includes/deferred/SqlDataUpdate.php

   1 <?php
   2 /**
   3  * Base code for update jobs that put some secondary data extracted
   4  * from article content into the database.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with this program; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  19  * http://www.gnu.org/copyleft/gpl.html
  20  *
  21  * @file
  22  */
  23
  24 /**
  25  * Abstract base class for update jobs that put some secondary data extracted
  26  * from article content into the database.
  27  *
  28  * @note: subclasses should NOT start or commit transactions in their doUpdate() method,
  29  *        a transaction will automatically be wrapped around the update. Starting another
  30  *        one would break the outer transaction bracket. If need be, subclasses can override
  31  *        the beginTransaction() and commitTransaction() methods.
  32  */
  33 abstract class SqlDataUpdate extends DataUpdate {
  34         /** @var DatabaseBase Database connection reference */
  35         protected $mDb;
  36
  37         /** @var array SELECT options to be used (array) */
  38         protected $mOptions;
  39
  40         /** @var bool Whether a transaction is open on this object (internal use only!) */
  41         private $mHasTransaction;
  42
  43         /** @var bool Whether this update should be wrapped in a transaction */
  44         protected $mUseTransaction;
  45
  46         /**
  47          * Constructor
  48          *
  49          * @param bool $withTransaction whether this update should be wrapped in a
  50          *   transaction (default: true). A transaction is only started if no
  51          *   transaction is already in progress, see beginTransaction() for details.
  52          */
  53         public function __construct( $withTransaction = true ) {
  54                 global $wgAntiLockFlags;
  55
  56                 parent::__construct();
  57
  58                 if ( $wgAntiLockFlags & ALF_NO_LINK_LOCK ) {
  59                         $this->mOptions = array();
  60                 } else {
  61                         $this->mOptions = array( 'FOR UPDATE' );
  62                 }
  63
  64                 // @todo Get connection only when it's needed? Make sure that doesn't
  65                 // break anything, especially transactions!
  66                 $this->mDb = wfGetDB( DB_MASTER );
  67
  68                 $this->mWithTransaction = $withTransaction;
  69                 $this->mHasTransaction = false;
  70         }
  71
  72         /**
  73          * Begin a database transaction, if $withTransaction was given as true in
  74          * the constructor for this SqlDataUpdate.
  75          *
  76          * Because nested transactions are not supported by the Database class,
  77          * this implementation checks Database::trxLevel() and only opens a
  78          * transaction if none is already active.
  79          */
  80         public function beginTransaction() {
  81                 if ( !$this->mWithTransaction ) {
  82                         return;
  83                 }
  84
  85                 // NOTE: nested transactions are not supported, only start a transaction if none is open
  86                 if ( $this->mDb->trxLevel() === 0 ) {
  87                         $this->mDb->begin( get_class( $this ) . '::beginTransaction' );
  88                         $this->mHasTransaction = true;
  89                 }
  90         }
  91
  92         /**
  93          * Commit the database transaction started via beginTransaction (if any).
  94          */
  95         public function commitTransaction() {
  96                 if ( $this->mHasTransaction ) {
  97                         $this->mDb->commit( get_class( $this ) . '::commitTransaction' );
  98                         $this->mHasTransaction = false;
  99                 }
 100         }
 101
 102         /**
 103          * Abort the database transaction started via beginTransaction (if any).
 104          */
 105         public function abortTransaction() {
 106                 if ( $this->mHasTransaction ) { //XXX: actually... maybe always?
 107                         $this->mDb->rollback( get_class( $this ) . '::abortTransaction' );
 108                         $this->mHasTransaction = false;
 109                 }
 110         }
 111
 112         /**
 113          * Invalidate the cache of a list of pages from a single namespace.
 114          * This is intended for use by subclasses.
 115          *
 116          * @param int $namespace Namespace number
 117          * @param array $dbkeys
 118          */
 119         protected function invalidatePages( $namespace, array $dbkeys ) {
 120                 if ( $dbkeys === array() ) {
 121                         return;
 122                 }
 123
 124                 /**
 125                  * Determine which pages need to be updated
 126                  * This is necessary to prevent the job queue from smashing the DB with
 127                  * large numbers of concurrent invalidations of the same page
 128                  */
 129                 $now = $this->mDb->timestamp();
 130                 $ids = array();
 131                 $res = $this->mDb->select( 'page', array( 'page_id' ),
 132                         array(
 133                                 'page_namespace' => $namespace,
 134                                 'page_title' => $dbkeys,
 135                                 'page_touched < ' . $this->mDb->addQuotes( $now )
 136                         ), __METHOD__
 137                 );
 138
 139                 foreach ( $res as $row ) {
 140                         $ids[] = $row->page_id;
 141                 }
 142
 143                 if ( $ids === array() ) {
 144                         return;
 145                 }
 146
 147                 /**
 148                  * Do the update
 149                  * We still need the page_touched condition, in case the row has changed since
 150                  * the non-locking select above.
 151                  */
 152                 $this->mDb->update( 'page', array( 'page_touched' => $now ),
 153                         array(
 154                                 'page_id' => $ids,
 155                                 'page_touched < ' . $this->mDb->addQuotes( $now )
 156                         ), __METHOD__
 157                 );
 158         }
 159 }