includes/libs/rdbms/database/DatabasePostgres.php

   1 <?php
   2 /**
   3  * This is the Postgres database abstraction layer.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Database
  22  */
  23 namespace Wikimedia\Rdbms;
  24
  25 use Wikimedia\Timestamp\ConvertibleTimestamp;
  26 use Wikimedia\WaitConditionLoop;
  27 use Wikimedia;
  28 use Exception;
  29
  30 /**
  31  * @ingroup Database
  32  */
  33 class DatabasePostgres extends Database {
  34         /** @var int|bool */
  35         protected $port;
  36
  37         /** @var resource */
  38         protected $lastResultHandle = null;
  39         /** @var int The number of rows affected as an integer */
  40         protected $lastAffectedRowCount = null;
  41
  42         /** @var float|string */
  43         private $numericVersion = null;
  44         /** @var string Connect string to open a PostgreSQL connection */
  45         private $connectString;
  46         /** @var string */
  47         private $coreSchema;
  48         /** @var string[] Map of (reserved table name => alternate table name) */
  49         private $keywordTableMap = [];
  50
  51         /**
  52          * @see Database::__construct()
  53          * @param array $params Additional parameters include:
  54          *   - keywordTableMap : Map of reserved table names to alternative table names to use
  55          */
  56         public function __construct( array $params ) {
  57                 $this->port = isset( $params['port'] ) ? $params['port'] : false;
  58                 $this->keywordTableMap = isset( $params['keywordTableMap'] )
  59                         ? $params['keywordTableMap']
  60                         : [];
  61
  62                 parent::__construct( $params );
  63         }
  64
  65         public function getType() {
  66                 return 'postgres';
  67         }
  68
  69         public function implicitGroupby() {
  70                 return false;
  71         }
  72
  73         public function implicitOrderby() {
  74                 return false;
  75         }
  76
  77         public function hasConstraint( $name ) {
  78                 $conn = $this->getBindingHandle();
  79
  80                 $sql = "SELECT 1 FROM pg_catalog.pg_constraint c, pg_catalog.pg_namespace n " .
  81                         "WHERE c.connamespace = n.oid AND conname = '" .
  82                         pg_escape_string( $conn, $name ) . "' AND n.nspname = '" .
  83                         pg_escape_string( $conn, $this->getCoreSchema() ) . "'";
  84                 $res = $this->doQuery( $sql );
  85
  86                 return $this->numRows( $res );
  87         }
  88
  89         public function open( $server, $user, $password, $dbName ) {
  90                 # Test for Postgres support, to avoid suppressed fatal error
  91                 if ( !function_exists( 'pg_connect' ) ) {
  92                         throw new DBConnectionError(
  93                                 $this,
  94                                 "Postgres functions missing, have you compiled PHP with the --with-pgsql\n" .
  95                                 "option? (Note: if you recently installed PHP, you may need to restart your\n" .
  96                                 "webserver and database)\n"
  97                         );
  98                 }
  99
 100                 $this->server = $server;
 101                 $this->user = $user;
 102                 $this->password = $password;
 103                 $this->dbName = $dbName;
 104
 105                 $connectVars = [
 106                         // pg_connect() user $user as the default database. Since a database is *required*,
 107                         // at least pick a "don't care" database that is more likely to exist. This case
 108                         // arrises when LoadBalancer::getConnection( $i, [], '' ) is used.
 109                         'dbname' => strlen( $dbName ) ? $dbName : 'postgres',
 110                         'user' => $user,
 111                         'password' => $password
 112                 ];
 113                 if ( $server != false && $server != '' ) {
 114                         $connectVars['host'] = $server;
 115                 }
 116                 if ( (int)$this->port > 0 ) {
 117                         $connectVars['port'] = (int)$this->port;
 118                 }
 119                 if ( $this->flags & self::DBO_SSL ) {
 120                         $connectVars['sslmode'] = 1;
 121                 }
 122
 123                 $this->connectString = $this->makeConnectionString( $connectVars );
 124                 $this->close();
 125                 $this->installErrorHandler();
 126
 127                 try {
 128                         // Use new connections to let LoadBalancer/LBFactory handle reuse
 129                         $this->conn = pg_connect( $this->connectString, PGSQL_CONNECT_FORCE_NEW );
 130                 } catch ( Exception $ex ) {
 131                         $this->restoreErrorHandler();
 132                         throw $ex;
 133                 }
 134
 135                 $phpError = $this->restoreErrorHandler();
 136
 137                 if ( !$this->conn ) {
 138                         $this->queryLogger->debug(
 139                                 "DB connection error\n" .
 140                                 "Server: $server, Database: $dbName, User: $user, Password: " .
