includes/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
  35         protected $mDb;            //!< Database connection reference
  36         protected $mOptions;       //!< SELECT options to be used (array)
  37
  38         private   $mHasTransaction; //!< bool whether a transaction is open on this object (internal use only!)
  39         protected $mUseTransaction; //!< bool whether this update should be wrapped in a transaction
  40
  41         /**
  42          * Constructor
  43          *
  44          * @param bool $withTransaction whether this update should be wrapped in a transaction (default: true).
  45          *             A transaction is only started if no transaction is already in progress,
  46          *             see beginTransaction() for details.
  47          **/
  48         public function __construct( $withTransaction = true ) {
  49                 global $wgAntiLockFlags;
  50
  51                 parent::__construct();
  52
  53                 if ( $wgAntiLockFlags & ALF_NO_LINK_LOCK ) {
  54                         $this->mOptions = array();
  55                 } else {
  56                         $this->mOptions = array( 'FOR UPDATE' );
  57                 }
  58
  59                 // @todo get connection only when it's needed? make sure that doesn't break anything, especially transactions!
  60                 $this->mDb = wfGetDB( DB_MASTER );
  61
  62                 $this->mWithTransaction = $withTransaction;
  63                 $this->mHasTransaction = false;
  64         }
  65
  66         /**
  67          * Begin a database transaction, if $withTransaction was given as true in the constructor for this SqlDataUpdate.
  68          *
  69          * Because nested transactions are not supported by the Database class, this implementation
  70          * checks Database::trxLevel() and only opens a transaction if none is already active.
  71          */
  72         public function beginTransaction() {
  73                 if ( !$this->mWithTransaction ) {
  74                         return;
  75                 }
  76
  77                 // NOTE: nested transactions are not supported, only start a transaction if none is open
  78                 if ( $this->mDb->trxLevel() === 0 ) {
  79                         $this->mDb->begin( get_class( $this ) . '::beginTransaction' );
  80                         $this->mHasTransaction = true;
  81                 }
  82         }
  83
  84         /**
  85          * Commit the database transaction started via beginTransaction (if any).
  86          */
  87         public function commitTransaction() {
  88                 if ( $this->mHasTransaction ) {
  89                         $this->mDb->commit( get_class( $this ) . '::commitTransaction' );
  90                         $this->mHasTransaction = false;
  91                 }
  92         }
  93
  94         /**
  95          * Abort the database transaction started via beginTransaction (if any).
  96          */
  97         public function abortTransaction() {
  98                 if ( $this->mHasTransaction ) { //XXX: actually... maybe always?
  99                         $this->mDb->rollback( get_class( $this ) . '::abortTransaction' );
 100                         $this->mHasTransaction = false;
 101                 }
 102         }
 103
 104         /**
 105          * Invalidate the cache of a list of pages from a single namespace.
 106          * This is intended for use by subclasses.
 107          *
 108          * @param $namespace Integer
 109          * @param $dbkeys Array
 110          */
 111         protected function invalidatePages( $namespace, array $dbkeys ) {
 112                 if ( $dbkeys === array() ) {
 113                         return;
 114                 }
 115
 116                 /**
 117                  * Determine which pages need to be updated
 118                  * This is necessary to prevent the job queue from smashing the DB with
 119                  * large numbers of concurrent invalidations of the same page
 120                  */
 121                 $now = $this->mDb->timestamp();
 122                 $ids = array();
 123                 $res = $this->mDb->select( 'page', array( 'page_id' ),
 124                         array(
 125                                 'page_namespace' => $namespace,
 126                                 'page_title' => $dbkeys,
 127                                 'page_touched < ' . $this->mDb->addQuotes( $now )
 128                         ), __METHOD__
 129                 );
 130
 131                 foreach ( $res as $row ) {
 132                         $ids[] = $row->page_id;
 133                 }
 134
 135                 if ( $ids === array() ) {
 136                         return;
 137                 }
 138
 139                 /**
 140                  * Do the update
 141                  * We still need the page_touched condition, in case the row has changed since
 142                  * the non-locking select above.
 143                  */
 144                 $this->mDb->update( 'page', array( 'page_touched' => $now ),
 145                         array(
 146                                 'page_id' => $ids,
 147                                 'page_touched < ' . $this->mDb->addQuotes( $now )
 148                         ), __METHOD__
 149                 );
 150         }
 151
 152 }