Merge "ResourceLoader: Deprecate ResourceLoader::makeConfigSetScript"

[mediawiki.git] / includes / libs / rdbms / database / DatabasePostgres.php

<?php
/**
 * 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
 */

// Suppress UnusedPluginSuppression because Phan on PHP 7.4 and PHP 8.1 need different suppressions
// @phan-file-suppress UnusedPluginSuppression,UnusedPluginFileSuppression

namespace Wikimedia\Rdbms;

use RuntimeException;
use Wikimedia\Rdbms\Platform\PostgresPlatform;
use Wikimedia\Rdbms\Replication\ReplicationReporter;
use Wikimedia\WaitConditionLoop;

/**
 * Postgres database abstraction layer.
 *
 * @ingroup Database
 */
class DatabasePostgres extends Database {
        /** @var int */
        private $port;
        /** @var string */
        private $tempSchema;
        /** @var float|string|null */
        private $numericVersion;

        /** @var resource|null */
        private $lastResultHandle;

        /** @var PostgresPlatform */
        protected $platform;

        /**
         * @see Database::__construct()
         * @param array $params Additional parameters include:
         *   - port: A port to append to the hostname
         */
        public function __construct( array $params ) {
                $this->port = intval( $params['port'] ?? null );
                parent::__construct( $params );

                $this->platform = new PostgresPlatform(
                        $this,
                        $this->logger,
                        $this->currentDomain,
                        $this->errorLogger
                );
                $this->replicationReporter = new ReplicationReporter(
                        $params['topologyRole'],
                        $this->logger,
                        $params['srvCache']
                );
        }

        public function getType() {
                return 'postgres';
        }

        protected function open( $server, $user, $password, $db, $schema, $tablePrefix ) {
                if ( !function_exists( 'pg_connect' ) ) {
                        throw $this->newExceptionAfterConnectError(
                                "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)"
                        );
                }

                $this->close( __METHOD__ );

                $connectVars = [
                        // A database must be specified in order to connect to Postgres. If $dbName is not
                        // specified, then use the standard "postgres" database that should exist by default.
                        'dbname' => ( $db !== null && $db !== '' ) ? $db : 'postgres',
                        'user' => $user,
                        'password' => $password
                ];
                if ( $server !== null && $server !== '' ) {
                        $connectVars['host'] = $server;
                }
                if ( $this->port > 0 ) {
                        $connectVars['port'] = $this->port;
                }
                if ( $this->ssl ) {
                        $connectVars['sslmode'] = 'require';
                }
                $connectString = $this->makeConnectionString( $connectVars );

                $this->installErrorHandler();
                try {
                        $this->conn = pg_connect( $connectString, PGSQL_CONNECT_FORCE_NEW ) ?: null;
                } catch ( RuntimeException $e ) {
                        $this->restoreErrorHandler();
                        throw $this->newExceptionAfterConnectError( $e->getMessage() );
                }
                $error = $this->restoreErrorHandler();

                if ( !$this->conn ) {
                        throw $this->newExceptionAfterConnectError( $error ?: $this->lastError() );
                }

                try {
                        // Since no transaction is active at this point, any SET commands should apply
                        // for the entire session (e.g. will not be reverted on transaction rollback).
                        // See https://www.postgresql.org/docs/8.3/sql-set.html
                        $variables = [
                                'client_encoding' => 'UTF8',
                                'datestyle' => 'ISO, YMD',
                                'timezone' => 'GMT',
                                'standard_conforming_strings' => 'on',
                                'bytea_output' => 'escape',
                                'client_min_messages' => 'ERROR'
                        ];
                        foreach ( $variables as $var => $val ) {
                                $sql = 'SET ' . $this->platform->addIdentifierQuotes( $var ) . ' = ' . $this->addQuotes( $val );
                                $query = new Query( $sql, self::QUERY_NO_RETRY | self::QUERY_CHANGE_TRX, 'SET' );
                                $this->query( $query, __METHOD__ );
                        }
                        $this->determineCoreSchema( $schema );
                        $this->currentDomain = new DatabaseDomain( $db, $schema, $tablePrefix );
                        $this->platform->setCurrentDomain( $this->currentDomain );
                } catch ( RuntimeException $e ) {
                        throw $this->newExceptionAfterConnectError( $e->getMessage() );
                }
        }

        public function databasesAreIndependent() {
                return true;
        }