 141                                 substr( $password, 0, 3 ) . "...\n"
 142                         );
 143                         $this->queryLogger->debug( $this->lastError() . "\n" );
 144                         throw new DBConnectionError( $this, str_replace( "\n", ' ', $phpError ) );
 145                 }
 146
 147                 $this->opened = true;
 148
 149                 # If called from the command-line (e.g. importDump), only show errors
 150                 if ( $this->cliMode ) {
 151                         $this->doQuery( "SET client_min_messages = 'ERROR'" );
 152                 }
 153
 154                 $this->query( "SET client_encoding='UTF8'", __METHOD__ );
 155                 $this->query( "SET datestyle = 'ISO, YMD'", __METHOD__ );
 156                 $this->query( "SET timezone = 'GMT'", __METHOD__ );
 157                 $this->query( "SET standard_conforming_strings = on", __METHOD__ );
 158                 if ( $this->getServerVersion() >= 9.0 ) {
 159                         $this->query( "SET bytea_output = 'escape'", __METHOD__ ); // PHP bug 53127
 160                 }
 161
 162                 $this->determineCoreSchema( $this->schema );
 163                 // The schema to be used is now in the search path; no need for explicit qualification
 164                 $this->schema = '';
 165
 166                 return $this->conn;
 167         }
 168
 169         public function databasesAreIndependent() {
 170                 return true;
 171         }
 172
 173         /**
 174          * Postgres doesn't support selectDB in the same way MySQL does. So if the
 175          * DB name doesn't match the open connection, open a new one
 176          * @param string $db
 177          * @return bool
 178          * @throws DBUnexpectedError
 179          */
 180         public function selectDB( $db ) {
 181                 if ( $this->dbName !== $db ) {
 182                         return (bool)$this->open( $this->server, $this->user, $this->password, $db );
 183                 } else {
 184                         return true;
 185                 }
 186         }
 187
 188         /**
 189          * @param string[] $vars
 190          * @return string
 191          */
 192         private function makeConnectionString( $vars ) {
 193                 $s = '';
 194                 foreach ( $vars as $name => $value ) {
 195                         $s .= "$name='" . str_replace( "'", "\\'", $value ) . "' ";
 196                 }
 197
 198                 return $s;
 199         }
 200
 201         protected function closeConnection() {
 202                 return $this->conn ? pg_close( $this->conn ) : true;
 203         }
 204
 205         protected function isTransactableQuery( $sql ) {
 206                 return parent::isTransactableQuery( $sql ) &&
 207                         !preg_match( '/^SELECT\s+pg_(try_|)advisory_\w+\(/', $sql );
 208         }
 209
 210         public function doQuery( $sql ) {
 211                 $conn = $this->getBindingHandle();
 212
 213                 $sql = mb_convert_encoding( $sql, 'UTF-8' );
 214                 // Clear previously left over PQresult
 215                 while ( $res = pg_get_result( $conn ) ) {
 216                         pg_free_result( $res );
 217                 }
 218                 if ( pg_send_query( $conn, $sql ) === false ) {
 219                         throw new DBUnexpectedError( $this, "Unable to post new query to PostgreSQL\n" );
 220                 }
 221                 $this->lastResultHandle = pg_get_result( $conn );
 222                 $this->lastAffectedRowCount = null;
 223                 if ( pg_result_error( $this->lastResultHandle ) ) {
 224                         return false;
 225                 }
 226
 227                 return $this->lastResultHandle;
 228         }
 229
 230         protected function dumpError() {
 231                 $diags = [
 232                         PGSQL_DIAG_SEVERITY,
 233                         PGSQL_DIAG_SQLSTATE,
 234                         PGSQL_DIAG_MESSAGE_PRIMARY,
 235                         PGSQL_DIAG_MESSAGE_DETAIL,
 236                         PGSQL_DIAG_MESSAGE_HINT,
 237                         PGSQL_DIAG_STATEMENT_POSITION,
 238                         PGSQL_DIAG_INTERNAL_POSITION,
 239                         PGSQL_DIAG_INTERNAL_QUERY,
 240                         PGSQL_DIAG_CONTEXT,
 241                         PGSQL_DIAG_SOURCE_FILE,
 242                         PGSQL_DIAG_SOURCE_LINE,
 243                         PGSQL_DIAG_SOURCE_FUNCTION
 244                 ];
 245                 foreach ( $diags as $d ) {
 246                         $this->queryLogger->debug( sprintf( "PgSQL ERROR(%d): %s\n",
 247                                 $d, pg_result_error_field( $this->lastResultHandle, $d ) ) );
 248                 }
 249         }
 250
 251         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
 252                 if ( $tempIgnore ) {
 253                         /* Check for constraint violation */
 254                         if ( $errno === '23505' ) {
 255                                 parent::reportQueryError( $error, $errno, $sql, $fname, $tempIgnore );
 256
 257                                 return;
 258                         }
 259                 }
 260                 /* Transaction stays in the ERROR state until rolled back */
 261                 if ( $this->trxLevel ) {
 262                         // Throw away the transaction state, then raise the error as normal.
 263                         // Note that if this connection is managed by LBFactory, it's already expected
 264                         // that the other transactions LBFactory manages will be rolled back.
 265                         $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
 266                 }
 267                 parent::reportQueryError( $error, $errno, $sql, $fname, false );
 268         }
 269
 270         public function freeResult( $res ) {
 271                 if ( $res instanceof ResultWrapper ) {
 272                         $res = $res->result;
 273                 }
 274                 Wikimedia\suppressWarnings();
 275                 $ok = pg_free_result( $res );
 276                 Wikimedia\restoreWarnings();
 277                 if ( !$ok ) {
 278                         throw new DBUnexpectedError( $this, "Unable to free Postgres result\n" );
 279                 }
 280         }
 281
 282         public function fetchObject( $res ) {
 283                 if ( $res instanceof ResultWrapper ) {
 284                         $res = $res->result;
 285                 }
 286                 Wikimedia\suppressWarnings();
 287                 $row = pg_fetch_object( $res );
 288                 Wikimedia\restoreWarnings();
 289                 # @todo FIXME: HACK HACK HACK HACK debug
 290
 291                 # @todo hashar: not sure if the following test really trigger if the object
 292                 #          fetching failed.
 293                 $conn = $this->getBindingHandle();
 294                 if ( pg_last_error( $conn ) ) {
 295                         throw new DBUnexpectedError(
 296                                 $this,
 297                                 'SQL error: ' . htmlspecialchars( pg_last_error( $conn ) )
 298                         );
 299                 }
 300
 301                 return $row;
 302         }
 303
 304         public function fetchRow( $res ) {
 305                 if ( $res instanceof ResultWrapper ) {
 306                         $res = $res->result;
 307                 }
 308                 Wikimedia\suppressWarnings();
 309                 $row = pg_fetch_array( $res );
 310                 Wikimedia\restoreWarnings();
 311
 312                 $conn = $this->getBindingHandle();
 313                 if ( pg_last_error( $conn ) ) {
 314                         throw new DBUnexpectedError(
 315                                 $this,
 316                                 'SQL error: ' . htmlspecialchars( pg_last_error( $conn ) )
 317                         );
 318                 }
 319
 320                 return $row;
 321         }
 322
 323         public function numRows( $res ) {
 324                 if ( $res instanceof ResultWrapper ) {
 325                         $res = $res->result;
 326                 }
 327                 Wikimedia\suppressWarnings();
 328                 $n = pg_num_rows( $res );
 329                 Wikimedia\restoreWarnings();
 330
 331                 $conn = $this->getBindingHandle();
 332                 if ( pg_last_error( $conn ) ) {
 333                         throw new DBUnexpectedError(
 334                                 $this,
 335                                 'SQL error: ' . htmlspecialchars( pg_last_error( $conn ) )
