Current File : //data/www_bck/varak.net_bck/havranipapuce.varak.net/includes/externalstore/ExternalStoreDB.php
<?php
/**
* External storage in SQL database.
*
* 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
*/
/**
* DB accessable external objects.
*
* In this system, each store "location" maps to a database "cluster".
* The clusters must be defined in the normal LBFactory configuration.
*
* @ingroup ExternalStorage
*/
class ExternalStoreDB extends ExternalStoreMedium {
/**
* The provided URL is in the form of DB://cluster/id
* or DB://cluster/id/itemid for concatened storage.
*
* @see ExternalStoreMedium::fetchFromURL()
*/
public function fetchFromURL( $url ) {
list( $cluster, $id, $itemID ) = $this->parseURL( $url );
$ret = $this->fetchBlob( $cluster, $id, $itemID );
if ( $itemID !== false && $ret !== false ) {
return $ret->getItem( $itemID );
}
return $ret;
}
/**
* Fetch data from given external store URLs.
* The provided URLs are in the form of DB://cluster/id
* or DB://cluster/id/itemid for concatened storage.
*
* @param array $urls An array of external store URLs
* @return array A map from url to stored content. Failed results
* are not represented.
*/
public function batchFetchFromURLs( array $urls ) {
$batched = $inverseUrlMap = array();
foreach ( $urls as $url ) {
list( $cluster, $id, $itemID ) = $this->parseURL( $url );
$batched[$cluster][$id][] = $itemID;
// false $itemID gets cast to int, but should be ok
// since we do === from the $itemID in $batched
$inverseUrlMap[$cluster][$id][$itemID] = $url;
}
$ret = array();
foreach ( $batched as $cluster => $batchByCluster ) {
$res = $this->batchFetchBlobs( $cluster, $batchByCluster );
/** @var HistoryBlob $blob */
foreach ( $res as $id => $blob ) {
foreach ( $batchByCluster[$id] as $itemID ) {
$url = $inverseUrlMap[$cluster][$id][$itemID];
if ( $itemID === false ) {
$ret[$url] = $blob;
} else {
$ret[$url] = $blob->getItem( $itemID );
}
}
}
}
return $ret;
}
/**
* @see ExternalStoreMedium::store()
*/
public 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 = $dbw->insertId();
if ( !$id ) {
throw new MWException( __METHOD__ . ': no insert ID' );
}
return "DB://$cluster/$id";
}
/**
* Get a LoadBalancer for the specified cluster
*
* @param string $cluster Cluster name
* @return LoadBalancer
*/
function getLoadBalancer( $cluster ) {
$wiki = isset( $this->params['wiki'] ) ? $this->params['wiki'] : false;
return wfGetLBFactory()->getExternalLB( $cluster, $wiki );
}
/**
* Get a slave database connection for the specified cluster
*
* @param string $cluster Cluster name
* @return DatabaseBase
*/
function getSlave( $cluster ) {
global $wgDefaultExternalStore;
$wiki = isset( $this->params['wiki'] ) ? $this->params['wiki'] : false;
$lb = $this->getLoadBalancer( $cluster );
if ( !in_array( "DB://" . $cluster, (array)$wgDefaultExternalStore ) ) {
wfDebug( "read only external store\n" );
$lb->allowLagged( true );
} else {
wfDebug( "writable external store\n" );
}
$db = $lb->getConnection( DB_SLAVE, array(), $wiki );
$db->clearFlag( DBO_TRX ); // sanity
return $db;
}
/**
* Get a master database connection for the specified cluster
*
* @param string $cluster Cluster name
* @return DatabaseBase
*/
function getMaster( $cluster ) {
$wiki = isset( $this->params['wiki'] ) ? $this->params['wiki'] : false;
$lb = $this->getLoadBalancer( $cluster );
$db = $lb->getConnection( DB_MASTER, array(), $wiki );
$db->clearFlag( DBO_TRX ); // sanity
return $db;
}
/**
* Get the 'blobs' table name for this database
*
* @param DatabaseBase $db
* @return string Table name ('blobs' by default)
*/
function getTable( $db ) {
$table = $db->getLBInfo( 'blobs table' );
if ( is_null( $table ) ) {
$table = 'blobs';
}
return $table;
}
/**
* 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 string $cluster
* @param string $id
* @param string $itemID
* @return mixed
* @private
*/
function fetchBlob( $cluster, $id, $itemID ) {
/**
* 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.
