Current File : /www/varak.net/wiki.varak.net/includes/dao/DBAccessObjectUtils.php
<?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 ];
}
}
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