test SQL for our QueryPages objects

[mediawiki.git] / includes / db / DatabasePostgres.php

<?php
/**
 * This is the Postgres database abstraction layer.
 *
 * @file
 * @ingroup Database
 */

class PostgresField implements Field {
        private $name, $tablename, $type, $nullable, $max_length, $deferred, $deferrable, $conname;

        /**
         * @param $db DatabaseBase
         * @param  $table
         * @param  $field
         * @return null|PostgresField
         */
        static function fromText( $db, $table, $field ) {
                global $wgDBmwschema;

                $q = <<<SQL
SELECT
 attnotnull, attlen, COALESCE(conname, '') AS conname,
 COALESCE(condeferred, 'f') AS deferred,
 COALESCE(condeferrable, 'f') AS deferrable,
 CASE WHEN typname = 'int2' THEN 'smallint'
  WHEN typname = 'int4' THEN 'integer'
  WHEN typname = 'int8' THEN 'bigint'
  WHEN typname = 'bpchar' THEN 'char'
 ELSE typname END AS typname
FROM pg_class c
JOIN pg_namespace n ON (n.oid = c.relnamespace)
JOIN pg_attribute a ON (a.attrelid = c.oid)
JOIN pg_type t ON (t.oid = a.atttypid)
LEFT JOIN pg_constraint o ON (o.conrelid = c.oid AND a.attnum = ANY(o.conkey) AND o.contype = 'f')
WHERE relkind = 'r'
AND nspname=%s
AND relname=%s
AND attname=%s;
SQL;

                $table = $db->tableName( $table, 'raw' );
                $res = $db->query(
                        sprintf( $q,
                                $db->addQuotes( $wgDBmwschema ),
                                $db->addQuotes( $table ),
                                $db->addQuotes( $field )
                        )
                );
                $row = $db->fetchObject( $res );
                if ( !$row ) {
                        return null;
                }
                $n = new PostgresField;
                $n->type = $row->typname;
                $n->nullable = ( $row->attnotnull == 'f' );
                $n->name = $field;
                $n->tablename = $table;
                $n->max_length = $row->attlen;
                $n->deferrable = ( $row->deferrable == 't' );
                $n->deferred = ( $row->deferred == 't' );
                $n->conname = $row->conname;
                return $n;
        }

        function name() {
                return $this->name;
        }

        function tableName() {
                return $this->tablename;
        }

        function type() {
                return $this->type;
        }

        function isNullable() {
                return $this->nullable;
        }

        function maxLength() {
                return $this->max_length;
        }

        function is_deferrable() {
                return $this->deferrable;
        }

        function is_deferred() {
                return $this->deferred;
        }

        function conname() {
                return $this->conname;
        }

}

/**
 * @ingroup Database
 */
class DatabasePostgres extends DatabaseBase {
        var $mInsertId = null;
        var $mLastResult = null;
        var $numeric_version = null;
        var $mAffectedRows = null;

        function getType() {
                return 'postgres';
        }

        function cascadingDeletes() {
                return true;
        }
        function cleanupTriggers() {
                return true;
        }
        function strictIPs() {
                return true;
        }
        function realTimestamps() {
                return true;
        }
        function implicitGroupby() {
                return false;
        }
        function implicitOrderby() {
                return false;
        }
        function searchableIPs() {
                return true;
        }
        function functionalIndexes() {
                return true;
        }

        function hasConstraint( $name ) {
                global $wgDBmwschema;
                $SQL = "SELECT 1 FROM pg_catalog.pg_constraint c, pg_catalog.pg_namespace n WHERE c.connamespace = n.oid AND conname = '" .
                                pg_escape_string( $this->mConn, $name ) . "' AND n.nspname = '" . pg_escape_string( $this->mConn, $wgDBmwschema ) ."'";
                $res = $this->doQuery( $SQL );
                return $this->numRows( $res );
        }

        /**
         * Usually aborts on failure
         */
        function open( $server, $user, $password, $dbName ) {
                # Test for Postgres support, to avoid suppressed fatal error
                if ( !function_exists( 'pg_connect' ) ) {
                        throw new DBConnectionError( $this, "Postgres functions missing, have you compiled PHP with the --with-pgsql option?\n (Note: if you recently installed PHP, you may need to restart your webserver and database)\n" );
                }

                global $wgDBport;

                if ( !strlen( $user ) ) { # e.g. the class is being loaded
                        return;
                }

