From: addshore <addshorewiki@gmail.com>
Date: Wed, 24 Jan 2018 23:41:01 +0000 (-0800)
Subject: Pass $key into CommentStore methods and use MediawikiServices
X-Git-Tag: 1.31.0-rc.0~689^2
X-Git-Url: http://git.cyclocoop.org/%24self?a=commitdiff_plain;h=e5879da149afe183ce889ef6f4158086c9b4735f;p=lhc%2Fweb%2Fwiklou.git

Pass $key into CommentStore methods and use MediawikiServices

This allows CommentStore to be added to MediaWikiServices
without the need of an aditional Factory.

This change includes a compatability layer to allow the behaviour
from 1.30 to continue to be used while deprecated.

CommentStore::newKey has been deprecated.
Keys are now passed into the public methods of CommentStore
where needed.
The following CommentStore methods have had their signatures changed
to introduced a $key parameter, but when used in conjunction with
CommentStore::newKey behaviour will remain unchanged:
  * CommentStore::getFields
  * CommentStore::getJoin
  * CommentStore::getComment
  * CommentStore::getCommentLegacy
  * CommentStore::insert
  * CommentStore::insertWithTemplate

Change-Id: I3abb62a5cfb0dcd456da9f4eb35583476ae41cfb
---

diff --git a/RELEASE-NOTES-1.31 b/RELEASE-NOTES-1.31
index b46d3d60ab..8261a39fe2 100644
--- a/RELEASE-NOTES-1.31
+++ b/RELEASE-NOTES-1.31
@@ -214,6 +214,15 @@ changes to languages because of Phabricator reports.
 * The no-op method Skin::showIPinHeader(), deprecated in 1.27, was removed.
 * \ObjectFactory (no namespace) is deprecated, the namespaced \Wikimedia\ObjectFactory
   from the wikimedia/object-factory library should be used instead.
+* CommentStore::newKey is deprecated. Get an instance from MediaWikiServices instead.
+* The following CommentStore methods have had their signatures changed to introduce a $key parameter,
+  usage of the methods on instances retrieved from CommentStore::newKey will remain unchanged but deprecated:
+  * CommentStore::getFields
+  * CommentStore::getJoin
+  * CommentStore::getComment
+  * CommentStore::getCommentLegacy
+  * CommentStore::insert
+  * CommentStore::insertWithTemplate
 
 == Compatibility ==
 MediaWiki 1.31 requires PHP 5.5.9 or later. Although HHVM 3.18.5 or later is supported,
diff --git a/includes/Block.php b/includes/Block.php
index 0999ad2063..bdc6702f91 100644
--- a/includes/Block.php
+++ b/includes/Block.php
@@ -222,7 +222,7 @@ class Block {
 			'ipb_block_email',
 			'ipb_allow_usertalk',
 			'ipb_parent_block_id',
-		] + CommentStore::newKey( 'ipb_reason' )->getFields();
+		] + CommentStore::getStore()->getFields( 'ipb_reason' );
 	}
 
 	/**
@@ -235,7 +235,7 @@ class Block {
 	 *   - joins: (array) to include in the `$join_conds` to `IDatabase->select()`
 	 */
 	public static function getQueryInfo() {
-		$commentQuery = CommentStore::newKey( 'ipb_reason' )->getJoin();
+		$commentQuery = CommentStore::getStore()->getJoin( 'ipb_reason' );
 		return [
 			'tables' => [ 'ipblocks' ] + $commentQuery['tables'],
 			'fields' => [
@@ -460,9 +460,9 @@ class Block {
 		// I wish I didn't have to do this
 		$db = wfGetDB( DB_REPLICA );
 		$this->mExpiry = $db->decodeExpiry( $row->ipb_expiry );
-		$this->mReason = CommentStore::newKey( 'ipb_reason' )
+		$this->mReason = CommentStore::getStore()
 			// Legacy because $row may have come from self::selectFields()
-			->getCommentLegacy( $db, $row )->text;
+			->getCommentLegacy( $db, 'ipb_reason', $row )->text;
 
 		$this->isHardblock( !$row->ipb_anon_only );
 		$this->isAutoblocking( $row->ipb_enable_autoblock );
@@ -654,7 +654,7 @@ class Block {
 			'ipb_block_email'      => $this->prevents( 'sendemail' ),
 			'ipb_allow_usertalk'   => !$this->prevents( 'editownusertalk' ),
 			'ipb_parent_block_id'  => $this->mParentBlockId
-		] + CommentStore::newKey( 'ipb_reason' )->insert( $dbw, $this->mReason );
+		] + CommentStore::getStore()->insert( $dbw, 'ipb_reason', $this->mReason );
 
 		return $a;
 	}
@@ -670,7 +670,7 @@ class Block {
 			'ipb_create_account'   => $this->prevents( 'createaccount' ),
 			'ipb_deleted'          => (int)$this->mHideName, // typecast required for SQLite
 			'ipb_allow_usertalk'   => !$this->prevents( 'editownusertalk' ),
-		] + CommentStore::newKey( 'ipb_reason' )->insert( $dbw, $this->mReason );
+		] + CommentStore::getStore()->insert( $dbw, 'ipb_reason', $this->mReason );
 	}
 
 	/**
diff --git a/includes/CommentStore.php b/includes/CommentStore.php
index 0d679d37db..8447b2c797 100644
--- a/includes/CommentStore.php
+++ b/includes/CommentStore.php
@@ -20,6 +20,7 @@
  * @file
  */
 
+use MediaWiki\MediaWikiServices;
 use Wikimedia\Rdbms\IDatabase;
 
 /**
@@ -79,40 +80,71 @@ class CommentStore {
 	 */
 	protected static $formerTempTables = [];
 
-	/** @var string */
-	protected $key;
+	/**
+	 * @since 1.30
+	 * @deprecated in 1.31
+	 * @var string|null
+	 */
+	protected $key = null;
 
 	/** @var int One of the MIGRATION_* constants */
 	protected $stage;
 
-	/** @var array|null Cache for `self::getJoin()` */
-	protected $joinCache = null;
+	/** @var array[] Cache for `self::getJoin()` */
+	protected $joinCache = [];
 
 	/** @var Language Language to use for comment truncation */
 	protected $lang;
 
 	/**
-	 * @param string $key A key such as "rev_comment" identifying the comment
-	 *  field being fetched.
 	 * @param Language $lang Language to use for comment truncation. Defaults
 	 *  to $wgContLang.
+	 * @param int $migrationStage One of the MIGRATION_* constants
 	 */
-	public function __construct( $key, Language $lang = null ) {
-		global $wgCommentTableSchemaMigrationStage, $wgContLang;
-
-		$this->key = $key;
-		$this->stage = $wgCommentTableSchemaMigrationStage;
-		$this->lang = $lang ?: $wgContLang;
+	public function __construct( Language $lang, $migrationStage ) {
+		$this->stage = $migrationStage;
+		$this->lang = $lang;
 	}
 
 	/**
 	 * Static constructor for easier chaining
+	 * @deprecated in 1.31 Should not be constructed with a $key, use CommentStore::getStore
 	 * @param string $key A key such as "rev_comment" identifying the comment
 	 *  field being fetched.
 	 * @return CommentStore
 	 */
 	public static function newKey( $key ) {
-		return new CommentStore( $key );
+		global $wgCommentTableSchemaMigrationStage, $wgContLang;
+		// TODO uncomment once not used in extensions
+		// wfDeprecated( __METHOD__, '1.31' );
+		$store = new CommentStore( $wgContLang, $wgCommentTableSchemaMigrationStage );
+		$store->key = $key;
+		return $store;
+	}
+
+	/**
+	 * @since 1.31
+	 * @deprecated in 1.31 Use DI to inject a CommentStore instance into your class.
+	 * @return CommentStore
+	 */
+	public static function getStore() {
+		return MediaWikiServices::getInstance()->getCommentStore();
+	}
+
+	/**
+	 * Compat method allowing use of self::newKey until removed.
+	 * @param string|null $methodKey
+	 * @throw InvalidArgumentException
+	 * @return string
+	 */
+	private function getKey( $methodKey = null ) {
+		$key = $this->key !== null ? $this->key : $methodKey;
+		if ( $key === null ) {
+			// @codeCoverageIgnoreStart
+			throw new InvalidArgumentException( '$key should not be null' );
+			// @codeCoverageIgnoreEnd
+		}
+		return $key;
 	}
 
 	/**
@@ -123,23 +155,29 @@ class CommentStore {
 	 *
 	 * @note Use of this method may require a subsequent database query to
 	 *  actually fetch the comment. If possible, use `self::getJoin()` instead.
+	 *
+	 * @since 1.30
+	 * @since 1.31 Method signature changed, $key parameter added (with deprecated back compat)
+	 * @param string $key A key such as "rev_comment" identifying the comment
+	 *  field being fetched.
 	 * @return string[] to include in the `$vars` to `IDatabase->select()`. All
 	 *  fields are aliased, so `+` is safe to use.
 	 */
-	public function getFields() {
+	public function getFields( $key = null ) {
+		$key = $this->getKey( $key );
 		$fields = [];
 		if ( $this->stage === MIGRATION_OLD ) {
-			$fields["{$this->key}_text"] = $this->key;
-			$fields["{$this->key}_data"] = 'NULL';
-			$fields["{$this->key}_cid"] = 'NULL';
+			$fields["{$key}_text"] = $key;
+			$fields["{$key}_data"] = 'NULL';
+			$fields["{$key}_cid"] = 'NULL';
 		} else {
 			if ( $this->stage < MIGRATION_NEW ) {
-				$fields["{$this->key}_old"] = $this->key;
+				$fields["{$key}_old"] = $key;
 			}
-			if ( isset( self::$tempTables[$this->key] ) ) {
-				$fields["{$this->key}_pk"] = self::$tempTables[$this->key]['joinPK'];
+			if ( isset( self::$tempTables[$key] ) ) {
+				$fields["{$key}_pk"] = self::$tempTables[$key]['joinPK'];
 			} else {
-				$fields["{$this->key}_id"] = "{$this->key}_id";
+				$fields["{$key}_id"] = "{$key}_id";
 			}
 		}
 		return $fields;
@@ -151,56 +189,61 @@ class CommentStore {
 	 * Each resulting row should be passed to `self::getComment()` to get the
 	 * actual comment.
 	 *
+	 * @since 1.30
+	 * @since 1.31 Method signature changed, $key parameter added (with deprecated back compat)
+	 * @param string $key A key such as "rev_comment" identifying the comment
+	 *  field being fetched.
 	 * @return array With three keys:
 	 *   - tables: (string[]) to include in the `$table` to `IDatabase->select()`
 	 *   - fields: (string[]) to include in the `$vars` to `IDatabase->select()`
 	 *   - joins: (array) to include in the `$join_conds` to `IDatabase->select()`
 	 *  All tables, fields, and joins are aliased, so `+` is safe to use.
 	 */
-	public function getJoin() {
-		if ( $this->joinCache === null ) {
+	public function getJoin( $key = null ) {
+		$key = $this->getKey( $key );
+		if ( !array_key_exists( $key, $this->joinCache ) ) {
 			$tables = [];
 			$fields = [];
 			$joins = [];
 
 			if ( $this->stage === MIGRATION_OLD ) {
-				$fields["{$this->key}_text"] = $this->key;
-				$fields["{$this->key}_data"] = 'NULL';
-				$fields["{$this->key}_cid"] = 'NULL';
+				$fields["{$key}_text"] = $key;
+				$fields["{$key}_data"] = 'NULL';
+				$fields["{$key}_cid"] = 'NULL';
 			} else {
 				$join = $this->stage === MIGRATION_NEW ? 'JOIN' : 'LEFT JOIN';
 
-				if ( isset( self::$tempTables[$this->key] ) ) {
-					$t = self::$tempTables[$this->key];
-					$alias = "temp_$this->key";
+				if ( isset( self::$tempTables[$key] ) ) {
+					$t = self::$tempTables[$key];
+					$alias = "temp_$key";
 					$tables[$alias] = $t['table'];
 					$joins[$alias] = [ $join, "{$alias}.{$t['pk']} = {$t['joinPK']}" ];
 					$joinField = "{$alias}.{$t['field']}";
 				} else {
-					$joinField = "{$this->key}_id";
+					$joinField = "{$key}_id";
 				}
 
-				$alias = "comment_$this->key";
+				$alias = "comment_$key";
 				$tables[$alias] = 'comment';
 				$joins[$alias] = [ $join, "{$alias}.comment_id = {$joinField}" ];
 
 				if ( $this->stage === MIGRATION_NEW ) {
-					$fields["{$this->key}_text"] = "{$alias}.comment_text";
+					$fields["{$key}_text"] = "{$alias}.comment_text";
 				} else {
-					$fields["{$this->key}_text"] = "COALESCE( {$alias}.comment_text, $this->key )";
+					$fields["{$key}_text"] = "COALESCE( {$alias}.comment_text, $key )";
 				}
-				$fields["{$this->key}_data"] = "{$alias}.comment_data";
-				$fields["{$this->key}_cid"] = "{$alias}.comment_id";
+				$fields["{$key}_data"] = "{$alias}.comment_data";
+				$fields["{$key}_cid"] = "{$alias}.comment_id";
 			}
 
-			$this->joinCache = [
+			$this->joinCache[$key] = [
 				'tables' => $tables,
 				'fields' => $fields,
 				'joins' => $joins,
 			];
 		}
 