 336                         );
 337                 }
 338
 339                 return $n;
 340         }
 341
 342         public function numFields( $res ) {
 343                 if ( $res instanceof ResultWrapper ) {
 344                         $res = $res->result;
 345                 }
 346
 347                 return pg_num_fields( $res );
 348         }
 349
 350         public function fieldName( $res, $n ) {
 351                 if ( $res instanceof ResultWrapper ) {
 352                         $res = $res->result;
 353                 }
 354
 355                 return pg_field_name( $res, $n );
 356         }
 357
 358         public function insertId() {
 359                 $res = $this->query( "SELECT lastval()" );
 360                 $row = $this->fetchRow( $res );
 361                 return is_null( $row[0] ) ? null : (int)$row[0];
 362         }
 363
 364         public function dataSeek( $res, $row ) {
 365                 if ( $res instanceof ResultWrapper ) {
 366                         $res = $res->result;
 367                 }
 368
 369                 return pg_result_seek( $res, $row );
 370         }
 371
 372         public function lastError() {
 373                 if ( $this->conn ) {
 374                         if ( $this->lastResultHandle ) {
 375                                 return pg_result_error( $this->lastResultHandle );
 376                         } else {
 377                                 return pg_last_error();
 378                         }
 379                 }
 380
 381                 return $this->getLastPHPError() ?: 'No database connection';
 382         }
 383
 384         public function lastErrno() {
 385                 if ( $this->lastResultHandle ) {
 386                         return pg_result_error_field( $this->lastResultHandle, PGSQL_DIAG_SQLSTATE );
 387                 } else {
 388                         return false;
 389                 }
 390         }
 391
 392         protected function fetchAffectedRowCount() {
 393                 if ( !is_null( $this->lastAffectedRowCount ) ) {
 394                         // Forced result for simulated queries
 395                         return $this->lastAffectedRowCount;
 396                 }
 397                 if ( empty( $this->lastResultHandle ) ) {
 398                         return 0;
 399                 }
 400
 401                 return pg_affected_rows( $this->lastResultHandle );
 402         }
 403
 404         /**
 405          * Estimate rows in dataset
 406          * Returns estimated count, based on EXPLAIN output
 407          * This is not necessarily an accurate estimate, so use sparingly
 408          * Returns -1 if count cannot be found
 409          * Takes same arguments as Database::select()
 410          *
 411          * @param string $table
 412          * @param string $vars
 413          * @param string $conds
 414          * @param string $fname
 415          * @param array $options
 416          * @return int
 417          */
 418         public function estimateRowCount( $table, $vars = '*', $conds = '',
 419                 $fname = __METHOD__, $options = []
 420         ) {
 421                 $options['EXPLAIN'] = true;
 422                 $res = $this->select( $table, $vars, $conds, $fname, $options );
 423                 $rows = -1;
 424                 if ( $res ) {
 425                         $row = $this->fetchRow( $res );
 426                         $count = [];
 427                         if ( preg_match( '/rows=(\d+)/', $row[0], $count ) ) {
 428                                 $rows = (int)$count[1];
 429                         }
 430                 }
 431
 432                 return $rows;
 433         }
 434
 435         public function indexInfo( $table, $index, $fname = __METHOD__ ) {
 436                 $sql = "SELECT indexname FROM pg_indexes WHERE tablename='$table'";
 437                 $res = $this->query( $sql, $fname );
 438                 if ( !$res ) {
 439                         return null;
 440                 }
 441                 foreach ( $res as $row ) {
 442                         if ( $row->indexname == $this->indexName( $index ) ) {
 443                                 return $row;
 444                         }
 445                 }
 446
 447                 return false;
 448         }
 449
 450         public function indexAttributes( $index, $schema = false ) {
 451                 if ( $schema === false ) {
 452                         $schema = $this->getCoreSchema();
 453                 }
 454                 /*
 455                  * A subquery would be not needed if we didn't care about the order
 456                  * of attributes, but we do
 457                  */
 458                 $sql = <<<__INDEXATTR__
 459
 460                         SELECT opcname,
 461                                 attname,
 462                                 i.indoption[s.g] as option,
 463                                 pg_am.amname
 464                         FROM
 465                                 (SELECT generate_series(array_lower(isub.indkey,1), array_upper(isub.indkey,1)) AS g
 466                                         FROM
 467                                                 pg_index isub
 468                                         JOIN pg_class cis
 469                                                 ON cis.oid=isub.indexrelid
 470                                         JOIN pg_namespace ns
 471                                                 ON cis.relnamespace = ns.oid
 472                                         WHERE cis.relname='$index' AND ns.nspname='$schema') AS s,
 473                                 pg_attribute,
 474                                 pg_opclass opcls,
 475                                 pg_am,
 476                                 pg_class ci
 477                                 JOIN pg_index i
 478                                         ON ci.oid=i.indexrelid
 479                                 JOIN pg_class ct
 480                                         ON ct.oid = i.indrelid
 481                                 JOIN pg_namespace n
 482                                         ON ci.relnamespace = n.oid
 483                                 WHERE
 484                                         ci.relname='$index' AND n.nspname='$schema'
 485                                         AND     attrelid = ct.oid
 486                                         AND     i.indkey[s.g] = attnum
 487                                         AND     i.indclass[s.g] = opcls.oid
 488                                         AND     pg_am.oid = opcls.opcmethod
 489 __INDEXATTR__;
 490                 $res = $this->query( $sql, __METHOD__ );
 491                 $a = [];
 492                 if ( $res ) {
 493                         foreach ( $res as $row ) {
 494                                 $a[] = [
 495                                         $row->attname,
 496                                         $row->opcname,
 497                                         $row->amname,
 498                                         $row->option ];
 499                         }
 500                 } else {
 501                         return null;
 502                 }
 503
 504                 return $a;
 505         }
 506
 507         public function indexUnique( $table, $index, $fname = __METHOD__ ) {
 508                 $sql = "SELECT indexname FROM pg_indexes WHERE tablename='{$table}'" .
 509                         " AND indexdef LIKE 'CREATE UNIQUE%(" .
 510                         $this->strencode( $this->indexName( $index ) ) .
 511                         ")'";
 512                 $res = $this->query( $sql, $fname );
 513                 if ( !$res ) {
 514                         return null;
 515                 }
 516
 517                 return $res->numRows() > 0;
 518         }
 519
 520         public function selectSQLText(
 521                 $table, $vars, $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
 522         ) {
 523                 if ( is_string( $options ) ) {
 524                         $options = [ $options ];
 525                 }
 526
 527                 // Change the FOR UPDATE option as necessary based on the join conditions. Then pass
 528                 // to the parent function to get the actual SQL text.
 529                 // In Postgres when using FOR UPDATE, only the main table and tables that are inner joined
 530                 // can be locked. That means tables in an outer join cannot be FOR UPDATE locked. Trying to
 531                 // do so causes a DB error. This wrapper checks which tables can be locked and adjusts it
 532                 // accordingly.
 533                 // MySQL uses "ORDER BY NULL" as an optimization hint, but that is illegal in PostgreSQL.