                $this->close();
                $this->mServer = $server;
                $port = $wgDBport;
                $this->mUser = $user;
                $this->mPassword = $password;
                $this->mDBname = $dbName;

                $connectVars = array(
                        'dbname' => $dbName,
                        'user' => $user,
                        'password' => $password
                );
                if ( $server != false && $server != '' ) {
                        $connectVars['host'] = $server;
                }
                if ( $port != false && $port != '' ) {
                        $connectVars['port'] = $port;
                }
                $connectString = $this->makeConnectionString( $connectVars, PGSQL_CONNECT_FORCE_NEW );

                $this->installErrorHandler();
                $this->mConn = pg_connect( $connectString );
                $phpError = $this->restoreErrorHandler();

                if ( !$this->mConn ) {
                        wfDebug( "DB connection error\n" );
                        wfDebug( "Server: $server, Database: $dbName, User: $user, Password: " . substr( $password, 0, 3 ) . "...\n" );
                        wfDebug( $this->lastError() . "\n" );
                        throw new DBConnectionError( $this, str_replace( "\n", ' ', $phpError ) );
                }

                $this->mOpened = true;

                global $wgCommandLineMode;
                # If called from the command-line (e.g. importDump), only show errors
                if ( $wgCommandLineMode ) {
                        $this->doQuery( "SET client_min_messages = 'ERROR'" );
                }

                $this->query( "SET client_encoding='UTF8'", __METHOD__ );
                $this->query( "SET datestyle = 'ISO, YMD'", __METHOD__ );
                $this->query( "SET timezone = 'GMT'", __METHOD__ );
                $this->query( "SET standard_conforming_strings = on", __METHOD__ );

                global $wgDBmwschema;
                if ( $this->schemaExists( $wgDBmwschema ) ) {
                        $safeschema = $this->addIdentifierQuotes( $wgDBmwschema );
                        $this->doQuery( "SET search_path = $safeschema" );
                } else {
                        $this->doQuery( "SET search_path = public" );
                }

                return $this->mConn;
        }

        /**
         * Postgres doesn't support selectDB in the same way MySQL does. So if the
         * DB name doesn't match the open connection, open a new one
         * @return
         */
        function selectDB( $db ) {
                if ( $this->mDBname !== $db ) {
                        return (bool)$this->open( $this->mServer, $this->mUser, $this->mPassword, $db );
                } else {
                        return true;
                }
        }

        function makeConnectionString( $vars ) {
                $s = '';
                foreach ( $vars as $name => $value ) {
                        $s .= "$name='" . str_replace( "'", "\\'", $value ) . "' ";
                }
                return $s;
        }

        /**
         * Closes a database connection, if it is open
         * Returns success, true if already closed
         */
        function close() {
                $this->mOpened = false;
                if ( $this->mConn ) {
                        return pg_close( $this->mConn );
                } else {
                        return true;
                }
        }

        protected function doQuery( $sql ) {
                if ( function_exists( 'mb_convert_encoding' ) ) {
                        $sql = mb_convert_encoding( $sql, 'UTF-8' );
                }
                $this->mLastResult = pg_query( $this->mConn, $sql );
                $this->mAffectedRows = null; // use pg_affected_rows(mLastResult)
                return $this->mLastResult;
        }

        function queryIgnore( $sql, $fname = 'DatabasePostgres::queryIgnore' ) {
                return $this->query( $sql, $fname, true );
        }

        function freeResult( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                wfSuppressWarnings();
                $ok = pg_free_result( $res );
                wfRestoreWarnings();
                if ( !$ok ) {
                        throw new DBUnexpectedError( $this, "Unable to free Postgres result\n" );
                }
        }

        function fetchObject( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                wfSuppressWarnings();
                $row = pg_fetch_object( $res );
                wfRestoreWarnings();
                # @todo FIXME: HACK HACK HACK HACK debug

