PostgresUpdater.php

Go to the documentation of this file.

<?php
namespace MediaWiki\Installer;
 
use FixInconsistentRedirects;
use FixWrongPasswordPrefixes;
use MediaWiki\Maintenance\FixAutoblockLogTitles;
use MigrateExternallinks;
use MigrateRevisionCommentTemp;
use PopulateUserIsTemp;
use Wikimedia\Rdbms\DatabasePostgres;
 
class PostgresUpdater extends DatabaseUpdater {
 
    protected $db;
 
    protected function getCoreUpdateList() {
        return [
            // 1.40
            [ 'addField', 'externallinks', 'el_to_path', 'patch-externallinks-el_to_path.sql' ],
 
            // 1.41
            [ 'addField', 'user', 'user_is_temp', 'patch-user-user_is_temp.sql' ],
            [ 'runMaintenance', MigrateRevisionCommentTemp::class ],
            [ 'dropTable', 'revision_comment_temp' ],
            [ 'runMaintenance', MigrateExternallinks::class ],
            [ 'modifyField', 'externallinks', 'el_to', 'patch-externallinks-el_to_default.sql' ],
            [ 'addField', 'pagelinks', 'pl_target_id', 'patch-pagelinks-target_id.sql' ],
            [ 'dropField', 'externallinks', 'el_to', 'patch-externallinks-drop-el_to.sql' ],
            [ 'runMaintenance', FixInconsistentRedirects::class ],
            [ 'modifyField', 'image', 'img_size', 'patch-image-img_size_to_bigint.sql' ],
            [ 'modifyField', 'filearchive', 'fa_size', 'patch-filearchive-fa_size_to_bigint.sql' ],
            [ 'modifyField', 'oldimage', 'oi_size', 'patch-oldimage-oi_size_to_bigint.sql' ],
            [ 'modifyField', 'uploadstash', 'us_size', 'patch-uploadstash-us_size_to_bigint.sql' ],
 
            // 1.42
            [ 'addField', 'user_autocreate_serial', 'uas_year', 'patch-user_autocreate_serial-uas_year.sql' ],
            [ 'addTable', 'block_target', 'patch-block_target.sql' ],
            [ 'dropIndex', 'categorylinks', 'cl_collation_ext', 'patch-drop-cl_collation_ext.sql' ],
            [ 'runMaintenance', PopulateUserIsTemp::class ],
            // Attempt a rename from `site_groups` to `site_group` prior to dropping the `sites` indexes,
            // due to a typo in the original index-renaming database update from MW 1.36. (T374042)
            [ 'renameIndex', 'sites', 'sites_group', 'site_group' ],
            [ 'dropIndex', 'sites', 'site_type', 'patch-sites-drop_indexes.sql' ],
            // Re-attempt to drop most of the dropped `sites`-table indexes:
            // If a Postgres wiki previously ran `update.php` on MW 1.42 or above, the script would have errored after
            // reaching the "DROP INDEX site_group;" line of `patch-sites-drop_indexes.sql` (due to a previous
            // index-renaming typo from MW 1.36).
            // However, as the `site_type` index itself _would_ have been successfully dropped, the `.sql` file listed
            // in the `dropIndex` line above will not be re-applied on any future runs of `update.php`.
            // Therefore, to ensure that the remaining indexes are definitely dropped on these wikis, we need to
            // separately attempt to drop them again. (T374042; T374042#11017896)
            [ 'dropIndex', 'sites', 'site_group', 'patch-sites-drop_site_group_index.sql' ],
            [ 'dropIndex', 'sites', 'site_source', 'patch-sites-drop_site_source_index.sql' ],
            [ 'dropIndex', 'sites', 'site_language', 'patch-sites-drop_site_language_index.sql' ],
            [ 'dropIndex', 'sites', 'site_protocol', 'patch-sites-drop_site_protocol_index.sql' ],
            [ 'dropIndex', 'sites', 'site_domain', 'patch-sites-drop_site_domain_index.sql' ],
            [ 'dropIndex', 'sites', 'site_forward', 'patch-sites-drop_site_forward_index.sql' ],
            [ 'dropIndex', 'iwlinks', 'iwl_prefix_from_title', 'patch-iwlinks-drop-iwl_prefix_from_title.sql' ],
 