 534                 if ( is_array( $options ) ) {
 535                         $forUpdateKey = array_search( 'FOR UPDATE', $options, true );
 536                         if ( $forUpdateKey !== false && $join_conds ) {
 537                                 unset( $options[$forUpdateKey] );
 538                                 $options['FOR UPDATE'] = [];
 539
 540                                 $toCheck = $table;
 541                                 reset( $toCheck );
 542                                 while ( $toCheck ) {
 543                                         $alias = key( $toCheck );
 544                                         $name = $toCheck[$alias];
 545                                         unset( $toCheck[$alias] );
 546
 547                                         $hasAlias = !is_numeric( $alias );
 548                                         if ( !$hasAlias && is_string( $name ) ) {
 549                                                 $alias = $name;
 550                                         }
 551
 552                                         if ( !isset( $join_conds[$alias] ) ||
 553                                                 !preg_match( '/^(?:LEFT|RIGHT|FULL)(?: OUTER)? JOIN$/i', $join_conds[$alias][0] )
 554                                         ) {
 555                                                 if ( is_array( $name ) ) {
 556                                                         // It's a parenthesized group, process all the tables inside the group.
 557                                                         $toCheck = array_merge( $toCheck, $name );
 558                                                 } else {
 559                                                         // Quote alias names so $this->tableName() won't mangle them
 560                                                         $options['FOR UPDATE'][] = $hasAlias ? $this->addIdentifierQuotes( $alias ) : $alias;
 561                                                 }
 562                                         }
 563                                 }
 564                         }
 565
 566                         if ( isset( $options['ORDER BY'] ) && $options['ORDER BY'] == 'NULL' ) {
 567                                 unset( $options['ORDER BY'] );
 568                         }
 569                 }
 570
 571                 return parent::selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
 572         }
 573
 574         /**
 575          * INSERT wrapper, inserts an array into a table
 576          *
 577          * $args may be a single associative array, or an array of these with numeric keys,
 578          * for multi-row insert (Postgres version 8.2 and above only).
 579          *
 580          * @param string $table Name of the table to insert to.
 581          * @param array $args Items to insert into the table.
 582          * @param string $fname Name of the function, for profiling
 583          * @param array|string $options String or array. Valid options: IGNORE
 584          * @return bool Success of insert operation. IGNORE always returns true.
 585          */
 586         public function insert( $table, $args, $fname = __METHOD__, $options = [] ) {
 587                 if ( !count( $args ) ) {
 588                         return true;
 589                 }
 590
 591                 $table = $this->tableName( $table );
 592                 if ( !isset( $this->numericVersion ) ) {
 593                         $this->getServerVersion();
 594                 }
 595
 596                 if ( !is_array( $options ) ) {
 597                         $options = [ $options ];
 598                 }
 599
 600                 if ( isset( $args[0] ) && is_array( $args[0] ) ) {
 601                         $multi = true;
 602                         $keys = array_keys( $args[0] );
 603                 } else {
 604                         $multi = false;
 605                         $keys = array_keys( $args );
 606                 }
 607
 608                 // If IGNORE is set, we use savepoints to emulate mysql's behavior
 609                 // @todo If PostgreSQL 9.5+, we could use ON CONFLICT DO NOTHING instead
 610                 $savepoint = $olde = null;
 611                 $numrowsinserted = 0;
 612                 if ( in_array( 'IGNORE', $options ) ) {
 613                         $savepoint = new SavepointPostgres( $this, 'mw', $this->queryLogger );
 614                         $olde = error_reporting( 0 );
 615                         // For future use, we may want to track the number of actual inserts
 616                         // Right now, insert (all writes) simply return true/false
 617                 }
 618
 619                 $sql = "INSERT INTO $table (" . implode( ',', $keys ) . ') VALUES ';
 620
 621                 if ( $multi ) {
 622                         if ( $this->numericVersion >= 8.2 && !$savepoint ) {
 623                                 $first = true;
 624                                 foreach ( $args as $row ) {
 625                                         if ( $first ) {
 626                                                 $first = false;
 627                                         } else {
 628                                                 $sql .= ',';
 629                                         }
 630                                         $sql .= '(' . $this->makeList( $row ) . ')';
 631                                 }
 632                                 $res = (bool)$this->query( $sql, $fname, $savepoint );
 633                         } else {
 634                                 $res = true;
 635                                 $origsql = $sql;
 636                                 foreach ( $args as $row ) {
 637                                         $tempsql = $origsql;
 638                                         $tempsql .= '(' . $this->makeList( $row ) . ')';
 639
 640                                         if ( $savepoint ) {
 641                                                 $savepoint->savepoint();
 642                                         }
 643
 644                                         $tempres = (bool)$this->query( $tempsql, $fname, $savepoint );
 645
 646                                         if ( $savepoint ) {
 647                                                 $bar = pg_result_error( $this->lastResultHandle );
 648                                                 if ( $bar != false ) {
 649                                                         $savepoint->rollback();
 650                                                 } else {
 651                                                         $savepoint->release();
 652                                                         $numrowsinserted++;
 653                                                 }
 654                                         }
 655
 656                                         // If any of them fail, we fail overall for this function call
 657                                         // Note that this will be ignored if IGNORE is set
 658                                         if ( !$tempres ) {
 659                                                 $res = false;
 660                                         }
 661                                 }
 662                         }
 663                 } else {
 664                         // Not multi, just a lone insert
 665                         if ( $savepoint ) {
 666                                 $savepoint->savepoint();
 667                         }
 668
 669                         $sql .= '(' . $this->makeList( $args ) . ')';
 670                         $res = (bool)$this->query( $sql, $fname, $savepoint );
 671                         if ( $savepoint ) {
 672                                 $bar = pg_result_error( $this->lastResultHandle );
 673                                 if ( $bar != false ) {
 674                                         $savepoint->rollback();
 675                                 } else {
 676                                         $savepoint->release();
 677                                         $numrowsinserted++;
 678                                 }
 679                         }
 680                 }
 681                 if ( $savepoint ) {
 682                         error_reporting( $olde );
 683                         $savepoint->commit();
 684
 685                         // Set the affected row count for the whole operation
 686                         $this->lastAffectedRowCount = $numrowsinserted;
 687
 688                         // IGNORE always returns true
 689                         return true;
 690                 }
 691
 692                 return $res;
 693         }
 694
 695         /**
 696          * INSERT SELECT wrapper
 697          * $varMap must be an associative array of the form [ 'dest1' => 'source1', ... ]
 698          * Source items may be literals rather then field names, but strings should
 699          * be quoted with Database::addQuotes()
 700          * $conds may be "*" to copy the whole table
 701          * srcTable may be an array of tables.
