Implement extension registration from an extension.json file

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

<?php
/**
 * This is the Postgres database abstraction layer.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @ingroup Database
 */

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

        /**
         * @param DatabaseBase $db
         * @param string $table
         * @param string $field
         * @return null|PostgresField
         */
        static function fromText( $db, $table, $field ) {
                $q = <<<SQL
SELECT
 attnotnull, attlen, conname AS conname,
 atthasdef,
 adsrc,
 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')
LEFT JOIN pg_attrdef d on c.oid=d.adrelid and a.attnum=d.adnum
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( $db->getCoreSchema() ),
                                $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;
                $n->has_default = ( $row->atthasdef === 't' );
                $n->default = $row->adsrc;

                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;
        }

        /**
         * @since 1.19
         * @return bool|mixed
         */
        function defaultValue() {
                if ( $this->has_default ) {
                        return $this->default;
                } else {
                        return false;
                }
        }
}

/**
 * Used to debug transaction processing
 * Only used if $wgDebugDBTransactions is true
 *
 * @since 1.19
 * @ingroup Database
 */
class PostgresTransactionState {
        private static $WATCHED = array(
                array(
                        "desc" => "%s: Connection state changed from %s -> %s\n",
                        "states" => array(
                                PGSQL_CONNECTION_OK => "OK",
                                PGSQL_CONNECTION_BAD => "BAD"
                        )
                ),
                array(
                        "desc" => "%s: Transaction state changed from %s -> %s\n",
                        "states" => array(
                                PGSQL_TRANSACTION_IDLE => "IDLE",
                                PGSQL_TRANSACTION_ACTIVE => "ACTIVE",
                                PGSQL_TRANSACTION_INTRANS => "TRANS",
                                PGSQL_TRANSACTION_INERROR => "ERROR",
                                PGSQL_TRANSACTION_UNKNOWN => "UNKNOWN"
                        )
                )
        );

        /** @var array */
        private $mNewState;

        /** @var array */
        private $mCurrentState;

        public function __construct( $conn ) {
                $this->mConn = $conn;
                $this->update();
                $this->mCurrentState = $this->mNewState;
        }

        public function update() {
                $this->mNewState = array(
                        pg_connection_status( $this->mConn ),
                        pg_transaction_status( $this->mConn )
                );
        }

        public function check() {
                global $wgDebugDBTransactions;
                $this->update();
                if ( $wgDebugDBTransactions ) {
                        if ( $this->mCurrentState !== $this->mNewState ) {
                                $old = reset( $this->mCurrentState );
                                $new = reset( $this->mNewState );
                                foreach ( self::$WATCHED as $watched ) {
                                        if ( $old !== $new ) {
                                                $this->log_changed( $old, $new, $watched );
                                        }
                                        $old = next( $this->mCurrentState );
                                        $new = next( $this->mNewState );
                                }
                        }
                }
                $this->mCurrentState = $this->mNewState;
        }

        protected function describe_changed( $status, $desc_table ) {
                if ( isset( $desc_table[$status] ) ) {
                        return $desc_table[$status];
                } else {
                        return "STATUS " . $status;
                }
        }

        protected function log_changed( $old, $new, $watched ) {
                wfDebug( sprintf( $watched["desc"],
                        $this->mConn,
                        $this->describe_changed( $old, $watched["states"] ),
                        $this->describe_changed( $new, $watched["states"] )
                ) );
        }
}

/**
 * Manage savepoints within a transaction
 * @ingroup Database
 * @since 1.19
 */
class SavepointPostgres {
        /** @var DatabaseBase Establish a savepoint within a transaction */
        protected $dbw;
        protected $id;
        protected $didbegin;

        /**
         * @param DatabaseBase $dbw
         * @param int $id
         */
        public function __construct( $dbw, $id ) {
                $this->dbw = $dbw;
                $this->id = $id;
                $this->didbegin = false;
                /* If we are not in a transaction, we need to be for savepoint trickery */
                if ( !$dbw->trxLevel() ) {
                        $dbw->begin( "FOR SAVEPOINT" );
                        $this->didbegin = true;
                }
        }

        public function __destruct() {
                if ( $this->didbegin ) {
                        $this->dbw->rollback();
                        $this->didbegin = false;
                }
        }

        public function commit() {
                if ( $this->didbegin ) {
                        $this->dbw->commit();
                        $this->didbegin = false;
                }
        }