-		return $this->joinCache;
+		return $this->joinCache[$key];
 	}
 
 	/**
@@ -209,12 +252,13 @@ class CommentStore {
 	 * Shared implementation for getComment() and getCommentLegacy()
 	 *
 	 * @param IDatabase|null $db Database handle for getCommentLegacy(), or null for getComment()
+	 * @param string $key A key such as "rev_comment" identifying the comment
+	 *  field being fetched.
 	 * @param object|array $row
 	 * @param bool $fallback
 	 * @return CommentStoreComment
 	 */
-	private function getCommentInternal( IDatabase $db = null, $row, $fallback = false ) {
-		$key = $this->key;
+	private function getCommentInternal( IDatabase $db = null, $key, $row, $fallback = false ) {
 		$row = (array)$row;
 		if ( array_key_exists( "{$key}_text", $row ) && array_key_exists( "{$key}_data", $row ) ) {
 			$cid = isset( $row["{$key}_cid"] ) ? $row["{$key}_cid"] : null;
@@ -333,12 +377,27 @@ class CommentStore {
 	 * If you need to fake a comment in a row for some reason, set fields
 	 * `{$key}_text` (string) and `{$key}_data` (JSON string or null).
 	 *
+	 * @since 1.30
+	 * @since 1.31 Method signature changed, $key parameter added (with deprecated back compat)
+	 * @param string $key A key such as "rev_comment" identifying the comment
+	 *  field being fetched.
 	 * @param object|array $row Result row.
 	 * @param bool $fallback If true, fall back as well as possible instead of throwing an exception.
 	 * @return CommentStoreComment
 	 */
-	public function getComment( $row, $fallback = false ) {
-		return $this->getCommentInternal( null, $row, $fallback );
+	public function getComment( $key, $row = null, $fallback = false ) {
+		// Compat for method sig change in 1.31 (introduction of $key)
+		if ( $this->key !== null ) {
+			$fallback = $row;
+			$row = $key;
+			$key = $this->getKey();
+		}
+		if ( $row === null ) {
+			// @codeCoverageIgnoreStart
+			throw new InvalidArgumentException( '$row must not be null' );
+			// @codeCoverageIgnoreEnd
+		}
+		return $this->getCommentInternal( null, $key, $row, $fallback );
 	}
 
 	/**
@@ -351,13 +410,28 @@ class CommentStore {
 	 * If you need to fake a comment in a row for some reason, set fields
 	 * `{$key}_text` (string) and `{$key}_data` (JSON string or null).
 	 *
+	 * @since 1.30
+	 * @since 1.31 Method signature changed, $key parameter added (with deprecated back compat)
 	 * @param IDatabase $db Database handle to use for lookup
+	 * @param string $key A key such as "rev_comment" identifying the comment
+	 *  field being fetched.
 	 * @param object|array $row Result row.
 	 * @param bool $fallback If true, fall back as well as possible instead of throwing an exception.
 	 * @return CommentStoreComment
 	 */
-	public function getCommentLegacy( IDatabase $db, $row, $fallback = false ) {
-		return $this->getCommentInternal( $db, $row, $fallback );
+	public function getCommentLegacy( IDatabase $db, $key, $row = null, $fallback = false ) {
+		// Compat for method sig change in 1.31 (introduction of $key)
+		if ( $this->key !== null ) {
+			$fallback = $row;
+			$row = $key;
+			$key = $this->getKey();
+		}
+		if ( $row === null ) {
+			// @codeCoverageIgnoreStart
+			throw new InvalidArgumentException( '$row must not be null' );
+			// @codeCoverageIgnoreEnd
+		}
+		return $this->getCommentInternal( $db, $key, $row, $fallback );
 	}
 
 	/**
@@ -443,23 +517,25 @@ class CommentStore {
 	/**
 	 * Implementation for `self::insert()` and `self::insertWithTempTable()`
 	 * @param IDatabase $dbw
+	 * @param string $key A key such as "rev_comment" identifying the comment
+	 *  field being fetched.
 	 * @param string|Message|CommentStoreComment $comment
 	 * @param array|null $data
 	 * @return array [ array $fields, callable $callback ]
 	 */
-	private function insertInternal( IDatabase $dbw, $comment, $data ) {
+	private function insertInternal( IDatabase $dbw, $key, $comment, $data ) {
 		$fields = [];
 		$callback = null;
 
 		$comment = $this->createComment( $dbw, $comment, $data );
 
 		if ( $this->stage <= MIGRATION_WRITE_BOTH ) {
-			$fields[$this->key] = $this->lang->truncate( $comment->text, 255 );
+			$fields[$key] = $this->lang->truncate( $comment->text, 255 );
 		}
 
 		if ( $this->stage >= MIGRATION_WRITE_BOTH ) {
-			if ( isset( self::$tempTables[$this->key] ) ) {
-				$t = self::$tempTables[$this->key];
+			if ( isset( self::$tempTables[$key] ) ) {
+				$t = self::$tempTables[$key];
 				$func = __METHOD__;
 				$commentId = $comment->id;
 				$callback = function ( $id ) use ( $dbw, $commentId, $t, $func ) {
@@ -473,7 +549,7 @@ class CommentStore {
 					);
 				};
 			} else {
-				$fields["{$this->key}_id"] = $comment->id;
+				$fields["{$key}_id"] = $comment->id;
 			}
 		}
 
@@ -485,17 +561,34 @@ class CommentStore {
 	 *
 	 * @note It's recommended to include both the call to this method and the
 	 *  row insert in the same transaction.
+	 *
+	 * @since 1.30
+	 * @since 1.31 Method signature changed, $key parameter added (with deprecated back compat)
 	 * @param IDatabase $dbw Database handle to insert on
+	 * @param string $key A key such as "rev_comment" identifying the comment
+	 *  field being fetched.
 	 * @param string|Message|CommentStoreComment $comment As for `self::createComment()`
 	 * @param array|null $data As for `self::createComment()`
 	 * @return array Fields for the insert or update
 	 */
-	public function insert( IDatabase $dbw, $comment, $data = null ) {
-		if ( isset( self::$tempTables[$this->key] ) ) {
-			throw new InvalidArgumentException( "Must use insertWithTempTable() for $this->key" );
+	public function insert( IDatabase $dbw, $key, $comment = null, $data = null ) {
+		// Compat for method sig change in 1.31 (introduction of $key)
+		if ( $this->key !== null ) {
+			$data = $comment;
+			$comment = $key;
+			$key = $this->key;
+		}
+		if ( $comment === null ) {
+			// @codeCoverageIgnoreStart
+			throw new InvalidArgumentException( '$comment can not be null' );
+			// @codeCoverageIgnoreEnd
+		}
+
+		if ( isset( self::$tempTables[$key] ) ) {
+			throw new InvalidArgumentException( "Must use insertWithTempTable() for $key" );
 		}
 
-		list( $fields ) = $this->insertInternal( $dbw, $comment, $data );
+		list( $fields ) = $this->insertInternal( $dbw, $key, $comment, $data );
 		return $fields;
 	}
 
@@ -507,7 +600,12 @@ class CommentStore {
 	 *
 	 * @note It's recommended to include both the call to this method and the
 	 *  row insert in the same transaction.
+	 *
+	 * @since 1.30
+	 * @since 1.31 Method signature changed, $key parameter added (with deprecated back compat)
 	 * @param IDatabase $dbw Database handle to insert on
+	 * @param string $key A key such as "rev_comment" identifying the comment
+	 *  field being fetched.
 	 * @param string|Message|CommentStoreComment $comment As for `self::createComment()`
 	 * @param array|null $data As for `self::createComment()`
 	 * @return array Two values:
@@ -515,14 +613,26 @@ class CommentStore {
 	 *  - callable Function to call when the primary key of the row being
 	 *    inserted/updated is known. Pass it that primary key.
 	 */
-	public function insertWithTempTable( IDatabase $dbw, $comment, $data = null ) {
-		if ( isset( self::$formerTempTables[$this->key] ) ) {
-			wfDeprecated( __METHOD__ . " for $this->key", self::$formerTempTables[$this->key] );
-		} elseif ( !isset( self::$tempTables[$this->key] ) ) {
-			throw new InvalidArgumentException( "Must use insert() for $this->key" );
+	public function insertWithTempTable( IDatabase $dbw, $key, $comment = null, $data = null ) {
+		// Compat for method sig change in 1.31 (introduction of $key)
+		if ( $this->key !== null ) {
+			$data = $comment;
+			$comment = $key;
+			$key = $this->getKey();
+		}
+		if ( $comment === null ) {
+			// @codeCoverageIgnoreStart
+			throw new InvalidArgumentException( '$comment can not be null' );
+			// @codeCoverageIgnoreEnd
+		}
+
+		if ( isset( self::$formerTempTables[$key] ) ) {
+			wfDeprecated( __METHOD__ . " for $key", self::$formerTempTables[$key] );
+		} elseif ( !isset( self::$tempTables[$key] ) ) {
+			throw new InvalidArgumentException( "Must use insert() for $key" );
 		}
 
-		list( $fields, $callback ) = $this->insertInternal( $dbw, $comment, $data );
+		list( $fields, $callback ) = $this->insertInternal( $dbw, $key, $comment, $data );
 		if ( !$callback ) {
 			$callback = function () {
 				// Do nothing.
diff --git a/includes/EditPage.php b/includes/EditPage.php
index 6bf3c89213..6fbeed7b4d 100644
--- a/includes/EditPage.php
+++ b/includes/EditPage.php
@@ -2798,7 +2798,8 @@ ERROR;
 
 		if ( $this->wasDeletedSinceLastEdit() && 'save' == $this->formtype ) {
 			$username = $this->lastDelete->user_name;
-			$comment = CommentStore::newKey( 'log_comment' )->getComment( $this->lastDelete )->text;
+			$comment = CommentStore::getStore()
+				->getComment( 'log_comment', $this->lastDelete )->text;
 
 			// It is better to not parse the comment at all than to have templates expanded in the middle
 			// TODO: can the checkLabel be moved outside of the div so that wrapWikiMsg could be used?
@@ -3810,7 +3811,7 @@ ERROR;
 	 */
 	protected function getLastDelete() {
 		$dbr = wfGetDB( DB_REPLICA );
-		$commentQuery = CommentStore::newKey( 'log_comment' )->getJoin();
+		$commentQuery = CommentStore::getStore()->getJoin( 'log_comment' );
 		$data = $dbr->selectRow(
 			[ 'logging', 'user' ] + $commentQuery['tables'],
 			[
diff --git a/includes/FeedUtils.php b/includes/FeedUtils.php
index 6108ca1d46..4dde52d0b4 100644
--- a/includes/FeedUtils.php
+++ b/includes/FeedUtils.php
@@ -89,7 +89,7 @@ class FeedUtils {
 			$timestamp,
 			$row->rc_deleted & Revision::DELETED_COMMENT
 				? wfMessage( 'rev-deleted-comment' )->escaped()
-				: CommentStore::newKey( 'rc_comment' )->getComment( $row )->text,
+				: CommentStore::getStore()->getComment( 'rc_comment', $row )->text,
 			$actiontext
 		);
 	}
diff --git a/includes/MediaWikiServices.php b/includes/MediaWikiServices.php
index c283793a91..9077666ddf 100644
--- a/includes/MediaWikiServices.php
+++ b/includes/MediaWikiServices.php
@@ -1,6 +1,7 @@
 <?php
 namespace MediaWiki;
 
+use CommentStore;
 use Config;
 use ConfigFactory;
 use CryptHKDF;
@@ -761,6 +762,14 @@ class MediaWikiServices extends ServiceContainer {
 		return $this->getService( 'HttpRequestFactory' );
 	}
 
+	/**
+	 * @since 1.31
+	 * @return CommentStore
+	 */
+	public function getCommentStore() {
+		return $this->getService( 'CommentStore' );
+	}
+
 	///////////////////////////////////////////////////////////////////////////
 	// NOTE: When adding a service getter here, don't forget to add a test
 	// case for it in MediaWikiServicesTest::provideGetters() and in
diff --git a/includes/Revision.php b/includes/Revision.php
index d5449b4ee4..eba563cfda 100644
--- a/includes/Revision.php
+++ b/includes/Revision.php
@@ -357,7 +357,7 @@ class Revision implements IDBAccessObject {
 			'rev_sha1',
 		];
 
-		$fields += CommentStore::newKey( 'rev_comment' )->getFields();
+		$fields += CommentStore::getStore()->getFields( 'rev_comment' );
 
 		if ( $wgContentHandlerUseDB ) {
 			$fields[] = 'rev_content_format';
@@ -394,7 +394,7 @@ class Revision implements IDBAccessObject {
 			'ar_sha1',
 		];
 
-		$fields += CommentStore::newKey( 'ar_comment' )->getFields();
+		$fields += CommentStore::getStore()->getFields( 'ar_comment' );
 
 		if ( $wgContentHandlerUseDB ) {
 			$fields[] = 'ar_content_format';
diff --git a/includes/ServiceWiring.php b/includes/ServiceWiring.php
index 847c1bb23c..dc397a2cc3 100644
--- a/includes/ServiceWiring.php
+++ b/includes/ServiceWiring.php
@@ -521,6 +521,14 @@ return [
 		return new \MediaWiki\Http\HttpRequestFactory();
 	},
 
+	'CommentStore' => function ( MediaWikiServices $services ) {
+		global $wgContLang;
+		return new CommentStore(
+			$wgContLang,
+			$services->getMainConfig()->get( 'CommentTableSchemaMigrationStage' )
+		);
+	}
+
 	///////////////////////////////////////////////////////////////////////////
 	// NOTE: When adding a service here, don't forget to add a getter function
 	// in the MediaWikiServices class. The convenience getter should just call
diff --git a/includes/Storage/RevisionStore.php b/includes/Storage/RevisionStore.php
index 79ecec691f..b358631aa0 100644
--- a/includes/Storage/RevisionStore.php
+++ b/includes/Storage/RevisionStore.php
@@ -360,7 +360,7 @@ class RevisionStore implements IDBAccessObject, RevisionFactory, RevisionLookup
 		}
 
 		list( $commentFields, $commentCallback ) =
-			CommentStore::newKey( 'rev_comment' )->insertWithTempTable( $dbw, $comment );
+			CommentStore::getStore()->insertWithTempTable( $dbw, 'rev_comment', $comment );
 		$row += $commentFields;
 
 		if ( $this->contentHandlerUseDB ) {
@@ -1036,9 +1036,9 @@ class RevisionStore implements IDBAccessObject, RevisionFactory, RevisionLookup
 