 702          * @todo FIXME: Implement this a little better (seperate select/insert)?
 703          *
 704          * @param string $destTable
 705          * @param array|string $srcTable
 706          * @param array $varMap
 707          * @param array $conds
 708          * @param string $fname
 709          * @param array $insertOptions
 710          * @param array $selectOptions
 711          * @param array $selectJoinConds
 712          * @return bool
 713          */
 714         public function nativeInsertSelect(
 715                 $destTable, $srcTable, $varMap, $conds, $fname = __METHOD__,
 716                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
 717         ) {
 718                 if ( !is_array( $insertOptions ) ) {
 719                         $insertOptions = [ $insertOptions ];
 720                 }
 721
 722                 /*
 723                  * If IGNORE is set, use the non-native version.
 724                  * @todo If PostgreSQL 9.5+, we could use ON CONFLICT DO NOTHING
 725                  */
 726                 if ( in_array( 'IGNORE', $insertOptions ) ) {
 727                         return $this->nonNativeInsertSelect(
 728                                 $destTable, $srcTable, $varMap, $conds, $fname, $insertOptions, $selectOptions, $selectJoinConds
 729                         );
 730                 }
 731
 732                 return parent::nativeInsertSelect( $destTable, $srcTable, $varMap, $conds, $fname,
 733                         $insertOptions, $selectOptions, $selectJoinConds );
 734         }
 735
 736         public function tableName( $name, $format = 'quoted' ) {
 737                 // Replace reserved words with better ones
 738                 $name = $this->remappedTableName( $name );
 739
 740                 return parent::tableName( $name, $format );
 741         }
 742
 743         /**
 744          * @param string $name
 745          * @return string Value of $name or remapped name if $name is a reserved keyword
 746          */
 747         public function remappedTableName( $name ) {
 748                 return isset( $this->keywordTableMap[$name] ) ? $this->keywordTableMap[$name] : $name;
 749         }
 750
 751         /**
 752          * @param string $name
 753          * @param string $format
 754          * @return string Qualified and encoded (if requested) table name
 755          */
 756         public function realTableName( $name, $format = 'quoted' ) {
 757                 return parent::tableName( $name, $format );
 758         }
 759
 760         public function nextSequenceValue( $seqName ) {
 761                 return new NextSequenceValue;
 762         }
 763
 764         /**
 765          * Return the current value of a sequence. Assumes it has been nextval'ed in this session.
 766          *
 767          * @param string $seqName
 768          * @return int
 769          */
 770         public function currentSequenceValue( $seqName ) {
 771                 $safeseq = str_replace( "'", "''", $seqName );
 772                 $res = $this->query( "SELECT currval('$safeseq')" );
 773                 $row = $this->fetchRow( $res );
 774                 $currval = $row[0];
 775
 776                 return $currval;
 777         }
 778
 779         public function textFieldSize( $table, $field ) {
 780                 $table = $this->tableName( $table );
 781                 $sql = "SELECT t.typname as ftype,a.atttypmod as size
 782                         FROM pg_class c, pg_attribute a, pg_type t
 783                         WHERE relname='$table' AND a.attrelid=c.oid AND
 784                                 a.atttypid=t.oid and a.attname='$field'";
 785                 $res = $this->query( $sql );
 786                 $row = $this->fetchObject( $res );
 787                 if ( $row->ftype == 'varchar' ) {
 788                         $size = $row->size - 4;
 789                 } else {
 790                         $size = $row->size;
 791                 }
 792
 793                 return $size;
 794         }
 795
 796         public function limitResult( $sql, $limit, $offset = false ) {
 797                 return "$sql LIMIT $limit " . ( is_numeric( $offset ) ? " OFFSET {$offset} " : '' );
 798         }
 799
 800         public function wasDeadlock() {
 801                 return $this->lastErrno() == '40P01';
 802         }
 803
 804         public function duplicateTableStructure(
 805                 $oldName, $newName, $temporary = false, $fname = __METHOD__
 806         ) {
 807                 $newName = $this->addIdentifierQuotes( $newName );
 808                 $oldName = $this->addIdentifierQuotes( $oldName );
 809
 810                 return $this->query( 'CREATE ' . ( $temporary ? 'TEMPORARY ' : '' ) . " TABLE $newName " .
 811                         "(LIKE $oldName INCLUDING DEFAULTS INCLUDING INDEXES)", $fname );
 812         }
 813
 814         public function listTables( $prefix = null, $fname = __METHOD__ ) {
 815                 $eschema = $this->addQuotes( $this->getCoreSchema() );
 816                 $result = $this->query(
 817                         "SELECT tablename FROM pg_tables WHERE schemaname = $eschema", $fname );
 818                 $endArray = [];
 819
 820                 foreach ( $result as $table ) {
 821                         $vars = get_object_vars( $table );
 822                         $table = array_pop( $vars );
 823                         if ( !$prefix || strpos( $table, $prefix ) === 0 ) {
 824                                 $endArray[] = $table;
 825                         }
 826                 }
 827
 828                 return $endArray;
 829         }
 830
 831         public function timestamp( $ts = 0 ) {
 832                 $ct = new ConvertibleTimestamp( $ts );
 833
 834                 return $ct->getTimestamp( TS_POSTGRES );
 835         }
 836
 837         /**
 838          * Posted by cc[plus]php[at]c2se[dot]com on 25-Mar-2009 09:12
 839          * to https://secure.php.net/manual/en/ref.pgsql.php
 840          *
 841          * Parsing a postgres array can be a tricky problem, he's my
 842          * take on this, it handles multi-dimensional arrays plus
 843          * escaping using a nasty regexp to determine the limits of each
 844          * data-item.