        public function doSelectDomain( DatabaseDomain $domain ) {
                $database = $domain->getDatabase();
                if ( $database === null ) {
                        // A null database means "don't care" so leave it as is and update the table prefix
                        $this->currentDomain = new DatabaseDomain(
                                $this->currentDomain->getDatabase(),
                                $domain->getSchema() ?? $this->currentDomain->getSchema(),
                                $domain->getTablePrefix()
                        );
                        $this->platform->setCurrentDomain( $this->currentDomain );
                } elseif ( $this->getDBname() !== $database ) {
                        // 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
                        $this->open(
                                $this->connectionParams[self::CONN_HOST],
                                $this->connectionParams[self::CONN_USER],
                                $this->connectionParams[self::CONN_PASSWORD],
                                $database,
                                $domain->getSchema(),
                                $domain->getTablePrefix()
                        );
                } else {
                        $this->currentDomain = $domain;
                        $this->platform->setCurrentDomain( $domain );
                }

                return true;
        }

        /**
         * @param string[] $vars
         * @return string
         */
        private function makeConnectionString( $vars ) {
                $s = '';
                foreach ( $vars as $name => $value ) {
                        $s .= "$name='" . str_replace( [ "\\", "'" ], [ "\\\\", "\\'" ], $value ) . "' ";
                }

                return $s;
        }

        protected function closeConnection() {
                return $this->conn ? pg_close( $this->conn ) : true;
        }

        public function doSingleStatementQuery( string $sql ): QueryStatus {
                $conn = $this->getBindingHandle();

                $sql = mb_convert_encoding( $sql, 'UTF-8' );
                // Clear any previously left over result
                // phpcs:ignore Generic.CodeAnalysis.AssignmentInCondition.FoundInWhileCondition
                while ( $priorRes = pg_get_result( $conn ) ) {
                        pg_free_result( $priorRes );
                }

                if ( pg_send_query( $conn, $sql ) === false ) {
                        throw new DBUnexpectedError( $this, "Unable to post new query to PostgreSQL\n" );
                }

                // Newer PHP versions use PgSql\Result instead of resource variables
                // https://www.php.net/manual/en/function.pg-get-result.php
                $pgRes = pg_get_result( $conn );
                // Phan on PHP 7.4 and PHP 8.1 need different suppressions
                // @phan-suppress-next-line PhanTypeMismatchProperty,PhanTypeMismatchPropertyProbablyReal
                $this->lastResultHandle = $pgRes;
                $res = pg_result_error( $pgRes ) ? false : $pgRes;

                return new QueryStatus(
                        // @phan-suppress-next-line PhanTypeMismatchArgument
                        is_bool( $res ) ? $res : new PostgresResultWrapper( $this, $conn, $res ),
                        $pgRes ? pg_affected_rows( $pgRes ) : 0,
                        $this->lastError(),
                        $this->lastErrno()
                );
        }

        protected function dumpError() {
                $diags = [
                        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 ) {
                        $this->logger->debug( sprintf( "PgSQL ERROR(%d): %s",
                                // @phan-suppress-next-line PhanTypeMismatchArgumentInternal
                                $d, pg_result_error_field( $this->lastResultHandle, $d ) ) );
                }
        }

        protected function lastInsertId() {
                // Avoid using query() to prevent unwanted side-effects like changing affected
                // row counts or connection retries. Note that lastval() is connection-specific.
                // Note that this causes "lastval is not yet defined in this session" errors if
                // nextval() was never directly or implicitly triggered (error out any transaction).
                $qs = $this->doSingleStatementQuery( "SELECT lastval() AS id" );

                return $qs->res ? (int)$qs->res->fetchRow()['id'] : 0;
        }

        public function lastError() {
                if ( $this->conn ) {
                        if ( $this->lastResultHandle ) {
                                // @phan-suppress-next-line PhanTypeMismatchArgumentInternal
                                return pg_result_error( $this->lastResultHandle );
                        } else {
                                return pg_last_error() ?: $this->lastConnectError;
                        }
                }

                return $this->getLastPHPError() ?: 'No database connection';
        }

        public function lastErrno() {
                if ( $this->lastResultHandle ) {
                        // @phan-suppress-next-line PhanTypeMismatchArgumentInternal
                        $lastErrno = pg_result_error_field( $this->lastResultHandle, PGSQL_DIAG_SQLSTATE );
                        if ( $lastErrno !== false ) {
                                return $lastErrno;
                        }
                }

                return '00000';
        }

        public function estimateRowCount( $table, $var = '*', $conds = '',
                $fname = __METHOD__, $options = [], $join_conds = []
        ): int {
                $conds = $this->platform->normalizeConditions( $conds, $fname );
                $column = $this->platform->extractSingleFieldFromList( $var );
                if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
                        $conds[] = "$column IS NOT NULL";
                }

