL;
+
+ALTER TABLE &mw_prefix.logging DROP COLUMN log_comment;
+ALTER TABLE &mw_prefix.logging MODIFY log_comment_id DEFAULT NULL;
+
+ALTER TABLE &mw_prefix.protected_titles DROP COLUMN pt_reason;
+ALTER TABLE &mw_prefix.protected_titles MODIFY pt_reason_id DEFAULT NULL;
diff --git a/maintenance/oracle/tables.sql b/maintenance/oracle/tables.sql
index 2c20ffffd8..7a8160fca3 100644
--- a/maintenance/oracle/tables.sql
+++ b/maintenance/oracle/tables.sql
@@ -248,8 +248,7 @@ CREATE TABLE &mw_prefix.archive (
   ar_id          NUMBER NOT NULL,
   ar_namespace   NUMBER    DEFAULT 0 NOT NULL,
   ar_title       VARCHAR2(255)         NOT NULL,
-  ar_comment     VARCHAR2(255),
-  ar_comment_id  NUMBER DEFAULT 0 NOT NULL,
+  ar_comment_id  NUMBER NOT NULL,
   ar_user        NUMBER          DEFAULT 0 NOT NULL,
   ar_user_text   VARCHAR2(255)         NULL,
   ar_actor       NUMBER          DEFAULT 0 NOT NULL,
@@ -497,8 +496,7 @@ CREATE TABLE &mw_prefix.ipblocks (
   ipb_by                NUMBER      DEFAULT 0 NOT NULL,
   ipb_by_text           VARCHAR2(255)      NULL,
   ipb_by_actor          NUMBER      DEFAULT 0 NOT NULL,
-  ipb_reason            VARCHAR2(255)      NULL,
-  ipb_reason_id         NUMBER DEFAULT 0 NOT NULL,
+  ipb_reason_id         NUMBER NOT NULL,
   ipb_timestamp         TIMESTAMP(6) WITH TIME ZONE  NOT NULL,
   ipb_auto              CHAR(1)         DEFAULT '0' NOT NULL,
   ipb_anon_only         CHAR(1)         DEFAULT '0' NOT NULL,
@@ -549,8 +547,7 @@ CREATE TABLE &mw_prefix.image (
   img_media_type   VARCHAR2(32),
   img_major_mime   VARCHAR2(32) DEFAULT 'unknown',
   img_minor_mime   VARCHAR2(100) DEFAULT 'unknown',
-  img_description  VARCHAR2(255),
-  img_description_id  NUMBER DEFAULT 0 NOT NULL,
+  img_description_id  NUMBER NOT NULL,
   img_user         NUMBER       DEFAULT 0 NOT NULL,
   img_user_text    VARCHAR2(255)      NULL,
   img_actor        NUMBER       DEFAULT 0 NOT NULL,
@@ -574,8 +571,7 @@ CREATE TABLE &mw_prefix.oldimage (
   oi_width         NUMBER      DEFAULT 0 NOT NULL,
   oi_height        NUMBER      DEFAULT 0 NOT NULL,
   oi_bits          NUMBER      DEFAULT 0 NOT NULL,
-  oi_description   VARCHAR2(255),
-  oi_description_id  NUMBER DEFAULT 0 NOT NULL,
+  oi_description_id  NUMBER NOT NULL,
   oi_user          NUMBER          DEFAULT 0 NOT NULL,
   oi_user_text     VARCHAR2(255)         NULL,
   oi_actor         NUMBER          DEFAULT 0 NOT NULL,
@@ -606,8 +602,7 @@ CREATE TABLE &mw_prefix.filearchive (
   fa_storage_key        VARCHAR2(64),
   fa_deleted_user       NUMBER          DEFAULT 0 NOT NULL,
   fa_deleted_timestamp  TIMESTAMP(6) WITH TIME ZONE  NOT NULL,
-  fa_deleted_reason     CLOB,
-  fa_deleted_reason_id  NUMBER DEFAULT 0 NOT NULL,
+  fa_deleted_reason_id  NUMBER NOT NULL,
   fa_size               NUMBER     DEFAULT 0 NOT NULL,
   fa_width              NUMBER     DEFAULT 0 NOT NULL,
   fa_height             NUMBER     DEFAULT 0 NOT NULL,
@@ -616,8 +611,7 @@ CREATE TABLE &mw_prefix.filearchive (
   fa_media_type         VARCHAR2(32) DEFAULT NULL,
   fa_major_mime         VARCHAR2(32) DEFAULT 'unknown',
   fa_minor_mime         VARCHAR2(100) DEFAULT 'unknown',
-  fa_description        VARCHAR2(255),
-  fa_description_id     NUMBER DEFAULT 0 NOT NULL,
+  fa_description_id     NUMBER NOT NULL,
   fa_user               NUMBER          DEFAULT 0 NOT NULL,
   fa_user_text          VARCHAR2(255)         NULL,
   fa_actor              NUMBER          DEFAULT 0 NOT NULL,
@@ -687,8 +681,7 @@ CREATE TABLE &mw_prefix.recentchanges (
   rc_actor           NUMBER          DEFAULT 0 NOT NULL,
   rc_namespace       NUMBER     DEFAULT 0 NOT NULL,
   rc_title           VARCHAR2(255)         NOT NULL,
-  rc_comment         VARCHAR2(255),
-  rc_comment_id      NUMBER DEFAULT 0 NOT NULL,
+  rc_comment_id      NUMBER NOT NULL,
   rc_minor           CHAR(1)         DEFAULT '0' NOT NULL,
   rc_bot             CHAR(1)         DEFAULT '0' NOT NULL,
   rc_new             CHAR(1)         DEFAULT '0' NOT NULL,
@@ -788,8 +781,7 @@ CREATE TABLE &mw_prefix.logging (
   log_namespace   NUMBER     DEFAULT 0 NOT NULL,
   log_title       VARCHAR2(255)         NOT NULL,
   log_page 				NUMBER,
-  log_comment     VARCHAR2(255),
-  log_comment_id  NUMBER DEFAULT 0 NOT NULL,
+  log_comment_id  NUMBER NOT NULL,
   log_params      CLOB,
   log_deleted     CHAR(1)      DEFAULT '0' NOT NULL
 );
@@ -906,8 +898,7 @@ CREATE TABLE &mw_prefix.protected_titles (
   pt_namespace   NUMBER           DEFAULT 0 NOT NULL,
   pt_title       VARCHAR2(255)    NOT NULL,
   pt_user        NUMBER	          NOT NULL,
-  pt_reason      VARCHAR2(255),
-  pt_reason_id   NUMBER DEFAULT 0 NOT NULL,
+  pt_reason_id   NUMBER NOT NULL,
   pt_timestamp   TIMESTAMP(6) WITH TIME ZONE  NOT NULL,
   pt_expiry      VARCHAR2(14) NOT NULL,
   pt_create_perm VARCHAR2(60) NOT NULL
diff --git a/maintenance/postgres/tables.sql b/maintenance/postgres/tables.sql
index b6858c543f..87fb3967a1 100644
--- a/maintenance/postgres/tables.sql
+++ b/maintenance/postgres/tables.sql
@@ -243,8 +243,7 @@ CREATE TABLE archive (
   ar_page_id        INTEGER          NULL,
   ar_parent_id      INTEGER          NULL,
   ar_sha1           TEXT         NOT NULL DEFAULT '',
-  ar_comment        TEXT         NOT NULL DEFAULT '',
-  ar_comment_id     INTEGER      NOT NULL DEFAULT 0,
+  ar_comment_id     INTEGER      NOT NULL,
   ar_user           INTEGER      NOT NULL DEFAULT 0 REFERENCES mwuser(user_id) ON DELETE SET NULL DEFERRABLE INITIALLY DEFERRED,
   ar_user_text      TEXT         NOT NULL DEFAULT '',
   ar_actor          INTEGER      NOT NULL DEFAULT 0,
@@ -408,8 +407,7 @@ CREATE TABLE ipblocks (
   ipb_by                INTEGER      NOT NULL  DEFAULT 0 REFERENCES mwuser(user_id) ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED,
   ipb_by_text           TEXT         NOT NULL  DEFAULT '',
   ipb_by_actor          INTEGER      NOT NULL  DEFAULT 0,
-  ipb_reason            TEXT         NOT NULL  DEFAULT '',
-  ipb_reason_id         INTEGER      NOT NULL  DEFAULT 0,
+  ipb_reason_id         INTEGER      NOT NULL,
   ipb_timestamp         TIMESTAMPTZ  NOT NULL,
   ipb_auto              SMALLINT     NOT NULL  DEFAULT 0,
   ipb_anon_only         SMALLINT     NOT NULL  DEFAULT 0,
@@ -449,8 +447,7 @@ CREATE TABLE image (
   img_media_type   TEXT,
   img_major_mime   TEXT                DEFAULT 'unknown',
   img_minor_mime   TEXT                DEFAULT 'unknown',
-  img_description  TEXT      NOT NULL  DEFAULT '',
-  img_description_id INTEGER NOT NULL  DEFAULT 0,
+  img_description_id INTEGER NOT NULL,
   img_user         INTEGER   NOT NULL  DEFAULT 0 REFERENCES mwuser(user_id) ON DELETE SET NULL DEFERRABLE INITIALLY DEFERRED,
   img_user_text    TEXT      NOT NULL  DEFAULT '',
   img_actor        INTEGER   NOT NULL  DEFAULT 0,
@@ -468,8 +465,7 @@ CREATE TABLE oldimage (
   oi_width         INTEGER      NOT NULL,
   oi_height        INTEGER      NOT NULL,
   oi_bits          SMALLINT         NULL,
-  oi_description   TEXT         NOT NULL DEFAULT '',
-  oi_description_id INTEGER     NOT NULL DEFAULT 0,
+  oi_description_id INTEGER     NOT NULL,
   oi_user          INTEGER      NOT NULL DEFAULT 0  REFERENCES mwuser(user_id) ON DELETE SET NULL DEFERRABLE INITIALLY DEFERRED,
   oi_user_text     TEXT         NOT NULL DEFAULT '',
   oi_actor         INTEGER      NOT NULL DEFAULT 0,
@@ -496,8 +492,7 @@ CREATE TABLE filearchive (
   fa_storage_key        TEXT,
   fa_deleted_user       INTEGER          NULL  REFERENCES mwuser(user_id) ON DELETE SET NULL DEFERRABLE INITIALLY DEFERRED,
   fa_deleted_timestamp  TIMESTAMPTZ  NOT NULL,
-  fa_deleted_reason     TEXT         NOT NULL  DEFAULT '',
-  fa_deleted_reason_id  INTEGER      NOT NULL  DEFAULT 0,
+  fa_deleted_reason_id  INTEGER      NOT NULL,
   fa_size               INTEGER      NOT NULL,
   fa_width              INTEGER      NOT NULL,
   fa_height             INTEGER      NOT NULL,
@@ -506,8 +501,7 @@ CREATE TABLE filearchive (
   fa_media_type         TEXT,
   fa_major_mime         TEXT                   DEFAULT 'unknown',
   fa_minor_mime         TEXT                   DEFAULT 'unknown',
-  fa_description        TEXT         NOT NULL DEFAULT '',
-  fa_description_id     INTEGER      NOT NULL DEFAULT 0,
+  fa_description_id     INTEGER      NOT NULL,
   fa_user               INTEGER      NOT NULL DEFAULT 0 REFERENCES mwuser(user_id) ON DELETE SET NULL DEFERRABLE INITIALLY DEFERRED,
   fa_user_text          TEXT         NOT NULL DEFAULT '',
   fa_actor              INTEGER      NOT NULL DEFAULT 0,
@@ -559,8 +553,7 @@ CREATE TABLE recentchanges (
   rc_actor           INTEGER      NOT NULL  DEFAULT 0,
   rc_namespace       SMALLINT     NOT NULL,
   rc_title           TEXT         NOT NULL,
-  rc_comment         TEXT         NOT NULL  DEFAULT '',
-  rc_comment_id      INTEGER      NOT NULL  DEFAULT 0,
+  rc_comment_id      INTEGER      NOT NULL,
   rc_minor           SMALLINT     NOT NULL  DEFAULT 0,
   rc_bot             SMALLINT     NOT NULL  DEFAULT 0,
   rc_new             SMALLINT     NOT NULL  DEFAULT 0,
@@ -657,8 +650,7 @@ CREATE TABLE logging (
   log_actor       INTEGER      NOT NULL DEFAULT 0,
   log_namespace   SMALLINT     NOT NULL,
   log_title       TEXT         NOT NULL,
-  log_comment     TEXT         NOT NULL DEFAULT '',
-  log_comment_id  INTEGER      NOT NULL DEFAULT 0,
+  log_comment_id  INTEGER      NOT NULL,
   log_params      TEXT,
   log_deleted     SMALLINT     NOT NULL DEFAULT 0,
   log_user_text   TEXT         NOT NULL DEFAULT '',
@@ -767,8 +759,7 @@ CREATE TABLE protected_titles (
   pt_namespace   SMALLINT    NOT NULL,
   pt_title       TEXT        NOT NULL,
   pt_user        INTEGER         NULL  REFERENCES mwuser(user_id) ON DELETE SET NULL DEFERRABLE INITIALLY DEFERRED,
-  pt_reason      TEXT        NOT NULL DEFAULT '',
-  pt_reason_id   INTEGER     NOT NULL DEFAULT 0,
+  pt_reason_id   INTEGER     NOT NULL,
   pt_timestamp   TIMESTAMPTZ NOT NULL,
   pt_expiry      TIMESTAMPTZ     NULL,
   pt_create_perm TEXT        NOT NULL DEFAULT '',
diff --git a/maintenance/sqlite/archives/patch-archive-drop-ar_comment.sql b/maintenance/sqlite/archives/patch-archive-drop-ar_comment.sql
new file mode 100644
index 0000000000..b412ebbaa5
--- /dev/null
+++ b/maintenance/sqlite/archives/patch-archive-drop-ar_comment.sql
@@ -0,0 +1,47 @@
+--
+-- patch-archive-drop-ar_comment.sql
+--
+-- T166732. Drop old xx_comment fields, and defaults from xx_comment_id fields.
+
+BEGIN;
+
+DROP TABLE IF EXISTS /*_*/archive_tmp;
+CREATE TABLE /*_*/archive_tmp (
+  ar_id int unsigned NOT NULL PRIMARY KEY AUTO_INCREMENT,
+  ar_namespace int NOT NULL default 0,
+  ar_title varchar(255) binary NOT NULL default '',
+  ar_comment_id bigint unsigned NOT NULL,
+  ar_user int unsigned NOT NULL default 0,
+  ar_user_text varchar(255) binary NOT NULL DEFAULT '',
+  ar_actor bigint unsigned NOT NULL DEFAULT 0,
+  ar_timestamp binary(14) NOT NULL default '',
+  ar_minor_edit tinyint NOT NULL default 0,
+  ar_rev_id int unsigned NOT NULL,
+  ar_text_id int unsigned NOT NULL DEFAULT 0,
+  ar_deleted tinyint unsigned NOT NULL default 0,
+  ar_len int unsigned,
+  ar_page_id int unsigned,
+  ar_parent_id int unsigned default NULL,
+  ar_sha1 varbinary(32) NOT NULL default '',
+  ar_content_model varbinary(32) DEFAULT NULL,
+  ar_content_format varbinary(64) DEFAULT NULL
+) /*$wgDBTableOptions*/;
+
+INSERT OR IGNORE INTO /*_*/archive_tmp (
+	ar_id, ar_namespace, ar_title, ar_comment_id, ar_user, ar_user_text, ar_actor,
+	ar_timestamp, ar_minor_edit, ar_rev_id, ar_text_id, ar_deleted,
+	ar_len, ar_page_id, ar_parent_id, ar_sha1, ar_content_model, ar_content_format
+  ) SELECT
+	ar_id, ar_namespace, ar_title, ar_comment_id, ar_user, ar_user_text, ar_actor,
+	ar_timestamp, ar_minor_edit, ar_rev_id, ar_text_id, ar_deleted,
+	ar_len, ar_page_id, ar_parent_id, ar_sha1, ar_content_model, ar_content_format
+  FROM /*_*/archive;
+
+DROP TABLE /*_*/archive;
+ALTER TABLE /*_*/archive_tmp RENAME TO /*_*/archive;
+CREATE INDEX /*i*/name_title_timestamp ON /*_*/archive (ar_namespace,ar_title,ar_timestamp);
+CREATE INDEX /*i*/ar_usertext_timestamp ON /*_*/archive (ar_user_text,ar_timestamp);
+CREATE INDEX /*i*/ar_actor_timestamp ON /*_*/archive (ar_actor,ar_timestamp);
+CREATE UNIQUE INDEX /*i*/ar_revid_uniq ON /*_*/archive (ar_rev_id);
+
+COMMIT;
diff --git a/maintenance/sqlite/archives/patch-filearchive-drop-fa_description.sql b/maintenance/sqlite/archives/patch-filearchive-drop-fa_description.sql
new file mode 100644
index 0000000000..58800313d3
--- /dev/null
+++ b/maintenance/sqlite/archives/patch-filearchive-drop-fa_description.sql
@@ -0,0 +1,58 @@
+--
+-- patch-filearchive-drop-fa_description.sql
+--
+-- T166732. Drop old xx_comment fields, and defaults from xx_comment_id fields.
+
+BEGIN;
+
+DROP TABLE IF EXISTS /*_*/filearchive_tmp;
+CREATE TABLE /*_*/filearchive_tmp (
+  fa_id int NOT NULL PRIMARY KEY AUTO_INCREMENT,
+  fa_name varchar(255) binary NOT NULL default '',
+  fa_archive_name varchar(255) binary default '',
+  fa_storage_group varbinary(16),
+  fa_storage_key varbinary(64) default '',
+  fa_deleted_user int,
+  fa_deleted_timestamp binary(14) default '',
+  fa_deleted_reason_id bigint unsigned NOT NULL,
+  fa_size int unsigned default 0,
+  fa_width int default 0,
+  fa_height int default 0,
+  fa_metadata mediumblob,
+  fa_bits int default 0,
+  fa_media_type ENUM("UNKNOWN", "BITMAP", "DRAWING", "AUDIO", "VIDEO", "MULTIMEDIA", "OFFICE", "TEXT", "EXECUTABLE", "ARCHIVE", "3D") default NULL,
+  fa_major_mime ENUM("unknown", "application", "audio", "image", "text", "video", "message", "model", "multipart", "chemical") default "unknown",
+  fa_minor_mime varbinary(100) default "unknown",
+  fa_description_id bigint unsigned NOT NULL,
+  fa_user int unsigned default 0,
+  fa_user_text varchar(255) binary DEFAULT '',
+  fa_actor bigint unsigned NOT NULL DEFAULT 0,
+  fa_timestamp binary(14) default '',
+  fa_deleted tinyint unsigned NOT NULL default 0,
+  fa_sha1 varbinary(32) NOT NULL default ''
+) /*$wgDBTableOptions*/;
+
+INSERT OR IGNORE INTO /*_*/filearchive_tmp (
+	fa_id, fa_name, fa_archive_name, fa_storage_group, fa_storage_key,
+	fa_deleted_user, fa_deleted_timestamp, fa_deleted_reason_id,
+	fa_size, fa_width, fa_height, fa_metadata, fa_bits,
+	fa_media_type, fa_major_mime, fa_minor_mime, fa_description_id,
+	fa_user, fa_user_text, fa_actor, fa_timestamp, fa_deleted, fa_sha1
+  ) SELECT
+	fa_id, fa_name, fa_archive_name, fa_storage_group, fa_storage_key,
+	fa_deleted_user, fa_deleted_timestamp, fa_deleted_reason_id,
+	fa_size, fa_width, fa_height, fa_metadata, fa_bits,
+	fa_media_type, fa_major_mime, fa_minor_mime, fa_description_id,
+	fa_user, fa_user_text, fa_actor, fa_timestamp, fa_deleted, fa_sha1
+  FROM /*_*/filearchive;
+
+DROP TABLE /*_*/filearchive;
+ALTER TABLE /*_*/filearchive_tmp RENAME TO /*_*/filearchive;
+CREATE INDEX /*i*/fa_name ON /*_*/filearchive (fa_name, fa_timestamp);
+CREATE INDEX /*i*/fa_storage_group ON /*_*/filearchive (fa_storage_group, fa_storage_key);
+CREATE INDEX /*i*/fa_deleted_timestamp ON /*_*/filearchive (fa_deleted_timestamp);
+CREATE INDEX /*i*/fa_user_timestamp ON /*_*/filearchive (fa_user_text,fa_timestamp);
+CREATE INDEX /*i*/fa_actor_timestamp ON /*_*/filearchive (fa_actor,fa_timestamp);
+CREATE INDEX /*i*/fa_sha1 ON /*_*/filearchive (fa_sha1(10));