*/
static $externalBlobCache = array();
$cacheID = ( $itemID === false ) ? "$cluster/$id" : "$cluster/$id/";
if ( isset( $externalBlobCache[$cacheID] ) ) {
wfDebugLog( 'ExternalStoreDB-cache',
"ExternalStoreDB::fetchBlob cache hit on $cacheID" );
return $externalBlobCache[$cacheID];
}
wfDebugLog( 'ExternalStoreDB-cache',
"ExternalStoreDB::fetchBlob cache miss on $cacheID" );
$dbr = $this->getSlave( $cluster );
$ret = $dbr->selectField( $this->getTable( $dbr ),
'blob_text', array( 'blob_id' => $id ), __METHOD__ );
if ( $ret === false ) {
wfDebugLog( 'ExternalStoreDB',
"ExternalStoreDB::fetchBlob master fallback on $cacheID" );
// Try the master
$dbw = $this->getMaster( $cluster );
$ret = $dbw->selectField( $this->getTable( $dbw ),
'blob_text', array( 'blob_id' => $id ), __METHOD__ );
if ( $ret === false ) {
wfDebugLog( 'ExternalStoreDB',
"ExternalStoreDB::fetchBlob master failed to find $cacheID" );
}
}
if ( $itemID !== false && $ret !== false ) {
// Unserialise object; caller extracts item
$ret = unserialize( $ret );
}
$externalBlobCache = array( $cacheID => $ret );
return $ret;
}
/**
* Fetch multiple blob items out of the database
*
* @param string $cluster A cluster name valid for use with LBFactory
* @param array $ids A map from the blob_id's to look for to the requested itemIDs in the blobs
* @return array A map from the blob_id's requested to their content.
* Unlocated ids are not represented
*/
function batchFetchBlobs( $cluster, array $ids ) {
$dbr = $this->getSlave( $cluster );
$res = $dbr->select( $this->getTable( $dbr ),
array( 'blob_id', 'blob_text' ), array( 'blob_id' => array_keys( $ids ) ), __METHOD__ );
$ret = array();
if ( $res !== false ) {
$this->mergeBatchResult( $ret, $ids, $res );
}
if ( $ids ) {
wfDebugLog( __CLASS__, __METHOD__ .
" master fallback on '$cluster' for: " .
implode( ',', array_keys( $ids ) ) );
// Try the master
$dbw = $this->getMaster( $cluster );
$res = $dbw->select( $this->getTable( $dbr ),
array( 'blob_id', 'blob_text' ),
array( 'blob_id' => array_keys( $ids ) ),
__METHOD__ );
if ( $res === false ) {
wfDebugLog( __CLASS__, __METHOD__ . " master failed on '$cluster'" );
} else {
$this->mergeBatchResult( $ret, $ids, $res );
}
}
if ( $ids ) {
wfDebugLog( __CLASS__, __METHOD__ .
" master on '$cluster' failed locating items: " .
implode( ',', array_keys( $ids ) ) );
}
return $ret;
}
/**
* Helper function for self::batchFetchBlobs for merging master/slave results
* @param array &$ret Current self::batchFetchBlobs return value
* @param array &$ids Map from blob_id to requested itemIDs
* @param mixed $res DB result from DatabaseBase::select
*/
private function mergeBatchResult( array &$ret, array &$ids, $res ) {
foreach ( $res as $row ) {
$id = $row->blob_id;
$itemIDs = $ids[$id];
unset( $ids[$id] ); // to track if everything is found
if ( count( $itemIDs ) === 1 && reset( $itemIDs ) === false ) {
// single result stored per blob
$ret[$id] = $row->blob_text;
} else {
// multi result stored per blob
$ret[$id] = unserialize( $row->blob_text );
}
}
}
/**
* @param string $url
* @return array
*/
protected function parseURL( $url ) {
$path = explode( '/', $url );
return array(
$path[2], // cluster
$path[3], // id
isset( $path[4] ) ? $path[4] : false // itemID
);
}
}
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