                # @todo hashar: not sure if the following test really trigger if the object
                #          fetching failed.
                if( pg_last_error( $this->mConn ) ) {
                        throw new DBUnexpectedError( $this, 'SQL error: ' . htmlspecialchars( pg_last_error( $this->mConn ) ) );
                }
                return $row;
        }

        function fetchRow( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                wfSuppressWarnings();
                $row = pg_fetch_array( $res );
                wfRestoreWarnings();
                if( pg_last_error( $this->mConn ) ) {
                        throw new DBUnexpectedError( $this, 'SQL error: ' . htmlspecialchars( pg_last_error( $this->mConn ) ) );
                }
                return $row;
        }

        function numRows( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                wfSuppressWarnings();
                $n = pg_num_rows( $res );
                wfRestoreWarnings();
                if( pg_last_error( $this->mConn ) ) {
                        throw new DBUnexpectedError( $this, 'SQL error: ' . htmlspecialchars( pg_last_error( $this->mConn ) ) );
                }
                return $n;
        }

        function numFields( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                return pg_num_fields( $res );
        }

        function fieldName( $res, $n ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                return pg_field_name( $res, $n );
        }

        /**
         * This must be called after nextSequenceVal
         */
        function insertId() {
                return $this->mInsertId;
        }

        function dataSeek( $res, $row ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                return pg_result_seek( $res, $row );
        }

        function lastError() {
                if ( $this->mConn ) {
                        return pg_last_error();
                } else {
                        return 'No database connection';
                }
        }
        function lastErrno() {
                return pg_last_error() ? 1 : 0;
        }

        function affectedRows() {
                if ( !is_null( $this->mAffectedRows ) ) {
                        // Forced result for simulated queries
                        return $this->mAffectedRows;
                }
                if( empty( $this->mLastResult ) ) {
                        return 0;
                }
                return pg_affected_rows( $this->mLastResult );
        }

        /**
         * Estimate rows in dataset
         * Returns estimated count, based on EXPLAIN output
         * This is not necessarily an accurate estimate, so use sparingly
         * Returns -1 if count cannot be found
         * Takes same arguments as Database::select()
         */
        function estimateRowCount( $table, $vars = '*', $conds='', $fname = 'DatabasePostgres::estimateRowCount', $options = array() ) {
                $options['EXPLAIN'] = true;
                $res = $this->select( $table, $vars, $conds, $fname, $options );
                $rows = -1;
                if ( $res ) {
                        $row = $this->fetchRow( $res );
                        $count = array();
                        if( preg_match( '/rows=(\d+)/', $row[0], $count ) ) {
                                $rows = $count[1];
                        }
                }
                return $rows;
        }

        /**
         * Returns information about an index
         * If errors are explicitly ignored, returns NULL on failure
         */
        function indexInfo( $table, $index, $fname = 'DatabasePostgres::indexInfo' ) {
                $sql = "SELECT indexname FROM pg_indexes WHERE tablename='$table'";
                $res = $this->query( $sql, $fname );
                if ( !$res ) {
                        return null;
                }
                foreach ( $res as $row ) {
                        if ( $row->indexname == $this->indexName( $index ) ) {
                                return $row;
                        }
                }
                return false;
        }

        function indexUnique( $table, $index, $fname = 'DatabasePostgres::indexUnique' ) {
                $sql = "SELECT indexname FROM pg_indexes WHERE tablename='{$table}'".
                        " AND indexdef LIKE 'CREATE UNIQUE%(" .
                        $this->strencode( $this->indexName( $index ) ) .
                        ")'";
                $res = $this->query( $sql, $fname );
                if ( !$res ) {
                        return null;
                }
                foreach ( $res as $row ) {
                        return true;
                }
                return false;
        }

        /**
         * INSERT wrapper, inserts an array into a table
         *
         * $args may be a single associative array, or an array of these with numeric keys,
         * for multi-row insert (Postgres version 8.2 and above only).
         *
         * @param $table   String: Name of the table to insert to.
         * @param $args    Array: Items to insert into the table.
         * @param $fname   String: Name of the function, for profiling
         * @param $options String or Array. Valid options: IGNORE
         *
         * @return bool Success of insert operation. IGNORE always returns true.
         */
        function insert( $table, $args, $fname = 'DatabasePostgres::insert', $options = array() ) {
                if ( !count( $args ) ) {
                        return true;
                }

                $table = $this->tableName( $table );
                if (! isset( $this->numeric_version ) ) {
                        $this->getServerVersion();
                }

                if ( !is_array( $options ) ) {
                        $options = array( $options );
                }

                if ( isset( $args[0] ) && is_array( $args[0] ) ) {
                        $multi = true;
                        $keys = array_keys( $args[0] );
                } else {
                        $multi = false;
                        $keys = array_keys( $args );
                }