+
+COMMIT;
diff --git a/maintenance/sqlite/archives/patch-image-drop-img_description.sql b/maintenance/sqlite/archives/patch-image-drop-img_description.sql
new file mode 100644
index 0000000000..c7bb90ce29
--- /dev/null
+++ b/maintenance/sqlite/archives/patch-image-drop-img_description.sql
@@ -0,0 +1,47 @@
+--
+-- patch-image-drop-img_description.sql
+--
+-- T166732. Drop old xx_comment fields, and defaults from xx_comment_id fields.
+
+BEGIN;
+
+DROP TABLE IF EXISTS /*_*/image_tmp;
+CREATE TABLE /*_*/image_tmp (
+  img_name varchar(255) binary NOT NULL default '' PRIMARY KEY,
+  img_size int unsigned NOT NULL default 0,
+  img_width int NOT NULL default 0,
+  img_height int NOT NULL default 0,
+  img_metadata mediumblob NOT NULL,
+  img_bits int NOT NULL default 0,
+  img_media_type ENUM("UNKNOWN", "BITMAP", "DRAWING", "AUDIO", "VIDEO", "MULTIMEDIA", "OFFICE", "TEXT", "EXECUTABLE", "ARCHIVE", "3D") default NULL,
+  img_major_mime ENUM("unknown", "application", "audio", "image", "text", "video", "message", "model", "multipart", "chemical") NOT NULL default "unknown",
+  img_minor_mime varbinary(100) NOT NULL default "unknown",
+  img_description_id bigint unsigned NOT NULL,
+  img_user int unsigned NOT NULL default 0,
+  img_user_text varchar(255) binary NOT NULL DEFAULT '',
+  img_actor bigint unsigned NOT NULL DEFAULT 0,
+  img_timestamp varbinary(14) NOT NULL default '',
+  img_sha1 varbinary(32) NOT NULL default ''
+) /*$wgDBTableOptions*/;
+
+INSERT OR IGNORE INTO /*_*/image_tmp (
+	img_name, img_size, img_width, img_height, img_metadata, img_bits,
+	img_media_type, img_major_mime, img_minor_mime, img_description_id, img_user,
+	img_user_text, img_actor, img_timestamp, img_sha1
+  ) SELECT
+	img_name, img_size, img_width, img_height, img_metadata, img_bits,
+	img_media_type, img_major_mime, img_minor_mime, img_description_id, img_user,
+	img_user_text, img_actor, img_timestamp, img_sha1
+  FROM /*_*/image;
+
+DROP TABLE /*_*/image;
+ALTER TABLE /*_*/image_tmp RENAME TO /*_*/image;
+CREATE INDEX /*i*/img_user_timestamp ON /*_*/image (img_user,img_timestamp);
+CREATE INDEX /*i*/img_usertext_timestamp ON /*_*/image (img_user_text,img_timestamp);
+CREATE INDEX /*i*/img_actor_timestamp ON /*_*/image (img_actor,img_timestamp);
+CREATE INDEX /*i*/img_size ON /*_*/image (img_size);
+CREATE INDEX /*i*/img_timestamp ON /*_*/image (img_timestamp);
+CREATE INDEX /*i*/img_sha1 ON /*_*/image (img_sha1(10));
+CREATE INDEX /*i*/img_media_mime ON /*_*/image (img_media_type,img_major_mime,img_minor_mime);
+
+COMMIT;
diff --git a/maintenance/sqlite/archives/patch-ipblocks-drop-ipb_reason.sql b/maintenance/sqlite/archives/patch-ipblocks-drop-ipb_reason.sql
new file mode 100644
index 0000000000..de5faa0761
--- /dev/null
+++ b/maintenance/sqlite/archives/patch-ipblocks-drop-ipb_reason.sql
@@ -0,0 +1,53 @@
+--
+-- patch-ipblocks-drop-ipb_reason.sql
+--
+-- T166732. Drop old xx_comment fields, and defaults from xx_comment_id fields.
+
+BEGIN;
+
+DROP TABLE IF EXISTS ipblocks_tmp;
+CREATE TABLE /*_*/ipblocks_tmp (
+  ipb_id int NOT NULL PRIMARY KEY AUTO_INCREMENT,
+  ipb_address tinyblob NOT NULL,
+  ipb_user int unsigned NOT NULL default 0,
+  ipb_by int unsigned NOT NULL default 0,
+  ipb_by_text varchar(255) binary NOT NULL default '',
+  ipb_by_actor bigint unsigned NOT NULL DEFAULT 0,
+  ipb_reason_id bigint unsigned NOT NULL,
+  ipb_timestamp binary(14) NOT NULL default '',
+  ipb_auto bool NOT NULL default 0,
+  ipb_anon_only bool NOT NULL default 0,
+  ipb_create_account bool NOT NULL default 1,
+  ipb_enable_autoblock bool NOT NULL default '1',
+  ipb_expiry varbinary(14) NOT NULL default '',
+  ipb_range_start tinyblob NOT NULL,
+  ipb_range_end tinyblob NOT NULL,
+  ipb_deleted bool NOT NULL default 0,
+  ipb_block_email bool NOT NULL default 0,
+  ipb_allow_usertalk bool NOT NULL default 0,
+  ipb_parent_block_id int default NULL,
+  ipb_sitewide bool NOT NULL default 1
+) /*$wgDBTableOptions*/;
+
+INSERT OR IGNORE INTO /*_*/ipblocks_tmp (
+	ipb_id, ipb_address, ipb_user, ipb_by, ipb_by_text, ipb_by_actor, ipb_reason_id,
+	ipb_timestamp, ipb_auto, ipb_anon_only, ipb_create_account,
+	ipb_enable_autoblock, ipb_expiry, ipb_range_start, ipb_range_end,
+	ipb_deleted, ipb_block_email, ipb_allow_usertalk, ipb_parent_block_id, ipb_sitewide
+  ) SELECT
+	ipb_id, ipb_address, ipb_user, ipb_by, ipb_by_text, ipb_by_actor, ipb_reason_id,
+	ipb_timestamp, ipb_auto, ipb_anon_only, ipb_create_account,
+	ipb_enable_autoblock, ipb_expiry, ipb_range_start, ipb_range_end,
+	ipb_deleted, ipb_block_email, ipb_allow_usertalk, ipb_parent_block_id, ipb_sitewide
+  FROM /*_*/ipblocks;
+
+DROP TABLE /*_*/ipblocks;
+ALTER TABLE /*_*/ipblocks_tmp RENAME TO /*_*/ipblocks;
+CREATE UNIQUE INDEX /*i*/ipb_address ON /*_*/ipblocks (ipb_address(255), ipb_user, ipb_auto, ipb_anon_only);
+CREATE INDEX /*i*/ipb_user ON /*_*/ipblocks (ipb_user);
+CREATE INDEX /*i*/ipb_range ON /*_*/ipblocks (ipb_range_start(8), ipb_range_end(8));
+CREATE INDEX /*i*/ipb_timestamp ON /*_*/ipblocks (ipb_timestamp);
+CREATE INDEX /*i*/ipb_expiry ON /*_*/ipblocks (ipb_expiry);
+CREATE INDEX /*i*/ipb_parent_block_id ON /*_*/ipblocks (ipb_parent_block_id);
+
+COMMIT;
diff --git a/maintenance/sqlite/archives/patch-logging-drop-log_comment.sql b/maintenance/sqlite/archives/patch-logging-drop-log_comment.sql
new file mode 100644
index 0000000000..0b53324bfe
--- /dev/null
+++ b/maintenance/sqlite/archives/patch-logging-drop-log_comment.sql
@@ -0,0 +1,47 @@
+--
+-- patch-logging-drop-log_comment.sql
+--
+-- T166732. Drop old xx_comment fields, and defaults from xx_comment_id fields.
+
+BEGIN;
+
+DROP TABLE IF EXISTS /*_*/logging_tmp;
+CREATE TABLE /*_*/logging_tmp (
+  log_id int unsigned NOT NULL PRIMARY KEY AUTO_INCREMENT,
+  log_type varbinary(32) NOT NULL default '',
+  log_action varbinary(32) NOT NULL default '',
+  log_timestamp binary(14) NOT NULL default '19700101000000',
+  log_user int unsigned NOT NULL default 0,
+  log_user_text varchar(255) binary NOT NULL default '',
+  log_actor bigint unsigned NOT NULL DEFAULT 0,
+  log_namespace int NOT NULL default 0,
+  log_title varchar(255) binary NOT NULL default '',
+  log_page int unsigned NULL,
+  log_comment_id bigint unsigned NOT NULL,
+  log_params blob NOT NULL,
+  log_deleted tinyint unsigned NOT NULL default 0
+) /*$wgDBTableOptions*/;
+
+INSERT OR IGNORE INTO /*_*/logging_tmp (
+	log_id, log_type, log_action, log_timestamp, log_user, log_user_text, log_actor,
+	log_namespace, log_title, log_page, log_comment_id, log_params, log_deleted
+  ) SELECT
+	log_id, log_type, log_action, log_timestamp, log_user, log_user_text, log_actor,
+	log_namespace, log_title, log_page, log_comment_id, log_params, log_deleted
+  FROM /*_*/logging;
+
+DROP TABLE /*_*/logging;
+ALTER TABLE /*_*/logging_tmp RENAME TO /*_*/logging;
+CREATE INDEX /*i*/type_time ON /*_*/logging (log_type, log_timestamp);
+CREATE INDEX /*i*/user_time ON /*_*/logging (log_user, log_timestamp);
+CREATE INDEX /*i*/actor_time ON /*_*/logging (log_actor, log_timestamp);
+CREATE INDEX /*i*/page_time ON /*_*/logging (log_namespace, log_title, log_timestamp);
+CREATE INDEX /*i*/times ON /*_*/logging (log_timestamp);
+CREATE INDEX /*i*/log_user_type_time ON /*_*/logging (log_user, log_type, log_timestamp);
+CREATE INDEX /*i*/log_actor_type_time ON /*_*/logging (log_actor, log_type, log_timestamp);
+CREATE INDEX /*i*/log_page_id_time ON /*_*/logging (log_page,log_timestamp);
+CREATE INDEX /*i*/log_type_action ON /*_*/logging (log_type, log_action, log_timestamp);
+CREATE INDEX /*i*/log_user_text_type_time ON /*_*/logging (log_user_text, log_type, log_timestamp);
+CREATE INDEX /*i*/log_user_text_time ON /*_*/logging (log_user_text, log_timestamp);
+
+COMMIT;
diff --git a/maintenance/sqlite/archives/patch-oldimage-drop-oi_description.sql b/maintenance/sqlite/archives/patch-oldimage-drop-oi_description.sql
new file mode 100644
index 0000000000..1c67cb0f58
--- /dev/null
+++ b/maintenance/sqlite/archives/patch-oldimage-drop-oi_description.sql
@@ -0,0 +1,47 @@
+--
+-- patch-oldimage-drop-oi_description.sql
+--
+-- T166732. Drop old xx_comment fields, and defaults from xx_comment_id fields.
+
+BEGIN;
+
+DROP TABLE IF EXISTS /*_*/oldimage_tmp;
+CREATE TABLE /*_*/oldimage_tmp (
+  oi_name varchar(255) binary NOT NULL default '',
+  oi_archive_name varchar(255) binary NOT NULL default '',
+  oi_size int unsigned NOT NULL default 0,
+  oi_width int NOT NULL default 0,
+  oi_height int NOT NULL default 0,
+  oi_bits int NOT NULL default 0,
+  oi_description_id bigint unsigned NOT NULL,
+  oi_user int unsigned NOT NULL default 0,
+  oi_user_text varchar(255) binary NOT NULL DEFAULT '',
+  oi_actor bigint unsigned NOT NULL DEFAULT 0,
+  oi_timestamp binary(14) NOT NULL default '',
+  oi_metadata mediumblob NOT NULL,
+  oi_media_type ENUM("UNKNOWN", "BITMAP", "DRAWING", "AUDIO", "VIDEO", "MULTIMEDIA", "OFFICE", "TEXT", "EXECUTABLE", "ARCHIVE", "3D") default NULL,
+  oi_major_mime ENUM("unknown", "application", "audio", "image", "text", "video", "message", "model", "multipart", "chemical") NOT NULL default "unknown",
+  oi_minor_mime varbinary(100) NOT NULL default "unknown",
+  oi_deleted tinyint unsigned NOT NULL default 0,
+  oi_sha1 varbinary(32) NOT NULL default ''
+) /*$wgDBTableOptions*/;
+
+INSERT OR IGNORE INTO /*_*/oldimage_tmp (
+	oi_name, oi_archive_name, oi_size, oi_width, oi_height, oi_bits,
+	oi_description_id, oi_user, oi_user_text, oi_actor, oi_timestamp, oi_metadata,
+	oi_media_type, oi_major_mime, oi_minor_mime, oi_deleted, oi_sha1
+  ) SELECT
+	oi_name, oi_archive_name, oi_size, oi_width, oi_height, oi_bits,
+	oi_description_id, oi_user, oi_user_text, oi_actor, oi_timestamp, oi_metadata,
+	oi_media_type, oi_major_mime, oi_minor_mime, oi_deleted, oi_sha1
+  FROM /*_*/oldimage;
+
+DROP TABLE /*_*/oldimage;
+ALTER TABLE /*_*/oldimage_tmp RENAME TO /*_*/oldimage;
+CREATE INDEX /*i*/oi_usertext_timestamp ON /*_*/oldimage (oi_user_text,oi_timestamp);
+CREATE INDEX /*i*/oi_actor_timestamp ON /*_*/oldimage (oi_actor,oi_timestamp);
+CREATE INDEX /*i*/oi_name_timestamp ON /*_*/oldimage (oi_name,oi_timestamp);
+CREATE INDEX /*i*/oi_name_archive_name ON /*_*/oldimage (oi_name,oi_archive_name(14));
+CREATE INDEX /*i*/oi_sha1 ON /*_*/oldimage (oi_sha1(10));
+
+COMMIT;
diff --git a/maintenance/sqlite/archives/patch-protected_titles-drop-pt_reason.sql b/maintenance/sqlite/archives/patch-protected_titles-drop-pt_reason.sql
new file mode 100644
index 0000000000..731b9d8144
--- /dev/null
+++ b/maintenance/sqlite/archives/patch-protected_titles-drop-pt_reason.sql
@@ -0,0 +1,30 @@
+--
+-- patch-protected_titles-drop-pt_reason.sql
+--
+-- T166732. Drop old xx_comment fields, and defaults from xx_comment_id fields.
+
+BEGIN;
+
+DROP TABLE IF EXISTS /*_*/protected_titles_tmp;
+CREATE TABLE /*_*/protected_titles_tmp (
+  pt_namespace int NOT NULL,
+  pt_title varchar(255) binary NOT NULL,
+  pt_user int unsigned NOT NULL,
+  pt_reason_id bigint unsigned NOT NULL,
+  pt_timestamp binary(14) NOT NULL,
+  pt_expiry varbinary(14) NOT NULL default '',
+  pt_create_perm varbinary(60) NOT NULL,
+  PRIMARY KEY (pt_namespace,pt_title)
+) /*$wgDBTableOptions*/;
+
+INSERT OR IGNORE INTO /*_*/protected_titles_tmp (
+	pt_namespace, pt_title, pt_user, pt_reason_id, pt_timestamp, pt_expiry, pt_create_perm
+  ) SELECT
+	pt_namespace, pt_title, pt_user, pt_reason_id, pt_timestamp, pt_expiry, pt_create_perm
+  FROM /*_*/protected_titles;
+
+DROP TABLE /*_*/protected_titles;
+ALTER TABLE /*_*/protected_titles_tmp RENAME TO /*_*/protected_titles;
+CREATE INDEX /*i*/pt_timestamp ON /*_*/protected_titles (pt_timestamp);
+
+COMMIT;
diff --git a/maintenance/sqlite/archives/patch-recentchanges-drop-rc_comment.sql b/maintenance/sqlite/archives/patch-recentchanges-drop-rc_comment.sql
new file mode 100644
index 0000000000..5ce52da237
--- /dev/null
+++ b/maintenance/sqlite/archives/patch-recentchanges-drop-rc_comment.sql
@@ -0,0 +1,63 @@
+--
+-- patch-recentchanges-drop-rc_comment.sql
+--
+-- T166732. Drop old xx_comment fields, and defaults from xx_comment_id fields.
+
+BEGIN;
+
+DROP TABLE IF EXISTS /*_*/recentchanges_tmp;
+CREATE TABLE /*_*/recentchanges_tmp (
+  rc_id int NOT NULL PRIMARY KEY AUTO_INCREMENT,
+  rc_timestamp varbinary(14) NOT NULL default '',
+  rc_user int unsigned NOT NULL default 0,
+  rc_user_text varchar(255) binary NOT NULL DEFAULT '',
+  rc_actor bigint unsigned NOT NULL DEFAULT 0,
+  rc_namespace int NOT NULL default 0,
+  rc_title varchar(255) binary NOT NULL default '',
+  rc_comment_id bigint unsigned NOT NULL,
+  rc_minor tinyint unsigned NOT NULL default 0,
+  rc_bot tinyint unsigned NOT NULL default 0,
+  rc_new tinyint unsigned NOT NULL default 0,
+  rc_cur_id int unsigned NOT NULL default 0,
+  rc_this_oldid int unsigned NOT NULL default 0,
+  rc_last_oldid int unsigned NOT NULL default 0,
+  rc_type tinyint unsigned NOT NULL default 0,
+  rc_source varchar(16) binary not null default '',
+  rc_patrolled tinyint unsigned NOT NULL default 0,
+  rc_ip varbinary(40) NOT NULL default '',
+  rc_old_len int,
+  rc_new_len int,
+  rc_deleted tinyint unsigned NOT NULL default 0,
+  rc_logid int unsigned NOT NULL default 0,
+  rc_log_type varbinary(255) NULL default NULL,
+  rc_log_action varbinary(255) NULL default NULL,
+  rc_params blob NULL
+) /*$wgDBTableOptions*/;
+
+INSERT OR IGNORE INTO /*_*/recentchanges_tmp (
+	rc_id, rc_timestamp, rc_user, rc_user_text, rc_actor, rc_namespace, rc_title,
+	rc_comment_id, rc_minor, rc_bot, rc_new, rc_cur_id, rc_this_oldid, rc_last_oldid,
+	rc_type, rc_source, rc_patrolled, rc_ip, rc_old_len, rc_new_len, rc_deleted,
+	rc_logid, rc_log_type, rc_log_action, rc_params
+  ) SELECT
+	rc_id, rc_timestamp, rc_user, rc_user_text, rc_actor, rc_namespace, rc_title,
+	rc_comment_id, rc_minor, rc_bot, rc_new, rc_cur_id, rc_this_oldid, rc_last_oldid,
+	rc_type, rc_source, rc_patrolled, rc_ip, rc_old_len, rc_new_len, rc_deleted,
+	rc_logid, rc_log_type, rc_log_action, rc_params
+  FROM /*_*/recentchanges;
+
+DROP TABLE /*_*/recentchanges;
+ALTER TABLE /*_*/recentchanges_tmp RENAME TO /*_*/recentchanges;
+CREATE INDEX /*i*/rc_timestamp ON /*_*/recentchanges (rc_timestamp);
+CREATE INDEX /*i*/rc_namespace_title_timestamp ON /*_*/recentchanges (rc_namespace, rc_title, rc_timestamp);
+CREATE INDEX /*i*/rc_cur_id ON /*_*/recentchanges (rc_cur_id);
+CREATE INDEX /*i*/new_name_timestamp ON /*_*/recentchanges (rc_new,rc_namespace,rc_timestamp);
+CREATE INDEX /*i*/rc_ip ON /*_*/recentchanges (rc_ip);
+CREATE INDEX /*i*/rc_ns_usertext ON /*_*/recentchanges (rc_namespace, rc_user_text);
+CREATE INDEX /*i*/rc_ns_actor ON /*_*/recentchanges (rc_namespace, rc_actor);
+CREATE INDEX /*i*/rc_user_text ON /*_*/recentchanges (rc_user_text, rc_timestamp);
+CREATE INDEX /*i*/rc_actor ON /*_*/recentchanges (rc_actor, rc_timestamp);
+CREATE INDEX /*i*/rc_name_type_patrolled_timestamp ON /*_*/recentchanges (rc_namespace, rc_type, rc_patrolled, rc_timestamp);
+CREATE INDEX /*i*/rc_this_oldid ON /*_*/recentchanges (rc_this_oldid);
+
+COMMIT;
diff --git a/maintenance/tables.sql b/maintenance/tables.sql
index 83ba4e2f1b..dac222ffcd 100644
--- a/maintenance/tables.sql
+++ b/maintenance/tables.sql
@@ -593,8 +593,7 @@ CREATE TABLE /*_*/archive (
   ar_title varchar(255) binary NOT NULL default '',
 
