Wikibase\TermStore\MediaWiki\PackagePrivate\DatabaseTermIdsResolver

Complexity

Total Complexity

18

Size/Duplication

Total Lines	131
Duplicated Lines	0 %

Coupling/Cohesion

Components	1
Dependencies	1

Importance

Changes

0

8 Methods

Rating	Name	Duplication	Size	Complexity
A	__construct()	0	9	1
A	resolveTermIds()	0	23	5
A	selectTerms()	0	13	1
A	preloadTypes()	0	10	3
A	addResultTerms()	0	6	1
A	lookupType()	0	8	2
A	getDbr()	0	7	2
A	getDbw()	0	11	3

<?php

namespace Wikibase\TermStore\MediaWiki\PackagePrivate;

use InvalidArgumentException;
use LogicException;
use stdClass;
use Wikimedia\Rdbms\IDatabase;
use Wikimedia\Rdbms\ILoadBalancer;
use Wikimedia\Rdbms\IResultWrapper;

/**
 * Term ID resolver using the normalized database schema.
 *
 * @license GPL-2.0-or-later
 */
class DatabaseTermIdsResolver implements TermIdsResolver {

	/** @var TypeIdsResolver */
	private $typeIdsResolver;

	/** @var ILoadBalancer */
	private $lb;

	/** @var bool */
	private $allowMasterFallback;

	/** @var IDatabase */
	private $dbr = null;

	/** @var IDatabase */
	private $dbw = null;

	/** @var string[] stash of data returned from the {@link TypeIdsResolver} */
	private $typeNames = [];

	/**
	 * @param TypeIdsResolver $typeIdsResolver
	 * @param ILoadBalancer $lb
	 * @param bool $allowMasterFallback Whether to fall back to the master database if the data from
	 * the replica database is detected to be stale.
	 */
	public function __construct(
		TypeIdsResolver $typeIdsResolver,
		ILoadBalancer $lb,
		$allowMasterFallback = false
	) {
		$this->typeIdsResolver = $typeIdsResolver;
		$this->lb = $lb;
		$this->allowMasterFallback = $allowMasterFallback;
	}

	/*
	 * Term data is first read from the replica; if that returns less rows than we asked for, then
	 * there are some new rows in the master that were not yet replicated, and we fall back to the
	 * master if allowed. As the internal relations of the term store never change (for example, a
	 * term_in_lang row will never suddenly point to a different text_in_lang), a master fallback
	 * should never be necessary in any other case. However, callers need to consider where they
	 * got the list of term IDs they pass into this method from: if it’s from a replica, they may
	 * still see outdated data overall.
	 */
	public function resolveTermIds( array $termIds ): array {
		$terms = [];

		$replicaResult = $this->selectTerms( $this->getDbr(), $termIds );
		$this->preloadTypes( $replicaResult );
		$replicaTermIds = [];

		foreach ( $replicaResult as $row ) {
			$replicaTermIds[] = $row->wbtl_id;
			$this->addResultTerms( $terms, $row );
		}

		if ( $this->allowMasterFallback && count( $replicaTermIds ) !== count( $termIds ) ) {
			$masterTermIds = array_values( array_diff( $termIds, $replicaTermIds ) );
			$masterResult = $this->selectTerms( $this->getDbw(), $masterTermIds );
			$this->preloadTypes( $masterResult );
			foreach ( $masterResult as $row ) {
				$this->addResultTerms( $terms, $row );
			}
		}

		return $terms;
	}

	private function selectTerms( IDatabase $db, array $termIds ): IResultWrapper {
		return $db->select(
			[ 'wbt_term_in_lang', 'wbt_text_in_lang', 'wbt_text' ],
			[ 'wbtl_id', 'wbtl_type_id', 'wbxl_language', 'wbx_text' ],
			[
				'wbtl_id' => $termIds,
				// join conditions
				'wbtl_text_in_lang_id=wbxl_id',
				'wbxl_text_id=wbx_id',
			],
			__METHOD__
		);
	}

	private function preloadTypes( IResultWrapper $result ) {
		$typeIds = [];
		foreach ( $result as $row ) {
			$typeId = $row->wbtl_type_id;
			if ( !array_key_exists( $typeId, $this->typeNames ) ) {
				$typeIds[$typeId] = true;
			}
		}
		$this->typeNames += $this->typeIdsResolver->resolveTypeIds( array_keys( $typeIds ) );
	}

	private function addResultTerms( array &$terms, stdClass $row ) {
		$type = $this->lookupType( $row->wbtl_type_id );
		$lang = $row->wbxl_language;
		$text = $row->wbx_text;
		$terms[$type][$lang][] = $text;
	}

	private function lookupType( $typeId ) {
		$typeName = $this->typeNames[$typeId] ?? null;
		if ( $typeName === null ) {
			throw new InvalidArgumentException(
				'Type ID ' . $typeId . ' was requested but not preloaded!' );
		}
		return $typeName;
	}

	private function getDbr() {
		if ( $this->dbr === null ) {
			$this->dbr = $this->lb->getConnection( ILoadBalancer::DB_REPLICA );
		}

		return $this->dbr;
	}

	private function getDbw() {
		if ( !$this->allowMasterFallback ) {
			throw new LogicException( 'Master fallback not allowed!' );
		}

		if ( $this->dbw === null ) {
			$this->dbw = $this->lb->getConnection( ILoadBalancer::DB_MASTER );
		}

		return $this->dbw;
	}

}