            // 1.43
            [ 'migratePagelinks' ],
            [ 'dropDefault', 'revision', 'rev_actor' ],
            [ 'dropDefault', 'revision', 'rev_comment_id' ],
            [ 'changeField', 'revision', 'rev_id', 'BIGINT', '' ],
            [ 'changeField', 'revision', 'rev_parent_id', 'BIGINT', '' ],
            [ 'changeField', 'recentchanges', 'rc_id', 'BIGINT', '' ],
            [ 'changeField', 'change_tag', 'ct_rc_id', 'BIGINT', '' ],
            [ 'runMaintenance', \MigrateBlocks::class ],
            [ 'dropTable', 'ipblocks' ],
            [ 'dropField', 'pagelinks', 'pl_title', 'patch-pagelinks-drop-pl_title.sql' ],
            [ 'addPostDatabaseUpdateMaintenance', FixAutoblockLogTitles::class ],
            [ 'migrateSearchindex' ],
 
            // 1.44
            [ 'addTable', 'file', 'patch-file.sql' ],
            [ 'addField', 'categorylinks', 'cl_target_id', 'patch-categorylinks-target_id.sql' ],
            [ 'addTable', 'collation', 'patch-collation.sql' ],
            [ 'dropTable', 'module_deps' ],
 
            // 1.45
            [ 'addTable', 'existencelinks', 'patch-existencelinks.sql' ],
            [ 'runMaintenance', FixWrongPasswordPrefixes::class ],
            [ 'addIndex', 'categorylinks', 'cl_timestamp_id', 'patch-categorylinks-cl_timestamp_id.sql' ],
            [ 'migrateCategorylinks' ],
            [ 'normalizeCollation' ],
            [ 'modifyPrimaryKey', 'categorylinks', [ 'cl_from', 'cl_target_id' ], 'patch-categorylinks-pk.sql' ],
            [ 'addIndex', 'recentchanges', 'rc_source_name_timestamp',
                'patch-recentchanges-rc_source_name_timestamp.sql' ],
            [ 'addIndex', 'recentchanges', 'rc_name_source_patrolled_timestamp',
                'patch-recentchanges-rc_name_source_patrolled_timestamp.sql' ],
            [ 'dropField', 'recentchanges', 'rc_new', 'patch-recentchanges-drop-rc_new.sql' ],
            [ 'dropField', 'categorylinks', 'cl_to', 'patch-categorylinks-drop-cl_to-cl_collation.sql' ],
 
            // 1.46
            [ 'addTable', 'watchlist_label', 'patch-watchlist_label.sql' ],
            [ 'dropField', 'recentchanges', 'rc_type', 'patch-recentchanges-drop-rc_type.sql' ],
            [ 'dropField', 'archive', 'ar_sha1', 'patch-archive-drop-ar_sha1.sql' ],
            [ 'dropField', 'revision', 'rev_sha1', 'patch-revision-drop-rev_sha1.sql' ],
            [ 'dropField', 'objectcache', 'modtoken', 'patch-objectcache-drop-modtoken.sql' ],
            [ 'addField', 'imagelinks', 'il_target_id', 'patch-imagelinks-add-il_target_id.sql' ],
            [ 'migrateImagelinks' ],
            [ 'modifyPrimaryKey', 'imagelinks', [ 'il_from', 'il_target_id' ], 'patch-imagelinks-pk.sql' ],
            [ 'addMissingTalkPageWatchlistLabels' ],
            [ 'dropField', 'imagelinks', 'il_to', 'patch-imagelinks-drop-il_to.sql' ],
 
            // 1.47
            [ 'addField', 'site_stats', 'ss_temp_users', 'patch-site_stats-temp_users.sql' ],
        ];
    }
 
    protected function getInitialUpdateKeys() {
        return [
            'filearchive-fa_major_mime-patch-fa_major_mime-chemical.sql',
            'image-img_major_mime-patch-img_major_mime-chemical.sql',
            'oldimage-oi_major_mime-patch-oi_major_mime-chemical.sql',
            'user_groups-ug_group-patch-ug_group-length-increase-255.sql',
            'user_former_groups-ufg_group-patch-ufg_group-length-increase-255.sql',
            'user_properties-up_property-patch-up_property.sql',
        ];
    }
 
    protected function describeTable( $table ) {
        $q = <<<END
SELECT attname, attnum FROM pg_namespace, pg_class, pg_attribute
    WHERE pg_class.relnamespace = pg_namespace.oid
        AND attrelid=pg_class.oid AND attnum > 0
        AND relname=%s AND nspname=%s
END;
        $res = $this->db->query(
            sprintf( $q,
                $this->db->addQuotes( $table ),
                $this->db->addQuotes( $this->db->getCoreSchema() )
            ),
            __METHOD__
        );
        if ( !$res ) {
            return null;
        }
 
