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- <?php
- /**
- * External database storage will use one (or more) separate connection pools
- * from what the main wiki uses. If we load many revisions, such as when doing
- * bulk backups or maintenance, we want to keep them around over the lifetime
- * of the script.
- *
- * Associative array of LoadBalancer objects, indexed by cluster name.
- */
- global $wgExternalLoadBalancers;
- $wgExternalLoadBalancers = array();
- /**
- * One-step cache variable to hold base blobs; operations that
- * pull multiple revisions may often pull multiple times from
- * the same blob. By keeping the last-used one open, we avoid
- * redundant unserialization and decompression overhead.
- */
- global $wgExternalBlobCache;
- $wgExternalBlobCache = array();
- /**
- * DB accessable external objects
- * @ingroup ExternalStorage
- */
- class ExternalStoreDB {
- /** @todo Document.*/
- function &getLoadBalancer( $cluster ) {
- return wfGetLBFactory()->getExternalLB( $cluster );
- }
- /** @todo Document.*/
- function &getSlave( $cluster ) {
- $lb =& $this->getLoadBalancer( $cluster );
- return $lb->getConnection( DB_SLAVE );
- }
- /** @todo Document.*/
- function &getMaster( $cluster ) {
- $lb =& $this->getLoadBalancer( $cluster );
- return $lb->getConnection( DB_MASTER );
- }
- /** @todo Document.*/
- function getTable( &$db ) {
- $table = $db->getLBInfo( 'blobs table' );
- if ( is_null( $table ) ) {
- $table = 'blobs';
- }
- return $table;
- }
- /**
- * Fetch data from given URL
- * @param string $url An url of the form DB://cluster/id or DB://cluster/id/itemid for concatened storage.
- */
- function fetchFromURL( $url ) {
- $path = explode( '/', $url );
- $cluster = $path[2];
- $id = $path[3];
- if ( isset( $path[4] ) ) {
- $itemID = $path[4];
- } else {
- $itemID = false;
- }
- $ret =& $this->fetchBlob( $cluster, $id, $itemID );
- if ( $itemID !== false && $ret !== false ) {
- return $ret->getItem( $itemID );
- }
- return $ret;
- }
- /**
- * Fetch a blob item out of the database; a cache of the last-loaded
- * blob will be kept so that multiple loads out of a multi-item blob
- * can avoid redundant database access and decompression.
- * @param $cluster
- * @param $id
- * @param $itemID
- * @return mixed
- * @private
- */
- function &fetchBlob( $cluster, $id, $itemID ) {
- global $wgExternalBlobCache;
- $cacheID = ( $itemID === false ) ? "$cluster/$id" : "$cluster/$id/";
- if( isset( $wgExternalBlobCache[$cacheID] ) ) {
- wfDebug( "ExternalStoreDB::fetchBlob cache hit on $cacheID\n" );
- return $wgExternalBlobCache[$cacheID];
- }
- wfDebug( "ExternalStoreDB::fetchBlob cache miss on $cacheID\n" );
- $dbr =& $this->getSlave( $cluster );
- $ret = $dbr->selectField( $this->getTable( $dbr ), 'blob_text', array( 'blob_id' => $id ) );
- if ( $ret === false ) {
- wfDebugLog( 'ExternalStoreDB', "ExternalStoreDB::fetchBlob master fallback on $cacheID\n" );
- // Try the master
- $dbw =& $this->getMaster( $cluster );
- $ret = $dbw->selectField( $this->getTable( $dbw ), 'blob_text', array( 'blob_id' => $id ) );
- if( $ret === false) {
- wfDebugLog( 'ExternalStoreDB', "ExternalStoreDB::fetchBlob master failed to find $cacheID\n" );
- }
- }
- if( $itemID !== false && $ret !== false ) {
- // Unserialise object; caller extracts item
- $ret = unserialize( $ret );
- }
- $wgExternalBlobCache = array( $cacheID => &$ret );
- return $ret;
- }
- /**
- * Insert a data item into a given cluster
- *
- * @param $cluster String: the cluster name
- * @param $data String: the data item
- * @return string URL
- */
- function store( $cluster, $data ) {
- $dbw = $this->getMaster( $cluster );
- $id = $dbw->nextSequenceValue( 'blob_blob_id_seq' );
- $dbw->insert( $this->getTable( $dbw ),
- array( 'blob_id' => $id, 'blob_text' => $data ),
- __METHOD__ );
- $id = $dbw->insertId();
- if ( $dbw->getFlag( DBO_TRX ) ) {
- $dbw->immediateCommit();
- }
- return "DB://$cluster/$id";
- }
- }
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