        protected function query( $keyword, $msg_ok, $msg_failed ) {
                global $wgDebugDBTransactions;
                if ( $this->dbw->doQuery( $keyword . " " . $this->id ) !== false ) {
                        if ( $wgDebugDBTransactions ) {
                                wfDebug( sprintf( $msg_ok, $this->id ) );
                        }
                } else {
                        wfDebug( sprintf( $msg_failed, $this->id ) );
                }
        }

        public function savepoint() {
                $this->query( "SAVEPOINT",
                        "Transaction state: savepoint \"%s\" established.\n",
                        "Transaction state: establishment of savepoint \"%s\" FAILED.\n"
                );
        }

        public function release() {
                $this->query( "RELEASE",
                        "Transaction state: savepoint \"%s\" released.\n",
                        "Transaction state: release of savepoint \"%s\" FAILED.\n"
                );
        }

        public function rollback() {
                $this->query( "ROLLBACK TO",
                        "Transaction state: savepoint \"%s\" rolled back.\n",
                        "Transaction state: rollback of savepoint \"%s\" FAILED.\n"
                );
        }

        public function __toString() {
                return (string)$this->id;
        }
}

/**
 * @ingroup Database
 */
class DatabasePostgres extends DatabaseBase {
        /** @var resource */
        protected $mLastResult = null;

        /** @var int The number of rows affected as an integer */
        protected $mAffectedRows = null;

        /** @var int */
        private $mInsertId = null;

        /** @var float|string */
        private $numericVersion = null;

        /** @var string Connect string to open a PostgreSQL connection */
        private $connectString;

        /** @var PostgresTransactionState */
        private $mTransactionState;

        /** @var string */
        private $mCoreSchema;

        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 ) {
                $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, $this->getCoreSchema() ) . "'";
                $res = $this->doQuery( $sql );

                return $this->numRows( $res );
        }

        /**
         * Usually aborts on failure
         * @param string $server
         * @param string $user
         * @param string $password
         * @param string $dbName
         * @throws DBConnectionError|Exception
         * @return DatabaseBase|null
         */
        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\n" .
                                "option? (Note: if you recently installed PHP, you may need to restart your\n" .
                                "webserver and database)\n"
                        );
                }

                global $wgDBport;

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

                $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;
                }
                if ( $this->mFlags & DBO_SSL ) {
                        $connectVars['sslmode'] = 1;
                }

                $this->connectString = $this->makeConnectionString( $connectVars, PGSQL_CONNECT_FORCE_NEW );
                $this->close();
                $this->installErrorHandler();

                try {
                        $this->mConn = pg_connect( $this->connectString );
                } catch ( Exception $ex ) {
                        $this->restoreErrorHandler();
                        throw $ex;
                }

                $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;
                $this->mTransactionState = new PostgresTransactionState( $this->mConn );

                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__ );
                if ( $this->getServerVersion() >= 9.0 ) {
                        $this->query( "SET bytea_output = 'escape'", __METHOD__ ); // PHP bug 53127
                }

                global $wgDBmwschema;
                $this->determineCoreSchema( $wgDBmwschema );

                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
         * @param string $db
         * @return bool
         */
        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
         * @return bool
         */
        protected function closeConnection() {
                return pg_close( $this->mConn );
        }

        public function doQuery( $sql ) {
                if ( function_exists( 'mb_convert_encoding' ) ) {
                        $sql = mb_convert_encoding( $sql, 'UTF-8' );
                }
                $this->mTransactionState->check();
                if ( pg_send_query( $this->mConn, $sql ) === false ) {
                        throw new DBUnexpectedError( $this, "Unable to post new query to PostgreSQL\n" );
                }
                $this->mLastResult = pg_get_result( $this->mConn );
                $this->mTransactionState->check();
                $this->mAffectedRows = null;
                if ( pg_result_error( $this->mLastResult ) ) {
                        return false;
                }

