DBSerialProvider.php
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DBSerialProvider.php
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	<?php

	namespace MediaWiki\User\TempUser;

	use Wikimedia\Rdbms\IDatabase;
	use Wikimedia\Rdbms\RawSQLValue;

	/**
	* Base class for serial acquisition code shared between core and CentralAuth.
	*
	* @since 1.39
	*/
	abstract class DBSerialProvider implements SerialProvider {
	/** @var int */
	private $numShards;

	/**
	* @param array $config
	* - numShards (int, default 1): A small integer. This can be set to a
	* value greater than 1 to avoid acquiring a global lock when
	* allocating IDs, at the expense of making the IDs be non-monotonic.
	*/
	public function __construct( $config ) {
	$this->numShards = $config['numShards'] ?? 1;
	}

	public function acquireIndex( int $year = 0 ): int {
	if ( $this->numShards ) {
	$shard = mt_rand( 0, $this->numShards - 1 );
	} else {
	$shard = 0;
	}

	$dbw = $this->getDB();
	$table = $this->getTableName();
	$dbw->startAtomic( __METHOD__ );
	$dbw->newInsertQueryBuilder()
	->insertInto( $table )
	->row( [
	'uas_shard' => $shard,
	'uas_year' => $year,
	'uas_value' => 1
	] )
	->onDuplicateKeyUpdate()
	->uniqueIndexFields( [ 'uas_shard', 'uas_year' ] )
	->set( [ 'uas_value' => new RawSQLValue( 'uas_value+1' ) ] )
	->caller( __METHOD__ )->execute();
	$value = $dbw->newSelectQueryBuilder()
	->select( 'uas_value' )
	->from( $table )
	->where( [ 'uas_shard' => $shard ] )
	->andWhere( [ 'uas_year' => $year ] )
	->caller( __METHOD__ )
	->fetchField();
	$dbw->endAtomic( __METHOD__ );
	return $value * $this->numShards + $shard;
	}

	/**
	* @return IDatabase
	*/
	abstract protected function getDB();

	/**
	* @return string
	*/
	abstract protected function getTableName();
	}