484 lines
12 KiB
PHP
484 lines
12 KiB
PHP
<?php
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/**
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* Class to store objects in the database
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*
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* @ingroup Cache
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*/
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class SqlBagOStuff extends BagOStuff {
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/**
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* @var LoadBalancer
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*/
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var $lb;
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/**
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* @var DatabaseBase
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*/
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var $db;
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var $serverInfo;
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var $lastExpireAll = 0;
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var $purgePeriod = 100;
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var $shards = 1;
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var $tableName = 'objectcache';
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/**
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* Constructor. Parameters are:
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* - server: A server info structure in the format required by each
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* element in $wgDBServers.
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*
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* - purgePeriod: The average number of object cache requests in between
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* garbage collection operations, where expired entries
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* are removed from the database. Or in other words, the
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* reciprocal of the probability of purging on any given
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* request. If this is set to zero, purging will never be
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* done.
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*
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* - tableName: The table name to use, default is "objectcache".
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*
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* - shards: The number of tables to use for data storage. If this is
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* more than 1, table names will be formed in the style
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* objectcacheNNN where NNN is the shard index, between 0 and
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* shards-1. The number of digits will be the minimum number
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* required to hold the largest shard index. Data will be
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* distributed across all tables by key hash. This is for
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* MySQL bugs 61735 and 61736.
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*
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* @param $params array
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*/
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public function __construct( $params ) {
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if ( isset( $params['server'] ) ) {
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$this->serverInfo = $params['server'];
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$this->serverInfo['load'] = 1;
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}
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if ( isset( $params['purgePeriod'] ) ) {
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$this->purgePeriod = intval( $params['purgePeriod'] );
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}
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if ( isset( $params['tableName'] ) ) {
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$this->tableName = $params['tableName'];
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}
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if ( isset( $params['shards'] ) ) {
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$this->shards = intval( $params['shards'] );
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}
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}
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/**
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* @return DatabaseBase
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*/
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protected function getDB() {
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if ( !isset( $this->db ) ) {
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# If server connection info was given, use that
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if ( $this->serverInfo ) {
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$this->lb = new LoadBalancer( array(
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'servers' => array( $this->serverInfo ) ) );
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$this->db = $this->lb->getConnection( DB_MASTER );
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$this->db->clearFlag( DBO_TRX );
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} else {
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# We must keep a separate connection to MySQL in order to avoid deadlocks
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# However, SQLite has an opposite behaviour.
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# @todo Investigate behaviour for other databases
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if ( wfGetDB( DB_MASTER )->getType() == 'sqlite' ) {
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$this->db = wfGetDB( DB_MASTER );
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} else {
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$this->lb = wfGetLBFactory()->newMainLB();
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$this->db = $this->lb->getConnection( DB_MASTER );
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$this->db->clearFlag( DBO_TRX );
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}
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}
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}
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return $this->db;
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}
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/**
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* Get the table name for a given key
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* @return string
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*/
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protected function getTableByKey( $key ) {
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if ( $this->shards > 1 ) {
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$hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
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return $this->getTableByShard( $hash % $this->shards );
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} else {
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return $this->tableName;
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}
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}
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/**
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* Get the table name for a given shard index
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* @return string
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*/
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protected function getTableByShard( $index ) {
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if ( $this->shards > 1 ) {
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$decimals = strlen( $this->shards - 1 );
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return $this->tableName .