        $cols = [];
        foreach ( $res as $r ) {
            $cols[] = [
                "name" => $r[0],
                "ord" => $r[1],
            ];
        }
 
        return $cols;
    }
 
    protected function describeIndex( $idx ) {
        // first fetch the key (which is a list of columns ords) and
        // the table the index applies to (an oid)
        $q = <<<END
SELECT indkey, indrelid FROM pg_namespace, pg_class, pg_index
    WHERE nspname=%s
        AND pg_class.relnamespace = pg_namespace.oid
        AND relname=%s
        AND indexrelid=pg_class.oid
END;
        $res = $this->db->query(
            sprintf(
                $q,
                $this->db->addQuotes( $this->db->getCoreSchema() ),
                $this->db->addQuotes( $idx )
            ),
            __METHOD__
        );
        if ( !$res ) {
            return null;
        }
        $r = $res->fetchRow();
        if ( !$r ) {
            return null;
        }
 
        $indkey = $r[0];
        $relid = intval( $r[1] );
        $indkeys = explode( ' ', $indkey );
 
        $colnames = [];
        foreach ( $indkeys as $rid ) {
            $query = <<<END
SELECT attname FROM pg_class, pg_attribute
    WHERE attrelid=$relid
        AND attnum=%d
        AND attrelid=pg_class.oid
END;
            $r2 = $this->db->query( sprintf( $query, $rid ), __METHOD__ );
            if ( !$r2 ) {
                return null;
            }
            $row2 = $r2->fetchRow();
            if ( !$row2 ) {
                return null;
            }
            $colnames[] = $row2[0];
        }
 
        return $colnames;
    }
 
    protected function fkeyDeltype( $fkey ) {
        $q = <<<END
SELECT confdeltype FROM pg_constraint, pg_namespace
    WHERE connamespace=pg_namespace.oid
        AND nspname=%s
        AND conname=%s;
END;
        $r = $this->db->query(
            sprintf(
                $q,
                $this->db->addQuotes( $this->db->getCoreSchema() ),
                $this->db->addQuotes( $fkey )
            ),
            __METHOD__
        );
        $row = $r->fetchRow();
        return $row ? $row[0] : null;
    }
 
    protected function ruleDef( $table, $rule ) {
        $q = <<<END
SELECT definition FROM pg_rules
    WHERE schemaname = %s
        AND tablename = %s
        AND rulename = %s
END;
        $r = $this->db->query(
            sprintf(
                $q,
                $this->db->addQuotes( $this->db->getCoreSchema() ),
                $this->db->addQuotes( $table ),
                $this->db->addQuotes( $rule )
            ),
            __METHOD__
        );
        $row = $r->fetchRow();
        if ( !$row ) {
            return null;
        }
        $d = $row[0];
 
        return $d;
    }
 
    protected function addSequence( $table, $pkey, $ns ) {
        if ( !$this->db->sequenceExists( $ns ) ) {
            $this->output( "Creating sequence $ns\n" );
            if ( $pkey !== false ) {
                $table = $this->db->addIdentifierQuotes( $table );
                $this->db->query( "CREATE SEQUENCE $ns OWNED BY $table.$pkey", __METHOD__ );
                $this->setDefault( $table, $pkey, '"nextval"(\'"' . $ns . '"\'::"regclass")' );
            } else {
                $this->db->query( "CREATE SEQUENCE $ns", __METHOD__ );
            }
        }
    }
 
    protected function dropSequence( $table, $ns ) {
        if ( $this->db->sequenceExists( $ns ) ) {
            $this->output( "Dropping sequence $ns\n" );
            $this->db->query( "DROP SEQUENCE $ns CASCADE", __METHOD__ );
        }
    }
 
    protected function renameSequence( $old, $new ) {
        if ( $this->db->sequenceExists( $new ) ) {
            $this->output( "...sequence $new already exists.\n" );
 
            return;
        }
        if ( $this->db->sequenceExists( $old ) ) {
            $this->output( "Renaming sequence $old to $new\n" );
            $this->db->query( "ALTER SEQUENCE $old RENAME TO $new", __METHOD__ );
        }
    }
 