 845          *
 846          * This should really be handled by PHP PostgreSQL module
 847          *
 848          * @since 1.19
 849          * @param string $text Postgreql array returned in a text form like {a,b}
 850          * @param string[] $output
 851          * @param int|bool $limit
 852          * @param int $offset
 853          * @return string[]
 854          */
 855         private function pg_array_parse( $text, &$output, $limit = false, $offset = 1 ) {
 856                 if ( false === $limit ) {
 857                         $limit = strlen( $text ) - 1;
 858                         $output = [];
 859                 }
 860                 if ( '{}' == $text ) {
 861                         return $output;
 862                 }
 863                 do {
 864                         if ( '{' != $text[$offset] ) {
 865                                 preg_match( "/(\\{?\"([^\"\\\\]|\\\\.)*\"|[^,{}]+)+([,}]+)/",
 866                                         $text, $match, 0, $offset );
 867                                 $offset += strlen( $match[0] );
 868                                 $output[] = ( '"' != $match[1][0]
 869                                         ? $match[1]
 870                                         : stripcslashes( substr( $match[1], 1, -1 ) ) );
 871                                 if ( '},' == $match[3] ) {
 872                                         return $output;
 873                                 }
 874                         } else {
 875                                 $offset = $this->pg_array_parse( $text, $output, $limit, $offset + 1 );
 876                         }
 877                 } while ( $limit > $offset );
 878
 879                 return $output;
 880         }
 881
 882         public function aggregateValue( $valuedata, $valuename = 'value' ) {
 883                 return $valuedata;
 884         }
 885
 886         public function getSoftwareLink() {
 887                 return '[{{int:version-db-postgres-url}} PostgreSQL]';
 888         }
 889
 890         /**
 891          * Return current schema (executes SELECT current_schema())
 892          * Needs transaction
 893          *
 894          * @since 1.19
 895          * @return string Default schema for the current session
 896          */
 897         public function getCurrentSchema() {
 898                 $res = $this->query( "SELECT current_schema()", __METHOD__ );
 899                 $row = $this->fetchRow( $res );
 900
 901                 return $row[0];
 902         }
 903
 904         /**
 905          * Return list of schemas which are accessible without schema name
 906          * This is list does not contain magic keywords like "$user"
 907          * Needs transaction
 908          *
 909          * @see getSearchPath()
 910          * @see setSearchPath()
 911          * @since 1.19
 912          * @return array List of actual schemas for the current sesson
 913          */
 914         public function getSchemas() {
 915                 $res = $this->query( "SELECT current_schemas(false)", __METHOD__ );
 916                 $row = $this->fetchRow( $res );
 917                 $schemas = [];
 918
 919                 /* PHP pgsql support does not support array type, "{a,b}" string is returned */
 920
 921                 return $this->pg_array_parse( $row[0], $schemas );
 922         }
 923
 924         /**
 925          * Return search patch for schemas
 926          * This is different from getSchemas() since it contain magic keywords
 927          * (like "$user").
 928          * Needs transaction
 929          *
 930          * @since 1.19
 931          * @return array How to search for table names schemas for the current user
 932          */
 933         public function getSearchPath() {
 934                 $res = $this->query( "SHOW search_path", __METHOD__ );
 935                 $row = $this->fetchRow( $res );
 936
 937                 /* PostgreSQL returns SHOW values as strings */
 938
 939                 return explode( ",", $row[0] );
 940         }
 941
 942         /**
 943          * Update search_path, values should already be sanitized
 944          * Values may contain magic keywords like "$user"
 945          * @since 1.19
 946          *
 947          * @param array $search_path List of schemas to be searched by default
 948          */
 949         private function setSearchPath( $search_path ) {
 950                 $this->query( "SET search_path = " . implode( ", ", $search_path ) );
 951         }
 952
 953         /**
 954          * Determine default schema for the current application
 955          * Adjust this session schema search path if desired schema exists
 956          * and is not alread there.
 957          *
 958          * We need to have name of the core schema stored to be able
 959          * to query database metadata.
 960          *
 961          * This will be also called by the installer after the schema is created
 962          *
 963          * @since 1.19
 964          *
 965          * @param string $desiredSchema
 966          */
 967         public function determineCoreSchema( $desiredSchema ) {
 968                 $this->begin( __METHOD__, self::TRANSACTION_INTERNAL );
 969                 if ( $this->schemaExists( $desiredSchema ) ) {
 970                         if ( in_array( $desiredSchema, $this->getSchemas() ) ) {
 971                                 $this->coreSchema = $desiredSchema;
 972                                 $this->queryLogger->debug(
 973                                         "Schema \"" . $desiredSchema . "\" already in the search path\n" );
 974                         } else {
 975                                 /**
 976                                  * Prepend our schema (e.g. 'mediawiki') in front
 977                                  * of the search path
 978                                  * Fixes T17816
 979                                  */
 980                                 $search_path = $this->getSearchPath();
 981                                 array_unshift( $search_path,
 982                                         $this->addIdentifierQuotes( $desiredSchema ) );
 983                                 $this->setSearchPath( $search_path );
 984                                 $this->coreSchema = $desiredSchema;
 985                                 $this->queryLogger->debug(
 986                                         "Schema \"" . $desiredSchema . "\" added to the search path\n" );
 987                         }
 988                 } else {
 989                         $this->coreSchema = $this->getCurrentSchema();
 990                         $this->queryLogger->debug(
 991                                 "Schema \"" . $desiredSchema . "\" not found, using current \"" .
 992                                 $this->coreSchema . "\"\n" );
 993                 }
 994                 /* Commit SET otherwise it will be rollbacked on error or IGNORE SELECT */
 995                 $this->commit( __METHOD__, self::FLUSHING_INTERNAL );
 996         }
 997
 998         /**
 999          * Return schema name for core application tables
1000          *
1001          * @since 1.19
1002          * @return string Core schema name
1003          */
1004         public function getCoreSchema() {
1005                 return $this->coreSchema;
1006         }
1007
1008         public function getServerVersion() {
1009                 if ( !isset( $this->numericVersion ) ) {
1010                         $conn = $this->getBindingHandle();
1011                         $versionInfo = pg_version( $conn );
1012                         if ( version_compare( $versionInfo['client'], '7.4.0', 'lt' ) ) {
1013                                 // Old client, abort install
1014                                 $this->numericVersion = '7.3 or earlier';
1015                         } elseif ( isset( $versionInfo['server'] ) ) {
1016                                 // Normal client
1017                                 $this->numericVersion = $versionInfo['server'];
1018                         } else {
1019                                 // T18937: broken pgsql extension from PHP<5.3
1020                                 $this->numericVersion = pg_parameter_status( $conn, 'server_version' );
1021                         }
1022                 }
1023
1024                 return $this->numericVersion;
1025         }
1026
1027         /**
1028          * Query whether a given relation exists (in the given schema, or the
1029          * default mw one if not given)
1030          * @param string $table
1031          * @param array|string $types
1032          * @param bool|string $schema
1033          * @return bool
1034          */
1035         private function relationExists( $table, $types, $schema = false ) {
1036                 if ( !is_array( $types ) ) {
1037                         $types = [ $types ];
1038                 }
1039                 if ( $schema === false ) {
1040                         $schema = $this->getCoreSchema();
1041                 }
1042                 $table = $this->realTableName( $table, 'raw' );
1043                 $etable = $this->addQuotes( $table );
1044                 $eschema = $this->addQuotes( $schema );
1045                 $sql = "SELECT 1 FROM pg_catalog.pg_class c, pg_catalog.pg_namespace n "
1046                         . "WHERE c.relnamespace = n.oid AND c.relname = $etable AND n.nspname = $eschema "
1047                         . "AND c.relkind IN ('" . implode( "','", $types ) . "')";
1048                 $res = $this->query( $sql );
1049                 $count = $res ? $res->numRows() : 0;
1050
1051                 return (bool)$count;
1052         }
1053
1054         /**
1055          * For backward compatibility, this function checks both tables and views.
