Prepare newNullRevision for MCR.

Bug: T174024
Change-Id: I8c607ed666295a5072c4fbfad1cf91d74d743abb

diff --git a/includes/Storage/RevisionStore.php b/includes/Storage/RevisionStore.php
index 3f852b0..b691288 100644 (file)
--- a/includes/Storage/RevisionStore.php
+++ b/includes/Storage/RevisionStore.php
@@ -681,16 +681,21 @@ class RevisionStore
         * Such revisions can for instance identify page rename
         * operations and other such meta-modifications.
         *
+        * @note: This method grabs a FOR UPDATE lock on the relevant row of the page table,
+        * to prevent a new revision from being inserted before the null revision has been written
+        * to the database.
+        *
         * MCR migration note: this replaces Revision::newNullRevision
         *
         * @todo Introduce newFromParentRevision(). newNullRevision can then be based on that
         * (or go away).
         *
-        * @param IDatabase $dbw
+        * @param IDatabase $dbw used for obtaining the lock on the page table row
         * @param Title $title Title of the page to read from
         * @param CommentStoreComment $comment RevisionRecord's summary
         * @param bool $minor Whether the revision should be considered as minor
         * @param User $user The user to attribute the revision to
+        *
         * @return RevisionRecord|null RevisionRecord or null on error
         */
        public function newNullRevision(
@@ -702,62 +707,34 @@ class RevisionStore
        ) {
                $this->checkDatabaseWikiId( $dbw );
 
-               $fields = [ 'page_latest', 'page_namespace', 'page_title',
-                       'rev_id', 'rev_text_id', 'rev_len', 'rev_sha1' ];
-
-               if ( $this->mcrMigrationStage < MIGRATION_NEW ) {
-                       $fields[] = 'rev_text_id';
-                       if ( $this->contentHandlerUseDB ) {
-                               $fields[] = 'rev_content_model';
-                               $fields[] = 'rev_content_format';
-                       }
-               }
-
-               // Don't use getQueryInfo() top avoid locking extra tables, compare T191892.
-               // XXX: perhaps getQueryInfo() could support 'no-comment' and 'no-actor' as options.
-               $current = $dbw->selectRow(
-                       [ 'page', 'revision' ],
-                       $fields,
-                       [
-                               'page_id' => $title->getArticleID(),
-                       ],
+               // T51581: Lock the page table row to ensure no other process
+               // is adding a revision to the page at the same time.
+               // Avoid locking extra tables, compare T191892.
+               $pageLatest = $dbw->selectField(
+                       'page',
+                       'page_latest',
+                       [ 'page_id' => $title->getArticleID() ],
                        __METHOD__,
-                       [ 'FOR UPDATE' ], // T51581
-                       [ 'page' => [ 'JOIN', 'page_latest=rev_id' ] ]
+                       [ 'FOR UPDATE' ]
                );
 
-               if ( $current ) {
-                       $fields = [
-                               'page'        => $title->getArticleID(),
-                               'user_text'   => $user->getName(),
-                               'user'        => $user->getId(),
-                               'actor'       => $user->getActorId(),
-                               'comment'     => $comment,
-                               'minor_edit'  => $minor,
-                               'parent_id'   => $current->page_latest,
-                               'slot_origin' => $current->page_latest,
-                               'len'         => $current->rev_len,
-                               'sha1'        => $current->rev_sha1
-                       ];
+               if ( !$pageLatest ) {
+                       return null;
+               }
 
-                       if ( $this->mcrMigrationStage < MIGRATION_NEW ) {
-                               $fields['text_id'] = $current->rev_text_id;
+               // Fetch the actual revision row, without locking all extra tables.
+               $oldRevision = $this->loadRevisionFromId( $dbw, $pageLatest );
 
-                               if ( $this->contentHandlerUseDB ) {
-                                       $fields['content_model'] = $current->rev_content_model;
-                                       $fields['content_format'] = $current->rev_content_format;
-                               }
-                       }
+               // Construct the new revision
+               $timestamp = wfTimestampNow(); // TODO: use a callback, so we can override it for testing.
+               $newRevision = MutableRevisionRecord::newFromParentRevision( $oldRevision );
 
-                       $mainSlot = $this->emulateMainSlot_1_29( $fields, self::READ_LATEST, $title );
-                       $revision = new MutableRevisionRecord( $title, $this->wikiId );
-                       $this->initializeMutableRevisionFromArray( $revision, $fields );
-                       $revision->setSlot( $mainSlot );
-               } else {
-                       $revision = null;
-               }
+               $newRevision->setComment( $comment );
+               $newRevision->setUser( $user );
+               $newRevision->setTimestamp( $timestamp );
+               $newRevision->setMinorEdit( $minor );
 
-               return $revision;
+               return $newRevision;
        }
 
        /**