 		$user = $this->getUserIdentityFromRowObject( $row, 'ar_' );
 
-		$comment = CommentStore::newKey( 'ar_comment' )
+		$comment = CommentStore::getStore()
 			// Legacy because $row may have come from self::selectFields()
-			->getCommentLegacy( $this->getDBConnection( DB_REPLICA ), $row, true );
+			->getCommentLegacy( $this->getDBConnection( DB_REPLICA ), 'ar_comment', $row, true );
 
 		$mainSlot = $this->emulateMainSlot_1_29( $row, $queryFlags, $title );
 		$slots = new RevisionSlots( [ 'main' => $mainSlot ] );
@@ -1106,9 +1106,9 @@ class RevisionStore implements IDBAccessObject, RevisionFactory, RevisionLookup
 
 		$user = $this->getUserIdentityFromRowObject( $row );
 
-		$comment = CommentStore::newKey( 'rev_comment' )
+		$comment = CommentStore::getStore()
 			// Legacy because $row may have come from self::selectFields()
-			->getCommentLegacy( $this->getDBConnection( DB_REPLICA ), $row, true );
+			->getCommentLegacy( $this->getDBConnection( DB_REPLICA ), 'rev_comment', $row, true );
 
 		$mainSlot = $this->emulateMainSlot_1_29( $row, $queryFlags, $title );
 		$slots = new RevisionSlots( [ 'main' => $mainSlot ] );
@@ -1581,7 +1581,7 @@ class RevisionStore implements IDBAccessObject, RevisionFactory, RevisionLookup
 			'rev_sha1',
 		] );
 
-		$commentQuery = CommentStore::newKey( 'rev_comment' )->getJoin();
+		$commentQuery = CommentStore::getStore()->getJoin( 'rev_comment' );
 		$ret['tables'] = array_merge( $ret['tables'], $commentQuery['tables'] );
 		$ret['fields'] = array_merge( $ret['fields'], $commentQuery['fields'] );
 		$ret['joins'] = array_merge( $ret['joins'], $commentQuery['joins'] );
@@ -1638,7 +1638,7 @@ class RevisionStore implements IDBAccessObject, RevisionFactory, RevisionLookup
 	 *   - joins: (array) to include in the `$join_conds` to `IDatabase->select()`
 	 */
 	public function getArchiveQueryInfo() {
-		$commentQuery = CommentStore::newKey( 'ar_comment' )->getJoin();
+		$commentQuery = CommentStore::getStore()->getJoin( 'ar_comment' );
 		$ret = [
 			'tables' => [ 'archive' ] + $commentQuery['tables'],
 			'fields' => [
diff --git a/includes/Title.php b/includes/Title.php
index c4cf434126..0cdea35e54 100644
--- a/includes/Title.php
+++ b/includes/Title.php
@@ -2735,8 +2735,8 @@ class Title implements LinkTarget {
 
 		if ( $this->mTitleProtection === null ) {
 			$dbr = wfGetDB( DB_REPLICA );
-			$commentStore = new CommentStore( 'pt_reason' );
-			$commentQuery = $commentStore->getJoin();
+			$commentStore = CommentStore::getStore();
+			$commentQuery = $commentStore->getJoin( 'pt_reason' );
 			$res = $dbr->select(
 				[ 'protected_titles' ] + $commentQuery['tables'],
 				[
@@ -2757,7 +2757,7 @@ class Title implements LinkTarget {
 					'user' => $row['user'],
 					'expiry' => $dbr->decodeExpiry( $row['expiry'] ),
 					'permission' => $row['permission'],
-					'reason' => $commentStore->getComment( $row )->text,
+					'reason' => $commentStore->getComment( 'pt_reason', $row )->text,
 				];
 			} else {
 				$this->mTitleProtection = false;
diff --git a/includes/api/ApiQueryAllUsers.php b/includes/api/ApiQueryAllUsers.php
index 65a4b32127..26844f3f26 100644
--- a/includes/api/ApiQueryAllUsers.php
+++ b/includes/api/ApiQueryAllUsers.php
@@ -45,7 +45,7 @@ class ApiQueryAllUsers extends ApiQueryBase {
 		$activeUserDays = $this->getConfig()->get( 'ActiveUserDays' );
 
 		$db = $this->getDB();
-		$commentStore = new CommentStore( 'ipb_reason' );
+		$commentStore = CommentStore::getStore();
 
 		$prop = $params['prop'];
 		if ( !is_null( $prop ) ) {
@@ -260,7 +260,7 @@ class ApiQueryAllUsers extends ApiQueryBase {
 				$data['blockedby'] = $row->ipb_by_text;
 				$data['blockedbyid'] = (int)$row->ipb_by;
 				$data['blockedtimestamp'] = wfTimestamp( TS_ISO_8601, $row->ipb_timestamp );
-				$data['blockreason'] = $commentStore->getComment( $row )->text;
+				$data['blockreason'] = $commentStore->getComment( 'ipb_reason', $row )->text;
 				$data['blockexpiry'] = $row->ipb_expiry;
 			}
 			if ( $row->ipb_deleted ) {
diff --git a/includes/api/ApiQueryBase.php b/includes/api/ApiQueryBase.php
index e0ab53adb6..57a70bccfa 100644
--- a/includes/api/ApiQueryBase.php
+++ b/includes/api/ApiQueryBase.php
@@ -451,7 +451,7 @@ abstract class ApiQueryBase extends ApiBase {
 				'ipb_expiry',
 				'ipb_timestamp'
 			] );
-			$commentQuery = CommentStore::newKey( 'ipb_reason' )->getJoin();
+			$commentQuery = CommentStore::getStore()->getJoin( 'ipb_reason' );
 			$this->addTables( $commentQuery['tables'] );
 			$this->addFields( $commentQuery['fields'] );
 			$this->addJoinConds( $commentQuery['joins'] );
diff --git a/includes/api/ApiQueryBlocks.php b/includes/api/ApiQueryBlocks.php
index d02fefa76f..10695b30ca 100644
--- a/includes/api/ApiQueryBlocks.php
+++ b/includes/api/ApiQueryBlocks.php
@@ -33,7 +33,7 @@ class ApiQueryBlocks extends ApiQueryBase {
 
 	public function execute() {
 		$db = $this->getDB();
-		$commentStore = new CommentStore( 'ipb_reason' );
+		$commentStore = CommentStore::getStore();
 		$params = $this->extractRequestParams();
 		$this->requireMaxOneParameter( $params, 'users', 'ip' );
 
@@ -64,7 +64,7 @@ class ApiQueryBlocks extends ApiQueryBase {
 			$fld_flags );
 
 		if ( $fld_reason ) {
-			$commentQuery = $commentStore->getJoin();
+			$commentQuery = $commentStore->getJoin( 'ipb_reason' );
 			$this->addTables( $commentQuery['tables'] );
 			$this->addFields( $commentQuery['fields'] );
 			$this->addJoinConds( $commentQuery['joins'] );
@@ -208,7 +208,7 @@ class ApiQueryBlocks extends ApiQueryBase {
 				$block['expiry'] = ApiResult::formatExpiry( $row->ipb_expiry );
 			}
 			if ( $fld_reason ) {
-				$block['reason'] = $commentStore->getComment( $row )->text;
+				$block['reason'] = $commentStore->getComment( 'ipb_reason', $row )->text;
 			}
 			if ( $fld_range && !$row->ipb_auto ) {
 				$block['rangestart'] = IP::formatHex( $row->ipb_range_start );
diff --git a/includes/api/ApiQueryDeletedrevs.php b/includes/api/ApiQueryDeletedrevs.php
index 5c1f6ba952..6e6757ecd1 100644
--- a/includes/api/ApiQueryDeletedrevs.php
+++ b/includes/api/ApiQueryDeletedrevs.php
@@ -40,7 +40,7 @@ class ApiQueryDeletedrevs extends ApiQueryBase {
 
 		$user = $this->getUser();
 		$db = $this->getDB();
-		$commentStore = new CommentStore( 'ar_comment' );
+		$commentStore = CommentStore::getStore();
 		$params = $this->extractRequestParams( false );
 		$prop = array_flip( $params['prop'] );
 		$fld_parentid = isset( $prop['parentid'] );
@@ -117,7 +117,7 @@ class ApiQueryDeletedrevs extends ApiQueryBase {
 		$this->addFieldsIf( 'ar_sha1', $fld_sha1 );
 
 		if ( $fld_comment || $fld_parsedcomment ) {
-			$commentQuery = $commentStore->getJoin();
+			$commentQuery = $commentStore->getJoin( 'ar_comment' );
 			$this->addTables( $commentQuery['tables'] );
 			$this->addFields( $commentQuery['fields'] );
 			$this->addJoinConds( $commentQuery['joins'] );
@@ -325,7 +325,7 @@ class ApiQueryDeletedrevs extends ApiQueryBase {
 					$anyHidden = true;
 				}
 				if ( Revision::userCanBitfield( $row->ar_deleted, Revision::DELETED_COMMENT, $user ) ) {
-					$comment = $commentStore->getComment( $row )->text;
+					$comment = $commentStore->getComment( 'ar_comment', $row )->text;
 					if ( $fld_comment ) {
 						$rev['comment'] = $comment;
 					}
diff --git a/includes/api/ApiQueryFilearchive.php b/includes/api/ApiQueryFilearchive.php
index d401511059..ebffb151c8 100644
--- a/includes/api/ApiQueryFilearchive.php
+++ b/includes/api/ApiQueryFilearchive.php
@@ -41,7 +41,7 @@ class ApiQueryFilearchive extends ApiQueryBase {
 
 		$user = $this->getUser();
 		$db = $this->getDB();
-		$commentStore = new CommentStore( 'fa_description' );
+		$commentStore = CommentStore::getStore();
 
 		$params = $this->extractRequestParams();
 
@@ -155,7 +155,7 @@ class ApiQueryFilearchive extends ApiQueryBase {
 			if ( $fld_description &&
 				Revision::userCanBitfield( $row->fa_deleted, File::DELETED_COMMENT, $user )
 			) {
-				$file['description'] = $commentStore->getComment( $row )->text;
+				$file['description'] = $commentStore->getComment( 'fa_description', $row )->text;
 				if ( isset( $prop['parseddescription'] ) ) {
 					$file['parseddescription'] = Linker::formatComment(
 						$file['description'], $title );
diff --git a/includes/api/ApiQueryLogEvents.php b/includes/api/ApiQueryLogEvents.php
index 9d247940d2..f3453001c4 100644
--- a/includes/api/ApiQueryLogEvents.php
+++ b/includes/api/ApiQueryLogEvents.php
@@ -41,7 +41,7 @@ class ApiQueryLogEvents extends ApiQueryBase {
 	public function execute() {
 		$params = $this->extractRequestParams();
 		$db = $this->getDB();
-		$this->commentStore = new CommentStore( 'log_comment' );
+		$this->commentStore = CommentStore::getStore();
 		$this->requireMaxOneParameter( $params, 'title', 'prefix', 'namespace' );
 
 		$prop = array_flip( $params['prop'] );
@@ -93,7 +93,7 @@ class ApiQueryLogEvents extends ApiQueryBase {
 		$this->addFieldsIf( 'log_params', $this->fld_details );
 
 		if ( $this->fld_comment || $this->fld_parsedcomment ) {
-			$commentQuery = $this->commentStore->getJoin();
+			$commentQuery = $this->commentStore->getJoin( 'log_comment' );
 			$this->addTables( $commentQuery['tables'] );
 			$this->addFields( $commentQuery['fields'] );
 			$this->addJoinConds( $commentQuery['joins'] );
@@ -338,7 +338,7 @@ class ApiQueryLogEvents extends ApiQueryBase {
 				$anyHidden = true;
 			}
 			if ( LogEventsList::userCan( $row, LogPage::DELETED_COMMENT, $user ) ) {
-				$comment = $this->commentStore->getComment( $row )->text;
+				$comment = $this->commentStore->getComment( 'log_comment', $row )->text;
 				if ( $this->fld_comment ) {
 					$vals['comment'] = $comment;
 				}
diff --git a/includes/api/ApiQueryProtectedTitles.php b/includes/api/ApiQueryProtectedTitles.php
index 843e209ec0..f5266850bd 100644
--- a/includes/api/ApiQueryProtectedTitles.php
+++ b/includes/api/ApiQueryProtectedTitles.php
@@ -55,8 +55,8 @@ class ApiQueryProtectedTitles extends ApiQueryGeneratorBase {
 		$this->addFieldsIf( 'pt_create_perm', isset( $prop['level'] ) );
 
 		if ( isset( $prop['comment'] ) || isset( $prop['parsedcomment'] ) ) {
-			$commentStore = new CommentStore( 'pt_reason' );
-			$commentQuery = $commentStore->getJoin();
+			$commentStore = CommentStore::getStore();
+			$commentQuery = $commentStore->getJoin( 'pt_reason' );
 			$this->addTables( $commentQuery['tables'] );
 			$this->addFields( $commentQuery['fields'] );
 			$this->addJoinConds( $commentQuery['joins'] );
@@ -130,12 +130,12 @@ class ApiQueryProtectedTitles extends ApiQueryGeneratorBase {
 				}
 
 				if ( isset( $prop['comment'] ) ) {
-					$vals['comment'] = $commentStore->getComment( $row )->text;
+					$vals['comment'] = $commentStore->getComment( 'pt_reason', $row )->text;
 				}
 
 				if ( isset( $prop['parsedcomment'] ) ) {
 					$vals['parsedcomment'] = Linker::formatComment(
-						$commentStore->getComment( $row )->text, $titles
+						$commentStore->getComment( 'pt_reason', $row )->text, $titles
 					);
 				}
 
diff --git a/includes/api/ApiQueryRecentChanges.php b/includes/api/ApiQueryRecentChanges.php
index 517cf1f860..e289e42d9c 100644
--- a/includes/api/ApiQueryRecentChanges.php
+++ b/includes/api/ApiQueryRecentChanges.php
@@ -350,8 +350,8 @@ class ApiQueryRecentChanges extends ApiQueryGeneratorBase {
 		$this->token = $params['token'];
 
 		if ( $this->fld_comment || $this->fld_parsedcomment || $this->token ) {
-			$this->commentStore = new CommentStore( 'rc_comment' );
-			$commentQuery = $this->commentStore->getJoin();
+			$this->commentStore = CommentStore::getStore();
+			$commentQuery = $this->commentStore->getJoin( 'rc_comment' );
 			$this->addTables( $commentQuery['tables'] );
 			$this->addFields( $commentQuery['fields'] );
 			$this->addJoinConds( $commentQuery['joins'] );
@@ -506,7 +506,7 @@ class ApiQueryRecentChanges extends ApiQueryGeneratorBase {
 				$anyHidden = true;
 			}
 			if ( Revision::userCanBitfield( $row->rc_deleted, Revision::DELETED_COMMENT, $user ) ) {
-				$comment = $this->commentStore->getComment( $row )->text;
+				$comment = $this->commentStore->getComment( 'rc_comment', $row )->text;
 				if ( $this->fld_comment ) {
 					$vals['comment'] = $comment;
 				}
diff --git a/includes/api/ApiQueryUserContributions.php b/includes/api/ApiQueryUserContributions.php
index 99a582ed4c..1705c57361 100644
--- a/includes/api/ApiQueryUserContributions.php
+++ b/includes/api/ApiQueryUserContributions.php
@@ -41,7 +41,7 @@ class ApiQueryContributions extends ApiQueryBase {
 		// Parse some parameters
 		$this->params = $this->extractRequestParams();
 