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sprintf( "%0{$decimals}d", $index );
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} else {
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return $this->tableName;
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}
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}
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public function get( $key ) {
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# expire old entries if any
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$this->garbageCollect();
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$db = $this->getDB();
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$tableName = $this->getTableByKey( $key );
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$row = $db->selectRow( $tableName, array( 'value', 'exptime' ),
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array( 'keyname' => $key ), __METHOD__ );
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if ( !$row ) {
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$this->debug( 'get: no matching rows' );
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return false;
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}
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$this->debug( "get: retrieved data; expiry time is " . $row->exptime );
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if ( $this->isExpired( $row->exptime ) ) {
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$this->debug( "get: key has expired, deleting" );
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try {
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$db->begin( __METHOD__ );
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# Put the expiry time in the WHERE condition to avoid deleting a
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# newly-inserted value
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$db->delete( $tableName,
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array(
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'keyname' => $key,
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'exptime' => $row->exptime
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), __METHOD__ );
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$db->commit( __METHOD__ );
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} catch ( DBQueryError $e ) {
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$this->handleWriteError( $e );
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}
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return false;
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}
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return $this->unserialize( $db->decodeBlob( $row->value ) );
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}
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public function set( $key, $value, $exptime = 0 ) {
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$db = $this->getDB();
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$exptime = intval( $exptime );
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if ( $exptime < 0 ) {
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$exptime = 0;
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}
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if ( $exptime == 0 ) {
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$encExpiry = $this->getMaxDateTime();
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} else {
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if ( $exptime < 3.16e8 ) { # ~10 years
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$exptime += time();
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}
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$encExpiry = $db->timestamp( $exptime );
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}
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try {
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$db->begin( __METHOD__ );
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// (bug 24425) use a replace if the db supports it instead of
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// delete/insert to avoid clashes with conflicting keynames
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$db->replace(
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$this->getTableByKey( $key ),
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array( 'keyname' ),
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array(
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'keyname' => $key,
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'value' => $db->encodeBlob( $this->serialize( $value ) ),
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'exptime' => $encExpiry
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), __METHOD__ );
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$db->commit( __METHOD__ );
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} catch ( DBQueryError $e ) {
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$this->handleWriteError( $e );
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return false;
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}
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return true;
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}
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public function delete( $key, $time = 0 ) {
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$db = $this->getDB();
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try {
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$db->begin( __METHOD__ );
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$db->delete(
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$this->getTableByKey( $key ),
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array( 'keyname' => $key ),
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__METHOD__ );
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$db->commit( __METHOD__ );
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} catch ( DBQueryError $e ) {
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$this->handleWriteError( $e );
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return false;
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}
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return true;
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}
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public function incr( $key, $step = 1 ) {
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$db = $this->getDB();
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$tableName = $this->getTableByKey( $key );
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$step = intval( $step );
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try {
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$db->begin( __METHOD__ );
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$row = $db->selectRow(
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$tableName,
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array( 'value', 'exptime' ),
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array( 'keyname' => $key ),
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__METHOD__,
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array( 'FOR UPDATE' ) );
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if ( $row === false ) {
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// Missing
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$db->commit( __METHOD__ );
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return null;
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}
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$db->delete( $tableName, array( 'keyname' => $key ), __METHOD__ );
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if ( $this->isExpired( $row->exptime ) ) {
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// Expired, do not reinsert
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$db->commit( __METHOD__ );
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return null;
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}
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$oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
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$newValue = $oldValue + $step;
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$db->insert( $tableName,
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array(
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'keyname' => $key,
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'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
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'exptime' => $row->exptime
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), __METHOD__, 'IGNORE' );
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if ( $db->affectedRows() == 0 ) {
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// Race condition. See bug 28611
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$newValue = null;
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}
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$db->commit( __METHOD__ );
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} catch ( DBQueryError $e ) {
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$this->handleWriteError( $e );
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return null;
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}
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return $newValue;
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}
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public function keys() {
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$db = $this->getDB();
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$result = array();
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for ( $i = 0; $i < $this->shards; $i++ ) {
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$res = $db->select( $this->getTableByShard( $i ),
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array( 'keyname' ), false, __METHOD__ );
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foreach ( $res as $row ) {
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$result[] = $row->keyname;
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}
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}
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return $result;
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}
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protected function isExpired( $exptime ) {
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return $exptime != $this->getMaxDateTime() && wfTimestamp( TS_UNIX, $exptime ) < time();
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}
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protected function getMaxDateTime() {
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if ( time() > 0x7fffffff ) {
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return $this->getDB()->timestamp( 1 << 62 );
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} else {
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return $this->getDB()->timestamp( 0x7fffffff );
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}
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}
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protected function garbageCollect() {
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if ( !$this->purgePeriod ) {
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// Disabled
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return;
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}
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// Only purge on one in every $this->purgePeriod requests.
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if ( $this->purgePeriod !== 1 && mt_rand( 0, $this->purgePeriod - 1 ) ) {
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return;
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}
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$now = time();
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// Avoid repeating the delete within a few seconds
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if ( $now > ( $this->lastExpireAll + 1 ) ) {
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$this->lastExpireAll = $now;
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$this->expireAll();
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}
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}
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public function expireAll() {
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$this->deleteObjectsExpiringBefore( wfTimestampNow() );
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}
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/**
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* Delete objects from the database which expire before a certain date.
