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Diffstat (limited to 'www/wiki/maintenance/runBatchedQuery.php')
| -rw-r--r-- | www/wiki/maintenance/runBatchedQuery.php | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/www/wiki/maintenance/runBatchedQuery.php b/www/wiki/maintenance/runBatchedQuery.php new file mode 100644 index 00000000..64eca950 --- /dev/null +++ b/www/wiki/maintenance/runBatchedQuery.php @@ -0,0 +1,115 @@ +<?php +/** + * Run a database query in batches and wait for replica DBs. This is used on large + * wikis to prevent replication lag from going through the roof when executing + * large write queries. + * + * 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 Maintenance + */ + +require_once __DIR__ . '/Maintenance.php'; + +use Wikimedia\Rdbms\IDatabase; + +/** + * Maintenance script to run a database query in batches and wait for replica DBs. + * + * @ingroup Maintenance + */ +class BatchedQueryRunner extends Maintenance { + public function __construct() { + parent::__construct(); + $this->addDescription( + "Run an update query on all rows of a table. " . + "Waits for replicas at appropriate intervals." ); + $this->addOption( 'table', 'The table name', true, true ); + $this->addOption( 'set', 'The SET clause', true, true ); + $this->addOption( 'where', 'The WHERE clause', false, true ); + $this->addOption( 'key', 'A column name, the values of which are unique', true, true ); + $this->addOption( 'batch-size', 'The batch size (default 1000)', false, true ); + $this->addOption( 'db', 'The database name, or omit to use the current wiki.', false, true ); + } + + public function execute() { + $table = $this->getOption( 'table' ); + $key = $this->getOption( 'key' ); + $set = $this->getOption( 'set' ); + $where = $this->getOption( 'where', null ); + $where = $where === null ? [] : [ $where ]; + $batchSize = $this->getOption( 'batch-size', 1000 ); + + $dbName = $this->getOption( 'db', null ); + if ( $dbName === null ) { + $dbw = $this->getDB( DB_MASTER ); + } else { + $lbf = MediaWiki\MediaWikiServices::getInstance()->getDBLoadBalancerFactory(); + $lb = $lbf->getMainLB( $dbName ); + $dbw = $lb->getConnection( DB_MASTER, [], $dbName ); + } + + $selectConds = $where; + $prevEnd = false; + + $n = 1; + do { + $this->output( "Batch $n: " ); + $n++; + + // Note that the update conditions do not rely on atomicity of the + // SELECT query in order to guarantee that all rows are updated. The + // results of the SELECT are merely a partitioning hint. Simultaneous + // updates merely result in the wrong number of rows being updated + // in a batch. + + $res = $dbw->select( $table, $key, $selectConds, __METHOD__, + [ 'ORDER BY' => $key, 'LIMIT' => $batchSize ] ); + if ( $res->numRows() ) { + $res->seek( $res->numRows() - 1 ); + $row = $res->fetchObject(); + $end = $dbw->addQuotes( $row->$key ); + $selectConds = array_merge( $where, [ "$key > $end" ] ); + $updateConds = array_merge( $where, [ "$key <= $end" ] ); + } else { + $updateConds = $where; + } + if ( $prevEnd !== false ) { + $updateConds = array_merge( [ "$key > $prevEnd" ], $updateConds ); + } + + $query = "UPDATE " . $dbw->tableName( $table ) . + " SET " . $set . + " WHERE " . $dbw->makeList( $updateConds, IDatabase::LIST_AND ); + + $dbw->query( $query, __METHOD__ ); + + $prevEnd = $end; + + $affected = $dbw->affectedRows(); + $this->output( "$affected rows affected\n" ); + wfWaitForSlaves(); + } while ( $res->numRows() ); + } + + public function getDbType() { + return Maintenance::DB_ADMIN; + } +} + +$maintClass = BatchedQueryRunner::class; +require_once RUN_MAINTENANCE_IF_MAIN; |