    protected function setSequenceOwner( $table, $pkey, $seq ) {
        if ( $this->db->sequenceExists( $seq ) ) {
            $this->output( "Setting sequence $seq owner to $table.$pkey\n" );
            $table = $this->db->addIdentifierQuotes( $table );
            $this->db->query( "ALTER SEQUENCE $seq OWNED BY $table.$pkey", __METHOD__ );
        }
    }
 
    protected function renameTable( $old, $new, $patch = false ) {
        $updateMsg = "Renaming table $old to $new";
        if ( !$this->checkSchemaAltersAllowed( $updateMsg ) ) {
            return;
        }
 
        if ( $this->db->tableExists( $old, __METHOD__ ) ) {
            $this->output( "$updateMsg\n" );
            $old = $this->db->addIdentifierQuotes( $old );
            $new = $this->db->addIdentifierQuotes( $new );
            $this->db->query( "ALTER TABLE $old RENAME TO $new", __METHOD__ );
            if ( $patch !== false ) {
                $this->applyPatch( $patch );
            }
        }
    }
 
    protected function renameIndex(
        $table, $old, $new, $skipBothIndexExistWarning = false, $a = false, $b = false
    ) {
        if ( !$this->checkSchemaAltersAllowed(
            "Renaming index $old to $new in table $table"
        ) ) {
            return false;
        }
 
        // First requirement: the table must exist
        if ( !$this->db->tableExists( $table, __METHOD__ ) ) {
            $this->output( "...skipping: '$table' table doesn't exist yet.\n" );
 
            return true;
        }
 
        // Second requirement: the new index must be missing
        if ( $this->db->indexExists( $table, $new, __METHOD__ ) ) {
            $this->output( "...index $new already set on $table table.\n" );
            if ( !$skipBothIndexExistWarning
                && $this->db->indexExists( $table, $old, __METHOD__ )
            ) {
                $this->output( "...WARNING: $old still exists, despite it has been " .
                    "renamed into $new (which also exists).\n" .
                    "            $old should be manually removed if not needed anymore.\n" );
            }
 
            return true;
        }
 
        // Third requirement: the old index must exist
        if ( !$this->db->indexExists( $table, $old, __METHOD__ ) ) {
            $this->output( "...skipping: index $old doesn't exist.\n" );
 
            return true;
        }
 
        $this->db->query( "ALTER INDEX $old RENAME TO $new", __METHOD__ );
        return true;
    }
 
    protected function dropPgField( $table, $field ) {
        $updateMsg = "Dropping column '$table.$field'";
        if ( !$this->checkSchemaAltersAllowed( $updateMsg ) ) {
            return;
        }
 
        $fi = $this->db->fieldInfo( $table, $field );
        if ( $fi === null ) {
            $this->output( "...$table table does not contain $field field.\n" );
        } else {
            $this->output( "$updateMsg\n" );
            $table = $this->db->addIdentifierQuotes( $table );
            $this->db->query( "ALTER TABLE $table DROP COLUMN $field", __METHOD__ );
        }
    }
 
    protected function addPgField( $table, $field, $type ) {
        $updateMsg = "Adding column '$table.$field'";
        if ( !$this->checkSchemaAltersAllowed( $updateMsg ) ) {
            return;
        }
 
        $fi = $this->db->fieldInfo( $table, $field );
        if ( $fi !== null ) {
            $this->output( "...column '$table.$field' already exists\n" );
        } else {
            $this->output( "$updateMsg'\n" );
            $table = $this->db->addIdentifierQuotes( $table );
            $this->db->query( "ALTER TABLE $table ADD $field $type", __METHOD__ );
        }
    }
 
    protected function changeField( $table, $field, $newtype, $default ) {
        if ( !$this->checkSchemaAltersAllowed( "Changing column type of '$table.$field' to '$newtype'" ) ) {
            return;
        }
 
        if ( !$this->db->tableExists( $table, __METHOD__ ) ) {
            $this->output( "...$table table does not exist, skipping default change.\n" );
            return;
        }
        $fi = $this->db->fieldInfo( $table, $field );
        if ( $fi === null ) {
            $this->output( "...ERROR: expected column $table.$field to exist\n" );
            exit( 1 );
        }
 