                // If IGNORE is set, we use savepoints to emulate mysql's behavior
                $ignore = in_array( 'IGNORE', $options ) ? 'mw' : '';

                // If we are not in a transaction, we need to be for savepoint trickery
                $didbegin = 0;
                if ( $ignore ) {
                        if ( !$this->mTrxLevel ) {
                                $this->begin();
                                $didbegin = 1;
                        }
                        $olde = error_reporting( 0 );
                        // For future use, we may want to track the number of actual inserts
                        // Right now, insert (all writes) simply return true/false
                        $numrowsinserted = 0;
                }

                $sql = "INSERT INTO $table (" . implode( ',', $keys ) . ') VALUES ';

                if ( $multi ) {
                        if ( $this->numeric_version >= 8.2 && !$ignore ) {
                                $first = true;
                                foreach ( $args as $row ) {
                                        if ( $first ) {
                                                $first = false;
                                        } else {
                                                $sql .= ',';
                                        }
                                        $sql .= '(' . $this->makeList( $row ) . ')';
                                }
                                $res = (bool)$this->query( $sql, $fname, $ignore );
                        } else {
                                $res = true;
                                $origsql = $sql;
                                foreach ( $args as $row ) {
                                        $tempsql = $origsql;
                                        $tempsql .= '(' . $this->makeList( $row ) . ')';

                                        if ( $ignore ) {
                                                pg_query( $this->mConn, "SAVEPOINT $ignore" );
                                        }

                                        $tempres = (bool)$this->query( $tempsql, $fname, $ignore );

                                        if ( $ignore ) {
                                                $bar = pg_last_error();
                                                if ( $bar != false ) {
                                                        pg_query( $this->mConn, "ROLLBACK TO $ignore" );
                                                } else {
                                                        pg_query( $this->mConn, "RELEASE $ignore" );
                                                        $numrowsinserted++;
                                                }
                                        }

                                        // If any of them fail, we fail overall for this function call
                                        // Note that this will be ignored if IGNORE is set
                                        if ( !$tempres ) {
                                                $res = false;
                                        }
                                }
                        }
                } else {
                        // Not multi, just a lone insert
                        if ( $ignore ) {
                                pg_query($this->mConn, "SAVEPOINT $ignore");
                        }

                        $sql .= '(' . $this->makeList( $args ) . ')';
                        $res = (bool)$this->query( $sql, $fname, $ignore );
                        if ( $ignore ) {
                                $bar = pg_last_error();
                                if ( $bar != false ) {
                                        pg_query( $this->mConn, "ROLLBACK TO $ignore" );
                                } else {
                                        pg_query( $this->mConn, "RELEASE $ignore" );
                                        $numrowsinserted++;
                                }
                        }
                }
                if ( $ignore ) {
                        $olde = error_reporting( $olde );
                        if ( $didbegin ) {
                                $this->commit();
                        }

                        // Set the affected row count for the whole operation
                        $this->mAffectedRows = $numrowsinserted;

                        // IGNORE always returns true
                        return true;
                }

                return $res;
        }

        /**
         * INSERT SELECT wrapper
         * $varMap must be an associative array of the form array( 'dest1' => 'source1', ...)
         * Source items may be literals rather then field names, but strings should be quoted with Database::addQuotes()
         * $conds may be "*" to copy the whole table
         * srcTable may be an array of tables.
         * @todo FIXME: Implement this a little better (seperate select/insert)?
         */
        function insertSelect( $destTable, $srcTable, $varMap, $conds, $fname = 'DatabasePostgres::insertSelect',
                $insertOptions = array(), $selectOptions = array() )
        {
                $destTable = $this->tableName( $destTable );

                // If IGNORE is set, we use savepoints to emulate mysql's behavior
                $ignore = in_array( 'IGNORE', $insertOptions ) ? 'mw' : '';

                if( is_array( $insertOptions ) ) {
                        $insertOptions = implode( ' ', $insertOptions ); // FIXME: This is unused
                }
                if( !is_array( $selectOptions ) ) {
                        $selectOptions = array( $selectOptions );
                }
                list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
                if( is_array( $srcTable ) ) {
                        $srcTable = implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
                } else {
                        $srcTable = $this->tableName( $srcTable );
                }