                return $this->mLastResult;
        }

        protected function dumpError() {
                $diags = array(
                        PGSQL_DIAG_SEVERITY,
                        PGSQL_DIAG_SQLSTATE,
                        PGSQL_DIAG_MESSAGE_PRIMARY,
                        PGSQL_DIAG_MESSAGE_DETAIL,
                        PGSQL_DIAG_MESSAGE_HINT,
                        PGSQL_DIAG_STATEMENT_POSITION,
                        PGSQL_DIAG_INTERNAL_POSITION,
                        PGSQL_DIAG_INTERNAL_QUERY,
                        PGSQL_DIAG_CONTEXT,
                        PGSQL_DIAG_SOURCE_FILE,
                        PGSQL_DIAG_SOURCE_LINE,
                        PGSQL_DIAG_SOURCE_FUNCTION
                );
                foreach ( $diags as $d ) {
                        wfDebug( sprintf( "PgSQL ERROR(%d): %s\n",
                                $d, pg_result_error_field( $this->mLastResult, $d ) ) );
                }
        }

        function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
                if ( $tempIgnore ) {
                        /* Check for constraint violation */
                        if ( $errno === '23505' ) {
                                parent::reportQueryError( $error, $errno, $sql, $fname, $tempIgnore );

                                return;
                        }
                }
                /* Transaction stays in the ERROR state until rolledback */
                if ( $this->mTrxLevel ) {
                        $this->rollback( __METHOD__ );
                };
                parent::reportQueryError( $error, $errno, $sql, $fname, false );
        }

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

        /**
         * @param stdClass|ResultWrapper $res
         * @throws DBUnexpectedError
         */
        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" );
                }
        }

        /**
         * @param ResultWrapper|stdClass $res
         * @return stdClass
         * @throws DBUnexpectedError
         */
        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 );
        }

        /**
         * Return the result of the last call to nextSequenceValue();
         * This must be called after nextSequenceValue().
         *
         * @return int|null
         */
        function insertId() {
                return $this->mInsertId;
        }

        /**
         * @param mixed $res
         * @param int $row
         * @return bool
         */
        function dataSeek( $res, $row ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }

                return pg_result_seek( $res, $row );
        }

        function lastError() {
                if ( $this->mConn ) {
                        if ( $this->mLastResult ) {
                                return pg_result_error( $this->mLastResult );
                        } else {
                                return pg_last_error();
                        }
                } else {
                        return 'No database connection';
                }
        }

        function lastErrno() {
                if ( $this->mLastResult ) {
                        return pg_result_error_field( $this->mLastResult, PGSQL_DIAG_SQLSTATE );
                } else {
                        return false;
                }
        }

        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()
         *
         * @param string $table
         * @param string $vars
         * @param string $conds
         * @param string $fname
         * @param array $options
         * @return int
         */
        function estimateRowCount( $table, $vars = '*', $conds = '',
                $fname = __METHOD__, $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
         *
         * @param string $table
         * @param string $index
         * @param string $fname
         * @return bool|null
         */
        function indexInfo( $table, $index, $fname = __METHOD__ ) {
                $sql = "SELECT indexname FROM pg_indexes WHERE tablename='$table'";
                $res = $this->query( $sql, $fname );
                if ( !$res ) {
                        return null;
                }
                foreach ( $res as $row ) {
                        if ( $row->indexname == $this->indexName( $index ) ) {
                                return $row;
                        }
                }

                return false;
        }

        /**
         * Returns is of attributes used in index
         *
         * @since 1.19
         * @param string $index
         * @param bool|string $schema
         * @return array
         */
        function indexAttributes( $index, $schema = false ) {
                if ( $schema === false ) {
                        $schema = $this->getCoreSchema();
                }
                /*
                 * A subquery would be not needed if we didn't care about the order
                 * of attributes, but we do
                 */
                $sql = <<<__INDEXATTR__

                        SELECT opcname,
                                attname,
                                i.indoption[s.g] as option,
                                pg_am.amname
                        FROM
                                (SELECT generate_series(array_lower(isub.indkey,1), array_upper(isub.indkey,1)) AS g
                                        FROM
                                                pg_index isub
                                        JOIN pg_class cis
                                                ON cis.oid=isub.indexrelid
                                        JOIN pg_namespace ns
                                                ON cis.relnamespace = ns.oid
                                        WHERE cis.relname='$index' AND ns.nspname='$schema') AS s,
                                pg_attribute,
                                pg_opclass opcls,
                                pg_am,
                                pg_class ci
                                JOIN pg_index i
                                        ON ci.oid=i.indexrelid
                                JOIN pg_class ct
                                        ON ct.oid = i.indrelid
                                JOIN pg_namespace n
                                        ON ci.relnamespace = n.oid
                                WHERE
                                        ci.relname='$index' AND n.nspname='$schema'
                                        AND     attrelid = ct.oid
                                        AND     i.indkey[s.g] = attnum
                                        AND     i.indclass[s.g] = opcls.oid
                                        AND     pg_am.oid = opcls.opcmethod
__INDEXATTR__;
                $res = $this->query( $sql, __METHOD__ );
                $a = array();
                if ( $res ) {
                        foreach ( $res as $row ) {
                                $a[] = array(
                                        $row->attname,
                                        $row->opcname,
                                        $row->amname,
                                        $row->option );
                        }
                } else {
                        return null;
                }