1056          * @param string $table
1057          * @param string $fname
1058          * @param bool|string $schema
1059          * @return bool
1060          */
1061         public function tableExists( $table, $fname = __METHOD__, $schema = false ) {
1062                 return $this->relationExists( $table, [ 'r', 'v' ], $schema );
1063         }
1064
1065         public function sequenceExists( $sequence, $schema = false ) {
1066                 return $this->relationExists( $sequence, 'S', $schema );
1067         }
1068
1069         public function triggerExists( $table, $trigger ) {
1070                 $q = <<<SQL
1071         SELECT 1 FROM pg_class, pg_namespace, pg_trigger
1072                 WHERE relnamespace=pg_namespace.oid AND relkind='r'
1073                         AND tgrelid=pg_class.oid
1074                         AND nspname=%s AND relname=%s AND tgname=%s
1075 SQL;
1076                 $res = $this->query(
1077                         sprintf(
1078                                 $q,
1079                                 $this->addQuotes( $this->getCoreSchema() ),
1080                                 $this->addQuotes( $table ),
1081                                 $this->addQuotes( $trigger )
1082                         )
1083                 );
1084                 if ( !$res ) {
1085                         return null;
1086                 }
1087                 $rows = $res->numRows();
1088
1089                 return $rows;
1090         }
1091
1092         public function ruleExists( $table, $rule ) {
1093                 $exists = $this->selectField( 'pg_rules', 'rulename',
1094                         [
1095                                 'rulename' => $rule,
1096                                 'tablename' => $table,
1097                                 'schemaname' => $this->getCoreSchema()
1098                         ]
1099                 );
1100
1101                 return $exists === $rule;
1102         }
1103
1104         public function constraintExists( $table, $constraint ) {
1105                 $sql = sprintf( "SELECT 1 FROM information_schema.table_constraints " .
1106                         "WHERE constraint_schema = %s AND table_name = %s AND constraint_name = %s",
1107                         $this->addQuotes( $this->getCoreSchema() ),
1108                         $this->addQuotes( $table ),
1109                         $this->addQuotes( $constraint )
1110                 );
1111                 $res = $this->query( $sql );
1112                 if ( !$res ) {
1113                         return null;
1114                 }
1115                 $rows = $res->numRows();
1116
1117                 return $rows;
1118         }
1119
1120         /**
1121          * Query whether a given schema exists. Returns true if it does, false if it doesn't.
1122          * @param string $schema
1123          * @return bool
1124          */
1125         public function schemaExists( $schema ) {
1126                 if ( !strlen( $schema ) ) {
1127                         return false; // short-circuit
1128                 }
1129
1130                 $exists = $this->selectField(
1131                         '"pg_catalog"."pg_namespace"', 1, [ 'nspname' => $schema ], __METHOD__ );
1132
1133                 return (bool)$exists;
1134         }
1135
1136         /**
1137          * Returns true if a given role (i.e. user) exists, false otherwise.
1138          * @param string $roleName
1139          * @return bool
1140          */
1141         public function roleExists( $roleName ) {
1142                 $exists = $this->selectField( '"pg_catalog"."pg_roles"', 1,
1143                         [ 'rolname' => $roleName ], __METHOD__ );
1144
1145                 return (bool)$exists;
1146         }
1147
1148         /**
1149          * @param string $table
1150          * @param string $field
1151          * @return PostgresField|null
1152          */
1153         public function fieldInfo( $table, $field ) {
1154                 return PostgresField::fromText( $this, $table, $field );
1155         }
1156
1157         /**
1158          * pg_field_type() wrapper
1159          * @param ResultWrapper|resource $res ResultWrapper or PostgreSQL query result resource
1160          * @param int $index Field number, starting from 0
1161          * @return string
1162          */
1163         public function fieldType( $res, $index ) {
1164                 if ( $res instanceof ResultWrapper ) {
1165                         $res = $res->result;
1166                 }
1167
1168                 return pg_field_type( $res, $index );
1169         }
1170
1171         public function encodeBlob( $b ) {
1172                 return new PostgresBlob( pg_escape_bytea( $b ) );
1173         }
1174
1175         public function decodeBlob( $b ) {
1176                 if ( $b instanceof PostgresBlob ) {
1177                         $b = $b->fetch();
1178                 } elseif ( $b instanceof Blob ) {
1179                         return $b->fetch();
1180                 }
1181
1182                 return pg_unescape_bytea( $b );
1183         }
1184
1185         public function strencode( $s ) {
1186                 // Should not be called by us
1187                 return pg_escape_string( $this->getBindingHandle(), (string)$s );
1188         }
1189
1190         public function addQuotes( $s ) {
1191                 $conn = $this->getBindingHandle();
1192
1193                 if ( is_null( $s ) ) {
1194                         return 'NULL';
1195                 } elseif ( is_bool( $s ) ) {
1196                         return intval( $s );
1197                 } elseif ( $s instanceof Blob ) {
1198                         if ( $s instanceof PostgresBlob ) {
1199                                 $s = $s->fetch();
1200                         } else {
1201                                 $s = pg_escape_bytea( $conn, $s->fetch() );
1202                         }
1203                         return "'$s'";
1204                 } elseif ( $s instanceof NextSequenceValue ) {
1205                         return 'DEFAULT';
1206                 }
1207
1208                 return "'" . pg_escape_string( $conn, (string)$s ) . "'";
1209         }
1210
1211         /**
1212          * Postgres specific version of replaceVars.