   -- Basic revision stuff...
-  ar_comment varbinary(767) NOT NULL default '', -- Deprecated in favor of ar_comment_id
-  ar_comment_id bigint unsigned NOT NULL DEFAULT 0, -- ("DEFAULT 0" is temporary, signaling that ar_comment should be used)
+  ar_comment_id bigint unsigned NOT NULL,
   ar_user int unsigned NOT NULL default 0, -- Deprecated in favor of ar_actor
   ar_user_text varchar(255) binary NOT NULL DEFAULT '', -- Deprecated in favor of ar_actor
   ar_actor bigint unsigned NOT NULL DEFAULT 0, -- ("DEFAULT 0" is temporary, signaling that ar_user/ar_user_text should be used)
@@ -1044,12 +1043,8 @@ CREATE TABLE /*_*/ipblocks (
   -- Actor who made the block.
   ipb_by_actor bigint unsigned NOT NULL DEFAULT 0, -- ("DEFAULT 0" is temporary, signaling that ipb_by/ipb_by_text should be used)
 
-  -- Text comment made by blocker. Deprecated in favor of ipb_reason_id
-  ipb_reason varbinary(767) NOT NULL default '',
-
   -- Key to comment_id. Text comment made by blocker.
-  -- ("DEFAULT 0" is temporary, signaling that ipb_reason should be used)
-  ipb_reason_id bigint unsigned NOT NULL DEFAULT 0,
+  ipb_reason_id bigint unsigned NOT NULL,
 