                return $a;
        }

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

                return $res->numRows() > 0;
        }

        /**
         * Change the FOR UPDATE option as necessary based on the join conditions. Then pass
         * to the parent function to get the actual SQL text.
         *
         * In Postgres when using FOR UPDATE, only the main table and tables that are inner joined
         * can be locked. That means tables in an outer join cannot be FOR UPDATE locked. Trying to do
         * so causes a DB error. This wrapper checks which tables can be locked and adjusts it accordingly.
         *
         * MySQL uses "ORDER BY NULL" as an optimization hint, but that syntax is illegal in PostgreSQL.
         * @see DatabaseBase::selectSQLText
         */
        function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
                $options = array(), $join_conds = array()
        ) {
                if ( is_array( $options ) ) {
                        $forUpdateKey = array_search( 'FOR UPDATE', $options, true );
                        if ( $forUpdateKey !== false && $join_conds ) {
                                unset( $options[$forUpdateKey] );

                                foreach ( $join_conds as $table_cond => $join_cond ) {
                                        if ( 0 === preg_match( '/^(?:LEFT|RIGHT|FULL)(?: OUTER)? JOIN$/i', $join_cond[0] ) ) {
                                                $options['FOR UPDATE'][] = $table_cond;
                                        }
                                }
                        }

                        if ( isset( $options['ORDER BY'] ) && $options['ORDER BY'] == 'NULL' ) {
                                unset( $options['ORDER BY'] );
                        }
                }

                return parent::selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
        }

        /**
         * 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 string $table Name of the table to insert to.
         * @param array $args Items to insert into the table.
         * @param string $fname Name of the function, for profiling
         * @param array|string $options String or array. Valid options: IGNORE
         * @return bool Success of insert operation. IGNORE always returns true.
         */
        function insert( $table, $args, $fname = __METHOD__, $options = array() ) {
                if ( !count( $args ) ) {
                        return true;
                }

                $table = $this->tableName( $table );
                if ( !isset( $this->numericVersion ) ) {
                        $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
                $savepoint = null;
                if ( in_array( 'IGNORE', $options ) ) {
                        $savepoint = new SavepointPostgres( $this, 'mw' );
                        $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 ( $this->numericVersion >= 8.2 && !$savepoint ) {
                                $first = true;
                                foreach ( $args as $row ) {
                                        if ( $first ) {
                                                $first = false;
                                        } else {
                                                $sql .= ',';
                                        }
                                        $sql .= '(' . $this->makeList( $row ) . ')';
                                }
                                $res = (bool)$this->query( $sql, $fname, $savepoint );
                        } else {
                                $res = true;
                                $origsql = $sql;
                                foreach ( $args as $row ) {
                                        $tempsql = $origsql;
                                        $tempsql .= '(' . $this->makeList( $row ) . ')';

                                        if ( $savepoint ) {
                                                $savepoint->savepoint();
                                        }

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

                                        if ( $savepoint ) {
                                                $bar = pg_last_error();
                                                if ( $bar != false ) {
                                                        $savepoint->rollback();
                                                } else {
                                                        $savepoint->release();
                                                        $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 ( $savepoint ) {
                                $savepoint->savepoint();
                        }

                        $sql .= '(' . $this->makeList( $args ) . ')';
                        $res = (bool)$this->query( $sql, $fname, $savepoint );
                        if ( $savepoint ) {
                                $bar = pg_last_error();
                                if ( $bar != false ) {
                                        $savepoint->rollback();
                                } else {
                                        $savepoint->release();
                                        $numrowsinserted++;
                                }
                        }
                }
                if ( $savepoint ) {
                        error_reporting( $olde );
                        $savepoint->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)?
         *
         * @param string $destTable
         * @param array|string $srcTable
         * @param array $varMap
         * @param array $conds
         * @param string $fname
         * @param array $insertOptions
         * @param array $selectOptions
         * @return bool
         */
        function insertSelect( $destTable, $srcTable, $varMap, $conds, $fname = __METHOD__,
                $insertOptions = array(), $selectOptions = array() ) {
                $destTable = $this->tableName( $destTable );

