compressOld.php

Go to the documentation of this file.

<?php
require_once( dirname( __FILE__ ) . '/../Maintenance.php' );

class CompressOld extends Maintenance {
        const LS_INDIVIDUAL = 0;
        const LS_CHUNKED    = 1;

        public function __construct() {
                parent::__construct();
                $this->mDescription = 'Compress the text of a wiki';
                $this->addOption( 'type', 'Set compression type to either: gzip|concat', false, true, 't' );
                $this->addOption( 'chunksize', 'Maximum number of revisions in a concat chunk', false, true, 'c' );
                $this->addOption( 'begin-date', 'Earliest date to check for uncompressed revisions', false, true, 'b' );
                $this->addOption( 'end-date', 'Latest revision date to compress', false, true, 'e' );
                $this->addOption( 'startid', 'The old_id to start from', false, true, 's' );
                $this->addOption( 'extdb', 'Store specified revisions in an external cluster (untested)', false, true );
                $this->addOption( 'endid', 'Stop at this old_id', false, true, 'n' );
        }

        public function execute() {
                global $wgDBname;
                if ( !function_exists( "gzdeflate" ) ) {
                        $this->error( "You must enable zlib support in PHP to compress old revisions!\n" .
                                "Please see http://www.php.net/manual/en/ref.zlib.php\n", true );
                }

                $type = $this->getOption( 'type', 'concat' );
                $chunkSize = $this->getOption( 'chunksize', 20 );
                $startId = $this->getOption( 'startid', 0 );
                $beginDate = $this->getOption( 'begin-date', '' );
                $endDate = $this->getOption( 'end-date', '' );
                $extDB = $this->getOption( 'extdb', '' );
                $endId = $this->getOption( 'endid', false );

                if ( $type != 'concat' && $type != 'gzip' ) {
                        $this->error( "Type \"{$type}\" not supported" );
                }

                if ( $extDB != '' ) {
                        $this->output( "Compressing database {$wgDBname} to external cluster {$extDB}\n"
                                . str_repeat( '-', 76 ) . "\n\n" );
                } else {
                        $this->output( "Compressing database {$wgDBname}\n"
                                . str_repeat( '-', 76 ) . "\n\n" );
                }

                $success = true;
                if ( $type == 'concat' ) {
                        $success = $this->compressWithConcat( $startId, $chunkSize, $beginDate,
                                $endDate, $extDB, $endId );
                } else {
                        $this->compressOldPages( $startId, $extDB );
                }

                if ( $success ) {
                        $this->output( "Done.\n" );
                }
        }

        private function compressOldPages( $start = 0, $extdb = '' ) {
                $chunksize = 50;
                $this->output( "Starting from old_id $start...\n" );
                $dbw = wfGetDB( DB_MASTER );
                do {
                        $res = $dbw->select( 'text', array( 'old_id','old_flags','old_text' ),
                                "old_id>=$start", __METHOD__, array( 'ORDER BY' => 'old_id', 'LIMIT' => $chunksize, 'FOR UPDATE' ) );
                        if( $dbw->numRows( $res ) == 0 ) {
                                break;
                        }
                        $last = $start;
                        foreach ( $res as $row ) {
                                # print "  {$row->old_id} - {$row->old_namespace}:{$row->old_title}\n";
                                $this->compressPage( $row, $extdb );
                                $last = $row->old_id;
                        }
                        $start = $last + 1; # Deletion may leave long empty stretches
                        $this->output( "$start...\n" );
                } while( true );
        }

        private function compressPage( $row, $extdb ) {
                if ( false !== strpos( $row->old_flags, 'gzip' ) || false !== strpos( $row->old_flags, 'object' ) ) {
                        #print "Already compressed row {$row->old_id}\n";
                        return false;
                }
                $dbw = wfGetDB( DB_MASTER );
                $flags = $row->old_flags ? "{$row->old_flags},gzip" : "gzip";
                $compress = gzdeflate( $row->old_text );

                # Store in external storage if required
                if ( $extdb !== '' ) {
                        $storeObj = new ExternalStoreDB;
                        $compress = $storeObj->store( $extdb, $compress );
                        if ( $compress === false ) {
                                $this->error( "Unable to store object" );
                                return false;
                        }
                }