                $options['EXPLAIN'] = true;
                $res = $this->select( $table, $var, $conds, $fname, $options, $join_conds );
                $rows = -1;
                if ( $res ) {
                        $row = $res->fetchRow();
                        $count = [];
                        if ( preg_match( '/rows=(\d+)/', $row[0], $count ) ) {
                                $rows = (int)$count[1];
                        }
                }

                return $rows;
        }

        public function indexInfo( $table, $index, $fname = __METHOD__ ) {
                $components = $this->platform->qualifiedTableComponents( $table );
                if ( count( $components ) === 1 ) {
                        $schema = $this->getCoreSchema();
                        $tableComponent = $components[0];
                } elseif ( count( $components ) === 2 ) {
                        [ $schema, $tableComponent ] = $components;
                } else {
                        [ , $schema, $tableComponent ] = $components;
                }
                $encSchema = $this->addQuotes( $schema );
                $encTable = $this->addQuotes( $tableComponent );
                $encIndex = $this->addQuotes( $this->platform->indexName( $index ) );
                $query = new Query(
                        "SELECT indexname,indexdef FROM pg_indexes " .
                                "WHERE schemaname=$encSchema AND tablename=$encTable AND indexname=$encIndex",
                        self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
                        'SELECT'
                );
                $res = $this->query( $query );
                $row = $res->fetchObject();

                if ( $row ) {
                        return [ 'unique' => ( strpos( $row->indexdef, 'CREATE UNIQUE ' ) === 0 ) ];
                }

                return false;
        }

        public function indexAttributes( $index, $schema = false ) {
                if ( $schema === false ) {
                        $schemas = $this->getCoreSchemas();
                } else {
                        $schemas = [ $schema ];
                }

                $eindex = $this->addQuotes( $index );

                $flags = self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE;
                foreach ( $schemas as $schema ) {
                        $eschema = $this->addQuotes( $schema );
                        /*
                         * 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=$eindex AND ns.nspname=$eschema) 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=$eindex AND n.nspname=$eschema
                                                AND     attrelid = ct.oid
                                                AND     i.indkey[s.g] = attnum
                                                AND     i.indclass[s.g] = opcls.oid
                                                AND     pg_am.oid = opcls.opcmethod
__INDEXATTR__;
                        $query = new Query( $sql, $flags, 'SELECT' );
                        $res = $this->query( $query, __METHOD__ );
                        $a = [];
                        if ( $res ) {
                                foreach ( $res as $row ) {
                                        $a[] = [
                                                $row->attname,
                                                $row->opcname,
                                                $row->amname,
                                                $row->option ];
                                }
                                return $a;
                        }
                }
                return null;
        }

        protected function doInsertSelectNative(
                $destTable,
                $srcTable,
                array $varMap,
                $conds,
                $fname,
                array $insertOptions,
                array $selectOptions,
                $selectJoinConds
        ) {
                if ( in_array( 'IGNORE', $insertOptions ) ) {
                        // Use "ON CONFLICT DO" if we have it for IGNORE
                        $destTableEnc = $this->tableName( $destTable );

                        $selectSql = $this->selectSQLText(
                                $srcTable,
                                array_values( $varMap ),
                                $conds,
                                $fname,
                                $selectOptions,
                                $selectJoinConds
                        );

                        $sql = "INSERT INTO $destTableEnc (" . implode( ',', array_keys( $varMap ) ) . ') ' .
                                $selectSql . ' ON CONFLICT DO NOTHING';
                        $query = new Query( $sql, self::QUERY_CHANGE_ROWS, 'INSERT', $destTable );
                        $this->query( $query, $fname );
                } else {
                        parent::doInsertSelectNative( $destTable, $srcTable, $varMap, $conds, $fname,
                                $insertOptions, $selectOptions, $selectJoinConds );
                }
        }

        public function getValueTypesForWithClause( $table ) {
                $typesByColumn = [];