        if ( $fi->type() === strtolower( $newtype ) ) {
            $this->output( "...column '$table.$field' is already of type '$newtype'\n" );
        } else {
            $this->output( "Changing column type of '$table.$field' from '{$fi->type()}' to '$newtype'\n" );
            $table = $this->db->addIdentifierQuotes( $table );
            $sql = "ALTER TABLE $table ALTER $field TYPE $newtype";
            if ( $default !== '' ) {
                $res = [];
                if ( preg_match( '/DEFAULT (.+)/', $default, $res ) ) {
                    $sqldef = "ALTER TABLE $table ALTER $field SET DEFAULT $res[1]";
                    $this->db->query( $sqldef, __METHOD__ );
                    $default = preg_replace( '/\s*DEFAULT .+/', '', $default );
                }
                $sql .= " USING $default";
            }
            $this->db->query( $sql, __METHOD__ );
        }
    }
 
    protected function changeFieldPurgeTable( $table, $field, $newtype, $default ) {
        if ( !$this->checkSchemaAltersAllowed(
            "Changing column type of '$table.$field' to '$newtype'"
        ) ) {
            return;
        }
 
        # # For a cache table, empty it if the field needs to be changed, because the old contents
        # # may be corrupted.  If the column is already the desired type, refrain from purging.
        $fi = $this->db->fieldInfo( $table, $field );
        if ( $fi === null ) {
            $this->output( "...ERROR: expected column $table.$field to exist\n" );
            exit( 1 );
        }
 
        if ( $fi->type() === $newtype ) {
            $this->output( "...column '$table.$field' is already of type '$newtype'\n" );
        } else {
            $this->output( "Purging data from cache table '$table'\n" );
            $table = $this->db->addIdentifierQuotes( $table );
            $this->db->query( "DELETE from $table", __METHOD__ );
            $this->output( "Changing column type of '$table.$field' from '{$fi->type()}' to '$newtype'\n" );
            $sql = "ALTER TABLE $table ALTER $field TYPE $newtype";
            if ( strlen( $default ) ) {
                $res = [];
                if ( preg_match( '/DEFAULT (.+)/', $default, $res ) ) {
                    $sqldef = "ALTER TABLE $table ALTER $field SET DEFAULT $res[1]";
                    $this->db->query( $sqldef, __METHOD__ );
                    $default = preg_replace( '/\s*DEFAULT .+/', '', $default );
                }
                $sql .= " USING $default";
            }
            $this->db->query( $sql, __METHOD__ );
        }
    }
 
    protected function setDefault( $table, $field, $default ) {
        $updateMsg = "Changing '$table.$field' default value";
        if ( !$this->checkSchemaAltersAllowed( $updateMsg ) ) {
            return;
        }
 
        if ( !$this->db->tableExists( $table, __METHOD__ ) ) {
            $this->output( "...$table table does not exist, skipping default change.\n" );
            return;
        }
        $info = $this->db->fieldInfo( $table, $field );
        if ( $info && $info->defaultValue() !== $default ) {
            $this->output( "$updateMsg\n" );
            $table = $this->db->addIdentifierQuotes( $table );
            $this->db->query( "ALTER TABLE $table ALTER $field SET DEFAULT "
                . $this->db->addQuotes( $default ), __METHOD__ );
        }
    }
 
    protected function dropDefault( $table, $field ) {
        $updateMsg = "Dropping '$table.$field' default value";
        if ( !$this->checkSchemaAltersAllowed( $updateMsg ) ) {
            return;
        }
 
        $info = $this->db->fieldInfo( $table, $field );
        if ( $info && $info->defaultValue() !== false ) {
            $this->output( "$updateMsg\n" );
            $table = $this->db->addIdentifierQuotes( $table );
            $this->db->query( "ALTER TABLE $table ALTER $field DROP DEFAULT", __METHOD__ );
        }
    }
 
    protected function changeNullableField( $table, $field, $null, $update = false ) {
        $updateMsg = "Changing field '$table.$field' to ";
        if ( $null === 'NOT NULL' ) {
            $updateMsg .= 'not allow NULLs';
        } else {
            $updateMsg .= 'allow NULLs';
        }
        if ( !$this->checkSchemaAltersAllowed( $updateMsg ) ) {
            return;
        }
 