                # Update text row
                $dbw->update( 'text',
                        array( /* SET */
                                'old_flags' => $flags,
                                'old_text' => $compress
                        ), array( /* WHERE */
                                'old_id' => $row->old_id
                        ), __METHOD__,
                        array( 'LIMIT' => 1 )
                );
                return true;
        }

        private function compressWithConcat( $startId, $maxChunkSize, $beginDate,
                $endDate, $extdb = "", $maxPageId = false )
        {
                $loadStyle = self::LS_CHUNKED;

                $dbr = wfGetDB( DB_SLAVE );
                $dbw = wfGetDB( DB_MASTER );

                # Set up external storage
                if ( $extdb != '' ) {
                        $storeObj = new ExternalStoreDB;
                }

                # Get all articles by page_id
                if ( !$maxPageId ) {
                        $maxPageId = $dbr->selectField( 'page', 'max(page_id)', '', __METHOD__ );
                }
                $this->output( "Starting from $startId of $maxPageId\n" );
                $pageConds = array();

                /*
                if ( $exclude_ns0 ) {
                        print "Excluding main namespace\n";
                        $pageConds[] = 'page_namespace<>0';
                }
                if ( $queryExtra ) {
                                        $pageConds[] = $queryExtra;
                }
                 */

                # For each article, get a list of revisions which fit the criteria

                # No recompression, use a condition on old_flags
                # Don't compress object type entities, because that might produce data loss when
                # overwriting bulk storage concat rows. Don't compress external references, because
                # the script doesn't yet delete rows from external storage.
                $conds = array(
                        'old_flags NOT ' . $dbr->buildLike( $dbr->anyString(), 'object', $dbr->anyString() ) . ' AND old_flags NOT '
                                . $dbr->buildLike( $dbr->anyString(), 'external', $dbr->anyString() ) );

                if ( $beginDate ) {
                        if ( !preg_match( '/^\d{14}$/', $beginDate ) ) {
                                $this->error( "Invalid begin date \"$beginDate\"\n" );
                                return false;
                        }
                        $conds[] = "rev_timestamp>'" . $beginDate . "'";
                }
                if ( $endDate )  {
                        if ( !preg_match( '/^\d{14}$/', $endDate ) ) {
                                $this->error( "Invalid end date \"$endDate\"\n" );
                                return false;
                        }
                        $conds[] = "rev_timestamp<'" . $endDate . "'";
                }
                if ( $loadStyle == self::LS_CHUNKED ) {
                        $tables = array( 'revision', 'text' );
                        $fields = array( 'rev_id', 'rev_text_id', 'old_flags', 'old_text' );
                        $conds[] = 'rev_text_id=old_id';
                        $revLoadOptions = 'FOR UPDATE';
                } else {
                        $tables = array( 'revision' );
                        $fields = array( 'rev_id', 'rev_text_id' );
                        $revLoadOptions = array();
                }

                # Don't work with current revisions
                # Don't lock the page table for update either -- TS 2006-04-04
                #$tables[] = 'page';
                #$conds[] = 'page_id=rev_page AND rev_id != page_latest';

                for ( $pageId = $startId; $pageId <= $maxPageId; $pageId++ ) {
                        wfWaitForSlaves();

                        # Wake up
                        $dbr->ping();

                        # Get the page row
                        $pageRes = $dbr->select( 'page',
                                array('page_id', 'page_namespace', 'page_title','page_latest'),
                                $pageConds + array('page_id' => $pageId), __METHOD__ );
                        if ( $dbr->numRows( $pageRes ) == 0 ) {
                                continue;
                        }
                        $pageRow = $dbr->fetchObject( $pageRes );

                        # Display progress
                        $titleObj = Title::makeTitle( $pageRow->page_namespace, $pageRow->page_title );
                        $this->output( "$pageId\t" . $titleObj->getPrefixedDBkey() . " " );

                        # Load revisions
                        $revRes = $dbw->select( $tables, $fields,
                                array_merge( array(
                                        'rev_page' => $pageRow->page_id,
                                        # Don't operate on the current revision
                                        # Use < instead of <> in case the current revision has changed
                                        # since the page select, which wasn't locking
                                        'rev_id < ' . $pageRow->page_latest
                                ), $conds ),
                                __METHOD__,
                                $revLoadOptions
                        );
                        $revs = array();
                        foreach ( $revRes as $revRow ) {
                                $revs[] = $revRow;
                        }

                        if ( count( $revs ) < 2) {
                                # No revisions matching, no further processing
                                $this->output( "\n" );
                                continue;
                        }