   -- Creation (or refresh) date in standard YMDHMS form.
   -- IP blocks expire automatically.
@@ -1180,10 +1175,7 @@ CREATE TABLE /*_*/image (
 
   -- Description field as entered by the uploader.
   -- This is displayed in image upload history and logs.
-  -- Deprecated in favor of img_description_id.
-  img_description varbinary(767) NOT NULL default '',
-
-  img_description_id bigint unsigned NOT NULL DEFAULT 0, -- ("DEFAULT 0" is temporary, signaling that img_description should be used)
+  img_description_id bigint unsigned NOT NULL,
 
   -- user_id and user_name of uploader.
   -- Deprecated in favor of img_actor.
@@ -1233,8 +1225,7 @@ CREATE TABLE /*_*/oldimage (
   oi_width int NOT NULL default 0,
   oi_height int NOT NULL default 0,
   oi_bits int NOT NULL default 0,
-  oi_description varbinary(767) NOT NULL default '', -- Deprecated.
-  oi_description_id bigint unsigned NOT NULL DEFAULT 0, -- ("DEFAULT 0" is temporary, signaling that oi_description should be used)
+  oi_description_id bigint unsigned NOT NULL,
   oi_user int unsigned NOT NULL default 0, -- Deprecated in favor of oi_actor
   oi_user_text varchar(255) binary NOT NULL DEFAULT '', -- Deprecated in favor of oi_actor
   oi_actor bigint unsigned NOT NULL DEFAULT 0, -- ("DEFAULT 0" is temporary, signaling that oi_user/oi_user_text should be used)
@@ -1284,8 +1275,7 @@ CREATE TABLE /*_*/filearchive (
   -- Deletion information, if this file is deleted.
   fa_deleted_user int,
   fa_deleted_timestamp binary(14) default '',
-  fa_deleted_reason varbinary(767) default '', -- Deprecated
-  fa_deleted_reason_id bigint unsigned NOT NULL DEFAULT 0, -- ("DEFAULT 0" is temporary, signaling that fa_deleted_reason should be used)
+  fa_deleted_reason_id bigint unsigned NOT NULL,
 
   -- Duped fields from image
   fa_size int unsigned default 0,
@@ -1296,8 +1286,7 @@ CREATE TABLE /*_*/filearchive (
   fa_media_type ENUM("UNKNOWN", "BITMAP", "DRAWING", "AUDIO", "VIDEO", "MULTIMEDIA", "OFFICE", "TEXT", "EXECUTABLE", "ARCHIVE", "3D") default NULL,
   fa_major_mime ENUM("unknown", "application", "audio", "image", "text", "video", "message", "model", "multipart", "chemical") default "unknown",
   fa_minor_mime varbinary(100) default "unknown",
-  fa_description varbinary(767) default '', -- Deprecated
-  fa_description_id bigint unsigned NOT NULL DEFAULT 0, -- ("DEFAULT 0" is temporary, signaling that fa_description should be used)
+  fa_description_id bigint unsigned NOT NULL,
   fa_user int unsigned default 0, -- Deprecated in favor of fa_actor
   fa_user_text varchar(255) binary DEFAULT '', -- Deprecated in favor of fa_actor
   fa_actor bigint unsigned NOT NULL DEFAULT 0, -- ("DEFAULT 0" is temporary, signaling that fa_user/fa_user_text should be used)
@@ -1398,8 +1387,7 @@ CREATE TABLE /*_*/recentchanges (
   rc_title varchar(255) binary NOT NULL default '',
 
   -- as in revision...
-  rc_comment varbinary(767) NOT NULL default '', -- Deprecated.
-  rc_comment_id bigint unsigned NOT NULL DEFAULT 0, -- ("DEFAULT 0" is temporary, signaling that rc_comment should be used)
+  rc_comment_id bigint unsigned NOT NULL,
   rc_minor tinyint unsigned NOT NULL default 0,
 
   -- Edits by user accounts with the 'bot' rights key are
@@ -1622,13 +1610,8 @@ CREATE TABLE /*_*/logging (
   log_title varchar(255) binary NOT NULL default '',
   log_page int unsigned NULL,
 
-  -- Freeform text. Interpreted as edit history comments.
-  -- Deprecated in favor of log_comment_id.
-  log_comment varbinary(767) NOT NULL default '',
-
   -- Key to comment_id. Comment summarizing the change.
-  -- ("DEFAULT 0" is temporary, signaling that log_comment should be used)
-  log_comment_id bigint unsigned NOT NULL DEFAULT 0,
+  log_comment_id bigint unsigned NOT NULL,
 
   -- miscellaneous parameters:
   -- LF separated list (old system) or serialized PHP array (new system)
@@ -1805,8 +1788,7 @@ CREATE TABLE /*_*/protected_titles (
   pt_namespace int NOT NULL,
   pt_title varchar(255) binary NOT NULL,
   pt_user int unsigned NOT NULL,
-  pt_reason varbinary(767) default '', -- Deprecated.
-  pt_reason_id bigint unsigned NOT NULL DEFAULT 0, -- ("DEFAULT 0" is temporary, signaling that pt_reason should be used)
+  pt_reason_id bigint unsigned NOT NULL,
   pt_timestamp binary(14) NOT NULL,
   pt_expiry varbinary(14) NOT NULL default '',
   pt_create_perm varbinary(60) NOT NULL,
diff --git a/tests/parser/ParserTestRunner.php b/tests/parser/ParserTestRunner.php
index b6c7b03a6c..0e6a3eed77 100644
--- a/tests/parser/ParserTestRunner.php
+++ b/tests/parser/ParserTestRunner.php
@@ -1199,7 +1199,7 @@ class ParserTestRunner {
 	 * @return array
 	 */
 	private function listTables() {
-		global $wgCommentTableSchemaMigrationStage, $wgActorTableSchemaMigrationStage;
+		global $wgActorTableSchemaMigrationStage;
 
 		$tables = [ 'user', 'user_properties', 'user_former_groups', 'page', 'page_restrictions',
 			'protected_titles', 'revision', 'ip_changes', 'text', 'pagelinks', 'imagelinks',
@@ -1209,14 +1209,9 @@ class ParserTestRunner {
 			'querycache', 'objectcache', 'job', 'l10n_cache', 'redirect', 'querycachetwo',
 			'archive', 'user_groups', 'page_props', 'category',
 			'slots', 'content', 'slot_roles', 'content_models',
+			'comment', 'revision_comment_temp',
 		];
 
-		if ( $wgCommentTableSchemaMigrationStage >= MIGRATION_WRITE_BOTH ) {
-			// The new tables for comments are in use
-			$tables[] = 'comment';
-			$tables[] = 'revision_comment_temp';
-		}
-
 		if ( $wgActorTableSchemaMigrationStage & SCHEMA_COMPAT_WRITE_NEW ) {
 			// The new tables for actors are in use
 			$tables[] = 'actor';
diff --git a/tests/phpunit/includes/ActorMigrationTest.php b/tests/phpunit/includes/ActorMigrationTest.php
index b761d29758..15c70bce11 100644
--- a/tests/phpunit/includes/ActorMigrationTest.php
+++ b/tests/phpunit/includes/ActorMigrationTest.php
@@ -571,10 +571,8 @@ class ActorMigrationTest extends MediaWikiLangTestCase {
 	public static function provideInsertRoundTrip() {
 		$db = wfGetDB( DB_REPLICA ); // for timestamps
 