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* @return bool
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*/
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public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
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$db = $this->getDB();
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$dbTimestamp = $db->timestamp( $timestamp );
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$totalSeconds = false;
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$baseConds = array( 'exptime < ' . $db->addQuotes( $dbTimestamp ) );
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try {
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for ( $i = 0; $i < $this->shards; $i++ ) {
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$maxExpTime = false;
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while ( true ) {
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$conds = $baseConds;
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if ( $maxExpTime !== false ) {
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$conds[] = 'exptime > ' . $db->addQuotes( $maxExpTime );
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}
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$rows = $db->select(
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$this->getTableByShard( $i ),
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array( 'keyname', 'exptime' ),
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$conds,
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__METHOD__,
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array( 'LIMIT' => 100, 'ORDER BY' => 'exptime' ) );
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if ( !$rows->numRows() ) {
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break;
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}
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$keys = array();
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$row = $rows->current();
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$minExpTime = $row->exptime;
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if ( $totalSeconds === false ) {
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$totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
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- wfTimestamp( TS_UNIX, $minExpTime );
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}
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foreach ( $rows as $row ) {
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$keys[] = $row->keyname;
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$maxExpTime = $row->exptime;
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}
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$db->begin( __METHOD__ );
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$db->delete(
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$this->getTableByShard( $i ),
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array(
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'exptime >= ' . $db->addQuotes( $minExpTime ),
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'exptime < ' . $db->addQuotes( $dbTimestamp ),
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'keyname' => $keys
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),
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__METHOD__ );
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$db->commit( __METHOD__ );
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if ( $progressCallback ) {
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if ( intval( $totalSeconds ) === 0 ) {
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$percent = 0;
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} else {
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$remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
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- wfTimestamp( TS_UNIX, $maxExpTime );
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if ( $remainingSeconds > $totalSeconds ) {
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$totalSeconds = $remainingSeconds;
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}
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$percent = ( $i + $remainingSeconds / $totalSeconds )
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/ $this->shards * 100;
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}
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call_user_func( $progressCallback, $percent );
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}
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}
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}
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} catch ( DBQueryError $e ) {
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$this->handleWriteError( $e );
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}
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return true;
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}
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public function deleteAll() {
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$db = $this->getDB();
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try {
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for ( $i = 0; $i < $this->shards; $i++ ) {
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$db->begin( __METHOD__ );
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$db->delete( $this->getTableByShard( $i ), '*', __METHOD__ );
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$db->commit( __METHOD__ );
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}
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} catch ( DBQueryError $e ) {
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$this->handleWriteError( $e );
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}
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}
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/**
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* Serialize an object and, if possible, compress the representation.
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* On typical message and page data, this can provide a 3X decrease
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* in storage requirements.
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*
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* @param $data mixed
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* @return string
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*/
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protected function serialize( &$data ) {
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$serial = serialize( $data );
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if ( function_exists( 'gzdeflate' ) ) {
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return gzdeflate( $serial );
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} else {
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return $serial;
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}
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}
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/**
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* Unserialize and, if necessary, decompress an object.
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* @param $serial string
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* @return mixed
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*/
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protected function unserialize( $serial ) {
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if ( function_exists( 'gzinflate' ) ) {
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wfSuppressWarnings();
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$decomp = gzinflate( $serial );
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wfRestoreWarnings();
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if ( false !== $decomp ) {
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$serial = $decomp;
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}
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}
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$ret = unserialize( $serial );
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return $ret;
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}
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/**
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* Handle a DBQueryError which occurred during a write operation.
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* Ignore errors which are due to a read-only database, rethrow others.
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*/
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protected function handleWriteError( $exception ) {
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$db = $this->getDB();
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if ( !$db->wasReadOnlyError() ) {
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throw $exception;
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}
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try {
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$db->rollback( __METHOD__ );
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} catch ( DBQueryError $e ) {
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}
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wfDebug( __METHOD__ . ": ignoring query error\n" );
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$db->ignoreErrors( false );
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}
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/**
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* Create shard tables. For use from eval.php.
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*/
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public function createTables() {
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$db = $this->getDB();
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if ( $db->getType() !== 'mysql'
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|| version_compare( $db->getServerVersion(), '4.1.0', '<' ) )
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{
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throw new MWException( __METHOD__ . ' is not supported on this DB server' );
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}
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for ( $i = 0; $i < $this->shards; $i++ ) {
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$db->begin( __METHOD__ );
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$db->query(
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'CREATE TABLE ' . $db->tableName( $this->getTableByShard( $i ) ) .
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' LIKE ' . $db->tableName( 'objectcache' ),
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__METHOD__ );
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$db->commit( __METHOD__ );
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}
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}
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}
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/**
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* Backwards compatibility alias
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*/
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class MediaWikiBagOStuff extends SqlBagOStuff { }
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|