        $fi = $this->db->fieldInfo( $table, $field );
        if ( $fi === null ) {
            return;
        }
        if ( $fi->isNullable() ) {
            # # It's NULL - does it need to be NOT NULL?
            if ( $null === 'NOT NULL' ) {
                $this->output( "$updateMsg\n" );
                $table = $this->db->addIdentifierQuotes( $table );
                if ( $update ) {
                    $this->db->query( "UPDATE $table SET $field = DEFAULT WHERE $field IS NULL", __METHOD__ );
                }
                $this->db->query( "ALTER TABLE $table ALTER $field SET NOT NULL", __METHOD__ );
            } else {
                $this->output( "...column '$table.$field' is already set as NULL\n" );
            }
        } else {
            # # It's NOT NULL - does it need to be NULL?
            if ( $null === 'NULL' ) {
                $this->output( "$updateMsg\n" );
                $table = $this->db->addIdentifierQuotes( $table );
                $this->db->query( "ALTER TABLE $table ALTER $field DROP NOT NULL", __METHOD__ );
            } else {
                $this->output( "...column '$table.$field' is already set as NOT NULL\n" );
            }
        }
    }
 
    protected function addPgIndex( $table, $index, $type, $unique = false ) {
        $updateMsg = "Creating index '$index' on table '$table' $type";
        if ( !$this->checkSchemaAltersAllowed( $updateMsg ) ) {
            return;
        }
 
        if ( !$this->db->tableExists( $table, __METHOD__ ) ) {
            $this->output( "...$table table does not exist, skipping index.\n" );
        } elseif ( $this->db->indexExists( $table, $index, __METHOD__ ) ) {
            $this->output( "...index '$index' on table '$table' already exists\n" );
        } else {
            $this->output( "$updateMsg\n" );
            $table = $this->db->addIdentifierQuotes( $table );
            $unique = $unique ? 'UNIQUE' : '';
            $this->db->query( "CREATE $unique INDEX $index ON $table $type", __METHOD__ );
        }
    }
 
    protected function addPgExtIndex( $table, $index, $type ) {
        $updateMsg = "Creating index '$index' on table '$table'";
        if ( !$this->checkSchemaAltersAllowed( $updateMsg ) ) {
            return;
        }
 
        if ( $this->db->indexExists( $table, $index, __METHOD__ ) ) {
            $this->output( "...index '$index' on table '$table' already exists\n" );
        } elseif ( preg_match( '/^\‍(/', $type ) ) {
            $this->output( "Creating index '$index' on table '$table'\n" );
            $table = $this->db->addIdentifierQuotes( $table );
            $this->db->query( "CREATE INDEX $index ON $table $type", __METHOD__ );
        } else {
            $this->applyPatch( $type, true, $updateMsg );
        }
    }
 
    protected function dropFkey( $table, $field ) {
        $updateMsg = "Dropping foreign key constraint on '$table.$field'";
        if ( !$this->checkSchemaAltersAllowed( $updateMsg ) ) {
            return;
        }
 
        if ( !$this->db->tableExists( $table, __METHOD__ ) ) {
            $this->output( "...$table table does not exist, skipping constraint change.\n" );
            return;
        }
        $fi = $this->db->fieldInfo( $table, $field );
        if ( $fi === null ) {
            $this->output( "WARNING! Column '$table.$field' does not exist but it should! " .
                "Please report this.\n" );
            return;
        }
 
        if ( $this->dropConstraint( $table, $field, 'foreignkey', $fi->conname() ) ) {
            $this->output( "$updateMsg\n" );
        } else {
            $this->output( "...foreign key constraint on '$table.$field' already does not exist\n" );
        }
    }
 
    protected function changeFkeyDeferrable( $table, $field, $clause ) {
        $updateMsg = "Altering column '$table.$field' to be DEFERRABLE INITIALLY DEFERRED";
        if ( !$this->checkSchemaAltersAllowed( $updateMsg ) ) {
            return;
        }
 
        $fi = $this->db->fieldInfo( $table, $field );
        if ( $fi === null ) {
            $this->output( "WARNING! Column '$table.$field' does not exist but it should! " .
                "Please report this.\n" );
 
            return;
        }
        if ( $fi->is_deferred() && $fi->is_deferrable() ) {
            return;
        }
        $this->output( "$updateMsg\n" );
 
        $conname = $fi->conname();
        $conclause = "CONSTRAINT \"$conname\"";
 
        if ( !$this->dropConstraint( $table, $field, 'foreignkey', $conname ) ) {
            $this->output( "Column '$table.$field' does not have a foreign key " .
                "constraint, will be added\n" );
            $conclause = "";
        }
 