-		$this->commentStore = new CommentStore( 'rev_comment' );
+		$this->commentStore = CommentStore::getStore();
 
 		$prop = array_flip( $this->params['prop'] );
 		$this->fld_ids = isset( $prop['ids'] );
@@ -345,7 +345,7 @@ class ApiQueryContributions extends ApiQueryBase {
 		$this->addFieldsIf( 'rc_patrolled', $this->fld_patrolled );
 
 		if ( $this->fld_comment || $this->fld_parsedcomment ) {
-			$commentQuery = $this->commentStore->getJoin();
+			$commentQuery = $this->commentStore->getJoin( 'rev_comment' );
 			$this->addTables( $commentQuery['tables'] );
 			$this->addFields( $commentQuery['fields'] );
 			$this->addJoinConds( $commentQuery['joins'] );
@@ -432,7 +432,7 @@ class ApiQueryContributions extends ApiQueryBase {
 			);
 
 			if ( $userCanView ) {
-				$comment = $this->commentStore->getComment( $row )->text;
+				$comment = $this->commentStore->getComment( 'rev_comment', $row )->text;
 				if ( $this->fld_comment ) {
 					$vals['comment'] = $comment;
 				}
diff --git a/includes/api/ApiQueryUsers.php b/includes/api/ApiQueryUsers.php
index 6de512b878..824c4d5223 100644
--- a/includes/api/ApiQueryUsers.php
+++ b/includes/api/ApiQueryUsers.php
@@ -95,7 +95,7 @@ class ApiQueryUsers extends ApiQueryBase {
 
 	public function execute() {
 		$db = $this->getDB();
-		$commentStore = new CommentStore( 'ipb_reason' );
+		$commentStore = CommentStore::getStore();
 
 		$params = $this->extractRequestParams();
 		$this->requireMaxOneParameter( $params, 'userids', 'users' );
@@ -235,7 +235,8 @@ class ApiQueryUsers extends ApiQueryBase {
 					$data[$key]['blockedby'] = $row->ipb_by_text;
 					$data[$key]['blockedbyid'] = (int)$row->ipb_by;
 					$data[$key]['blockedtimestamp'] = wfTimestamp( TS_ISO_8601, $row->ipb_timestamp );
-					$data[$key]['blockreason'] = $commentStore->getComment( $row )->text;
+					$data[$key]['blockreason'] = $commentStore->getComment( 'ipb_reason', $row )
+						->text;
 					$data[$key]['blockexpiry'] = $row->ipb_expiry;
 				}
 
diff --git a/includes/api/ApiQueryWatchlist.php b/includes/api/ApiQueryWatchlist.php
index f9ac44a2b5..69f1838786 100644
--- a/includes/api/ApiQueryWatchlist.php
+++ b/includes/api/ApiQueryWatchlist.php
@@ -87,7 +87,7 @@ class ApiQueryWatchlist extends ApiQueryGeneratorBase {
 			}
 
 			if ( $this->fld_comment || $this->fld_parsedcomment ) {
-				$this->commentStore = new CommentStore( 'rc_comment' );
+				$this->commentStore = CommentStore::getStore();
 			}
 		}
 
@@ -357,7 +357,7 @@ class ApiQueryWatchlist extends ApiQueryGeneratorBase {
 				Revision::DELETED_COMMENT,
 				$user
 			) ) {
-				$comment = $this->commentStore->getComment( $recentChangeInfo )->text;
+				$comment = $this->commentStore->getComment( 'rc_comment', $recentChangeInfo )->text;
 				if ( $this->fld_comment ) {
 					$vals['comment'] = $comment;
 				}
diff --git a/includes/changes/RecentChange.php b/includes/changes/RecentChange.php
index a47186581a..678e39aa83 100644
--- a/includes/changes/RecentChange.php
+++ b/includes/changes/RecentChange.php
@@ -235,7 +235,7 @@ class RecentChange {
 			'rc_log_type',
 			'rc_log_action',
 			'rc_params',
-		] + CommentStore::newKey( 'rc_comment' )->getFields();
+		] + CommentStore::getStore()->getFields( 'rc_comment' );
 	}
 
 	/**
@@ -248,7 +248,7 @@ class RecentChange {
 	 *   - joins: (array) to include in the `$join_conds` to `IDatabase->select()`
 	 */
 	public static function getQueryInfo() {
-		$commentQuery = CommentStore::newKey( 'rc_comment' )->getJoin();
+		$commentQuery = CommentStore::getStore()->getJoin( 'rc_comment' );
 		return [
 			'tables' => [ 'recentchanges' ] + $commentQuery['tables'],
 			'fields' => [
@@ -372,7 +372,7 @@ class RecentChange {
 		$row = $this->mAttribs;
 		$comment = $row['rc_comment'];
 		unset( $row['rc_comment'], $row['rc_comment_text'], $row['rc_comment_data'] );
-		$row += CommentStore::newKey( 'rc_comment' )->insert( $dbw, $comment );
+		$row += CommentStore::getStore()->insert( $dbw, 'rc_comment', $comment );
 
 		# Don't reuse an existing rc_id for the new row, if one happens to be
 		# set for some reason.
@@ -995,9 +995,10 @@ class RecentChange {
 			}
 		}
 
-		$comment = CommentStore::newKey( 'rc_comment' )
+		$comment = CommentStore::getStore()
 			// Legacy because $row may have come from self::selectFields()
-			->getCommentLegacy( wfGetDB( DB_REPLICA ), $row, true )->text;
+			->getCommentLegacy( wfGetDB( DB_REPLICA ), 'rc_comment', $row, true )
+			->text;
 		$this->mAttribs['rc_comment'] = &$comment;
 		$this->mAttribs['rc_comment_text'] = &$comment;
 		$this->mAttribs['rc_comment_data'] = null;
@@ -1011,7 +1012,8 @@ class RecentChange {
 	 */
 	public function getAttribute( $name ) {
 		if ( $name === 'rc_comment' ) {
-			return CommentStore::newKey( 'rc_comment' )->getComment( $this->mAttribs, true )->text;
+			return CommentStore::getStore()
+				->getComment( 'rc_comment', $this->mAttribs, true )->text;
 		}
 		return isset( $this->mAttribs[$name] ) ? $this->mAttribs[$name] : null;
 	}
diff --git a/includes/export/WikiExporter.php b/includes/export/WikiExporter.php
index 6e2a5a4f0c..6ce55eaa4e 100644
--- a/includes/export/WikiExporter.php
+++ b/includes/export/WikiExporter.php
@@ -278,7 +278,7 @@ class WikiExporter {
 			}
 			$result = null; // Assuring $result is not undefined, if exception occurs early
 
-			$commentQuery = CommentStore::newKey( 'log_comment' )->getJoin();
+			$commentQuery = CommentStore::getStore()->getJoin( 'log_comment' );
 
 			try {
 				$result = $this->db->select( [ 'logging', 'user' ] + $commentQuery['tables'],
@@ -399,7 +399,7 @@ class WikiExporter {
 				Hooks::run( 'ModifyExportQuery',
 						[ $this->db, &$tables, &$cond, &$opts, &$join ] );
 
-				$commentQuery = CommentStore::newKey( 'rev_comment' )->getJoin();
+				$commentQuery = CommentStore::getStore()->getJoin( 'rev_comment' );
 
 				# Do the query!
 				$result = $this->db->select(
diff --git a/includes/export/XmlDumpWriter.php b/includes/export/XmlDumpWriter.php
index c46eb61ca3..e1c12de1b9 100644
--- a/includes/export/XmlDumpWriter.php
+++ b/includes/export/XmlDumpWriter.php
@@ -219,7 +219,7 @@ class XmlDumpWriter {
 		if ( isset( $row->rev_deleted ) && ( $row->rev_deleted & Revision::DELETED_COMMENT ) ) {
 			$out .= "      " . Xml::element( 'comment', [ 'deleted' => 'deleted' ] ) . "\n";
 		} else {
-			$comment = CommentStore::newKey( 'rev_comment' )->getComment( $row )->text;
+			$comment = CommentStore::getStore()->getComment( 'rev_comment', $row )->text;
 			if ( $comment != '' ) {
 				$out .= "      " . Xml::elementClean( 'comment', [], strval( $comment ) ) . "\n";
 			}
@@ -303,7 +303,7 @@ class XmlDumpWriter {
 		if ( $row->log_deleted & LogPage::DELETED_COMMENT ) {
 			$out .= "    " . Xml::element( 'comment', [ 'deleted' => 'deleted' ] ) . "\n";
 		} else {
-			$comment = CommentStore::newKey( 'log_comment' )->getComment( $row )->text;
+			$comment = CommentStore::getStore()->getComment( 'log_comment', $row )->text;
 			if ( $comment != '' ) {
 				$out .= "    " . Xml::elementClean( 'comment', null, strval( $comment ) ) . "\n";
 			}
diff --git a/includes/filerepo/file/ArchivedFile.php b/includes/filerepo/file/ArchivedFile.php
index 7f48659ba3..6577ab6742 100644
--- a/includes/filerepo/file/ArchivedFile.php
+++ b/includes/filerepo/file/ArchivedFile.php
@@ -242,7 +242,7 @@ class ArchivedFile {
 			'fa_deleted',
 			'fa_deleted_timestamp', /* Used by LocalFileRestoreBatch */
 			'fa_sha1',
-		] + CommentStore::newKey( 'fa_description' )->getFields();
+		] + CommentStore::getStore()->getFields( 'fa_description' );
 	}
 
 	/**
@@ -255,7 +255,7 @@ class ArchivedFile {
 	 *   - joins: (array) to include in the `$join_conds` to `IDatabase->select()`
 	 */
 	public static function getQueryInfo() {
-		$commentQuery = CommentStore::newKey( 'fa_description' )->getJoin();
+		$commentQuery = CommentStore::getStore()->getJoin( 'fa_description' );
 		return [
 			'tables' => [ 'filearchive' ] + $commentQuery['tables'],
 			'fields' => [
@@ -302,9 +302,9 @@ class ArchivedFile {
 		$this->metadata = $row->fa_metadata;
 		$this->mime = "$row->fa_major_mime/$row->fa_minor_mime";
 		$this->media_type = $row->fa_media_type;
-		$this->description = CommentStore::newKey( 'fa_description' )
+		$this->description = CommentStore::getStore()
 			// Legacy because $row may have come from self::selectFields()
-			->getCommentLegacy( wfGetDB( DB_REPLICA ), $row )->text;
+			->getCommentLegacy( wfGetDB( DB_REPLICA ), 'fa_description', $row )->text;
 		$this->user = $row->fa_user;
 		$this->user_text = $row->fa_user_text;
 		$this->timestamp = $row->fa_timestamp;
diff --git a/includes/filerepo/file/LocalFile.php b/includes/filerepo/file/LocalFile.php
index 7be8f06246..bf1181f74c 100644
--- a/includes/filerepo/file/LocalFile.php
+++ b/includes/filerepo/file/LocalFile.php
@@ -215,7 +215,7 @@ class LocalFile extends File {
 			'img_user_text',
 			'img_timestamp',
 			'img_sha1',
-		] + CommentStore::newKey( 'img_description' )->getFields();
+		] + CommentStore::getStore()->getFields( 'img_description' );
 	}
 
 	/**
@@ -230,7 +230,7 @@ class LocalFile extends File {
 	 *   - joins: (array) to include in the `$join_conds` to `IDatabase->select()`
 	 */
 	public static function getQueryInfo( array $options = [] ) {
-		$commentQuery = CommentStore::newKey( 'img_description' )->getJoin();
+		$commentQuery = CommentStore::getStore()->getJoin( 'img_description' );
 		$ret = [
 			'tables' => [ 'image' ] + $commentQuery['tables'],
 			'fields' => [
@@ -566,8 +566,8 @@ class LocalFile extends File {
 	function decodeRow( $row, $prefix = 'img_' ) {
 		$decoded = $this->unprefixRow( $row, $prefix );
 
-		$decoded['description'] = CommentStore::newKey( 'description' )
-			->getComment( (object)$decoded )->text;
+		$decoded['description'] = CommentStore::getStore()
+			->getComment( 'description', (object)$decoded )->text;
 