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

                /*
                 * If IGNORE is set, we use savepoints to emulate mysql's behavior
                 * Ignore LOW PRIORITY option, since it is MySQL-specific
                 */
                $savepoint = null;
                if ( in_array( 'IGNORE', $insertOptions ) ) {
                        $savepoint = new SavepointPostgres( $this, 'mw' );
                        $olde = error_reporting( 0 );
                        $numrowsinserted = 0;
                        $savepoint->savepoint();
                }

                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 );
                }

                $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, $savepoint );
                if ( $savepoint ) {
                        $bar = pg_last_error();
                        if ( $bar != false ) {
                                $savepoint->rollback();
                        } else {
                                $savepoint->release();
                                $numrowsinserted++;
                        }
                        error_reporting( $olde );
                        $savepoint->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 $this->realTableName( 'mwuser', $format );
                        case 'text':
                                return $this->realTableName( 'pagecontent', $format );
                        default:
                                return $this->realTableName( $name, $format );
                }
        }

        /* Don't cheat on installer */
        function realTableName( $name, $format = 'quoted' ) {
                return parent::tableName( $name, $format );
        }

        /**
         * Return the next in a sequence, save the value for retrieval via insertId()
         *
         * @param string $seqName
         * @return int|null
         */
        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.
         *
         * @param string $seqName
         * @return int
         */
        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 = __METHOD__ ) {
                $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 = __METHOD__ ) {
                $eschema = $this->addQuotes( $this->getCoreSchema() );
                $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 );
        }

        /**
         * Posted by cc[plus]php[at]c2se[dot]com on 25-Mar-2009 09:12
         * to http://www.php.net/manual/en/ref.pgsql.php
         *
         * Parsing a postgres array can be a tricky problem, he's my
         * take on this, it handles multi-dimensional arrays plus
         * escaping using a nasty regexp to determine the limits of each
         * data-item.
         *
         * This should really be handled by PHP PostgreSQL module
         *
         * @since 1.19
         * @param string $text Postgreql array returned in a text form like {a,b}
         * @param string $output
         * @param int $limit
         * @param int $offset
         * @return string
         */
        function pg_array_parse( $text, &$output, $limit = false, $offset = 1 ) {
                if ( false === $limit ) {
                        $limit = strlen( $text ) - 1;
                        $output = array();
                }
                if ( '{}' == $text ) {
                        return $output;
                }
                do {
                        if ( '{' != $text[$offset] ) {
                                preg_match( "/(\\{?\"([^\"\\\\]|\\\\.)*\"|[^,{}]+)+([,}]+)/",
                                        $text, $match, 0, $offset );
                                $offset += strlen( $match[0] );
                                $output[] = ( '"' != $match[1][0]
                                        ? $match[1]
                                        : stripcslashes( substr( $match[1], 1, -1 ) ) );
                                if ( '},' == $match[3] ) {
                                        return $output;
                                }
                        } else {
                                $offset = $this->pg_array_parse( $text, $output, $limit, $offset + 1 );
                        }
                } while ( $limit > $offset );

                return $output;
        }

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

        /**
         * @return string Wikitext of a link to the server software's web site
         */
        public function getSoftwareLink() {
                return '[{{int:version-db-postgres-url}} PostgreSQL]';
        }

        /**
         * Return current schema (executes SELECT current_schema())
         * Needs transaction
         *
         * @since 1.19
         * @return string Default schema for the current session
         */
        function getCurrentSchema() {
                $res = $this->query( "SELECT current_schema()", __METHOD__ );
                $row = $this->fetchRow( $res );

                return $row[0];
        }

        /**
         * Return list of schemas which are accessible without schema name
         * This is list does not contain magic keywords like "$user"
         * Needs transaction
         *
         * @see getSearchPath()
         * @see setSearchPath()
         * @since 1.19
         * @return array List of actual schemas for the current sesson
         */
        function getSchemas() {
                $res = $this->query( "SELECT current_schemas(false)", __METHOD__ );
                $row = $this->fetchRow( $res );
                $schemas = array();

