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[autoinstallsdev/mediawiki.git] / includes / dao / DBAccessObjectUtils.php

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+<?php
+/**
+ * This file contains database access object related constants.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup Database
+ */
+
+/**
+ * Helper class for DAO classes
+ *
+ * @since 1.26
+ */
+class DBAccessObjectUtils implements IDBAccessObject {
+       /**
+        * @param int $bitfield
+        * @param int $flags IDBAccessObject::READ_* constant
+        * @return bool Bitfield has flag $flag set
+        */
+       public static function hasFlags( $bitfield, $flags ) {
+               return ( $bitfield & $flags ) == $flags;
+       }
+
+       /**
+        * Get an appropriate DB index, options, and fallback DB index for a query
+        *
+        * The fallback DB index and options are to be used if the entity is not found
+        * with the initial DB index, typically querying the master DB to avoid lag
+        *
+        * @param int $bitfield Bitfield of IDBAccessObject::READ_* constants
+        * @return array List of DB indexes and options in this order:
+        *   - DB_MASTER or DB_REPLICA constant for the initial query
+        *   - SELECT options array for the initial query
+        *   - DB_MASTER constant for the fallback query; null if no fallback should happen
+        *   - SELECT options array for the fallback query; empty if no fallback should happen
+        */
+       public static function getDBOptions( $bitfield ) {
+               if ( self::hasFlags( $bitfield, self::READ_LATEST_IMMUTABLE ) ) {
+                       $index = DB_REPLICA; // override READ_LATEST if set
+                       $fallbackIndex = DB_MASTER;
+               } elseif ( self::hasFlags( $bitfield, self::READ_LATEST ) ) {
+                       $index = DB_MASTER;
+                       $fallbackIndex = null;
+               } else {
+                       $index = DB_REPLICA;
+                       $fallbackIndex = null;
+               }
+
+               $lockingOptions = [];
+               if ( self::hasFlags( $bitfield, self::READ_EXCLUSIVE ) ) {
+                       $lockingOptions[] = 'FOR UPDATE';
+               } elseif ( self::hasFlags( $bitfield, self::READ_LOCKING ) ) {
+                       $lockingOptions[] = 'LOCK IN SHARE MODE';
+               }
+
+               if ( $fallbackIndex !== null ) {
+                       $options = []; // locks on DB_REPLICA make no sense
+                       $fallbackOptions = $lockingOptions;
+               } else {
+                       $options = $lockingOptions;
+                       $fallbackOptions = []; // no fallback
+               }
+
+               return [ $index, $options, $fallbackIndex, $fallbackOptions ];
+       }
+}