 		$decoded['timestamp'] = wfTimestamp( TS_MW, $decoded['timestamp'] );
 
@@ -1424,9 +1424,9 @@ class LocalFile extends File {
 		# Test to see if the row exists using INSERT IGNORE
 		# This avoids race conditions by locking the row until the commit, and also
 		# doesn't deadlock. SELECT FOR UPDATE causes a deadlock for every race condition.
-		$commentStore = new CommentStore( 'img_description' );
+		$commentStore = CommentStore::getStore();
 		list( $commentFields, $commentCallback ) =
-			$commentStore->insertWithTempTable( $dbw, $comment );
+			$commentStore->insertWithTempTable( $dbw, 'img_description', $comment );
 		$dbw->insert( 'image',
 			[
 				'img_name' => $this->getName(),
@@ -1522,7 +1522,9 @@ class LocalFile extends File {
 					[ 'image_comment_temp' => [ 'LEFT JOIN', [ 'imgcomment_name = img_name' ] ] ]
 				);
 				foreach ( $res as $row ) {
-					list( , $callback ) = $commentStore->insertWithTempTable( $dbw, $row->img_description );
+					list( , $callback ) = $commentStore->insertWithTempTable(
+						$dbw, 'img_description', $row->img_description
+					);
 					$callback( $row->img_name );
 				}
 			}
@@ -2403,10 +2405,7 @@ class LocalFileDeleteBatch {
 		$now = time();
 		$dbw = $this->file->repo->getMasterDB();
 
-		$commentStoreImgDesc = new CommentStore( 'img_description' );
-		$commentStoreOiDesc = new CommentStore( 'oi_description' );
-		$commentStoreFaDesc = new CommentStore( 'fa_description' );
-		$commentStoreFaReason = new CommentStore( 'fa_deleted_reason' );
+		$commentStore = CommentStore::getStore();
 
 		$encTimestamp = $dbw->addQuotes( $dbw->timestamp( $now ) );
 		$encUserId = $dbw->addQuotes( $this->user->getId() );
@@ -2454,7 +2453,7 @@ class LocalFileDeleteBatch {
 
 			$fields += array_map(
 				[ $dbw, 'addQuotes' ],
-				$commentStoreFaReason->insert( $dbw, $this->reason )
+				$commentStore->insert( $dbw, 'fa_deleted_reason', $this->reason )
 			);
 
 			if ( $wgCommentTableSchemaMigrationStage <= MIGRATION_WRITE_BOTH ) {
@@ -2484,7 +2483,9 @@ class LocalFileDeleteBatch {
 					[ 'image_comment_temp' => [ 'LEFT JOIN', [ 'imgcomment_name = img_name' ] ] ]
 				);
 				foreach ( $res as $row ) {
-					list( , $callback ) = $commentStoreImgDesc->insertWithTempTable( $dbw, $row->img_description );
+					list( , $callback ) = $commentStore->insertWithTempTable(
+						$dbw, 'img_description', $row->img_description
+					);
 					$callback( $row->img_name );
 				}
 			}
@@ -2508,9 +2509,9 @@ class LocalFileDeleteBatch {
 			);
 			$rowsInsert = [];
 			if ( $res->numRows() ) {
-				$reason = $commentStoreFaReason->createComment( $dbw, $this->reason );
+				$reason = $commentStore->createComment( $dbw, 'fa_deleted_reason', $this->reason );
 				foreach ( $res as $row ) {
-					$comment = $commentStoreOiDesc->getComment( $row );
+					$comment = $commentStore->getComment( 'oi_description', $row );
 					$rowsInsert[] = [
 						// Deletion-specific fields
 						'fa_storage_group' => 'deleted',
@@ -2535,8 +2536,8 @@ class LocalFileDeleteBatch {
 						'fa_user_text' => $row->oi_user_text,
 						'fa_timestamp' => $row->oi_timestamp,
 						'fa_sha1' => $row->oi_sha1
-					] + $commentStoreFaReason->insert( $dbw, $reason )
-					+ $commentStoreFaDesc->insert( $dbw, $comment );
+					] + $commentStore->insert( $dbw, 'fa_deleted_reason', $reason )
+					+ $commentStore->insert( $dbw, 'fa_description', $comment );
 				}
 			}
 
@@ -2734,9 +2735,7 @@ class LocalFileRestoreBatch {
 
 		$dbw = $this->file->repo->getMasterDB();
 
-		$commentStoreImgDesc = new CommentStore( 'img_description' );
-		$commentStoreOiDesc = new CommentStore( 'oi_description' );
-		$commentStoreFaDesc = new CommentStore( 'fa_description' );
+		$commentStore = CommentStore::getStore();
 
 		$status = $this->file->repo->newGood();
 
@@ -2824,12 +2823,12 @@ class LocalFileRestoreBatch {
 				];
 			}
 
-			$comment = $commentStoreFaDesc->getComment( $row );
+			$comment = $commentStore->getComment( 'fa_description', $row );
 			if ( $first && !$exists ) {
 				// This revision will be published as the new current version
 				$destRel = $this->file->getRel();
 				list( $commentFields, $commentCallback ) =
-					$commentStoreImgDesc->insertWithTempTable( $dbw, $comment );
+					$commentStore->insertWithTempTable( $dbw, 'img_description', $comment );
 				$insertCurrent = [
 					'img_name' => $row->fa_name,
 					'img_size' => $row->fa_size,
@@ -2885,7 +2884,7 @@ class LocalFileRestoreBatch {
 					'oi_minor_mime' => $props['minor_mime'],
 					'oi_deleted' => $this->unsuppress ? 0 : $row->fa_deleted,
 					'oi_sha1' => $sha1
-				] + $commentStoreOiDesc->insert( $dbw, $comment );
+				] + $commentStore->insert( $dbw, 'oi_description', $comment );
 			}
 
 			$deleteIds[] = $row->fa_id;
diff --git a/includes/filerepo/file/OldLocalFile.php b/includes/filerepo/file/OldLocalFile.php
index 69e6896f0e..d08d0aefad 100644
--- a/includes/filerepo/file/OldLocalFile.php
+++ b/includes/filerepo/file/OldLocalFile.php
@@ -127,7 +127,7 @@ class OldLocalFile extends LocalFile {
 			'oi_timestamp',
 			'oi_deleted',
 			'oi_sha1',
-		] + CommentStore::newKey( 'oi_description' )->getFields();
+		] + CommentStore::getStore()->getFields( 'oi_description' );
 	}
 
 	/**
@@ -142,7 +142,7 @@ class OldLocalFile extends LocalFile {
 	 *   - joins: (array) to include in the `$join_conds` to `IDatabase->select()`
 	 */
 	public static function getQueryInfo( array $options = [] ) {
-		$commentQuery = CommentStore::newKey( 'oi_description' )->getJoin();
+		$commentQuery = CommentStore::getStore()->getJoin( 'oi_description' );
 		$ret = [
 			'tables' => [ 'oldimage' ] + $commentQuery['tables'],
 			'fields' => [
@@ -434,7 +434,7 @@ class OldLocalFile extends LocalFile {
 			return false;
 		}
 
-		$commentFields = CommentStore::newKey( 'oi_description' )->insert( $dbw, $comment );
+		$commentFields = CommentStore::getStore()->insert( $dbw, 'oi_description', $comment );
 		$dbw->insert( 'oldimage',
 			[
 				'oi_name' => $this->getName(),
diff --git a/includes/import/WikiRevision.php b/includes/import/WikiRevision.php
index edb0c9af1c..3513f8ce42 100644
--- a/includes/import/WikiRevision.php
+++ b/includes/import/WikiRevision.php
@@ -729,7 +729,7 @@ class WikiRevision {
 			'log_namespace' => $this->getTitle()->getNamespace(),
 			'log_title' => $this->getTitle()->getDBkey(),
 			'log_params' => $this->params
-		] + CommentStore::newKey( 'log_comment' )->insert( $dbw, $this->getComment() );
+		] + CommentStore::getStore()->insert( $dbw, 'log_comment', $this->getComment() );
 		$dbw->insert( 'logging', $data, __METHOD__ );
 
 		return true;
diff --git a/includes/logging/LogEntry.php b/includes/logging/LogEntry.php
index bf35d78d25..16b3593dd2 100644
--- a/includes/logging/LogEntry.php
+++ b/includes/logging/LogEntry.php
@@ -170,7 +170,7 @@ class DatabaseLogEntry extends LogEntryBase {
 	 * @return array
 	 */
 	public static function getSelectQueryData() {
-		$commentQuery = CommentStore::newKey( 'log_comment' )->getJoin();
+		$commentQuery = CommentStore::getStore()->getJoin( 'log_comment' );
 
 		$tables = [ 'logging', 'user' ] + $commentQuery['tables'];
 		$fields = [
@@ -324,7 +324,7 @@ class DatabaseLogEntry extends LogEntryBase {
 	}
 
 	public function getComment() {
-		return CommentStore::newKey( 'log_comment' )->getComment( $this->row )->text;
+		return CommentStore::getStore()->getComment( 'log_comment', $this->row )->text;
 	}
 
 	public function getDeleted() {
@@ -382,9 +382,9 @@ class RCDatabaseLogEntry extends DatabaseLogEntry {
 	}
 
 	public function getComment() {
-		return CommentStore::newKey( 'rc_comment' )
+		return CommentStore::getStore()
 			// Legacy because the row may have used RecentChange::selectFields()
-			->getCommentLegacy( wfGetDB( DB_REPLICA ), $this->row )->text;
+			->getCommentLegacy( wfGetDB( DB_REPLICA ), 'rc_comment', $this->row )->text;
 	}
 
 	public function getDeleted() {
@@ -626,7 +626,7 @@ class ManualLogEntry extends LogEntryBase {
 		if ( isset( $this->deleted ) ) {
 			$data['log_deleted'] = $this->deleted;
 		}
-		$data += CommentStore::newKey( 'log_comment' )->insert( $dbw, $comment );
+		$data += CommentStore::getStore()->insert( $dbw, 'log_comment', $comment );
 
 		$dbw->insert( 'logging', $data, __METHOD__ );
 		$this->id = $dbw->insertId();
diff --git a/includes/logging/LogPage.php b/includes/logging/LogPage.php
index 77d9aa21ba..c84352eb79 100644
--- a/includes/logging/LogPage.php
+++ b/includes/logging/LogPage.php
@@ -104,7 +104,7 @@ class LogPage {
 			'log_page' => $this->target->getArticleID(),
 			'log_params' => $this->params
 		];
-		$data += CommentStore::newKey( 'log_comment' )->insert( $dbw, $this->comment );
+		$data += CommentStore::getStore()->insert( $dbw, 'log_comment', $this->comment );
 		$dbw->insert( 'logging', $data, __METHOD__ );
 		$newId = $dbw->insertId();
 
diff --git a/includes/page/WikiPage.php b/includes/page/WikiPage.php
index a7f53df8be..a7eed5a98b 100644
--- a/includes/page/WikiPage.php
+++ b/includes/page/WikiPage.php
@@ -2517,7 +2517,7 @@ class WikiPage implements Page, IDBAccessObject {
 			$cascade = false;
 
 			if ( $limit['create'] != '' ) {
-				$commentFields = CommentStore::newKey( 'pt_reason' )->insert( $dbw, $reason );
+				$commentFields = CommentStore::getStore()->insert( $dbw, 'pt_reason', $reason );
 				$dbw->replace( 'protected_titles',
 					[ [ 'pt_namespace', 'pt_title' ] ],
 					[
@@ -2844,8 +2844,7 @@ class WikiPage implements Page, IDBAccessObject {
 			$content = null;
 		}
 
-		$revCommentStore = new CommentStore( 'rev_comment' );
-		$arCommentStore = new CommentStore( 'ar_comment' );
+		$commentStore = CommentStore::getStore();
 
 		$revQuery = Revision::getQueryInfo();
 		$bitfield = false;
@@ -2881,7 +2880,7 @@ class WikiPage implements Page, IDBAccessObject {
 		$ipRevIds = [];
 
 		foreach ( $res as $row ) {
-			$comment = $revCommentStore->getComment( $row );
+			$comment = $commentStore->getComment( 'rev_comment', $row );
 			$rowInsert = [
 				'ar_namespace'  => $namespace,
 				'ar_title'      => $dbKey,
@@ -2898,7 +2897,7 @@ class WikiPage implements Page, IDBAccessObject {
 				'ar_page_id'    => $id,
 				'ar_deleted'    => $suppress ? $bitfield : $row->rev_deleted,
 				'ar_sha1'       => $row->rev_sha1,
-			] + $arCommentStore->insert( $dbw, $comment );
+			] + $commentStore->insert( $dbw, 'ar_comment', $comment );
 			if ( $wgContentHandlerUseDB ) {
 				$rowInsert['ar_content_model'] = $row->rev_content_model;
 				$rowInsert['ar_content_format'] = $row->rev_content_format;
diff --git a/includes/rcfeed/IRCColourfulRCFeedFormatter.php b/includes/rcfeed/IRCColourfulRCFeedFormatter.php
index 531a3eb203..158ee5951f 100644
--- a/includes/rcfeed/IRCColourfulRCFeedFormatter.php
+++ b/includes/rcfeed/IRCColourfulRCFeedFormatter.php
@@ -94,7 +94,7 @@ class IRCColourfulRCFeedFormatter implements RCFeedFormatter {
 			$flag = $attribs['rc_log_action'];
 		} else {
 			$comment = self::cleanupForIRC(
-				CommentStore::newKey( 'rc_comment' )->getComment( $attribs )->text
+				CommentStore::getStore()->getComment( 'rc_comment', $attribs )->text
 			);
 			$flag = '';
 			if ( !$attribs['rc_patrolled']
diff --git a/includes/revisiondelete/RevDelLogItem.php b/includes/revisiondelete/RevDelLogItem.php
index 998c695f17..b8b0c5c466 100644
--- a/includes/revisiondelete/RevDelLogItem.php
+++ b/includes/revisiondelete/RevDelLogItem.php
@@ -102,7 +102,7 @@ class RevDelLogItem extends RevDelItem {
 		// User links and action text
 		$action = $formatter->getActionText();
 		// Comment
-		$comment = CommentStore::newKey( 'log_comment' )->getComment( $this->row )->text;
+		$comment = CommentStore::getStore()->getComment( 'log_comment', $this->row )->text;
 		$comment = $this->list->getLanguage()->getDirMark()
 			. Linker::commentBlock( $comment );
 