-		$ipbfields = [
-		];
-		$revfields = [
-		];
+		$comment = MediaWikiServices::getInstance()->getCommentStore()
+			->createComment( wfGetDB( DB_MASTER ), '' );
 
 		return [
 			'recentchanges' => [ 'recentchanges', 'rc_user', 'rc_id', [
@@ -584,12 +582,14 @@ class ActorMigrationTest extends MediaWikiLangTestCase {
 				'rc_this_oldid' => 42,
 				'rc_last_oldid' => 41,
 				'rc_source' => 'test',
+				'rc_comment_id' => $comment->id,
 			] ],
 			'ipblocks' => [ 'ipblocks', 'ipb_by', 'ipb_id', [
 				'ipb_range_start' => '',
 				'ipb_range_end' => '',
 				'ipb_timestamp' => $db->timestamp(),
 				'ipb_expiry' => $db->getInfinity(),
+				'ipb_reason_id' => $comment->id,
 			] ],
 			'revision' => [ 'revision', 'rev_user', 'rev_id', [
 				'rev_page' => 42,
diff --git a/tests/phpunit/includes/CommentStoreTest.php b/tests/phpunit/includes/CommentStoreTest.php
index 4360343981..78c5bf3a95 100644
--- a/tests/phpunit/includes/CommentStoreTest.php
+++ b/tests/phpunit/includes/CommentStoreTest.php
@@ -18,6 +18,17 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 		'comment',
 	];
 
+	protected function getSchemaOverrides( IMaintainableDatabase $db ) {
+		return [
+			'scripts' => [
+				__DIR__ . '/CommentStoreTest.sql',
+			],
+			'drop' => [],
+			'create' => [ 'commentstore1', 'commentstore2', 'commentstore2_temp' ],
+			'alter' => [],
+		];
+	}
+
 	/**
 	 * Create a store for a particular stage
 	 * @param int $stage
@@ -25,6 +36,16 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 	 */
 	protected function makeStore( $stage ) {
 		$store = new CommentStore( MediaWikiServices::getInstance()->getContentLanguage(), $stage );
+
+		TestingAccessWrapper::newFromObject( $store )->tempTables += [ 'cs2_comment' => [
+			'table' => 'commentstore2_temp',
+			'pk' => 'cs2t_id',
+			'field' => 'cs2t_comment_id',
+			'joinPK' => 'cs2_id',
+			'stage' => MIGRATION_OLD,
+			'deprecatedIn' => null,
+		] ];
+
 		return $store;
 	}
 
@@ -38,6 +59,16 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 		$this->hideDeprecated( 'CommentStore::newKey' );
 		$store = CommentStore::newKey( $key );
 		TestingAccessWrapper::newFromObject( $store )->stage = $stage;
+
+		TestingAccessWrapper::newFromObject( $store )->tempTables += [ 'cs2_comment' => [
+			'table' => 'commentstore2_temp',
+			'pk' => 'cs2t_id',
+			'field' => 'cs2t_comment_id',
+			'joinPK' => 'cs2_id',
+			'stage' => MIGRATION_OLD,
+			'deprecatedIn' => null,
+		] ];
+
 		return $store;
 	}
 
@@ -360,12 +391,13 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 	 * @param string $table
 	 * @param string $key
 	 * @param string $pk
-	 * @param string $extraFields
 	 * @param string|Message $comment
 	 * @param array|null $data
 	 * @param array $expect
 	 */
-	public function testInsertRoundTrip( $table, $key, $pk, $extraFields, $comment, $data, $expect ) {
+	public function testInsertRoundTrip( $table, $key, $pk, $comment, $data, $expect ) {
+		static $id = 1;
+
 		$expectOld = [
 			'text' => $expect['text'],
 			'message' => new RawMessage( '$1', [ $expect['text'] ] ),
@@ -381,12 +413,8 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 		];
 
 		foreach ( $stages as $writeStage => $possibleReadStages ) {
-			if ( $key === 'ipb_reason' ) {
-				$extraFields['ipb_address'] = __CLASS__ . "#$writeStage";
-			}
-
 			$wstore = $this->makeStore( $writeStage );
-			$usesTemp = $key === 'rev_comment';
+			$usesTemp = $key === 'cs2_comment';
 
 			if ( $usesTemp ) {
 				list( $fields, $callback ) = $wstore->insertWithTempTable(
@@ -407,8 +435,7 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 				$this->assertArrayNotHasKey( "{$key}_id", $fields, "new field, stage=$writeStage" );
 			}
 
-			$this->db->insert( $table, $extraFields + $fields, __METHOD__ );
-			$id = $this->db->insertId();
+			$this->db->insert( $table, [ $pk => ++$id ] + $fields, __METHOD__ );
 			if ( $usesTemp ) {
 				$callback( $id );
 			}
@@ -452,14 +479,15 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 	 * @param string $table
 	 * @param string $key
 	 * @param string $pk
-	 * @param string $extraFields
 	 * @param string|Message $comment
 	 * @param array|null $data
 	 * @param array $expect
 	 */
 	public function testInsertRoundTrip_withKeyConstruction(
-		$table, $key, $pk, $extraFields, $comment, $data, $expect
+		$table, $key, $pk, $comment, $data, $expect
 	) {
+		static $id = 1000;
+
 		$expectOld = [
 			'text' => $expect['text'],
 			'message' => new RawMessage( '$1', [ $expect['text'] ] ),
@@ -475,12 +503,8 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 		];
 
 		foreach ( $stages as $writeStage => $possibleReadStages ) {
-			if ( $key === 'ipb_reason' ) {
-				$extraFields['ipb_address'] = __CLASS__ . "#$writeStage";
-			}
-
 			$wstore = $this->makeStoreWithKey( $writeStage, $key );
-			$usesTemp = $key === 'rev_comment';
+			$usesTemp = $key === 'cs2_comment';
 
 			if ( $usesTemp ) {
 				list( $fields, $callback ) = $wstore->insertWithTempTable(
@@ -501,8 +525,7 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 				$this->assertArrayNotHasKey( "{$key}_id", $fields, "new field, stage=$writeStage" );
 			}
 
-			$this->db->insert( $table, $extraFields + $fields, __METHOD__ );
-			$id = $this->db->insertId();
+			$this->db->insert( $table, [ $pk => ++$id ] + $fields, __METHOD__ );
 			if ( $usesTemp ) {
 				$callback( $id );
 			}
@@ -547,60 +570,48 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 		$msgComment = new Message( 'parentheses', [ 'message comment' ] );
 		$textCommentMsg = new RawMessage( '$1', [ 'text comment' ] );
 		$nestedMsgComment = new Message( [ 'parentheses', 'rawmessage' ], [ new Message( 'mainpage' ) ] );
-		$ipbfields = [
-			'ipb_range_start' => '',
-			'ipb_range_end' => '',
-			'ipb_timestamp' => $db->timestamp(),
-			'ipb_expiry' => $db->getInfinity(),
-		];
-		$revfields = [
-			'rev_page' => 42,
-			'rev_text_id' => 42,
-			'rev_len' => 0,
-			'rev_timestamp' => $db->timestamp(),
-		];
 		$comStoreComment = new CommentStoreComment(
 			null, 'comment store comment', null, [ 'foo' => 'bar' ]
 		);
 
 		return [
 			'Simple table, text comment' => [
-				'ipblocks', 'ipb_reason', 'ipb_id', $ipbfields, 'text comment', null, [
+				'commentstore1', 'cs1_comment', 'cs1_id', 'text comment', null, [
 					'text' => 'text comment',
 					'message' => $textCommentMsg,
 					'data' => null,
 				]
 			],
 			'Simple table, text comment with data' => [
-				'ipblocks', 'ipb_reason', 'ipb_id', $ipbfields, 'text comment', [ 'message' => 42 ], [
+				'commentstore1', 'cs1_comment', 'cs1_id', 'text comment', [ 'message' => 42 ], [
 					'text' => 'text comment',
 					'message' => $textCommentMsg,
 					'data' => [ 'message' => 42 ],
 				]
 			],
 			'Simple table, message comment' => [
-				'ipblocks', 'ipb_reason', 'ipb_id', $ipbfields, $msgComment, null, [
+				'commentstore1', 'cs1_comment', 'cs1_id', $msgComment, null, [
 					'text' => '(message comment)',
 					'message' => $msgComment,
 					'data' => null,
 				]
 			],
 			'Simple table, message comment with data' => [
-				'ipblocks', 'ipb_reason', 'ipb_id', $ipbfields, $msgComment, [ 'message' => 42 ], [
+				'commentstore1', 'cs1_comment', 'cs1_id', $msgComment, [ 'message' => 42 ], [
 					'text' => '(message comment)',
 					'message' => $msgComment,
 					'data' => [ 'message' => 42 ],
 				]
 			],
 			'Simple table, nested message comment' => [
-				'ipblocks', 'ipb_reason', 'ipb_id', $ipbfields, $nestedMsgComment, null, [
+				'commentstore1', 'cs1_comment', 'cs1_id', $nestedMsgComment, null, [
 					'text' => '(Main Page)',
 					'message' => $nestedMsgComment,
 					'data' => null,
 				]
 			],
 			'Simple table, CommentStoreComment' => [
-				'ipblocks', 'ipb_reason', 'ipb_id', $ipbfields, clone $comStoreComment, [ 'baz' => 'baz' ], [
+				'commentstore1', 'cs1_comment', 'cs1_id', clone $comStoreComment, [ 'baz' => 'baz' ], [
 					'text' => 'comment store comment',
 					'message' => $comStoreComment->message,
 					'data' => [ 'foo' => 'bar' ],
@@ -608,42 +619,42 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 			],
 
 			'Revision, text comment' => [
-				'revision', 'rev_comment', 'rev_id', $revfields, 'text comment', null, [
+				'commentstore2', 'cs2_comment', 'cs2_id', 'text comment', null, [
 					'text' => 'text comment',
 					'message' => $textCommentMsg,
 					'data' => null,
 				]
 			],
 			'Revision, text comment with data' => [
-				'revision', 'rev_comment', 'rev_id', $revfields, 'text comment', [ 'message' => 42 ], [
+				'commentstore2', 'cs2_comment', 'cs2_id', 'text comment', [ 'message' => 42 ], [
 					'text' => 'text comment',
 					'message' => $textCommentMsg,
 					'data' => [ 'message' => 42 ],
 				]
 			],
 			'Revision, message comment' => [
-				'revision', 'rev_comment', 'rev_id', $revfields, $msgComment, null, [
+				'commentstore2', 'cs2_comment', 'cs2_id', $msgComment, null, [
 					'text' => '(message comment)',
 					'message' => $msgComment,
 					'data' => null,
 				]
 			],
 			'Revision, message comment with data' => [
-				'revision', 'rev_comment', 'rev_id', $revfields, $msgComment, [ 'message' => 42 ], [
+				'commentstore2', 'cs2_comment', 'cs2_id', $msgComment, [ 'message' => 42 ], [
 					'text' => '(message comment)',
 					'message' => $msgComment,
 					'data' => [ 'message' => 42 ],
 				]
 			],
 			'Revision, nested message comment' => [
-				'revision', 'rev_comment', 'rev_id', $revfields, $nestedMsgComment, null, [
+				'commentstore2', 'cs2_comment', 'cs2_id', $nestedMsgComment, null, [
 					'text' => '(Main Page)',
 					'message' => $nestedMsgComment,
 					'data' => null,
 				]
 			],
 			'Revision, CommentStoreComment' => [
-				'revision', 'rev_comment', 'rev_id', $revfields, clone $comStoreComment, [ 'baz' => 'baz' ], [
+				'commentstore2', 'cs2_comment', 'cs2_id', clone $comStoreComment, [ 'baz' => 'baz' ], [
 					'text' => 'comment store comment',
 					'message' => $comStoreComment->message,
 					'data' => [ 'foo' => 'bar' ],
diff --git a/tests/phpunit/includes/CommentStoreTest.sql b/tests/phpunit/includes/CommentStoreTest.sql
new file mode 100644
index 0000000000..f95781dd3e
--- /dev/null
+++ b/tests/phpunit/includes/CommentStoreTest.sql
@@ -0,0 +1,17 @@
+-- These are carefully crafted to work in all five supported databases
+
+CREATE TABLE /*_*/commentstore1 (
+  cs1_id integer not null,
+  cs1_comment varchar(200),
+  cs1_comment_id integer
+);
+
+CREATE TABLE /*_*/commentstore2 (
+  cs2_id integer not null,
+  cs2_comment varchar(200)
+);
+
+CREATE TABLE /*_*/commentstore2_temp (
+  cs2t_id integer not null,
+  cs2t_comment_id integer
+);
diff --git a/tests/phpunit/includes/Revision/RevisionQueryInfoTest.php b/tests/phpunit/includes/Revision/RevisionQueryInfoTest.php
index 7188cf50a7..9f1c69ce97 100644
--- a/tests/phpunit/includes/Revision/RevisionQueryInfoTest.php
+++ b/tests/phpunit/includes/Revision/RevisionQueryInfoTest.php
@@ -52,23 +52,6 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 		return $fields;
 	}
 