                $flags = self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE;
                $encTable = $this->addQuotes( $table );
                foreach ( $this->getCoreSchemas() as $schema ) {
                        $encSchema = $this->addQuotes( $schema );
                        $sql = "SELECT column_name,udt_name " .
                                "FROM information_schema.columns " .
                                "WHERE table_name = $encTable AND table_schema = $encSchema";
                        $query = new Query( $sql, $flags, 'SELECT' );
                        $res = $this->query( $query, __METHOD__ );
                        if ( $res->numRows() ) {
                                foreach ( $res as $row ) {
                                        $typesByColumn[$row->column_name] = $row->udt_name;
                                }
                                break;
                        }
                }

                return $typesByColumn;
        }

        protected function isConnectionError( $errno ) {
                // https://www.postgresql.org/docs/9.2/static/errcodes-appendix.html
                static $codes = [ '08000', '08003', '08006', '08001', '08004', '57P01', '57P03', '53300' ];

                return in_array( $errno, $codes, true );
        }

        protected function isQueryTimeoutError( $errno ) {
                // https://www.postgresql.org/docs/9.2/static/errcodes-appendix.html
                return ( $errno === '57014' );
        }

        protected function isKnownStatementRollbackError( $errno ) {
                return false; // transaction has to be rolled-back from error state
        }

        public function duplicateTableStructure(
                $oldName, $newName, $temporary = false, $fname = __METHOD__
        ) {
                $newNameE = $this->platform->addIdentifierQuotes( $newName );
                $oldNameE = $this->platform->addIdentifierQuotes( $oldName );

                $temporary = $temporary ? 'TEMPORARY' : '';
                $query = new Query(
                        "CREATE $temporary TABLE $newNameE " .
                        "(LIKE $oldNameE INCLUDING DEFAULTS INCLUDING INDEXES)",
                        self::QUERY_PSEUDO_PERMANENT | self::QUERY_CHANGE_SCHEMA,
                        $temporary ? 'CREATE TEMPORARY' : 'CREATE',
                        // Use a dot to avoid double-prefixing in Database::getTempTableWrites()
                        '.' . $newName
                );
                $ret = $this->query( $query, $fname );
                if ( !$ret ) {
                        return $ret;
                }

                $sql = 'SELECT attname FROM pg_class c'
                        . ' JOIN pg_namespace n ON (n.oid = c.relnamespace)'
                        . ' JOIN pg_attribute a ON (a.attrelid = c.oid)'
                        . ' JOIN pg_attrdef d ON (c.oid=d.adrelid and a.attnum=d.adnum)'
                        . ' WHERE relkind = \'r\''
                        . ' AND nspname = ' . $this->addQuotes( $this->getCoreSchema() )
                        . ' AND relname = ' . $this->addQuotes( $oldName )
                        . ' AND pg_get_expr(adbin, adrelid) LIKE \'nextval(%\'';
                $query = new Query(
                        $sql,
                        self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
                        'SELECT'
                );

                $res = $this->query( $query, $fname );
                $row = $res->fetchObject();
                if ( $row ) {
                        $field = $row->attname;
                        $newSeq = "{$newName}_{$field}_seq";
                        $fieldE = $this->platform->addIdentifierQuotes( $field );
                        $newSeqE = $this->platform->addIdentifierQuotes( $newSeq );
                        $newSeqQ = $this->addQuotes( $newSeq );
                        $query = new Query(
                                "CREATE $temporary SEQUENCE $newSeqE OWNED BY $newNameE.$fieldE",
                                self::QUERY_CHANGE_SCHEMA,
                                'CREATE',
                                // Do not treat this is as a table modification on top of the CREATE above.
                                null
                        );
                        $this->query( $query, $fname );
                        $query = new Query(
                                "ALTER TABLE $newNameE ALTER COLUMN $fieldE SET DEFAULT nextval({$newSeqQ}::regclass)",
                                self::QUERY_CHANGE_SCHEMA,
                                'ALTER',
                                // Do not treat this is as a table modification on top of the CREATE above.
                                null
                        );
                        $this->query( $query, $fname );
                }

                return $ret;
        }

        public function truncateTable( $table, $fname = __METHOD__ ) {
                $sql = "TRUNCATE TABLE " . $this->tableName( $table ) . " RESTART IDENTITY";
                $query = new Query( $sql, self::QUERY_CHANGE_SCHEMA, 'TRUNCATE', $table );
                $this->query( $query, $fname );
        }

