compressOld.php

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<?php
require_once __DIR__ . '/../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 id to start from (gzip -> text table, concat -> page table)', false, true, 's' );
        $this->addOption( 'extdb', 'Store specified revisions in an external cluster (untested)', false, true );
        $this->addOption( 'endid', 'The page_id to stop at (only when using concat compression type)', 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 ( $res->numRows() == 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 ( $pageRes->numRows() == 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( __METHOD__ );
                $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( __METHOD__ );
                $i += $thisChunkSize;
                wfWaitForSlaves();
            }
            $this->output( "\n" );
        }
        return true;
    }

}

$maintClass = 'CompressOld';
require_once RUN_MAINTENANCE_IF_MAIN;