                // If we are not in a transaction, we need to be for savepoint trickery
                $didbegin = 0;
                if ( $ignore ) {
                        if( !$this->mTrxLevel ) {
                                $this->begin();
                                $didbegin = 1;
                        }
                        $olde = error_reporting( 0 );
                        $numrowsinserted = 0;
                        pg_query( $this->mConn, "SAVEPOINT $ignore");
                }

                $sql = "INSERT INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
                                " SELECT $startOpts " . implode( ',', $varMap ) .
                                " FROM $srcTable $useIndex";

                if ( $conds != '*' ) {
                        $sql .= ' WHERE ' . $this->makeList( $conds, LIST_AND );
                }

                $sql .= " $tailOpts";

                $res = (bool)$this->query( $sql, $fname, $ignore );
                if( $ignore ) {
                        $bar = pg_last_error();
                        if( $bar != false ) {
                                pg_query( $this->mConn, "ROLLBACK TO $ignore" );
                        } else {
                                pg_query( $this->mConn, "RELEASE $ignore" );
                                $numrowsinserted++;
                        }
                        $olde = error_reporting( $olde );
                        if( $didbegin ) {
                                $this->commit();
                        }

                        // Set the affected row count for the whole operation
                        $this->mAffectedRows = $numrowsinserted;

                        // IGNORE always returns true
                        return true;
                }

                return $res;
        }

        function tableName( $name, $format = 'quoted' ) {
                # Replace reserved words with better ones
                switch( $name ) {
                        case 'user':
                                return 'mwuser';
                        case 'text':
                                return 'pagecontent';
                        default:
                                return parent::tableName( $name, $format );
                }
        }

        /**
         * Return the next in a sequence, save the value for retrieval via insertId()
         */
        function nextSequenceValue( $seqName ) {
                $safeseq = str_replace( "'", "''", $seqName );
                $res = $this->query( "SELECT nextval('$safeseq')" );
                $row = $this->fetchRow( $res );
                $this->mInsertId = $row[0];
                return $this->mInsertId;
        }

        /**
         * Return the current value of a sequence. Assumes it has been nextval'ed in this session.
         */
        function currentSequenceValue( $seqName ) {
                $safeseq = str_replace( "'", "''", $seqName );
                $res = $this->query( "SELECT currval('$safeseq')" );
                $row = $this->fetchRow( $res );
                $currval = $row[0];
                return $currval;
        }

        # Returns the size of a text field, or -1 for "unlimited"
        function textFieldSize( $table, $field ) {
                $table = $this->tableName( $table );
                $sql = "SELECT t.typname as ftype,a.atttypmod as size
                        FROM pg_class c, pg_attribute a, pg_type t
                        WHERE relname='$table' AND a.attrelid=c.oid AND
                                a.atttypid=t.oid and a.attname='$field'";
                $res =$this->query( $sql );
                $row = $this->fetchObject( $res );
                if ( $row->ftype == 'varchar' ) {
                        $size = $row->size - 4;
                } else {
                        $size = $row->size;
                }
                return $size;
        }

        function limitResult( $sql, $limit, $offset = false ) {
                return "$sql LIMIT $limit " . ( is_numeric( $offset ) ? " OFFSET {$offset} " : '' );
        }

        function wasDeadlock() {
                return $this->lastErrno() == '40P01';
        }

        function duplicateTableStructure( $oldName, $newName, $temporary = false, $fname = 'DatabasePostgres::duplicateTableStructure' ) {
                $newName = $this->addIdentifierQuotes( $newName );
                $oldName = $this->addIdentifierQuotes( $oldName );
                return $this->query( 'CREATE ' . ( $temporary ? 'TEMPORARY ' : '' ) . " TABLE $newName (LIKE $oldName INCLUDING DEFAULTS)", $fname );
        }

        function listTables( $prefix = null, $fname = 'DatabasePostgres::listTables' ) {
                global $wgDBmwschema;
                $eschema = $this->addQuotes( $wgDBmwschema );
                $result = $this->query( "SELECT tablename FROM pg_tables WHERE schemaname = $eschema", $fname );

                $endArray = array();

                foreach( $result as $table ) {
                        $vars = get_object_vars($table);
                        $table = array_pop( $vars );
                        if( !$prefix || strpos( $table, $prefix ) === 0 ) {
                                $endArray[] = $table;
                        }
                }

                return $endArray;
        }

        function timestamp( $ts = 0 ) {
                return wfTimestamp( TS_POSTGRES, $ts );
        }

