mirror of
https://github.com/YunoHost-Apps/mediawiki_ynh.git
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283 lines
8.6 KiB
PHP
283 lines
8.6 KiB
PHP
<?php
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/**
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* External storage in SQL database.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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* http://www.gnu.org/copyleft/gpl.html
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*
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* @file
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*/
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/**
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* DB accessable external objects.
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*
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* In this system, each store "location" maps to a database "cluster".
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* The clusters must be defined in the normal LBFactory configuration.
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*
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* @ingroup ExternalStorage
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*/
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class ExternalStoreDB extends ExternalStoreMedium {
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/**
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* The provided URL is in the form of DB://cluster/id
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* or DB://cluster/id/itemid for concatened storage.
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*
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* @see ExternalStoreMedium::fetchFromURL()
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*/
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public function fetchFromURL( $url ) {
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list( $cluster, $id, $itemID ) = $this->parseURL( $url );
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$ret =& $this->fetchBlob( $cluster, $id, $itemID );
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if ( $itemID !== false && $ret !== false ) {
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return $ret->getItem( $itemID );
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}
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return $ret;
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}
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/**
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* Fetch data from given external store URLs.
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* The provided URLs are in the form of DB://cluster/id
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* or DB://cluster/id/itemid for concatened storage.
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*
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* @param array $urls An array of external store URLs
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* @return array A map from url to stored content. Failed results
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* are not represented.
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*/
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public function batchFetchFromURLs( array $urls ) {
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$batched = $inverseUrlMap = array();
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foreach ( $urls as $url ) {
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list( $cluster, $id, $itemID ) = $this->parseURL( $url );
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$batched[$cluster][$id][] = $itemID;
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// false $itemID gets cast to int, but should be ok
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// since we do === from the $itemID in $batched
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$inverseUrlMap[$cluster][$id][$itemID] = $url;
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}
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$ret = array();
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foreach ( $batched as $cluster => $batchByCluster ) {
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$res = $this->batchFetchBlobs( $cluster, $batchByCluster );
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foreach ( $res as $id => $blob ) {
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foreach ( $batchByCluster[$id] as $itemID ) {
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$url = $inverseUrlMap[$cluster][$id][$itemID];
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if ( $itemID === false ) {
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$ret[$url] = $blob;
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} else {
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$ret[$url] = $blob->getItem( $itemID );
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}
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}
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}
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}
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return $ret;
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}
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/**
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* @see ExternalStoreMedium::store()
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*/
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public function store( $cluster, $data ) {
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$dbw = $this->getMaster( $cluster );
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$id = $dbw->nextSequenceValue( 'blob_blob_id_seq' );
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$dbw->insert( $this->getTable( $dbw ),
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array( 'blob_id' => $id, 'blob_text' => $data ),
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__METHOD__ );
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$id = $dbw->insertId();
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if ( !$id ) {
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throw new MWException( __METHOD__ . ': no insert ID' );
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}
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if ( $dbw->getFlag( DBO_TRX ) ) {
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$dbw->commit( __METHOD__ );
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}
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return "DB://$cluster/$id";
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}
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/**
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* Get a LoadBalancer for the specified cluster
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*
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* @param string $cluster cluster name
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* @return LoadBalancer object
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*/
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function &getLoadBalancer( $cluster ) {
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$wiki = isset( $this->params['wiki'] ) ? $this->params['wiki'] : false;
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return wfGetLBFactory()->getExternalLB( $cluster, $wiki );
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}
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/**
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* Get a slave database connection for the specified cluster
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*
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* @param string $cluster cluster name
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* @return DatabaseBase object
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*/
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function &getSlave( $cluster ) {
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global $wgDefaultExternalStore;
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$wiki = isset( $this->params['wiki'] ) ? $this->params['wiki'] : false;
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$lb =& $this->getLoadBalancer( $cluster );
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if ( !in_array( "DB://" . $cluster, (array)$wgDefaultExternalStore ) ) {
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wfDebug( "read only external store" );
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$lb->allowLagged( true );
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} else {
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wfDebug( "writable external store" );
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}
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return $lb->getConnection( DB_SLAVE, array(), $wiki );
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}
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/**
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* Get a master database connection for the specified cluster
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*
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* @param string $cluster cluster name
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* @return DatabaseBase object
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*/
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function &getMaster( $cluster ) {
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$wiki = isset( $this->params['wiki'] ) ? $this->params['wiki'] : false;
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$lb =& $this->getLoadBalancer( $cluster );
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return $lb->getConnection( DB_MASTER, array(), $wiki );
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}
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/**
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* Get the 'blobs' table name for this database
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*
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* @param $db DatabaseBase
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* @return String: table name ('blobs' by default)
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*/
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function getTable( &$db ) {
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$table = $db->getLBInfo( 'blobs table' );
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if ( is_null( $table ) ) {
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$table = 'blobs';
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}
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return $table;
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}
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/**
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* Fetch a blob item out of the database; a cache of the last-loaded
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* blob will be kept so that multiple loads out of a multi-item blob
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* can avoid redundant database access and decompression.