-	protected function getOldCommentQueryFields( $prefix ) {
-		return [
-			"{$prefix}_comment_text" => "{$prefix}_comment",
-			"{$prefix}_comment_data" => 'NULL',
-			"{$prefix}_comment_cid" => 'NULL',
-		];
-	}
-
-	protected function getCompatCommentQueryFields( $prefix ) {
-		return [
-			"{$prefix}_comment_text"
-				=> "COALESCE( comment_{$prefix}_comment.comment_text, {$prefix}_comment )",
-			"{$prefix}_comment_data" => "comment_{$prefix}_comment.comment_data",
-			"{$prefix}_comment_cid" => "comment_{$prefix}_comment.comment_id",
-		];
-	}
-
 	protected function getNewCommentQueryFields( $prefix ) {
 		return [
 			"{$prefix}_comment_text" => "comment_{$prefix}_comment.comment_text",
@@ -106,19 +89,6 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 		];
 	}
 
-	protected function getCompatCommentJoins( $prefix ) {
-		return [
-			"temp_{$prefix}_comment" => [
-				"LEFT JOIN",
-				"temp_{$prefix}_comment.revcomment_{$prefix} = {$prefix}_id",
-			],
-			"comment_{$prefix}_comment" => [
-				"LEFT JOIN",
-				"comment_{$prefix}_comment.comment_id = temp_{$prefix}_comment.revcomment_comment_id",
-			],
-		];
-	}
-
 	protected function getTextQueryFields() {
 		return [
 			'old_text',
@@ -154,7 +124,6 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 		yield 'MCR, comment, actor' => [
 			[
 				'wgMultiContentRevisionSchemaMigrationStage' => SCHEMA_COMPAT_NEW,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_NEW,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_NEW,
 			],
 			[
@@ -180,7 +149,6 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 				'wgContentHandlerUseDB' => true,
 				'wgMultiContentRevisionSchemaMigrationStage'
 					=> SCHEMA_COMPAT_WRITE_BOTH | SCHEMA_COMPAT_READ_NEW,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_WRITE_NEW,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_NEW,
 			],
 			[
@@ -192,11 +160,11 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 				'fields' => array_merge(
 					$this->getArchiveQueryFields( false ),
 					$this->getNewActorQueryFields( 'ar' ),
-					$this->getCompatCommentQueryFields( 'ar' )
+					$this->getNewCommentQueryFields( 'ar' )
 				),
 				'joins' => [
 					'comment_ar_comment'
-						=> [ 'LEFT JOIN', 'comment_ar_comment.comment_id = ar_comment_id' ],
+						=> [ 'JOIN', 'comment_ar_comment.comment_id = ar_comment_id' ],
 					'actor_ar_user' => [ 'JOIN', 'actor_ar_user.actor_id = ar_actor' ],
 				],
 			]
@@ -206,7 +174,6 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 				'wgContentHandlerUseDB' => true,
 				'wgMultiContentRevisionSchemaMigrationStage'
 					=> SCHEMA_COMPAT_WRITE_BOTH | SCHEMA_COMPAT_READ_OLD,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_WRITE_BOTH,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_WRITE_BOTH | SCHEMA_COMPAT_READ_OLD,
 			],
 			[
@@ -218,11 +185,11 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 					$this->getArchiveQueryFields( true ),
 					$this->getContentHandlerQueryFields( 'ar' ),
 					$this->getOldActorQueryFields( 'ar' ),
-					$this->getCompatCommentQueryFields( 'ar' )
+					$this->getNewCommentQueryFields( 'ar' )
 				),
 				'joins' => [
 					'comment_ar_comment'
-						=> [ 'LEFT JOIN', 'comment_ar_comment.comment_id = ar_comment_id' ],
+						=> [ 'JOIN', 'comment_ar_comment.comment_id = ar_comment_id' ],
 				],
 			]
 		];
@@ -230,19 +197,22 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 			[
 				'wgContentHandlerUseDB' => false,
 				'wgMultiContentRevisionSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_OLD,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
 			],
 			[
 				'tables' => [
 					'archive',
+					'comment_ar_comment' => 'comment',
 				],
 				'fields' => array_merge(
 					$this->getArchiveQueryFields( true ),
 					$this->getOldActorQueryFields( 'ar' ),
-					$this->getOldCommentQueryFields( 'ar' )
+					$this->getNewCommentQueryFields( 'ar' )
 				),
-				'joins' => [],
+				'joins' => [
+					'comment_ar_comment'
+						=> [ 'JOIN', 'comment_ar_comment.comment_id = ar_comment_id' ],
+				],
 			]
 		];
 	}
@@ -253,7 +223,6 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 			[
 				'wgContentHandlerUseDB' => true,
 				'wgMultiContentRevisionSchemaMigrationStage' => SCHEMA_COMPAT_NEW,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_NEW,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_NEW,
 			],
 			[ 'page', 'user' ],
@@ -298,7 +267,6 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 				'wgContentHandlerUseDB' => true,
 				'wgMultiContentRevisionSchemaMigrationStage'
 					=> SCHEMA_COMPAT_WRITE_BOTH | SCHEMA_COMPAT_READ_NEW,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_WRITE_NEW,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_WRITE_BOTH | SCHEMA_COMPAT_READ_NEW,
 			],
 			[ 'page', 'user' ],
@@ -317,7 +285,7 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 					$this->getPageQueryFields(),
 					$this->getUserQueryFields(),
 					$this->getNewActorQueryFields( 'rev', 'temp_rev_user.revactor_actor' ),
-					$this->getCompatCommentQueryFields( 'rev' )
+					$this->getNewCommentQueryFields( 'rev' )
 				),
 				'joins' => array_merge(
 					[
@@ -329,9 +297,11 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 								'user_id = actor_rev_user.actor_user',
 							]
 						],
+						'temp_rev_comment' => [ 'JOIN', 'temp_rev_comment.revcomment_rev = rev_id' ],
+						'comment_rev_comment'
+							=> [ 'JOIN', 'comment_rev_comment.comment_id = temp_rev_comment.revcomment_comment_id' ],
 					],
-					$this->getNewActorJoins( 'rev' ),
-					$this->getCompatCommentJoins( 'rev' )
+					$this->getNewActorJoins( 'rev' )
 				),
 			]
 		];
@@ -340,7 +310,6 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 				'wgContentHandlerUseDB' => true,
 				'wgMultiContentRevisionSchemaMigrationStage'
 					=> SCHEMA_COMPAT_WRITE_BOTH | SCHEMA_COMPAT_READ_NEW,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_WRITE_NEW,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_WRITE_BOTH | SCHEMA_COMPAT_READ_NEW,
 			],
 			[ 'page', 'user' ],
@@ -359,7 +328,7 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 					$this->getPageQueryFields(),
 					$this->getUserQueryFields(),
 					$this->getNewActorQueryFields( 'rev', 'temp_rev_user.revactor_actor' ),
-					$this->getCompatCommentQueryFields( 'rev' )
+					$this->getNewCommentQueryFields( 'rev' )
 				),
 				'joins' => array_merge(
 					[
@@ -371,9 +340,11 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 								'user_id = actor_rev_user.actor_user'
 							]
 						],
+						'temp_rev_comment' => [ 'JOIN', 'temp_rev_comment.revcomment_rev = rev_id' ],
+						'comment_rev_comment'
+							=> [ 'JOIN', 'comment_rev_comment.comment_id = temp_rev_comment.revcomment_comment_id' ],
 					],
-					$this->getNewActorJoins( 'rev' ),
-					$this->getCompatCommentJoins( 'rev' )
+					$this->getNewActorJoins( 'rev' )
 				),
 			]
 		];
@@ -382,7 +353,6 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 				'wgContentHandlerUseDB' => true,
 				'wgMultiContentRevisionSchemaMigrationStage'
 					=> SCHEMA_COMPAT_WRITE_BOTH | SCHEMA_COMPAT_READ_OLD,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_WRITE_BOTH,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_WRITE_BOTH | SCHEMA_COMPAT_READ_OLD,
 			],
 			[],
@@ -396,11 +366,13 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 					$this->getRevisionQueryFields( true ),
 					$this->getContentHandlerQueryFields( 'rev' ),
 					$this->getOldActorQueryFields( 'rev', 'temp_rev_user.revactor_actor' ),
-					$this->getCompatCommentQueryFields( 'rev' )
+					$this->getNewCommentQueryFields( 'rev' )
 				),
-			'joins' => array_merge(
-				$this->getCompatCommentJoins( 'rev' )
-			),
+				'joins' => [
+					'temp_rev_comment' => [ 'JOIN', 'temp_rev_comment.revcomment_rev = rev_id' ],
+					'comment_rev_comment'
+						=> [ 'JOIN', 'comment_rev_comment.comment_id = temp_rev_comment.revcomment_comment_id' ],
+				],
 			]
 		];
 		yield 'MCR write-both/read-old, page, user' => [
@@ -408,7 +380,6 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 				'wgContentHandlerUseDB' => true,
 				'wgMultiContentRevisionSchemaMigrationStage'
 					=> SCHEMA_COMPAT_WRITE_BOTH | SCHEMA_COMPAT_READ_OLD,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_WRITE_BOTH,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_WRITE_BOTH | SCHEMA_COMPAT_READ_OLD,
 			],
 			[ 'page', 'user' ],
@@ -426,7 +397,7 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 					$this->getUserQueryFields(),
 					$this->getPageQueryFields(),
 					$this->getOldActorQueryFields( 'rev', 'temp_rev_user.revactor_actor' ),
-					$this->getCompatCommentQueryFields( 'rev' )
+					$this->getNewCommentQueryFields( 'rev' )
 				),
 				'joins' => array_merge(
 					[
@@ -438,8 +409,10 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 								'user_id = rev_user'
 							]
 						],
-					],
-					$this->getCompatCommentJoins( 'rev' )
+						'temp_rev_comment' => [ 'JOIN', 'temp_rev_comment.revcomment_rev = rev_id' ],
+						'comment_rev_comment'
+							=> [ 'JOIN', 'comment_rev_comment.comment_id = temp_rev_comment.revcomment_comment_id' ],
+					]
 				),
 			]
 		];
@@ -447,42 +420,55 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 			[
 				'wgContentHandlerUseDB' => true,
 				'wgMultiContentRevisionSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_OLD,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
 			],
 			[],
 			[
-				'tables' => [ 'revision' ],
+				'tables' => [
+					'revision',
+					'temp_rev_comment' => 'revision_comment_temp',
+					'comment_rev_comment' => 'comment',
+				],
 				'fields' => array_merge(
 					$this->getRevisionQueryFields( true ),
 					$this->getContentHandlerQueryFields( 'rev' ),
 					$this->getOldActorQueryFields( 'rev' ),
-					$this->getOldCommentQueryFields( 'rev' )
+					$this->getNewCommentQueryFields( 'rev' )
 				),
-				'joins' => [],
+				'joins' => [
+					'temp_rev_comment' => [ 'JOIN', 'temp_rev_comment.revcomment_rev = rev_id' ],
+					'comment_rev_comment'
+						=> [ 'JOIN', 'comment_rev_comment.comment_id = temp_rev_comment.revcomment_comment_id' ],
+				],
 			]
 		];
 		yield 'pre-MCR, page, user' => [
 			[
 				'wgContentHandlerUseDB' => true,
 				'wgMultiContentRevisionSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_OLD,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
 			],
 			[ 'page', 'user' ],
 			[
-				'tables' => [ 'revision', 'page', 'user' ],
+				'tables' => [
+					'revision', 'page', 'user',
+					'temp_rev_comment' => 'revision_comment_temp',
+					'comment_rev_comment' => 'comment',
+				],
 				'fields' => array_merge(
 					$this->getRevisionQueryFields( true ),
 					$this->getContentHandlerQueryFields( 'rev' ),
 					$this->getPageQueryFields(),
 					$this->getUserQueryFields(),
 					$this->getOldActorQueryFields( 'rev' ),
-					$this->getOldCommentQueryFields( 'rev' )
+					$this->getNewCommentQueryFields( 'rev' )
 				),
 				'joins' => [
 					'page' => [ 'INNER JOIN', [ 'page_id = rev_page' ] ],
 					'user' => [ 'LEFT JOIN', [ 'rev_user != 0', 'user_id = rev_user' ] ],
+					'temp_rev_comment' => [ 'JOIN', 'temp_rev_comment.revcomment_rev = rev_id' ],
+					'comment_rev_comment'
+						=> [ 'JOIN', 'comment_rev_comment.comment_id = temp_rev_comment.revcomment_comment_id' ],
 				],
 			]
 		];
@@ -490,38 +476,51 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 			[
 				'wgContentHandlerUseDB' => false,
 				'wgMultiContentRevisionSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_OLD,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
 			],
 			[],
 			[
-				'tables' => [ 'revision' ],
+				'tables' => [
+					'revision',
+					'temp_rev_comment' => 'revision_comment_temp',
+					'comment_rev_comment' => 'comment',
+				],
 				'fields' => array_merge(
 					$this->getRevisionQueryFields( true ),
 					$this->getOldActorQueryFields( 'rev' ),
-					$this->getOldCommentQueryFields( 'rev' )
+					$this->getNewCommentQueryFields( 'rev' )
 				),
-				'joins' => [],
+				'joins' => [
+					'temp_rev_comment' => [ 'JOIN', 'temp_rev_comment.revcomment_rev = rev_id' ],
+					'comment_rev_comment'
+						=> [ 'JOIN', 'comment_rev_comment.comment_id = temp_rev_comment.revcomment_comment_id' ],
+				],
 			],
 		];
 		yield 'pre-MCR, no model, page' => [
 			[
 				'wgContentHandlerUseDB' => false,
 				'wgMultiContentRevisionSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_OLD,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
 			],
 			[ 'page' ],
 			[
-				'tables' => [ 'revision', 'page' ],
+				'tables' => [
+					'revision', 'page',
+					'temp_rev_comment' => 'revision_comment_temp',
+					'comment_rev_comment' => 'comment',
+				],
 				'fields' => array_merge(
 					$this->getRevisionQueryFields( true ),
 					$this->getPageQueryFields(),
 					$this->getOldActorQueryFields( 'rev' ),
-					$this->getOldCommentQueryFields( 'rev' )
+					$this->getNewCommentQueryFields( 'rev' )
 				),
 				'joins' => [
 					'page' => [ 'INNER JOIN', [ 'page_id = rev_page' ], ],
+					'temp_rev_comment' => [ 'JOIN', 'temp_rev_comment.revcomment_rev = rev_id' ],
+					'comment_rev_comment'
+						=> [ 'JOIN', 'comment_rev_comment.comment_id = temp_rev_comment.revcomment_comment_id' ],
 				],
 			],
 		];
@@ -529,20 +528,26 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 			[
 				'wgContentHandlerUseDB' => false,
 				'wgMultiContentRevisionSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_OLD,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
 			],
 			[ 'user' ],
 			[
-				'tables' => [ 'revision', 'user' ],
+				'tables' => [
+					'revision', 'user',
+					'temp_rev_comment' => 'revision_comment_temp',
+					'comment_rev_comment' => 'comment',
+				],
 				'fields' => array_merge(
 					$this->getRevisionQueryFields( true ),
 					$this->getUserQueryFields(),
 					$this->getOldActorQueryFields( 'rev' ),
-					$this->getOldCommentQueryFields( 'rev' )
+					$this->getNewCommentQueryFields( 'rev' )
 				),
 				'joins' => [
 					'user' => [ 'LEFT JOIN', [ 'rev_user != 0', 'user_id = rev_user' ] ],
+					'temp_rev_comment' => [ 'JOIN', 'temp_rev_comment.revcomment_rev = rev_id' ],
+					'comment_rev_comment'
+						=> [ 'JOIN', 'comment_rev_comment.comment_id = temp_rev_comment.revcomment_comment_id' ],
 				],
 			],
 		];
@@ -550,20 +555,26 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 			[
 				'wgContentHandlerUseDB' => false,
 				'wgMultiContentRevisionSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_OLD,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
 			],
 			[ 'text' ],
 			[
-				'tables' => [ 'revision', 'text' ],
+				'tables' => [
+					'revision', 'text',
+					'temp_rev_comment' => 'revision_comment_temp',
+					'comment_rev_comment' => 'comment',
+				],
 				'fields' => array_merge(
 					$this->getRevisionQueryFields( true ),
 					$this->getTextQueryFields(),
 					$this->getOldActorQueryFields( 'rev' ),
-					$this->getOldCommentQueryFields( 'rev' )
+					$this->getNewCommentQueryFields( 'rev' )
 				),
 				'joins' => [
 					'text' => [ 'INNER JOIN', [ 'rev_text_id=old_id' ] ],
+					'temp_rev_comment' => [ 'JOIN', 'temp_rev_comment.revcomment_rev = rev_id' ],
+					'comment_rev_comment'
+						=> [ 'JOIN', 'comment_rev_comment.comment_id = temp_rev_comment.revcomment_comment_id' ],
 				],
 			],
 		];
@@ -571,13 +582,14 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 			[
 				'wgContentHandlerUseDB' => false,
 				'wgMultiContentRevisionSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_OLD,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
 			],
 			[ 'text', 'page', 'user' ],
 			[
 				'tables' => [
-					'revision', 'page', 'user', 'text'
+					'revision', 'page', 'user', 'text',
+					'temp_rev_comment' => 'revision_comment_temp',
+					'comment_rev_comment' => 'comment',
 				],
 				'fields' => array_merge(
 					$this->getRevisionQueryFields( true ),
@@ -585,7 +597,7 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 					$this->getUserQueryFields(),
 					$this->getTextQueryFields(),
 					$this->getOldActorQueryFields( 'rev' ),
-					$this->getOldCommentQueryFields( 'rev' )
+					$this->getNewCommentQueryFields( 'rev' )
 				),
 				'joins' => [
 					'page' => [
@@ -603,6 +615,9 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 						'INNER JOIN',
 						[ 'rev_text_id=old_id' ],
 					],
+					'temp_rev_comment' => [ 'JOIN', 'temp_rev_comment.revcomment_rev = rev_id' ],
+					'comment_rev_comment'
+						=> [ 'JOIN', 'comment_rev_comment.comment_id = temp_rev_comment.revcomment_comment_id' ],
 				],
 			],
 		];
@@ -833,7 +848,6 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 		yield 'with model, comment, and actor' => [
 			[
 				'wgContentHandlerUseDB' => true,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_WRITE_BOTH,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_WRITE_BOTH | SCHEMA_COMPAT_READ_OLD,
 			],
 			'fields' => array_merge(
@@ -853,7 +867,6 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 				],
 				$this->getContentHandlerQueryFields( 'rev' ),
 				[
-					'rev_comment_old' => 'rev_comment',
 					'rev_comment_pk' => 'rev_id',
 				]
 			),
@@ -861,7 +874,6 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 		yield 'no mode, no comment, no actor' => [
 			[
 				'wgContentHandlerUseDB' => false,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_OLD,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
 			],
 			'fields' => array_merge(
@@ -878,8 +890,8 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 					'rev_len',
 					'rev_parent_id',
 					'rev_sha1',
-				],
-				$this->getOldCommentQueryFields( 'rev' )
+					'rev_comment_pk' => 'rev_id',
+				]
 			),
 		];
 	}
@@ -888,7 +900,6 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 		yield 'with model, comment, and actor' => [
 			[
 				'wgContentHandlerUseDB' => true,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_WRITE_BOTH,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_WRITE_BOTH | SCHEMA_COMPAT_READ_OLD,
 			],
 			'fields' => array_merge(
@@ -909,7 +920,6 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 				],
 				$this->getContentHandlerQueryFields( 'ar' ),
 				[
-					'ar_comment_old' => 'ar_comment',
 					'ar_comment_id' => 'ar_comment_id',
 				]
 			),
@@ -917,7 +927,6 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 		yield 'no mode, no comment, no actor' => [
 			[
 				'wgContentHandlerUseDB' => false,
-				'wgCommentTableSchemaMigrationStage' => MIGRATION_OLD,
 				'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
 			],
 			'fields' => array_merge(
@@ -935,8 +944,8 @@ class RevisionQueryInfoTest extends MediaWikiTestCase {
 					'ar_len',
 					'ar_parent_id',
 					'ar_sha1',
-				],
-				$this->getOldCommentQueryFields( 'ar' )
+					'ar_comment_id' => 'ar_comment_id',
+				]
 			),
 		];
 	}
diff --git a/tests/phpunit/includes/Revision/RevisionStoreDbTestBase.php b/tests/phpunit/includes/Revision/RevisionStoreDbTestBase.php
index 68632f3e68..018df48115 100644
--- a/tests/phpunit/includes/Revision/RevisionStoreDbTestBase.php
+++ b/tests/phpunit/includes/Revision/RevisionStoreDbTestBase.php
@@ -80,7 +80,6 @@ abstract class RevisionStoreDbTestBase extends MediaWikiTestCase {
 		$this->setMwGlobals( [
 			'wgMultiContentRevisionSchemaMigrationStage' => $this->getMcrMigrationStage(),
 			'wgContentHandlerUseDB' => $this->getContentHandlerUseDB(),
-			'wgCommentTableSchemaMigrationStage' => MIGRATION_NEW,
 			'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
 		] );
 