@@ -136,7 +136,8 @@ class RevDelLogItem extends RevDelItem {
 		}
 		if ( LogEventsList::userCan( $this->row, LogPage::DELETED_COMMENT, $user ) ) {
 			$ret += [
-				'comment' => CommentStore::newKey( 'log_comment' )->getComment( $this->row )->text,
+				'comment' => CommentStore::getStore()->getComment( 'log_comment', $this->row )
+					->text,
 			];
 		}
 
diff --git a/includes/revisiondelete/RevDelLogList.php b/includes/revisiondelete/RevDelLogList.php
index 728deb8e09..f4e4faffff 100644
--- a/includes/revisiondelete/RevDelLogList.php
+++ b/includes/revisiondelete/RevDelLogList.php
@@ -63,7 +63,7 @@ class RevDelLogList extends RevDelList {
 	public function doQuery( $db ) {
 		$ids = array_map( 'intval', $this->ids );
 
-		$commentQuery = CommentStore::newKey( 'log_comment' )->getJoin();
+		$commentQuery = CommentStore::getStore()->getJoin( 'log_comment' );
 
 		return $db->select(
 			[ 'logging' ] + $commentQuery['tables'],
diff --git a/includes/specials/SpecialNewpages.php b/includes/specials/SpecialNewpages.php
index 1639386e3b..ea0f0ed598 100644
--- a/includes/specials/SpecialNewpages.php
+++ b/includes/specials/SpecialNewpages.php
@@ -295,7 +295,7 @@ class SpecialNewpages extends IncludableSpecialPage {
 	 */
 	protected function revisionFromRcResult( stdClass $result, Title $title ) {
 		return new Revision( [
-			'comment' => CommentStore::newKey( 'rc_comment' )->getComment( $result )->text,
+			'comment' => CommentStore::getStore()->getComment( 'rc_comment', $result )->text,
 			'deleted' => $result->rc_deleted,
 			'user_text' => $result->rc_user_text,
 			'user' => $result->rc_user,
diff --git a/includes/specials/pagers/BlockListPager.php b/includes/specials/pagers/BlockListPager.php
index 924fd06cf0..fe7cac0dd1 100644
--- a/includes/specials/pagers/BlockListPager.php
+++ b/includes/specials/pagers/BlockListPager.php
@@ -173,7 +173,7 @@ class BlockListPager extends TablePager {
 				break;
 
 			case 'ipb_reason':
-				$value = CommentStore::newKey( 'ipb_reason' )->getComment( $row )->text;
+				$value = CommentStore::getStore()->getComment( 'ipb_reason', $row )->text;
 				$formatted = Linker::formatComment( $value );
 				break;
 
@@ -209,7 +209,7 @@ class BlockListPager extends TablePager {
 	}
 
 	function getQueryInfo() {
-		$commentQuery = CommentStore::newKey( 'ipb_reason' )->getJoin();
+		$commentQuery = CommentStore::getStore()->getJoin( 'ipb_reason' );
 
 		$info = [
 			'tables' => [ 'ipblocks', 'user' ] + $commentQuery['tables'],
diff --git a/includes/specials/pagers/DeletedContribsPager.php b/includes/specials/pagers/DeletedContribsPager.php
index 38a332e6a1..8a76efbb25 100644
--- a/includes/specials/pagers/DeletedContribsPager.php
+++ b/includes/specials/pagers/DeletedContribsPager.php
@@ -69,7 +69,7 @@ class DeletedContribsPager extends IndexPager {
 				' != ' . Revision::SUPPRESSED_USER;
 		}
 
-		$commentQuery = CommentStore::newKey( 'ar_comment' )->getJoin();
+		$commentQuery = CommentStore::getStore()->getJoin( 'ar_comment' );
 
 		return [
 			'tables' => [ 'archive' ] + $commentQuery['tables'],
@@ -256,7 +256,7 @@ class DeletedContribsPager extends IndexPager {
 		$rev = new Revision( [
 			'title' => $page,
 			'id' => $row->ar_rev_id,
-			'comment' => CommentStore::newKey( 'ar_comment' )->getComment( $row )->text,
+			'comment' => CommentStore::getStore()->getComment( 'ar_comment', $row )->text,
 			'user' => $row->ar_user,
 			'user_text' => $row->ar_user_text,
 			'timestamp' => $row->ar_timestamp,
diff --git a/includes/specials/pagers/ImageListPager.php b/includes/specials/pagers/ImageListPager.php
index d80946a544..ae19d59c87 100644
--- a/includes/specials/pagers/ImageListPager.php
+++ b/includes/specials/pagers/ImageListPager.php
@@ -267,7 +267,7 @@ class ImageListPager extends TablePager {
 		$options = $join_conds = [];
 
 		# Description field
-		$commentQuery = CommentStore::newKey( $prefix . '_description' )->getJoin();
+		$commentQuery = CommentStore::getStore()->getJoin( $prefix . '_description' );
 		$tables += $commentQuery['tables'];
 		$fields += $commentQuery['fields'];
 		$join_conds += $commentQuery['joins'];
@@ -498,7 +498,7 @@ class ImageListPager extends TablePager {
 				return htmlspecialchars( $this->getLanguage()->formatSize( $value ) );
 			case 'img_description':
 				$field = $this->mCurrentRow->description_field;
-				$value = CommentStore::newKey( $field )->getComment( $this->mCurrentRow )->text;
+				$value = CommentStore::getStore()->getComment( $field, $this->mCurrentRow )->text;
 				return Linker::formatComment( $value );
 			case 'count':
 				return $this->getLanguage()->formatNum( intval( $value ) + 1 );
diff --git a/includes/specials/pagers/NewPagesPager.php b/includes/specials/pagers/NewPagesPager.php
index a87bbb7567..61b648d4f6 100644
--- a/includes/specials/pagers/NewPagesPager.php
+++ b/includes/specials/pagers/NewPagesPager.php
@@ -90,7 +90,7 @@ class NewPagesPager extends ReverseChronologicalPager {
 			$conds['page_is_redirect'] = 0;
 		}
 
-		$commentQuery = CommentStore::newKey( 'rc_comment' )->getJoin();
+		$commentQuery = CommentStore::getStore()->getJoin( 'rc_comment' );
 
 		// Allow changes to the New Pages query
 		$tables = [ 'recentchanges', 'page' ] + $commentQuery['tables'];
diff --git a/includes/specials/pagers/ProtectedPagesPager.php b/includes/specials/pagers/ProtectedPagesPager.php
index af04703195..c4ea5f858e 100644
--- a/includes/specials/pagers/ProtectedPagesPager.php
+++ b/includes/specials/pagers/ProtectedPagesPager.php
@@ -234,7 +234,7 @@ class ProtectedPagesPager extends TablePager {
 						LogPage::DELETED_COMMENT,
 						$this->getUser()
 					) ) {
-						$value = CommentStore::newKey( 'log_comment' )->getComment( $row )->text;
+						$value = CommentStore::getStore()->getComment( 'log_comment', $row )->text;
 						$formatted = Linker::formatComment( $value !== null ? $value : '' );
 					} else {
 						$formatted = $this->msg( 'rev-deleted-comment' )->escaped();
@@ -283,7 +283,7 @@ class ProtectedPagesPager extends TablePager {
 			$conds[] = 'page_namespace=' . $this->mDb->addQuotes( $this->namespace );
 		}
 
-		$commentQuery = CommentStore::newKey( 'log_comment' )->getJoin();
+		$commentQuery = CommentStore::getStore()->getJoin( 'log_comment' );
 
 		return [
 			'tables' => [ 'page', 'page_restrictions', 'log_search', 'logging' ] + $commentQuery['tables'],
diff --git a/includes/watcheditem/WatchedItemQueryService.php b/includes/watcheditem/WatchedItemQueryService.php
index 3478b0894c..d546f0a4e8 100644
--- a/includes/watcheditem/WatchedItemQueryService.php
+++ b/includes/watcheditem/WatchedItemQueryService.php
@@ -56,12 +56,12 @@ class WatchedItemQueryService {
 	/** @var WatchedItemQueryServiceExtension[]|null */
 	private $extensions = null;
 
-	/**
-	 * @var CommentStore|null */
-	private $commentStore = null;
+	/** @var CommentStore */
+	private $commentStore;
 
 	public function __construct( LoadBalancer $loadBalancer ) {
 		$this->loadBalancer = $loadBalancer;
+		$this->commentStore = CommentStore::getStore();
 	}
 
 	/**
@@ -83,13 +83,6 @@ class WatchedItemQueryService {
 		return $this->loadBalancer->getConnectionRef( DB_REPLICA, [ 'watchlist' ] );
 	}
 
-	private function getCommentStore() {
-		if ( !$this->commentStore ) {
-			$this->commentStore = new CommentStore( 'rc_comment' );
-		}
-		return $this->commentStore;
-	}
-
 	/**
 	 * @param User $user
 	 * @param array $options Allowed keys:
@@ -334,7 +327,7 @@ class WatchedItemQueryService {
 			$tables[] = 'page';
 		}
 		if ( in_array( self::INCLUDE_COMMENT, $options['includeFields'] ) ) {
-			$tables += $this->getCommentStore()->getJoin()['tables'];
+			$tables += $this->commentStore->getJoin( 'rc_comment' )['tables'];
 		}
 		if ( in_array( self::INCLUDE_TAGS, $options['includeFields'] ) ) {
 			$tables[] = 'tag_summary';
@@ -377,7 +370,7 @@ class WatchedItemQueryService {
 			$fields[] = 'rc_user';
 		}
 		if ( in_array( self::INCLUDE_COMMENT, $options['includeFields'] ) ) {
-			$fields += $this->getCommentStore()->getJoin()['fields'];
+			$fields += $this->commentStore->getJoin( 'rc_comment' )['fields'];
 		}
 		if ( in_array( self::INCLUDE_PATROL_INFO, $options['includeFields'] ) ) {
 			$fields = array_merge( $fields, [ 'rc_patrolled', 'rc_log_type' ] );
@@ -684,7 +677,7 @@ class WatchedItemQueryService {
 			$joinConds['page'] = [ 'LEFT JOIN', 'rc_cur_id=page_id' ];
 		}
 		if ( in_array( self::INCLUDE_COMMENT, $options['includeFields'] ) ) {
-			$joinConds += $this->getCommentStore()->getJoin()['joins'];
+			$joinConds += $this->commentStore->getJoin( 'rc_comment' )['joins'];
 		}
 		if ( in_array( self::INCLUDE_TAGS, $options['includeFields'] ) ) {
 			$joinConds['tag_summary'] = [ 'LEFT JOIN', [ 'rc_id=ts_rc_id' ] ];
diff --git a/maintenance/orphans.php b/maintenance/orphans.php
index a1cf166a7d..945df32560 100644
--- a/maintenance/orphans.php
+++ b/maintenance/orphans.php
@@ -75,13 +75,13 @@ class Orphans extends Maintenance {
 	 */
 	private function checkOrphans( $fix ) {
 		$dbw = $this->getDB( DB_MASTER );
-		$commentStore = new CommentStore( 'rev_comment' );
+		$commentStore = CommentStore::getStore();
 
 		if ( $fix ) {
 			$this->lockTables( $dbw );
 		}
 
-		$commentQuery = $commentStore->getJoin();
+		$commentQuery = $commentStore->getJoin( 'rev_comment' );
 
 		$this->output( "Checking for orphan revision table entries... "
 			. "(this may take a while on a large wiki)\n" );
@@ -104,7 +104,7 @@ class Orphans extends Maintenance {
 			) );
 
 			foreach ( $result as $row ) {
-				$comment = $commentStore->getComment( $row )->text;
+				$comment = $commentStore->getComment( 'rev_comment', $row )->text;
 				if ( $comment !== '' ) {
 					$comment = '(' . $wgContLang->truncate( $comment, 40 ) . ')';
 				}
diff --git a/maintenance/rebuildrecentchanges.php b/maintenance/rebuildrecentchanges.php
index f26d8b3063..672bae86ce 100644
--- a/maintenance/rebuildrecentchanges.php
+++ b/maintenance/rebuildrecentchanges.php
@@ -80,8 +80,7 @@ class RebuildRecentchanges extends Maintenance {
 	 */
 	private function rebuildRecentChangesTablePass1() {
 		$dbw = $this->getDB( DB_MASTER );
-		$revCommentStore = new CommentStore( 'rev_comment' );
-		$rcCommentStore = new CommentStore( 'rc_comment' );
+		$commentStore = CommentStore::getStore();
 
 		if ( $this->hasOption( 'from' ) && $this->hasOption( 'to' ) ) {
 			$this->cutoffFrom = wfTimestamp( TS_UNIX, $this->getOption( 'from' ) );
@@ -116,7 +115,7 @@ class RebuildRecentchanges extends Maintenance {
 
 		$this->output( "Loading from page and revision tables...\n" );
 