        /**
         * @param string $prefix Only show tables with this prefix, e.g. mw_
         * @param string $fname Calling function name
         * @return string[]
         * @suppress SecurityCheck-SQLInjection array_map not recognized T204911
         */
        public function listTables( $prefix = '', $fname = __METHOD__ ) {
                $eschemas = implode( ',', array_map( [ $this, 'addQuotes' ], $this->getCoreSchemas() ) );
                $query = new Query(
                        "SELECT DISTINCT tablename FROM pg_tables WHERE schemaname IN ($eschemas)",
                        self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
                        'SELECT'
                );
                $result = $this->query( $query, $fname );
                $endArray = [];

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

                return $endArray;
        }

        /**
         * Posted by cc[plus]php[at]c2se[dot]com on 25-Mar-2009 09:12
         * to https://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|false $limit
         * @param int $offset
         * @return string[]
         */
        private function pg_array_parse( $text, &$output, $limit = false, $offset = 1 ) {
                if ( $limit === false ) {
                        $limit = strlen( $text ) - 1;
                        $output = [];
                }
                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;
        }

        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
         */
        public function getCurrentSchema() {
                $query = new Query(
                        "SELECT current_schema()",
                        self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
                        'SELECT'
                );
                $res = $this->query( $query, __METHOD__ );
                $row = $res->fetchRow();

                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 session
         */
        public function getSchemas() {
                $query = new Query(
                        "SELECT current_schemas(false)",
                        self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
                        'SELECT'
                );
                $res = $this->query( $query, __METHOD__ );
                $row = $res->fetchRow();
                $schemas = [];

                /* 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
         */
        public function getSearchPath() {
                $query = new Query(
                        "SHOW search_path",
                        self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
                        'SHOW'
                );
                $res = $this->query( $query, __METHOD__ );
                $row = $res->fetchRow();

                /* 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 string[] $search_path List of schemas to be searched by default
         */
        private function setSearchPath( $search_path ) {
                $query = new Query(
                        "SET search_path = " . implode( ", ", $search_path ),
                        self::QUERY_CHANGE_TRX,
                        'SET'
                );
                $this->query( $query, __METHOD__ );
        }

        /**
         * Determine default schema for the current application
         * Adjust this session schema search path if desired schema exists
         * and is not already 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|null $desiredSchema
         */
        public function determineCoreSchema( $desiredSchema ) {
                if ( $this->trxLevel() ) {
                        // We do not want the schema selection to change on ROLLBACK or INSERT SELECT.
                        // See https://www.postgresql.org/docs/8.3/sql-set.html
                        throw new DBUnexpectedError(
                                $this,
                                __METHOD__ . ": a transaction is currently active"
                        );
                }

                if ( $this->schemaExists( $desiredSchema ) ) {
                        if ( in_array( $desiredSchema, $this->getSchemas() ) ) {
                                $this->platform->setCoreSchema( $desiredSchema );
                                $this->logger->debug(
                                        "Schema \"" . $desiredSchema . "\" already in the search path\n" );
                        } else {
                                // Prepend the desired schema to the search path (T17816)
                                $search_path = $this->getSearchPath();
                                array_unshift( $search_path, $this->platform->addIdentifierQuotes( $desiredSchema ) );
                                $this->setSearchPath( $search_path );
                                $this->platform->setCoreSchema( $desiredSchema );
                                $this->logger->debug(
                                        "Schema \"" . $desiredSchema . "\" added to the search path\n" );
                        }
                } else {
                        $this->platform->setCoreSchema( $this->getCurrentSchema() );
                        $this->logger->debug(
                                "Schema \"" . $desiredSchema . "\" not found, using current \"" .
                                $this->getCoreSchema() . "\"\n" );
                }
        }

        /**
         * Return schema name for core application tables
         *
         * @since 1.19
         * @return string Core schema name
         */
        public function getCoreSchema() {
                return $this->platform->getCoreSchema();
        }