        /**
         * Return aggregated value function call
         */
        function aggregateValue( $valuedata, $valuename = 'value' ) {
                return $valuedata;
        }

        /**
         * @return string wikitext of a link to the server software's web site
         */
        public static function getSoftwareLink() {
                return '[http://www.postgresql.org/ PostgreSQL]';
        }

        /**
         * @return string Version information from the database
         */
        function getServerVersion() {
                if ( !isset( $this->numeric_version ) ) {
                        $versionInfo = pg_version( $this->mConn );
                        if ( version_compare( $versionInfo['client'], '7.4.0', 'lt' ) ) {
                                // Old client, abort install
                                $this->numeric_version = '7.3 or earlier';
                        } elseif ( isset( $versionInfo['server'] ) ) {
                                // Normal client
                                $this->numeric_version = $versionInfo['server'];
                        } else {
                                // Bug 16937: broken pgsql extension from PHP<5.3
                                $this->numeric_version = pg_parameter_status( $this->mConn, 'server_version' );
                        }
                }
                return $this->numeric_version;
        }

        /**
         * Query whether a given relation exists (in the given schema, or the
         * default mw one if not given)
         */
        function relationExists( $table, $types, $schema = false ) {
                global $wgDBmwschema;
                if ( !is_array( $types ) ) {
                        $types = array( $types );
                }
                if ( !$schema ) {
                        $schema = $wgDBmwschema;
                }
                $table = $this->tableName( $table, 'raw' );
                $etable = $this->addQuotes( $table );
                $eschema = $this->addQuotes( $schema );
                $SQL = "SELECT 1 FROM pg_catalog.pg_class c, pg_catalog.pg_namespace n "
                        . "WHERE c.relnamespace = n.oid AND c.relname = $etable AND n.nspname = $eschema "
                        . "AND c.relkind IN ('" . implode( "','", $types ) . "')";
                $res = $this->query( $SQL );
                $count = $res ? $res->numRows() : 0;
                return (bool)$count;
        }

        /**
         * For backward compatibility, this function checks both tables and
         * views.
         */
        function tableExists( $table, $schema = false ) {
                return $this->relationExists( $table, array( 'r', 'v' ), $schema );
        }

        function sequenceExists( $sequence, $schema = false ) {
                return $this->relationExists( $sequence, 'S', $schema );
        }

        function triggerExists( $table, $trigger ) {
                global $wgDBmwschema;

                $q = <<<SQL
        SELECT 1 FROM pg_class, pg_namespace, pg_trigger
                WHERE relnamespace=pg_namespace.oid AND relkind='r'
                          AND tgrelid=pg_class.oid
                          AND nspname=%s AND relname=%s AND tgname=%s
SQL;
                $res = $this->query(
                        sprintf(
                                $q,
                                $this->addQuotes( $wgDBmwschema ),
                                $this->addQuotes( $table ),
                                $this->addQuotes( $trigger )
                        )
                );
                if ( !$res ) {
                        return null;
                }
                $rows = $res->numRows();
                return $rows;
        }

        function ruleExists( $table, $rule ) {
                global $wgDBmwschema;
                $exists = $this->selectField( 'pg_rules', 'rulename',
                        array(
                                'rulename' => $rule,
                                'tablename' => $table,
                                'schemaname' => $wgDBmwschema
                        )
                );
                return $exists === $rule;
        }

        function constraintExists( $table, $constraint ) {
                global $wgDBmwschema;
                $SQL = sprintf( "SELECT 1 FROM information_schema.table_constraints ".
                           "WHERE constraint_schema = %s AND table_name = %s AND constraint_name = %s",
                        $this->addQuotes( $wgDBmwschema ),
                        $this->addQuotes( $table ),
                        $this->addQuotes( $constraint )
                );
                $res = $this->query( $SQL );
                if ( !$res ) {
                        return null;
                }
                $rows = $res->numRows();
                return $rows;
        }

        /**
         * Query whether a given schema exists. Returns true if it does, false if it doesn't.
         */
        function schemaExists( $schema ) {
                $exists = $this->selectField( '"pg_catalog"."pg_namespace"', 1,
                        array( 'nspname' => $schema ), __METHOD__ );
                return (bool)$exists;
        }