-		$commentQuery = $revCommentStore->getJoin();
+		$commentQuery = $commentStore->getJoin( 'rev_comment' );
 		$res = $dbw->select(
 			[ 'revision', 'page' ] + $commentQuery['tables'],
 			[
@@ -145,7 +144,7 @@ class RebuildRecentchanges extends Maintenance {
 		$this->output( "Inserting from page and revision tables...\n" );
 		$inserted = 0;
 		foreach ( $res as $row ) {
-			$comment = $revCommentStore->getComment( $row );
+			$comment = $commentStore->getComment( 'rev_comment', $row );
 			$dbw->insert(
 				'recentchanges',
 				[
@@ -163,7 +162,7 @@ class RebuildRecentchanges extends Maintenance {
 					'rc_type' => $row->page_is_new ? RC_NEW : RC_EDIT,
 					'rc_source' => $row->page_is_new ? RecentChange::SRC_NEW : RecentChange::SRC_EDIT,
 					'rc_deleted' => $row->rev_deleted
-				] + $rcCommentStore->insert( $dbw, $comment ),
+				] + $commentStore->insert( $dbw, 'rc_comment', $comment ),
 				__METHOD__
 			);
 			if ( ( ++$inserted % $this->getBatchSize() ) == 0 ) {
@@ -270,12 +269,11 @@ class RebuildRecentchanges extends Maintenance {
 		global $wgLogTypes, $wgLogRestrictions;
 
 		$dbw = $this->getDB( DB_MASTER );
-		$logCommentStore = new CommentStore( 'log_comment' );
-		$rcCommentStore = new CommentStore( 'rc_comment' );
+		$commentStore = CommentStore::getStore();
 
 		$this->output( "Loading from user, page, and logging tables...\n" );
 
-		$commentQuery = $logCommentStore->getJoin();
+		$commentQuery = $commentStore->getJoin( 'log_comment' );
 		$res = $dbw->select(
 			[ 'user', 'logging', 'page' ] + $commentQuery['tables'],
 			[
@@ -311,7 +309,7 @@ class RebuildRecentchanges extends Maintenance {
 
 		$inserted = 0;
 		foreach ( $res as $row ) {
-			$comment = $logCommentStore->getComment( $row );
+			$comment = $commentStore->getComment( 'log_comment', $row );
 			$dbw->insert(
 				'recentchanges',
 				[
@@ -336,7 +334,7 @@ class RebuildRecentchanges extends Maintenance {
 					'rc_logid' => $row->log_id,
 					'rc_params' => $row->log_params,
 					'rc_deleted' => $row->log_deleted
-				] + $rcCommentStore->insert( $dbw, $comment ),
+				] + $commentStore->insert( $dbw, 'rc_comment', $comment ),
 				__METHOD__
 			);
 
diff --git a/tests/phpunit/includes/CommentStoreTest.php b/tests/phpunit/includes/CommentStoreTest.php
index 9369f30629..84e1f3288e 100644
--- a/tests/phpunit/includes/CommentStoreTest.php
+++ b/tests/phpunit/includes/CommentStoreTest.php
@@ -20,11 +20,22 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 	/**
 	 * Create a store for a particular stage
 	 * @param int $stage
+	 * @return CommentStore
+	 */
+	protected function makeStore( $stage ) {
+		global $wgContLang;
+		$store = new CommentStore( $wgContLang, $stage );
+		return $store;
+	}
+
+	/**
+	 * Create a store for a particular stage and key (for testing deprecated behaviour)
+	 * @param int $stage
 	 * @param string $key
 	 * @return CommentStore
 	 */
-	protected function makeStore( $stage, $key ) {
-		$store = new CommentStore( $key );
+	protected function makeStoreWithKey( $stage, $key ) {
+		$store = CommentStore::newKey( $key );
 		TestingAccessWrapper::newFromObject( $store )->stage = $stage;
 		return $store;
 	}
@@ -35,12 +46,24 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 	 * @param string $key
 	 * @param array $expect
 	 */
-	public function testGetFields( $stage, $key, $expect ) {
-		$store = $this->makeStore( $stage, $key );
+	public function testGetFields_withKeyConstruction( $stage, $key, $expect ) {
+		$store = $this->makeStoreWithKey( $stage, $key );
 		$result = $store->getFields();
 		$this->assertEquals( $expect, $result );
 	}
 
+	/**
+	 * @dataProvider provideGetFields
+	 * @param int $stage
+	 * @param string $key
+	 * @param array $expect
+	 */
+	public function testGetFields( $stage, $key, $expect ) {
+		$store = $this->makeStore( $stage );
+		$result = $store->getFields( $key );
+		$this->assertEquals( $expect, $result );
+	}
+
 	public static function provideGetFields() {
 		return [
 			'Simple table, old' => [
@@ -110,12 +133,24 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 	 * @param string $key
 	 * @param array $expect
 	 */
-	public function testGetJoin( $stage, $key, $expect ) {
-		$store = $this->makeStore( $stage, $key );
+	public function testGetJoin_withKeyConstruction( $stage, $key, $expect ) {
+		$store = $this->makeStoreWithKey( $stage, $key );
 		$result = $store->getJoin();
 		$this->assertEquals( $expect, $result );
 	}
 
+	/**
+	 * @dataProvider provideGetJoin
+	 * @param int $stage
+	 * @param string $key
+	 * @param array $expect
+	 */
+	public function testGetJoin( $stage, $key, $expect ) {
+		$store = $this->makeStore( $stage );
+		$result = $store->getJoin( $key );
+		$this->assertEquals( $expect, $result );
+	}
+
 	public static function provideGetJoin() {
 		return [
 			'Simple table, old' => [
@@ -343,11 +378,106 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 				$extraFields['ipb_address'] = __CLASS__ . "#$writeStage";
 			}
 
-			$wstore = $this->makeStore( $writeStage, $key );
+			$wstore = $this->makeStore( $writeStage );
 			$usesTemp = $key === 'rev_comment';
 
 			if ( $usesTemp ) {
-				list( $fields, $callback ) = $wstore->insertWithTempTable( $this->db, $comment, $data );
+				list( $fields, $callback ) = $wstore->insertWithTempTable(
+					$this->db, $key, $comment, $data
+				);
+			} else {
+				$fields = $wstore->insert( $this->db, $key, $comment, $data );
+			}
+
+			if ( $writeStage <= MIGRATION_WRITE_BOTH ) {
+				$this->assertSame( $expect['text'], $fields[$key], "old field, stage=$writeStage" );
+			} else {
+				$this->assertArrayNotHasKey( $key, $fields, "old field, stage=$writeStage" );
+			}
+			if ( $writeStage >= MIGRATION_WRITE_BOTH && !$usesTemp ) {
+				$this->assertArrayHasKey( "{$key}_id", $fields, "new field, stage=$writeStage" );
+			} else {
+				$this->assertArrayNotHasKey( "{$key}_id", $fields, "new field, stage=$writeStage" );
+			}
+
+			$this->db->insert( $table, $extraFields + $fields, __METHOD__ );
+			$id = $this->db->insertId();
+			if ( $usesTemp ) {
+				$callback( $id );
+			}
+
+			for ( $readStage = $readRange[0]; $readStage <= $readRange[1]; $readStage++ ) {
+				$rstore = $this->makeStore( $readStage );
+
+				$fieldRow = $this->db->selectRow(
+					$table,
+					$rstore->getFields( $key ),
+					[ $pk => $id ],
+					__METHOD__
+				);
+
+				$queryInfo = $rstore->getJoin( $key );
+				$joinRow = $this->db->selectRow(
+					[ $table ] + $queryInfo['tables'],
+					$queryInfo['fields'],
+					[ $pk => $id ],
+					__METHOD__,
+					[],
+					$queryInfo['joins']
+				);
+
+				$this->assertComment(
+					$writeStage === MIGRATION_OLD || $readStage === MIGRATION_OLD ? $expectOld : $expect,
+					$rstore->getCommentLegacy( $this->db, $key, $fieldRow ),
+					"w=$writeStage, r=$readStage, from getFields()"
+				);
+				$this->assertComment(
+					$writeStage === MIGRATION_OLD || $readStage === MIGRATION_OLD ? $expectOld : $expect,
+					$rstore->getComment( $key, $joinRow ),
+					"w=$writeStage, r=$readStage, from getJoin()"
+				);
+			}
+		}
+	}
+
+	/**
+	 * @dataProvider provideInsertRoundTrip
+	 * @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
+	) {
+		$expectOld = [
+			'text' => $expect['text'],
+			'message' => new RawMessage( '$1', [ $expect['text'] ] ),
+			'data' => null,
+		];
+
+		$stages = [
+			MIGRATION_OLD => [ MIGRATION_OLD, MIGRATION_WRITE_NEW ],
+			MIGRATION_WRITE_BOTH => [ MIGRATION_OLD, MIGRATION_NEW ],
+			MIGRATION_WRITE_NEW => [ MIGRATION_WRITE_BOTH, MIGRATION_NEW ],
+			MIGRATION_NEW => [ MIGRATION_WRITE_BOTH, MIGRATION_NEW ],
+		];
+
+		foreach ( $stages as $writeStage => $readRange ) {
+			if ( $key === 'ipb_reason' ) {
+				$extraFields['ipb_address'] = __CLASS__ . "#$writeStage";
+			}
+
+			$wstore = $this->makeStoreWithKey( $writeStage, $key );
+			$usesTemp = $key === 'rev_comment';
+
+			if ( $usesTemp ) {
+				list( $fields, $callback ) = $wstore->insertWithTempTable(
+					$this->db, $comment, $data
+				);
 			} else {
 				$fields = $wstore->insert( $this->db, $comment, $data );
 			}
@@ -370,7 +500,7 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 			}
 
 			for ( $readStage = $readRange[0]; $readStage <= $readRange[1]; $readStage++ ) {
-				$rstore = $this->makeStore( $readStage, $key );
+				$rstore = $this->makeStoreWithKey( $readStage, $key );
 
 				$fieldRow = $this->db->selectRow(
 					$table,
@@ -521,23 +651,23 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 		MediaWiki\suppressWarnings();
 		$reset = new ScopedCallback( 'MediaWiki\restoreWarnings' );
 
-		$store = $this->makeStore( MIGRATION_OLD, 'dummy' );
-		$res = $store->getComment( [ 'dummy' => 'comment' ] );
+		$store = $this->makeStore( MIGRATION_OLD );
+		$res = $store->getComment( 'dummy', [ 'dummy' => 'comment' ] );
 		$this->assertSame( '', $res->text );
-		$res = $store->getComment( [ 'dummy' => 'comment' ], true );
+		$res = $store->getComment( 'dummy', [ 'dummy' => 'comment' ], true );
 		$this->assertSame( 'comment', $res->text );
 
-		$store = $this->makeStore( MIGRATION_NEW, 'dummy' );
+		$store = $this->makeStore( MIGRATION_NEW );
 		try {
-			$store->getComment( [ 'dummy' => 'comment' ] );
+			$store->getComment( 'dummy', [ 'dummy' => 'comment' ] );
 			$this->fail( 'Expected exception not thrown' );
 		} catch ( InvalidArgumentException $ex ) {
 			$this->assertSame( '$row does not contain fields needed for comment dummy', $ex->getMessage() );
 		}
-		$res = $store->getComment( [ 'dummy' => 'comment' ], true );
+		$res = $store->getComment( 'dummy', [ 'dummy' => 'comment' ], true );
 		$this->assertSame( 'comment', $res->text );
 		try {
-			$store->getComment( [ 'dummy_id' => 1 ] );
+			$store->getComment( 'dummy', [ 'dummy_id' => 1 ] );
 			$this->fail( 'Expected exception not thrown' );
 		} catch ( InvalidArgumentException $ex ) {
 			$this->assertSame(
@@ -547,19 +677,19 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 			);
 		}
 
-		$store = $this->makeStore( MIGRATION_NEW, 'rev_comment' );
+		$store = $this->makeStore( MIGRATION_NEW );
 		try {
-			$store->getComment( [ 'rev_comment' => 'comment' ] );
+			$store->getComment( 'rev_comment', [ 'rev_comment' => 'comment' ] );
 			$this->fail( 'Expected exception not thrown' );
 		} catch ( InvalidArgumentException $ex ) {
 			$this->assertSame(
 				'$row does not contain fields needed for comment rev_comment', $ex->getMessage()
 			);
 		}
-		$res = $store->getComment( [ 'rev_comment' => 'comment' ], true );
+		$res = $store->getComment( 'rev_comment', [ 'rev_comment' => 'comment' ], true );
 		$this->assertSame( 'comment', $res->text );
 		try {
-			$store->getComment( [ 'rev_comment_pk' => 1 ] );
+			$store->getComment( 'rev_comment', [ 'rev_comment_pk' => 1 ] );
 			$this->fail( 'Expected exception not thrown' );
 		} catch ( InvalidArgumentException $ex ) {
 			$this->assertSame(
@@ -586,8 +716,8 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 	 * @expectedExceptionMessage Must use insertWithTempTable() for rev_comment
 	 */
 	public function testInsertWrong( $stage ) {
-		$store = $this->makeStore( $stage, 'rev_comment' );
-		$store->insert( $this->db, 'foo' );
+		$store = $this->makeStore( $stage );
+		$store->insert( $this->db, 'rev_comment', 'foo' );
 	}
 
 	/**
@@ -597,8 +727,8 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 	 * @expectedExceptionMessage Must use insert() for ipb_reason
 	 */
 	public function testInsertWithTempTableWrong( $stage ) {
-		$store = $this->makeStore( $stage, 'ipb_reason' );
-		$store->insertWithTempTable( $this->db, 'foo' );
+		$store = $this->makeStore( $stage );
+		$store->insertWithTempTable( $this->db, 'ipb_reason', 'foo' );
 	}
 
 	/**
@@ -610,8 +740,8 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 		$wrap->formerTempTables += [ 'ipb_reason' => '1.30' ];
 
 		$this->hideDeprecated( 'CommentStore::insertWithTempTable for ipb_reason' );
-		$store = $this->makeStore( $stage, 'ipb_reason' );
-		list( $fields, $callback ) = $store->insertWithTempTable( $this->db, 'foo' );
+		$store = $this->makeStore( $stage );
+		list( $fields, $callback ) = $store->insertWithTempTable( $this->db, 'ipb_reason', 'foo' );
 		$this->assertTrue( is_callable( $callback ) );
 	}
 