                /* PHP pgsql support does not support array type, "{a,b}" string is returned */

                return $this->pg_array_parse( $row[0], $schemas );
        }

        /**
         * Return search patch for schemas
         * This is different from getSchemas() since it contain magic keywords
         * (like "$user").
         * Needs transaction
         *
         * @since 1.19
         * @return array How to search for table names schemas for the current user
         */
        function getSearchPath() {
                $res = $this->query( "SHOW search_path", __METHOD__ );
                $row = $this->fetchRow( $res );

                /* PostgreSQL returns SHOW values as strings */

                return explode( ",", $row[0] );
        }

        /**
         * Update search_path, values should already be sanitized
         * Values may contain magic keywords like "$user"
         * @since 1.19
         *
         * @param array $search_path List of schemas to be searched by default
         */
        function setSearchPath( $search_path ) {
                $this->query( "SET search_path = " . implode( ", ", $search_path ) );
        }

        /**
         * Determine default schema for MediaWiki core
         * Adjust this session schema search path if desired schema exists
         * and is not alread there.
         *
         * We need to have name of the core schema stored to be able
         * to query database metadata.
         *
         * This will be also called by the installer after the schema is created
         *
         * @since 1.19
         *
         * @param string $desiredSchema
         */
        function determineCoreSchema( $desiredSchema ) {
                $this->begin( __METHOD__ );
                if ( $this->schemaExists( $desiredSchema ) ) {
                        if ( in_array( $desiredSchema, $this->getSchemas() ) ) {
                                $this->mCoreSchema = $desiredSchema;
                                wfDebug( "Schema \"" . $desiredSchema . "\" already in the search path\n" );
                        } else {
                                /**
                                 * Prepend our schema (e.g. 'mediawiki') in front
                                 * of the search path
                                 * Fixes bug 15816
                                 */
                                $search_path = $this->getSearchPath();
                                array_unshift( $search_path,
                                        $this->addIdentifierQuotes( $desiredSchema ) );
                                $this->setSearchPath( $search_path );
                                $this->mCoreSchema = $desiredSchema;
                                wfDebug( "Schema \"" . $desiredSchema . "\" added to the search path\n" );
                        }
                } else {
                        $this->mCoreSchema = $this->getCurrentSchema();
                        wfDebug( "Schema \"" . $desiredSchema . "\" not found, using current \"" .
                                $this->mCoreSchema . "\"\n" );
                }
                /* Commit SET otherwise it will be rollbacked on error or IGNORE SELECT */
                $this->commit( __METHOD__ );
        }

        /**
         * Return schema name fore core MediaWiki tables
         *
         * @since 1.19
         * @return string Core schema name
         */
        function getCoreSchema() {
                return $this->mCoreSchema;
        }

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

                return $this->numericVersion;
        }

        /**
         * Query whether a given relation exists (in the given schema, or the
         * default mw one if not given)
         * @param string $table
         * @param array|string $types
         * @param bool|string $schema
         * @return bool
         */
        function relationExists( $table, $types, $schema = false ) {
                if ( !is_array( $types ) ) {
                        $types = array( $types );
                }
                if ( !$schema ) {
                        $schema = $this->getCoreSchema();
                }
                $table = $this->realTableName( $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.
         * @param string $table
         * @param string $fname
         * @param bool|string $schema
         * @return bool
         */
        function tableExists( $table, $fname = __METHOD__, $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 ) {
                $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( $this->getCoreSchema() ),
                                $this->addQuotes( $table ),
                                $this->addQuotes( $trigger )
                        )
                );
                if ( !$res ) {
                        return null;
                }
                $rows = $res->numRows();

                return $rows;
        }

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

                return $exists === $rule;
        }

        function constraintExists( $table, $constraint ) {
                $sql = sprintf( "SELECT 1 FROM information_schema.table_constraints " .
                        "WHERE constraint_schema = %s AND table_name = %s AND constraint_name = %s",
                        $this->addQuotes( $this->getCoreSchema() ),
                        $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.
         * @param string $schema
         * @return bool
         */
        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.
         * @param string $roleName
         * @return bool
         */
        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
         * @param ResultWrapper|resource $res ResultWrapper or PostgreSQL query result resource
         * @param int $index Field number, starting from 0
         * @return string
         */
        function fieldType( $res, $index ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }

                return pg_field_type( $res, $index );
        }

        /**
         * @param string $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 null|bool|Blob $s
         * @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
         *
         * @param string $ins SQL string, read from a stream (usually tables.sql)
         * @return string SQL string
         */
        protected function replaceVars( $ins ) {
                $ins = parent::replaceVars( $ins );