        /**
         * Returns true if a given role (i.e. user) exists, false otherwise.
         */
        function roleExists( $roleName ) {
                $exists = $this->selectField( '"pg_catalog"."pg_roles"', 1,
                        array( 'rolname' => $roleName ), __METHOD__ );
                return (bool)$exists;
        }

        function fieldInfo( $table, $field ) {
                return PostgresField::fromText( $this, $table, $field );
        }

        /**
         * pg_field_type() wrapper
         */
        function fieldType( $res, $index ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                return pg_field_type( $res, $index );
        }

        /* Not even sure why this is used in the main codebase... */
        function limitResultForUpdate( $sql, $num ) {
                return $sql;
        }

        /**
         * @param $b
         * @return Blob
         */
        function encodeBlob( $b ) {
                return new Blob( pg_escape_bytea( $this->mConn, $b ) );
        }

        function decodeBlob( $b ) {
                if ( $b instanceof Blob ) {
                        $b = $b->fetch();
                }
                return pg_unescape_bytea( $b );
        }

        function strencode( $s ) { # Should not be called by us
                return pg_escape_string( $this->mConn, $s );
        }

        /**
         * @param $s null|bool|Blob
         * @return int|string
         */
        function addQuotes( $s ) {
                if ( is_null( $s ) ) {
                        return 'NULL';
                } elseif ( is_bool( $s ) ) {
                        return intval( $s );
                } elseif ( $s instanceof Blob ) {
                        return "'" . $s->fetch( $s ) . "'";
                }
                return "'" . pg_escape_string( $this->mConn, $s ) . "'";
        }

        /**
         * Postgres specific version of replaceVars.
         * Calls the parent version in Database.php
         *
         * @private
         *
         * @param $ins String: SQL string, read from a stream (usually tables.sql)
         *
         * @return string SQL string
         */
        protected function replaceVars( $ins ) {
                $ins = parent::replaceVars( $ins );

                if ( $this->numeric_version >= 8.3 ) {
                        // Thanks for not providing backwards-compatibility, 8.3
                        $ins = preg_replace( "/to_tsvector\s*\(\s*'default'\s*,/", 'to_tsvector(', $ins );
                }

                if ( $this->numeric_version <= 8.1 ) { // Our minimum version
                        $ins = str_replace( 'USING gin', 'USING gist', $ins );
                }

                return $ins;
        }

        /**
         * Various select options
         *
         * @private
         *
         * @param $options Array: an associative array of options to be turned into
         *              an SQL query, valid keys are listed in the function.
         * @return array
         */
        function makeSelectOptions( $options ) {
                $preLimitTail = $postLimitTail = '';
                $startOpts = $useIndex = '';

                $noKeyOptions = array();
                foreach ( $options as $key => $option ) {
                        if ( is_numeric( $key ) ) {
                                $noKeyOptions[$option] = true;
                        }
                }

                if ( isset( $options['GROUP BY'] ) ) {
                        $gb = is_array( $options['GROUP BY'] )
                                ? implode( ',', $options['GROUP BY'] )
                                : $options['GROUP BY'];
                        $preLimitTail .= " GROUP BY {$gb}";
                }

                if ( isset( $options['HAVING'] ) ) {
                        $preLimitTail .= " HAVING {$options['HAVING']}";
                }

                if ( isset( $options['ORDER BY'] ) ) {
                        $ob = is_array( $options['ORDER BY'] )
                                ? implode( ',', $options['ORDER BY'] )
                                : $options['ORDER BY'];
                        $preLimitTail .= " ORDER BY {$ob}";
                }

                //if ( isset( $options['LIMIT'] ) ) {
                //      $tailOpts .= $this->limitResult( '', $options['LIMIT'],
                //              isset( $options['OFFSET'] ) ? $options['OFFSET']
                //              : false );
                //}

                if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
                        $postLimitTail .= ' FOR UPDATE';
                }
                if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
                        $postLimitTail .= ' LOCK IN SHARE MODE';
                }
                if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
                        $startOpts .= 'DISTINCT';
                }

                return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
        }

        function setFakeMaster( $enabled = true ) {}

        function getDBname() {
                return $this->mDBname;
        }

        function getServer() {
                return $this->mServer;
        }

        function buildConcat( $stringList ) {
                return implode( ' || ', $stringList );
        }

        public function getSearchEngine() {
                return 'SearchPostgres';
        }
} // end DatabasePostgres class