@@ -620,8 +750,8 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 		$truncated1 = str_repeat( '💣', 63 ) . '...';
 		$truncated2 = str_repeat( '💣', CommentStore::COMMENT_CHARACTER_LIMIT - 3 ) . '...';
 
-		$store = $this->makeStore( MIGRATION_WRITE_BOTH, 'ipb_reason' );
-		$fields = $store->insert( $this->db, $comment );
+		$store = $this->makeStore( MIGRATION_WRITE_BOTH );
+		$fields = $store->insert( $this->db, 'ipb_reason', $comment );
 		$this->assertSame( $truncated1, $fields['ipb_reason'] );
 		$stored = $this->db->selectField(
 			'comment', 'comment_text', [ 'comment_id' => $fields['ipb_reason_id'] ], __METHOD__
@@ -634,13 +764,17 @@ class CommentStoreTest extends MediaWikiLangTestCase {
 	 * @expectedExceptionMessage Comment data is too long (65611 bytes, maximum is 65535)
 	 */
 	public function testInsertTooMuchData() {
-		$store = $this->makeStore( MIGRATION_WRITE_BOTH, 'ipb_reason' );
-		$store->insert( $this->db, 'foo', [
+		$store = $this->makeStore( MIGRATION_WRITE_BOTH );
+		$store->insert( $this->db, 'ipb_reason', 'foo', [
 			'long' => str_repeat( '💣', 16400 )
 		] );
 	}
 
-	public function testConstructor() {
+	public function testGetStore() {
+		$this->assertInstanceOf( CommentStore::class, CommentStore::getStore() );
+	}
+
+	public function testNewKey() {
 		$this->assertInstanceOf( CommentStore::class, CommentStore::newKey( 'dummy' ) );
 	}
 
diff --git a/tests/phpunit/includes/MediaWikiServicesTest.php b/tests/phpunit/includes/MediaWikiServicesTest.php
index 859a40fa5a..2e93f36516 100644
--- a/tests/phpunit/includes/MediaWikiServicesTest.php
+++ b/tests/phpunit/includes/MediaWikiServicesTest.php
@@ -344,6 +344,7 @@ class MediaWikiServicesTest extends MediaWikiTestCase {
 			'RevisionStore' => [ 'RevisionStore', RevisionStore::class ],
 			'RevisionLookup' => [ 'RevisionLookup', RevisionLookup::class ],
 			'HttpRequestFactory' => [ 'HttpRequestFactory', HttpRequestFactory::class ],
+			'CommentStore' => [ 'CommentStore', CommentStore::class ],
 		];
 	}
 
diff --git a/tests/phpunit/includes/PageArchiveTest.php b/tests/phpunit/includes/PageArchiveTest.php
index 15b26c23e6..6fbe053361 100644
--- a/tests/phpunit/includes/PageArchiveTest.php
+++ b/tests/phpunit/includes/PageArchiveTest.php
@@ -114,6 +114,9 @@ class PageArchiveTest extends MediaWikiTestCase {
 	 * @covers PageArchive::listRevisions
 	 */
 	public function testListRevisions() {
+		$this->setMwGlobals( 'wgCommentTableSchemaMigrationStage', MIGRATION_OLD );
+		$this->overrideMwServices();
+
 		$revisions = $this->archivedPage->listRevisions();
 		$this->assertEquals( 2, $revisions->numRows() );
 
diff --git a/tests/phpunit/includes/RevisionTest.php b/tests/phpunit/includes/RevisionTest.php
index 73d69a528c..4518e15ecf 100644
--- a/tests/phpunit/includes/RevisionTest.php
+++ b/tests/phpunit/includes/RevisionTest.php
@@ -934,6 +934,7 @@ class RevisionTest extends MediaWikiTestCase {
 		$this->hideDeprecated( 'Revision::selectFields' );
 		$this->setMwGlobals( 'wgContentHandlerUseDB', $contentHandlerUseDB );
 		$this->setMwGlobals( 'wgCommentTableSchemaMigrationStage', MIGRATION_OLD );
+		$this->overrideMwServices();
 		$this->assertEquals( $expected, Revision::selectFields() );
 	}
 
@@ -993,6 +994,7 @@ class RevisionTest extends MediaWikiTestCase {
 		$this->hideDeprecated( 'Revision::selectArchiveFields' );
 		$this->setMwGlobals( 'wgContentHandlerUseDB', $contentHandlerUseDB );
 		$this->setMwGlobals( 'wgCommentTableSchemaMigrationStage', MIGRATION_OLD );
+		$this->overrideMwServices();
 		$this->assertEquals( $expected, Revision::selectArchiveFields() );
 	}
 
diff --git a/tests/phpunit/includes/Storage/RevisionStoreTest.php b/tests/phpunit/includes/Storage/RevisionStoreTest.php
index c9e99780e1..b6aed7f2c2 100644
--- a/tests/phpunit/includes/Storage/RevisionStoreTest.php
+++ b/tests/phpunit/includes/Storage/RevisionStoreTest.php
@@ -224,9 +224,10 @@ class RevisionStoreTest extends MediaWikiTestCase {
 	 * @covers \MediaWiki\Storage\RevisionStore::getQueryInfo
 	 */
 	public function testGetQueryInfo( $contentHandlerUseDb, $options, $expected ) {
+		$this->setMwGlobals( 'wgCommentTableSchemaMigrationStage', MIGRATION_OLD );
+		$this->overrideMwServices();
 		$store = $this->getRevisionStore();
 		$store->setContentHandlerUseDB( $contentHandlerUseDb );
-		$this->setMwGlobals( 'wgCommentTableSchemaMigrationStage', MIGRATION_OLD );
 		$this->assertEquals( $expected, $store->getQueryInfo( $options ) );
 	}
 
@@ -254,9 +255,10 @@ class RevisionStoreTest extends MediaWikiTestCase {
 	 * @covers \MediaWiki\Storage\RevisionStore::getArchiveQueryInfo
 	 */
 	public function testGetArchiveQueryInfo_contentHandlerDb() {
+		$this->setMwGlobals( 'wgCommentTableSchemaMigrationStage', MIGRATION_OLD );
+		$this->overrideMwServices();
 		$store = $this->getRevisionStore();
 		$store->setContentHandlerUseDB( true );
-		$this->setMwGlobals( 'wgCommentTableSchemaMigrationStage', MIGRATION_OLD );
 		$this->assertEquals(
 			[
 				'tables' => [
@@ -282,9 +284,10 @@ class RevisionStoreTest extends MediaWikiTestCase {
 	 * @covers \MediaWiki\Storage\RevisionStore::getArchiveQueryInfo
 	 */
 	public function testGetArchiveQueryInfo_noContentHandlerDb() {
+		$this->setMwGlobals( 'wgCommentTableSchemaMigrationStage', MIGRATION_OLD );
+		$this->overrideMwServices();
 		$store = $this->getRevisionStore();
 		$store->setContentHandlerUseDB( false );
-		$this->setMwGlobals( 'wgCommentTableSchemaMigrationStage', MIGRATION_OLD );
 		$this->assertEquals(
 			[
 				'tables' => [
diff --git a/tests/phpunit/includes/page/WikiPageDbTestBase.php b/tests/phpunit/includes/page/WikiPageDbTestBase.php
index b7fe47e53d..6b680e56d6 100644
--- a/tests/phpunit/includes/page/WikiPageDbTestBase.php
+++ b/tests/phpunit/includes/page/WikiPageDbTestBase.php
@@ -1084,6 +1084,8 @@ more stuff
 	 */
 	public function testCommentMigrationOnDeletion( $writeStage, $readStage ) {
 		$this->setMwGlobals( 'wgCommentTableSchemaMigrationStage', $writeStage );
+		$this->overrideMwServices();
+
 		$dbr = wfGetDB( DB_REPLICA );
 
 		$page = $this->createPage(
@@ -1102,6 +1104,7 @@ more stuff
 		}
 
 		$this->setMwGlobals( 'wgCommentTableSchemaMigrationStage', $readStage );
+		$this->overrideMwServices();
 
 		$page->doDeleteArticle( "testing deletion" );
 
diff --git a/tests/phpunit/includes/watcheditem/WatchedItemQueryServiceUnitTest.php b/tests/phpunit/includes/watcheditem/WatchedItemQueryServiceUnitTest.php
index ef2486d152..cb0e376146 100644
--- a/tests/phpunit/includes/watcheditem/WatchedItemQueryServiceUnitTest.php
+++ b/tests/phpunit/includes/watcheditem/WatchedItemQueryServiceUnitTest.php
@@ -1,15 +1,32 @@
 <?php
 
-use Wikimedia\ScopedCallback;
 use Wikimedia\TestingAccessWrapper;
 
 /**
  * @covers WatchedItemQueryService
  */
-class WatchedItemQueryServiceUnitTest extends PHPUnit_Framework_TestCase {
+class WatchedItemQueryServiceUnitTest extends MediaWikiTestCase {
 
 	use MediaWikiCoversValidator;
 
+	private function overrideCommentStore() {
+		$mockStore = $this->getMockBuilder( CommentStore::class )
+			->disableOriginalConstructor()
+			->getMock();
+		$mockStore->expects( $this->any() )
+			->method( 'getFields' )
+			->willReturn( [ 'commentstore' => 'fields' ] );
+		$mockStore->expects( $this->any() )
+			->method( 'getJoin' )
+			->willReturn( [
+				'tables' => [ 'commentstore' => 'table' ],
+				'fields' => [ 'commentstore' => 'field' ],
+				'joins' => [ 'commentstore' => 'join' ],
+			] );
+
+		$this->setService( 'CommentStore', $mockStore );
+	}
+
 	/**
 	 * @return PHPUnit_Framework_MockObject_MockObject|Database
 	 */
@@ -477,58 +494,11 @@ class WatchedItemQueryServiceUnitTest extends PHPUnit_Framework_TestCase {
 			[
 				[ 'includeFields' => [ WatchedItemQueryService::INCLUDE_COMMENT ] ],
 				null,
-				[],
-				[
-					'rc_comment_text' => 'rc_comment',
-					'rc_comment_data' => 'NULL',
-					'rc_comment_cid' => 'NULL',
-				],
-				[],
-				[],
-				[],
-				[ 'wgCommentTableSchemaMigrationStage' => MIGRATION_OLD ],
-			],
-			[
-				[ 'includeFields' => [ WatchedItemQueryService::INCLUDE_COMMENT ] ],
-				null,
-				[ 'comment_rc_comment' => 'comment' ],
-				[
-					'rc_comment_text' => 'COALESCE( comment_rc_comment.comment_text, rc_comment )',
-					'rc_comment_data' => 'comment_rc_comment.comment_data',
-					'rc_comment_cid' => 'comment_rc_comment.comment_id',
-				],
+				[ 'commentstore' => 'table' ],
+				[ 'commentstore' => 'field' ],
 				[],
 				[],
-				[ 'comment_rc_comment' => [ 'LEFT JOIN', 'comment_rc_comment.comment_id = rc_comment_id' ] ],
-				[ 'wgCommentTableSchemaMigrationStage' => MIGRATION_WRITE_BOTH ],
-			],
-			[
-				[ 'includeFields' => [ WatchedItemQueryService::INCLUDE_COMMENT ] ],
-				null,
-				[ 'comment_rc_comment' => 'comment' ],
-				[
-					'rc_comment_text' => 'COALESCE( comment_rc_comment.comment_text, rc_comment )',
-					'rc_comment_data' => 'comment_rc_comment.comment_data',
-					'rc_comment_cid' => 'comment_rc_comment.comment_id',
-				],
-				[],
-				[],
-				[ 'comment_rc_comment' => [ 'LEFT JOIN', 'comment_rc_comment.comment_id = rc_comment_id' ] ],
-				[ 'wgCommentTableSchemaMigrationStage' => MIGRATION_WRITE_NEW ],
-			],
-			[
-				[ 'includeFields' => [ WatchedItemQueryService::INCLUDE_COMMENT ] ],
-				null,
-				[ 'comment_rc_comment' => 'comment' ],
-				[
-					'rc_comment_text' => 'comment_rc_comment.comment_text',
-					'rc_comment_data' => 'comment_rc_comment.comment_data',
-					'rc_comment_cid' => 'comment_rc_comment.comment_id',
-				],
-				[],
-				[],
-				[ 'comment_rc_comment' => [ 'JOIN', 'comment_rc_comment.comment_id = rc_comment_id' ] ],
-				[ 'wgCommentTableSchemaMigrationStage' => MIGRATION_NEW ],
+				[ 'commentstore' => 'join' ],
 			],
 			[
 				[ 'includeFields' => [ WatchedItemQueryService::INCLUDE_PATROL_INFO ] ],
@@ -836,22 +806,9 @@ class WatchedItemQueryServiceUnitTest extends PHPUnit_Framework_TestCase {
 		array $expectedExtraFields,
 		array $expectedExtraConds,
 		array $expectedDbOptions,
-		array $expectedExtraJoinConds,
-		array $globals = []
+		array $expectedExtraJoinConds
 	) {
-		// Sigh. This test class doesn't extend MediaWikiTestCase, so we have to reinvent setMwGlobals().
-		if ( $globals ) {
-			$resetGlobals = [];
-			foreach ( $globals as $k => $v ) {
-				$resetGlobals[$k] = $GLOBALS[$k];
-				$GLOBALS[$k] = $v;
-			}
-			$reset = new ScopedCallback( function () use ( $resetGlobals ) {
-				foreach ( $resetGlobals as $k => $v ) {
-					$GLOBALS[$k] = $v;
-				}
-			} );
-		}
+		$this->overrideCommentStore();
 
 		$expectedTables = array_merge( [ 'recentchanges', 'watchlist', 'page' ], $expectedExtraTables );
 		$expectedFields = array_merge(