diff --git a/tests/phpunit/includes/RevisionDbTestBase.php b/tests/phpunit/includes/RevisionDbTestBase.php
index 6c7b0e7d24..339dc30890 100644
--- a/tests/phpunit/includes/RevisionDbTestBase.php
+++ b/tests/phpunit/includes/RevisionDbTestBase.php
@@ -90,7 +90,6 @@ abstract class RevisionDbTestBase extends MediaWikiTestCase {
 		$this->setMwGlobals( [
 			'wgMultiContentRevisionSchemaMigrationStage' => $this->getMcrMigrationStage(),
 			'wgContentHandlerUseDB' => $this->getContentHandlerUseDB(),
-			'wgCommentTableSchemaMigrationStage' => MIGRATION_NEW,
 			'wgActorTableSchemaMigrationStage' => SCHEMA_COMPAT_OLD,
 		] );
 
diff --git a/tests/phpunit/includes/RevisionTest.php b/tests/phpunit/includes/RevisionTest.php
index 20689d608b..02a6c19d1f 100644
--- a/tests/phpunit/includes/RevisionTest.php
+++ b/tests/phpunit/includes/RevisionTest.php
@@ -281,7 +281,6 @@ class RevisionTest extends MediaWikiTestCase {
 	 * @covers \MediaWiki\Revision\RevisionStore::newMutableRevisionFromArray
 	 */
 	public function testConstructFromRowWithBadPageId() {
-		$this->setMwGlobals( 'wgCommentTableSchemaMigrationStage', MIGRATION_NEW );
 		$this->overrideMwServices();
 		Wikimedia\suppressWarnings();
 		$rev = new Revision( (object)[
@@ -602,7 +601,6 @@ class RevisionTest extends MediaWikiTestCase {
 	 * @covers Revision::loadFromTitle
 	 */
 	public function testLoadFromTitle() {
-		$this->setMwGlobals( 'wgCommentTableSchemaMigrationStage', MIGRATION_NEW );
 		$this->setMwGlobals( 'wgActorTableSchemaMigrationStage', SCHEMA_COMPAT_OLD );
 		$this->overrideMwServices();
 		$title = $this->getMockTitle();
diff --git a/tests/phpunit/includes/deferred/LinksUpdateTest.php b/tests/phpunit/includes/deferred/LinksUpdateTest.php
index ddc0798f1a..90a5ed17ff 100644
--- a/tests/phpunit/includes/deferred/LinksUpdateTest.php
+++ b/tests/phpunit/includes/deferred/LinksUpdateTest.php
@@ -379,33 +379,17 @@ class LinksUpdateTest extends MediaWikiLangTestCase {
 	protected function assertRecentChangeByCategorization(
 		Title $pageTitle, ParserOutput $parserOutput, Title $categoryTitle, $expectedRows
 	) {
-		global $wgCommentTableSchemaMigrationStage;
-
-		if ( $wgCommentTableSchemaMigrationStage <= MIGRATION_WRITE_BOTH ) {
-			$this->assertSelect(
-				'recentchanges',
-				'rc_title, rc_comment',
-				[
-					'rc_type' => RC_CATEGORIZE,
-					'rc_namespace' => NS_CATEGORY,
-					'rc_title' => $categoryTitle->getDBkey()
-				],
-				$expectedRows
-			);
-		}
-		if ( $wgCommentTableSchemaMigrationStage >= MIGRATION_WRITE_BOTH ) {
-			$this->assertSelect(
-				[ 'recentchanges', 'comment' ],
-				'rc_title, comment_text',
-				[
-					'rc_type' => RC_CATEGORIZE,
-					'rc_namespace' => NS_CATEGORY,
-					'rc_title' => $categoryTitle->getDBkey(),
-					'comment_id = rc_comment_id',
-				],
-				$expectedRows
-			);
-		}
+		$this->assertSelect(
+			[ 'recentchanges', 'comment' ],
+			'rc_title, comment_text',
+			[
+				'rc_type' => RC_CATEGORIZE,
+				'rc_namespace' => NS_CATEGORY,
+				'rc_title' => $categoryTitle->getDBkey(),
+				'comment_id = rc_comment_id',
+			],
+			$expectedRows
+		);
 	}
 
 	private function runAllRelatedJobs() {
diff --git a/tests/phpunit/includes/logging/DatabaseLogEntryTest.php b/tests/phpunit/includes/logging/DatabaseLogEntryTest.php
index e75b1739d2..b183cde1d2 100644
--- a/tests/phpunit/includes/logging/DatabaseLogEntryTest.php
+++ b/tests/phpunit/includes/logging/DatabaseLogEntryTest.php
@@ -29,18 +29,15 @@ class DatabaseLogEntryTest extends MediaWikiTestCase {
 	 * @param array $selectFields
 	 * @param string[]|null $row
 	 * @param string[]|null $expectedFields
-	 * @param int $commentMigration
 	 * @param int $actorMigration
 	 */
 	public function testNewFromId( $id,
 		array $selectFields,
 		array $row = null,
 		array $expectedFields = null,
-		$commentMigration,
 		$actorMigration
 	) {
 		$this->setMwGlobals( [
-			'wgCommentTableSchemaMigrationStage' => $commentMigration,
 			'wgActorTableSchemaMigrationStage' => $actorMigration,
 		] );
 