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

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

                return $ins;
        }

        /**
         * Various select options
         *
         * @param array $options 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;
                        }
                }

                $preLimitTail .= $this->makeGroupByWithHaving( $options );

                $preLimitTail .= $this->makeOrderBy( $options );

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

                if ( isset( $options['FOR UPDATE'] ) ) {
                        $postLimitTail .= ' FOR UPDATE OF ' .
                                implode( ', ', array_map( array( &$this, 'tableName' ), $options['FOR UPDATE'] ) );
                } elseif ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
                        $postLimitTail .= ' FOR UPDATE';
                }

                if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
                        $startOpts .= 'DISTINCT';
                }

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

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

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

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

        public function buildGroupConcatField(
                $delimiter, $table, $field, $conds = '', $options = array(), $join_conds = array()
        ) {
                $fld = "array_to_string(array_agg($field)," . $this->addQuotes( $delimiter ) . ')';

                return '(' . $this->selectSQLText( $table, $fld, $conds, null, array(), $join_conds ) . ')';
        }

        public function getSearchEngine() {
                return 'SearchPostgres';
        }

        public function streamStatementEnd( &$sql, &$newLine ) {
                # Allow dollar quoting for function declarations
                if ( substr( $newLine, 0, 4 ) == '$mw$' ) {
                        if ( $this->delimiter ) {
                                $this->delimiter = false;
                        } else {
                                $this->delimiter = ';';
                        }
                }

                return parent::streamStatementEnd( $sql, $newLine );
        }

        /**
         * Check to see if a named lock is available. This is non-blocking.
         * See http://www.postgresql.org/docs/8.2/static/functions-admin.html#FUNCTIONS-ADVISORY-LOCKS
         *
         * @param string $lockName Name of lock to poll
         * @param string $method Name of method calling us
         * @return bool
         * @since 1.20
         */
        public function lockIsFree( $lockName, $method ) {
                $key = $this->addQuotes( $this->bigintFromLockName( $lockName ) );
                $result = $this->query( "SELECT (CASE(pg_try_advisory_lock($key))
                        WHEN 'f' THEN 'f' ELSE pg_advisory_unlock($key) END) AS lockstatus", $method );
                $row = $this->fetchObject( $result );

                return ( $row->lockstatus === 't' );
        }

        /**
         * See http://www.postgresql.org/docs/8.2/static/functions-admin.html#FUNCTIONS-ADVISORY-LOCKS
         * @param string $lockName
         * @param string $method
         * @param int $timeout
         * @return bool
         */
        public function lock( $lockName, $method, $timeout = 5 ) {
                $key = $this->addQuotes( $this->bigintFromLockName( $lockName ) );
                for ( $attempts = 1; $attempts <= $timeout; ++$attempts ) {
                        $result = $this->query(
                                "SELECT pg_try_advisory_lock($key) AS lockstatus", $method );
                        $row = $this->fetchObject( $result );
                        if ( $row->lockstatus === 't' ) {
                                return true;
                        } else {
                                sleep( 1 );
                        }
                }
                wfDebug( __METHOD__ . " failed to acquire lock\n" );

                return false;
        }

        /**
         * See http://www.postgresql.org/docs/8.2/static/functions-admin.html#FUNCTIONS-ADVISORY-LOCKSFROM
         * PG DOCS: http://www.postgresql.org/docs/8.2/static/functions-admin.html#FUNCTIONS-ADVISORY-LOCKS
         * @param string $lockName
         * @param string $method
         * @return bool
         */
        public function unlock( $lockName, $method ) {
                $key = $this->addQuotes( $this->bigintFromLockName( $lockName ) );
                $result = $this->query( "SELECT pg_advisory_unlock($key) as lockstatus", $method );
                $row = $this->fetchObject( $result );

                return ( $row->lockstatus === 't' );
        }

        /**
         * @param string $lockName
         * @return string Integer
         */
        private function bigintFromLockName( $lockName ) {
                return wfBaseConvert( substr( sha1( $lockName ), 0, 15 ), 16, 10 );
        }
} // end DatabasePostgres class