1213          * Calls the parent version in Database.php
1214          *
1215          * @param string $ins SQL string, read from a stream (usually tables.sql)
1216          * @return string SQL string
1217          */
1218         protected function replaceVars( $ins ) {
1219                 $ins = parent::replaceVars( $ins );
1220
1221                 if ( $this->numericVersion >= 8.3 ) {
1222                         // Thanks for not providing backwards-compatibility, 8.3
1223                         $ins = preg_replace( "/to_tsvector\s*\(\s*'default'\s*,/", 'to_tsvector(', $ins );
1224                 }
1225
1226                 if ( $this->numericVersion <= 8.1 ) { // Our minimum version
1227                         $ins = str_replace( 'USING gin', 'USING gist', $ins );
1228                 }
1229
1230                 return $ins;
1231         }
1232
1233         public function makeSelectOptions( $options ) {
1234                 $preLimitTail = $postLimitTail = '';
1235                 $startOpts = $useIndex = $ignoreIndex = '';
1236
1237                 $noKeyOptions = [];
1238                 foreach ( $options as $key => $option ) {
1239                         if ( is_numeric( $key ) ) {
1240                                 $noKeyOptions[$option] = true;
1241                         }
1242                 }
1243
1244                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1245
1246                 $preLimitTail .= $this->makeOrderBy( $options );
1247
1248                 if ( isset( $options['FOR UPDATE'] ) ) {
1249                         $postLimitTail .= ' FOR UPDATE OF ' .
1250                                 implode( ', ', array_map( [ $this, 'tableName' ], $options['FOR UPDATE'] ) );
1251                 } elseif ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1252                         $postLimitTail .= ' FOR UPDATE';
1253                 }
1254
1255                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1256                         $startOpts .= 'DISTINCT';
1257                 }
1258
1259                 return [ $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ];
1260         }
1261
1262         public function getDBname() {
1263                 return $this->dbName;
1264         }
1265
1266         public function getServer() {
1267                 return $this->server;
1268         }
1269
1270         public function buildConcat( $stringList ) {
1271                 return implode( ' || ', $stringList );
1272         }
1273
1274         public function buildGroupConcatField(
1275                 $delimiter, $table, $field, $conds = '', $options = [], $join_conds = []
1276         ) {
1277                 $fld = "array_to_string(array_agg($field)," . $this->addQuotes( $delimiter ) . ')';
1278
1279                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
1280         }
1281
1282         public function buildStringCast( $field ) {
1283                 return $field . '::text';
1284         }
1285
1286         public function streamStatementEnd( &$sql, &$newLine ) {
1287                 # Allow dollar quoting for function declarations
1288                 if ( substr( $newLine, 0, 4 ) == '$mw$' ) {
1289                         if ( $this->delimiter ) {
1290                                 $this->delimiter = false;
1291                         } else {
1292                                 $this->delimiter = ';';
1293                         }
1294                 }
1295
1296                 return parent::streamStatementEnd( $sql, $newLine );
1297         }
1298
1299         public function doLockTables( array $read, array $write, $method ) {
1300                 $tablesWrite = [];
1301                 foreach ( $write as $table ) {
1302                         $tablesWrite[] = $this->tableName( $table );
1303                 }
1304                 $tablesRead = [];
1305                 foreach ( $read as $table ) {
1306                         $tablesRead[] = $this->tableName( $table );
1307                 }
1308
1309                 // Acquire locks for the duration of the current transaction...
1310                 if ( $tablesWrite ) {
1311                         $this->query(
1312                                 'LOCK TABLE ONLY ' . implode( ',', $tablesWrite ) . ' IN EXCLUSIVE MODE',
1313                                 $method
1314                         );
1315                 }
1316                 if ( $tablesRead ) {
1317                         $this->query(
1318                                 'LOCK TABLE ONLY ' . implode( ',', $tablesRead ) . ' IN SHARE MODE',
1319                                 $method
1320                         );
1321                 }
1322
1323                 return true;
1324         }
1325
1326         public function lockIsFree( $lockName, $method ) {
1327                 if ( !parent::lockIsFree( $lockName, $method ) ) {
1328                         return false; // already held
1329                 }
1330                 // http://www.postgresql.org/docs/8.2/static/functions-admin.html#FUNCTIONS-ADVISORY-LOCKS
1331                 $key = $this->addQuotes( $this->bigintFromLockName( $lockName ) );
1332                 $result = $this->query( "SELECT (CASE(pg_try_advisory_lock($key))
1333                         WHEN 'f' THEN 'f' ELSE pg_advisory_unlock($key) END) AS lockstatus", $method );
1334                 $row = $this->fetchObject( $result );
1335
1336                 return ( $row->lockstatus === 't' );
1337         }
1338
1339         public function lock( $lockName, $method, $timeout = 5 ) {
1340                 // http://www.postgresql.org/docs/8.2/static/functions-admin.html#FUNCTIONS-ADVISORY-LOCKS
1341                 $key = $this->addQuotes( $this->bigintFromLockName( $lockName ) );
1342                 $loop = new WaitConditionLoop(
1343                         function () use ( $lockName, $key, $timeout, $method ) {
1344                                 $res = $this->query( "SELECT pg_try_advisory_lock($key) AS lockstatus", $method );
1345                                 $row = $this->fetchObject( $res );
1346                                 if ( $row->lockstatus === 't' ) {
1347                                         parent::lock( $lockName, $method, $timeout ); // record
1348                                         return true;
1349                                 }
1350
1351                                 return WaitConditionLoop::CONDITION_CONTINUE;
1352                         },
1353                         $timeout
1354                 );
1355
1356                 return ( $loop->invoke() === $loop::CONDITION_REACHED );
1357         }
1358
1359         public function unlock( $lockName, $method ) {
1360                 // http://www.postgresql.org/docs/8.2/static/functions-admin.html#FUNCTIONS-ADVISORY-LOCKS
1361                 $key = $this->addQuotes( $this->bigintFromLockName( $lockName ) );
1362                 $result = $this->query( "SELECT pg_advisory_unlock($key) as lockstatus", $method );
1363                 $row = $this->fetchObject( $result );
1364
1365                 if ( $row->lockstatus === 't' ) {
1366                         parent::unlock( $lockName, $method ); // record
1367                         return true;
1368                 }
1369
1370                 $this->queryLogger->debug( __METHOD__ . " failed to release lock\n" );
1371
1372                 return false;
1373         }
1374
1375         public function serverIsReadOnly() {
1376                 $res = $this->query( "SHOW default_transaction_read_only", __METHOD__ );
1377                 $row = $this->fetchObject( $res );
1378
1379                 return $row ? ( strtolower( $row->default_transaction_read_only ) === 'on' ) : false;
1380         }
1381
1382         /**
1383          * @param string $lockName
1384          * @return string Integer
1385          */
1386         private function bigintFromLockName( $lockName ) {
1387                 return \Wikimedia\base_convert( substr( sha1( $lockName ), 0, 15 ), 16, 10 );
1388         }
1389 }
1390
1391 class_alias( DatabasePostgres::class, 'DatabasePostgres' );