@@ -71,7 +68,10 @@ class DatabaseLogEntryTest extends MediaWikiTestCase {
 
 	public function provideNewFromId() {
 		$oldTables = [
-			'tables' => [ 'logging', 'user' ],
+			'tables' => [
+				'logging', 'user',
+				'comment_log_comment' => 'comment',
+			],
 			'fields' => [
 				'log_id',
 				'log_type',
@@ -84,15 +84,18 @@ class DatabaseLogEntryTest extends MediaWikiTestCase {
 				'user_id',
 				'user_name',
 				'user_editcount',
-				'log_comment_text' => 'log_comment',
-				'log_comment_data' => 'NULL',
-				'log_comment_cid' => 'NULL',
+				'log_comment_text' => 'comment_log_comment.comment_text',
+				'log_comment_data' => 'comment_log_comment.comment_data',
+				'log_comment_cid' => 'comment_log_comment.comment_id',
 				'log_user' => 'log_user',
 				'log_user_text' => 'log_user_text',
 				'log_actor' => 'NULL',
 			],
 			'options' => [],
-			'join_conds' => [ 'user' => [ 'LEFT JOIN', 'user_id=log_user' ] ],
+			'join_conds' => [
+				'user' => [ 'LEFT JOIN', 'user_id=log_user' ],
+				'comment_log_comment' => [ 'JOIN', 'comment_log_comment.comment_id = log_comment_id' ],
+			],
 		];
 		$newTables = [
 			'tables' => [
@@ -133,7 +136,6 @@ class DatabaseLogEntryTest extends MediaWikiTestCase {
 				$oldTables + [ 'conds' => [ 'log_id' => 0 ] ],
 				null,
 				null,
-				MIGRATION_OLD,
 				SCHEMA_COMPAT_OLD,
 			],
 			[
@@ -146,7 +148,6 @@ class DatabaseLogEntryTest extends MediaWikiTestCase {
 					'log_comment_data' => null,
 				],
 				[ 'type' => 'foobarize', 'comment' => 'test!' ],
-				MIGRATION_OLD,
 				SCHEMA_COMPAT_OLD,
 			],
 			[
@@ -159,7 +160,6 @@ class DatabaseLogEntryTest extends MediaWikiTestCase {
 					'log_comment_data' => null,
 				],
 				[ 'type' => 'foobarize', 'comment' => 'test!' ],
-				MIGRATION_NEW,
 				SCHEMA_COMPAT_NEW,
 			],
 		];
diff --git a/tests/phpunit/includes/page/PageArchiveTestBase.php b/tests/phpunit/includes/page/PageArchiveTestBase.php
index 26b6b5234d..06c0456ac7 100644
--- a/tests/phpunit/includes/page/PageArchiveTestBase.php
+++ b/tests/phpunit/includes/page/PageArchiveTestBase.php
@@ -82,7 +82,6 @@ abstract class PageArchiveTestBase extends MediaWikiTestCase {
 
 		$this->tablesUsed += $this->getMcrTablesToReset();
 
-		$this->setMwGlobals( 'wgCommentTableSchemaMigrationStage', MIGRATION_NEW );
 		$this->setMwGlobals( 'wgActorTableSchemaMigrationStage', SCHEMA_COMPAT_OLD );
 		$this->setMwGlobals( 'wgContentHandlerUseDB', $this->getContentHandlerUseDB() );
 		$this->setMwGlobals(
diff --git a/tests/phpunit/includes/page/WikiPageDbTestBase.php b/tests/phpunit/includes/page/WikiPageDbTestBase.php
index 298dc52a3c..933e47dbcd 100644
--- a/tests/phpunit/includes/page/WikiPageDbTestBase.php
+++ b/tests/phpunit/includes/page/WikiPageDbTestBase.php
@@ -1560,89 +1560,6 @@ more stuff
 		$this->assertTrue( $page->wasLoadedFrom( IDBAccessObject::READ_EXCLUSIVE ) );
 	}
 
-	/**
-	 * @dataProvider provideCommentMigrationOnDeletion
-	 *
-	 * @param int $writeStage
-	 * @param int $readStage
-	 */
-	public function testCommentMigrationOnDeletion( $writeStage, $readStage ) {
-		$this->setMwGlobals( 'wgCommentTableSchemaMigrationStage', $writeStage );
-		$this->overrideMwServices();
-
-		$dbr = wfGetDB( DB_REPLICA );
-
-		$page = $this->createPage(
-			__METHOD__,
-			"foo",
-			CONTENT_MODEL_WIKITEXT
-		);
-		$revid = $page->getLatest();
-		if ( $writeStage > MIGRATION_OLD ) {
-			$comment_id = $dbr->selectField(
-				'revision_comment_temp',
-				'revcomment_comment_id',
-				[ 'revcomment_rev' => $revid ],
-				__METHOD__
-			);
-		}
-
-		$this->setMwGlobals( 'wgCommentTableSchemaMigrationStage', $readStage );
-		$this->overrideMwServices();
-
-		$page->doDeleteArticle( "testing deletion" );
-
-		if ( $readStage > MIGRATION_OLD ) {
-			// Didn't leave behind any 'revision_comment_temp' rows
-			$n = $dbr->selectField(
-				'revision_comment_temp', 'COUNT(*)', [ 'revcomment_rev' => $revid ], __METHOD__
-			);
-			$this->assertEquals( 0, $n, 'no entry in revision_comment_temp after deletion' );
-
-			// Copied or upgraded the comment_id, as applicable
-			$ar_comment_id = $dbr->selectField(
-				'archive',
-				'ar_comment_id',
-				[ 'ar_rev_id' => $revid ],
-				__METHOD__
-			);
-			if ( $writeStage > MIGRATION_OLD ) {
-				$this->assertSame( $comment_id, $ar_comment_id );
-			} else {
-				$this->assertNotEquals( 0, $ar_comment_id );
-			}
-		}
-
-		// Copied rev_comment, if applicable
-		if ( $readStage <= MIGRATION_WRITE_BOTH && $writeStage <= MIGRATION_WRITE_BOTH ) {
-			$ar_comment = $dbr->selectField(
-				'archive',
-				'ar_comment',
-				[ 'ar_rev_id' => $revid ],
-				__METHOD__
-			);
-			$this->assertSame( 'testing', $ar_comment );
-		}
-	}
-
-	public function provideCommentMigrationOnDeletion() {
-		return [
-			[ MIGRATION_OLD, MIGRATION_OLD ],
-			[ MIGRATION_OLD, MIGRATION_WRITE_BOTH ],
-			[ MIGRATION_OLD, MIGRATION_WRITE_NEW ],
-			[ MIGRATION_WRITE_BOTH, MIGRATION_OLD ],
-			[ MIGRATION_WRITE_BOTH, MIGRATION_WRITE_BOTH ],
-			[ MIGRATION_WRITE_BOTH, MIGRATION_WRITE_NEW ],
-			[ MIGRATION_WRITE_BOTH, MIGRATION_NEW ],
-			[ MIGRATION_WRITE_NEW, MIGRATION_WRITE_BOTH ],
-			[ MIGRATION_WRITE_NEW, MIGRATION_WRITE_NEW ],
-			[ MIGRATION_WRITE_NEW, MIGRATION_NEW ],
-			[ MIGRATION_NEW, MIGRATION_WRITE_BOTH ],
-			[ MIGRATION_NEW, MIGRATION_WRITE_NEW ],
-			[ MIGRATION_NEW, MIGRATION_NEW ],
-		];
-	}
-
 	/**
 	 * @covers WikiPage::updateCategoryCounts
 	 */
diff --git a/tests/phpunit/maintenance/deleteAutoPatrolLogsTest.php b/tests/phpunit/maintenance/deleteAutoPatrolLogsTest.php
index 42569d782d..b8d13838e9 100644
--- a/tests/phpunit/maintenance/deleteAutoPatrolLogsTest.php
+++ b/tests/phpunit/maintenance/deleteAutoPatrolLogsTest.php
@@ -30,6 +30,9 @@ class DeleteAutoPatrolLogsTest extends MaintenanceBaseTestCase {
 		$dbw = wfGetDB( DB_MASTER );
 		$logs = [];
 
+		$comment = \MediaWiki\MediaWikiServices::getInstance()->getCommentStore()
+			->createComment( $dbw, '' );
+
 		// Manual patrolling
 		$logs[] = [
 			'log_type' => 'patrol',
@@ -39,6 +42,7 @@ class DeleteAutoPatrolLogsTest extends MaintenanceBaseTestCase {
 			'log_timestamp' => $dbw->timestamp( '20041223210426' ),
 			'log_namespace' => NS_MAIN,
 			'log_title' => 'DeleteAutoPatrolLogs',
+			'log_comment_id' => $comment->id,
 		];
 
 		// Autopatrol #1
@@ -50,6 +54,7 @@ class DeleteAutoPatrolLogsTest extends MaintenanceBaseTestCase {
 			'log_timestamp' => $dbw->timestamp( '20051223210426' ),
 			'log_namespace' => NS_MAIN,
 			'log_title' => 'DeleteAutoPatrolLogs',
+			'log_comment_id' => $comment->id,
 		];
 
 		// Block
@@ -61,6 +66,7 @@ class DeleteAutoPatrolLogsTest extends MaintenanceBaseTestCase {
 			'log_timestamp' => $dbw->timestamp( '20061223210426' ),
 			'log_namespace' => NS_MAIN,
 			'log_title' => 'DeleteAutoPatrolLogs',
+			'log_comment_id' => $comment->id,
 		];
 
 		// Very old/ invalid patrol
@@ -72,6 +78,7 @@ class DeleteAutoPatrolLogsTest extends MaintenanceBaseTestCase {
 			'log_timestamp' => $dbw->timestamp( '20061223210426' ),
 			'log_namespace' => NS_MAIN,
 			'log_title' => 'DeleteAutoPatrolLogs',
+			'log_comment_id' => $comment->id,
 		];
 
 		// Autopatrol #2
@@ -83,6 +90,7 @@ class DeleteAutoPatrolLogsTest extends MaintenanceBaseTestCase {
 			'log_timestamp' => $dbw->timestamp( '20071223210426' ),
 			'log_namespace' => NS_MAIN,
 			'log_title' => 'DeleteAutoPatrolLogs',
+			'log_comment_id' => $comment->id,
 		];
 
 		// Autopatrol #3 old way
@@ -94,6 +102,7 @@ class DeleteAutoPatrolLogsTest extends MaintenanceBaseTestCase {
 			'log_timestamp' => $dbw->timestamp( '20081223210426' ),
 			'log_namespace' => NS_MAIN,
 			'log_title' => 'DeleteAutoPatrolLogs',
+			'log_comment_id' => $comment->id,
 		];
 
 		// Manual patrol #2 old way
@@ -105,6 +114,7 @@ class DeleteAutoPatrolLogsTest extends MaintenanceBaseTestCase {
 			'log_timestamp' => $dbw->timestamp( '20091223210426' ),
 			'log_namespace' => NS_MAIN,
 			'log_title' => 'DeleteAutoPatrolLogs',
+			'log_comment_id' => $comment->id,
 		];
 
 		// Autopatrol #4 very old way
@@ -116,6 +126,7 @@ class DeleteAutoPatrolLogsTest extends MaintenanceBaseTestCase {
 			'log_timestamp' => $dbw->timestamp( '20081223210426' ),
 			'log_namespace' => NS_MAIN,
 			'log_title' => 'DeleteAutoPatrolLogs',
+			'log_comment_id' => $comment->id,
 		];
 
 		// Manual patrol #3 very old way
@@ -127,6 +138,7 @@ class DeleteAutoPatrolLogsTest extends MaintenanceBaseTestCase {
 			'log_timestamp' => $dbw->timestamp( '20091223210426' ),
 			'log_namespace' => NS_MAIN,
 			'log_title' => 'DeleteAutoPatrolLogs',
+			'log_comment_id' => $comment->id,
 		];
 
 		$dbw->insert( 'logging', $logs );