rdbms: deprecate IMaintainableDatabase::(lock|unlock)Tables() methods

These methods are unused in WMF-hosted repos and are difficult to both
use and maintain due to RDBMS engine differences.

Bug: T294969
Change-Id: Ie2a5a81073efb85b4d7338ba159a12a8516fe1dc

RELEASE-NOTES-1.38

@@ -440,6 +440,9 @@ generic `mediawiki.pager.styles`.
   `updateAriaExpanded` in checkboxHack.js have been deprecated.
   `bindToggleOnSpaceEnter` has also been deprecated in favor of
   `bindToggleOnEnter`.
+* IDatabase::lockTables() and IDatabase::unlockTables() have been deprecated
+  with no replacement. Instead, callers should batch updates into atomic
+  transactions, using FOR UPDATE for SELECT queries.
 * The HTMLForm methods getPreText, setPreText, addPreText, getPostText,
   setPostText, addPostText, getHeaderText, setHeaderText, addHeaderText,
   getFooterText, setFooterText and addFooterText have been renamed to

includes/libs/rdbms/database/IMaintainableDatabase.php

@@ -276,6 +276,7 @@ interface IMaintainableDatabase extends IDatabase {
 	 * @param string $method Name of caller
 	 * @return bool
 	 * @since 1.29
+	 * @deprecated Since 1.38
 	 */
 	public function lockTables( array $read, array $write, $method );
 
@@ -287,6 +288,7 @@ interface IMaintainableDatabase extends IDatabase {
 	 *
 	 * @param string $method The caller
 	 * @return bool
+	 * @deprecated Since 1.38
 	 * @since 1.29
 	 */
 	public function unlockTables( $method );