        $command =
            "ALTER TABLE $table ADD $conclause " .
            "FOREIGN KEY ($field) REFERENCES $clause DEFERRABLE INITIALLY DEFERRED";
        $this->db->query( $command, __METHOD__ );
    }
 
    protected function dropPgIndex( $table, $index ) {
        $updateMsg = "Dropping obsolete index '$index'";
        if ( !$this->checkSchemaAltersAllowed( $updateMsg ) ) {
            return;
        }
 
        if ( $this->db->indexExists( $table, $index, __METHOD__ ) ) {
            $this->output( "$updateMsg\n" );
            $this->db->query( "DROP INDEX \"" . $index . "\"", __METHOD__ );
        }
    }
 
    protected function checkIndex( $index, $should_be, $good_def ) {
        if ( !$this->checkSchemaAltersAllowed(
            "Checking if index '$index' is up to date"
        ) ) {
            return;
        }
 
        $pu = $this->db->indexAttributes( $index );
        if ( $pu && $pu != $should_be ) {
            $this->output( "Dropping obsolete version of index '$index'\n" );
            $this->db->query( "DROP INDEX \"" . $index . "\"", __METHOD__ );
            $pu = [];
        } else {
            $this->output( "...no need to drop index '$index'\n" );
        }
 
        if ( !$pu ) {
            $this->output( "Creating index '$index'\n" );
            $this->db->query( $good_def, __METHOD__ );
        } else {
            $this->output( "...index '$index' exists\n" );
        }
    }
 
    protected function changePrimaryKey( $table, $shouldBe, $constraintName = null ) {
        if ( !$this->checkSchemaAltersAllowed( "Changing primary key on $table" ) ) {
            return;
        }
 
        // https://wiki.postgresql.org/wiki/Retrieve_primary_key_columns
        $result = $this->db->query(
            "SELECT a.attname as column " .
                "FROM pg_index i " .
                "JOIN pg_attribute a ON a.attrelid = i.indrelid " .
                "AND a.attnum = ANY(i.indkey) " .
                "WHERE i.indrelid = '\"$table\"'::regclass " .
                "AND i.indisprimary",
            __METHOD__
        );
        $currentColumns = [];
        foreach ( $result as $row ) {
            $currentColumns[] = $row->column;
        }
 
        if ( $currentColumns == $shouldBe ) {
            $this->output( "...no need to change primary key of '$table'\n" );
            return;
        }
 
        $this->dropConstraint( $table, '', 'primary', $constraintName );
 
        $table = $this->db->addIdentifierQuotes( $table );
        $this->db->query(
            "ALTER TABLE $table" .
            " ADD PRIMARY KEY (" . implode( ',', $shouldBe ) . ');',
            __METHOD__
        );
    }
 
    protected function dropConstraint( $table, $field, $type, $conname = null ) {
        if ( !$this->checkSchemaAltersAllowed( "Dropping constraint on $table for $field" ) ) {
            return false;
        }
 
        if ( $conname === null ) {
            if ( $type == 'primary' ) {
                $conname = "{$table}_pkey";
            } else {
                $map = [ 'unique' => 'key', 'check' => 'check', 'foreignkey' => 'fkey' ];
                $conname = "{$table}_{$field}_{$map[$type]}";
            }
        }
 
        if ( $this->db->constraintExists( $table, $conname ) ) {
            $table = $this->db->addIdentifierQuotes( $table );
            $this->db->query(
                "ALTER TABLE $table DROP CONSTRAINT $conname;",
                __METHOD__
            );
 
            return true;
        }
 
        return false;
    }
 
    protected function migrateSearchindex() {
        $updateKey = 'searchindex-pk-titlelength';
        if ( !$this->tableExists( 'searchindex' ) ) {
            return;
        }
 
        $primaryIndexExists = $this->db->indexExists( 'searchindex', 'searchindex_pkey', __METHOD__ );
        if ( $this->updateRowExists( $updateKey ) || ( $primaryIndexExists ) ) {
            $this->outputApplied( "...searchindex table has already been migrated.\n" );
            if ( !$this->updateRowExists( $updateKey ) ) {
                $this->insertUpdateRow( $updateKey );
            }
            return;
        }
 
        $apply = $this->applyPatch( 'patch-searchindex-pk-titlelength.sql', false, '...migrating searchindex table' );
 
        if ( $apply ) {
            $this->insertUpdateRow( $updateKey );
        }
    }
}