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* @param $cluster
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* @param $id
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* @param $itemID
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* @return mixed
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* @private
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*/
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function &fetchBlob( $cluster, $id, $itemID ) {
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/**
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* One-step cache variable to hold base blobs; operations that
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* pull multiple revisions may often pull multiple times from
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* the same blob. By keeping the last-used one open, we avoid
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* redundant unserialization and decompression overhead.
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*/
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static $externalBlobCache = array();
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$cacheID = ( $itemID === false ) ? "$cluster/$id" : "$cluster/$id/";
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if ( isset( $externalBlobCache[$cacheID] ) ) {
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wfDebugLog( 'ExternalStoreDB-cache',
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"ExternalStoreDB::fetchBlob cache hit on $cacheID\n" );
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return $externalBlobCache[$cacheID];
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}
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wfDebugLog( 'ExternalStoreDB-cache',
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"ExternalStoreDB::fetchBlob cache miss on $cacheID\n" );
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$dbr =& $this->getSlave( $cluster );
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$ret = $dbr->selectField( $this->getTable( $dbr ),
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'blob_text', array( 'blob_id' => $id ), __METHOD__ );
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if ( $ret === false ) {
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wfDebugLog( 'ExternalStoreDB',
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"ExternalStoreDB::fetchBlob master fallback on $cacheID\n" );
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// Try the master
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$dbw =& $this->getMaster( $cluster );
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$ret = $dbw->selectField( $this->getTable( $dbw ),
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'blob_text', array( 'blob_id' => $id ), __METHOD__ );
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if ( $ret === false ) {
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wfDebugLog( 'ExternalStoreDB',
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"ExternalStoreDB::fetchBlob master failed to find $cacheID\n" );
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}
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}
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if ( $itemID !== false && $ret !== false ) {
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// Unserialise object; caller extracts item
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$ret = unserialize( $ret );
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}
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$externalBlobCache = array( $cacheID => &$ret );
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return $ret;
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}
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/**
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* Fetch multiple blob items out of the database
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*
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* @param string $cluster A cluster name valid for use with LBFactory
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* @param array $ids A map from the blob_id's to look for to the requested itemIDs in the blobs
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* @return array A map from the blob_id's requested to their content. Unlocated ids are not represented
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*/
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function batchFetchBlobs( $cluster, array $ids ) {
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$dbr = $this->getSlave( $cluster );
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$res = $dbr->select( $this->getTable( $dbr ),
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array( 'blob_id', 'blob_text' ), array( 'blob_id' => array_keys( $ids ) ), __METHOD__ );
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$ret = array();
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if ( $res !== false ) {
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$this->mergeBatchResult( $ret, $ids, $res );
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}
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if ( $ids ) {
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wfDebugLog( __CLASS__, __METHOD__ .
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" master fallback on '$cluster' for: " .
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implode( ',', array_keys( $ids ) ) . "\n" );
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// Try the master
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$dbw = $this->getMaster( $cluster );
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$res = $dbw->select( $this->getTable( $dbr ),
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array( 'blob_id', 'blob_text' ),
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array( 'blob_id' => array_keys( $ids ) ),
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__METHOD__ );
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if ( $res === false ) {
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wfDebugLog( __CLASS__, __METHOD__ . " master failed on '$cluster'\n" );
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} else {
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$this->mergeBatchResult( $ret, $ids, $res );
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}
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}
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if ( $ids ) {
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wfDebugLog( __CLASS__, __METHOD__ .
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" master on '$cluster' failed locating items: " .
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implode( ',', array_keys( $ids ) ) . "\n" );
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}
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return $ret;
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}
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/**
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* Helper function for self::batchFetchBlobs for merging master/slave results
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* @param array &$ret Current self::batchFetchBlobs return value
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* @param array &$ids Map from blob_id to requested itemIDs
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* @param mixed $res DB result from DatabaseBase::select
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*/
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private function mergeBatchResult( array &$ret, array &$ids, $res ) {
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foreach ( $res as $row ) {
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$id = $row->blob_id;
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$itemIDs = $ids[$id];
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unset( $ids[$id] ); // to track if everything is found
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if ( count( $itemIDs ) === 1 && reset( $itemIDs ) === false ) {
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// single result stored per blob
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$ret[$id] = $row->blob_text;
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} else {
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// multi result stored per blob
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$ret[$id] = unserialize( $row->blob_text );
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}
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}
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}
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protected function parseURL( $url ) {
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$path = explode( '/', $url );
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return array(
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$path[2], // cluster
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$path[3], // id
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isset( $path[4] ) ? $path[4] : false // itemID
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);
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}
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}
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