                        # For each chunk
                        $i = 0;
                        while ( $i < count( $revs ) ) {
                                if ( $i < count( $revs ) - $maxChunkSize ) {
                                        $thisChunkSize = $maxChunkSize;
                                } else {
                                        $thisChunkSize = count( $revs ) - $i;
                                }

                                $chunk = new ConcatenatedGzipHistoryBlob();
                                $stubs = array();
                                $dbw->begin();
                                $usedChunk = false;
                                $primaryOldid = $revs[$i]->rev_text_id;

                                # Get the text of each revision and add it to the object
                                for ( $j = 0; $j < $thisChunkSize && $chunk->isHappy(); $j++ ) {
                                        $oldid = $revs[$i + $j]->rev_text_id;

                                        # Get text
                                        if ( $loadStyle == self::LS_INDIVIDUAL ) {
                                                $textRow = $dbw->selectRow( 'text',
                                                        array( 'old_flags', 'old_text' ),
                                                        array( 'old_id' => $oldid ),
                                                        __METHOD__,
                                                        'FOR UPDATE'
                                                );
                                                $text = Revision::getRevisionText( $textRow );
                                        } else {
                                                $text = Revision::getRevisionText( $revs[$i + $j] );
                                        }

                                        if ( $text === false ) {
                                                $this->error( "\nError, unable to get text in old_id $oldid" );
                                                #$dbw->delete( 'old', array( 'old_id' => $oldid ) );
                                        }

                                        if ( $extdb == "" && $j == 0 ) {
                                                $chunk->setText( $text );
                                                $this->output( '.' );
                                        } else {
                                                # Don't make a stub if it's going to be longer than the article
                                                # Stubs are typically about 100 bytes
                                                if ( strlen( $text ) < 120 ) {
                                                        $stub = false;
                                                        $this->output( 'x' );
                                                } else {
                                                        $stub = new HistoryBlobStub( $chunk->addItem( $text ) );
                                                        $stub->setLocation( $primaryOldid );
                                                        $stub->setReferrer( $oldid );
                                                        $this->output( '.' );
                                                        $usedChunk = true;
                                                }
                                                $stubs[$j] = $stub;
                                        }
                                }
                                $thisChunkSize = $j;

                                # If we couldn't actually use any stubs because the pages were too small, do nothing
                                if ( $usedChunk ) {
                                        if ( $extdb != "" ) {
                                                # Move blob objects to External Storage
                                                $stored = $storeObj->store( $extdb, serialize( $chunk ));
                                                if ($stored === false) {
                                                        $this->error(  "Unable to store object" );
                                                        return false;
                                                }
                                                # Store External Storage URLs instead of Stub placeholders
                                                foreach ($stubs as $stub) {
                                                        if ($stub===false)
                                                                continue;
                                                        # $stored should provide base path to a BLOB
                                                        $url = $stored."/".$stub->getHash();
                                                        $dbw->update( 'text',
                                                                array( /* SET */
                                                                        'old_text' => $url,
                                                                        'old_flags' => 'external,utf-8',
                                                                ), array ( /* WHERE */
                                                                        'old_id' => $stub->getReferrer(),
                                                                )
                                                        );
                                                }
                                        } else {
                                                # Store the main object locally
                                                $dbw->update( 'text',
                                                        array( /* SET */
                                                                'old_text' => serialize( $chunk ),
                                                                'old_flags' => 'object,utf-8',
                                                        ), array( /* WHERE */
                                                                'old_id' => $primaryOldid
                                                        )
                                                );

                                                # Store the stub objects
                                                for ( $j = 1; $j < $thisChunkSize; $j++ ) {
                                                        # Skip if not compressing and don't overwrite the first revision
                                                        if ( $stubs[$j] !== false && $revs[$i + $j]->rev_text_id != $primaryOldid ) {
                                                                $dbw->update( 'text',
                                                                        array( /* SET */
                                                                                'old_text' => serialize($stubs[$j]),
                                                                                'old_flags' => 'object,utf-8',
                                                                        ), array( /* WHERE */
                                                                                'old_id' => $revs[$i + $j]->rev_text_id
                                                                        )
                                                                );
                                                        }
                                                }
                                        }
                                }
                                # Done, next
                                $this->output( "/" );
                                $dbw->commit();
                                $i += $thisChunkSize;
                                wfWaitForSlaves();
                        }
                        $this->output( "\n" );
                }
                return true;
        }

}

$maintClass = 'CompressOld';
require_once( RUN_MAINTENANCE_IF_MAIN );