        /**
         * Return schema names for temporary tables and core application tables
         *
         * @since 1.31
         * @return string[] schema names
         */
        public function getCoreSchemas() {
                if ( $this->tempSchema ) {
                        return [ $this->tempSchema, $this->getCoreSchema() ];
                }
                $query = new Query(
                        "SELECT nspname FROM pg_catalog.pg_namespace n WHERE n.oid = pg_my_temp_schema()",
                        self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
                        'SELECT'
                );
                $res = $this->query( $query, __METHOD__ );
                $row = $res->fetchObject();
                if ( $row ) {
                        $this->tempSchema = $row->nspname;
                        return [ $this->tempSchema, $this->getCoreSchema() ];
                }

                return [ $this->getCoreSchema() ];
        }

        public function getServerVersion() {
                if ( $this->numericVersion === null ) {
                        // Works on PG 7.4+
                        $this->numericVersion = pg_version( $this->getBindingHandle() )['server'];
                }

                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
         * @return bool
         */
        private function relationExists( $table, $types ) {
                if ( !is_array( $types ) ) {
                        $types = [ $types ];
                }
                $schemas = $this->getCoreSchemas();
                $components = $this->platform->qualifiedTableComponents( $table );
                $etable = $this->addQuotes( end( $components ) );
                foreach ( $schemas as $schema ) {
                        $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 ) . "')";
                        $query = new Query(
                                $sql,
                                self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
                                'SELECT'
                        );
                        $res = $this->query( $query, __METHOD__ );
                        if ( $res && $res->numRows() ) {
                                return true;
                        }
                }

                return false;
        }

        public function tableExists( $table, $fname = __METHOD__ ) {
                return $this->relationExists( $table, [ 'r', 'v' ] );
        }

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

        public function constraintExists( $table, $constraint ) {
                foreach ( $this->getCoreSchemas() as $schema ) {
                        $sql = sprintf( "SELECT 1 FROM information_schema.table_constraints " .
                                "WHERE constraint_schema = %s AND table_name = %s AND constraint_name = %s",
                                $this->addQuotes( $schema ),
                                $this->addQuotes( $table ),
                                $this->addQuotes( $constraint )
                        );
                        $query = new Query(
                                $sql,
                                self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
                                'SELECT'
                        );
                        $res = $this->query( $query, __METHOD__ );
                        if ( $res && $res->numRows() ) {
                                return true;
                        }
                }
                return false;
        }

        /**
         * Query whether a given schema exists. Returns true if it does, false if it doesn't.
         * @param string|null $schema
         * @return bool
         */
        public function schemaExists( $schema ) {
                if ( !strlen( $schema ?? '' ) ) {
                        return false; // short-circuit
                }
                $query = new Query(
                        "SELECT 1 FROM pg_catalog.pg_namespace " .
                        "WHERE nspname = " . $this->addQuotes( $schema ) . " LIMIT 1",
                        self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
                        'SELECT'
                );
                $res = $this->query( $query, __METHOD__ );

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

        /**
         * Returns true if a given role (i.e. user) exists, false otherwise.
         * @param string $roleName
         * @return bool
         */
        public function roleExists( $roleName ) {
                $query = new Query(
                        "SELECT 1 FROM pg_catalog.pg_roles " .
                        "WHERE rolname = " . $this->addQuotes( $roleName ) . " LIMIT 1",
                        self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
                        'SELECT'
                );
                $res = $this->query( $query, __METHOD__ );

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

        /**
         * @param string $table
         * @param string $field
         * @return PostgresField|null
         */
        public function fieldInfo( $table, $field ) {
                return PostgresField::fromText( $this, $table, $field );
        }

        public function encodeBlob( $b ) {
                $conn = $this->getBindingHandle();

                return new PostgresBlob( pg_escape_bytea( $conn, $b ) );
        }

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

                return pg_unescape_bytea( $b );
        }

        public function strencode( $s ) {
                // Should not be called by us
                return pg_escape_string( $this->getBindingHandle(), (string)$s );
        }

        public function addQuotes( $s ) {
                if ( $s instanceof RawSQLValue ) {
                        return $s->toSql();
                }
                $conn = $this->getBindingHandle();

                if ( $s === null ) {
                        return 'NULL';
                } elseif ( is_bool( $s ) ) {
                        return (string)intval( $s );
                } elseif ( is_int( $s ) ) {
                        return (string)$s;
                } elseif ( $s instanceof Blob ) {
                        if ( $s instanceof PostgresBlob ) {
                                $s = $s->fetch();
                        } else {
                                $s = pg_escape_bytea( $conn, $s->fetch() );
                        }
                        return "'$s'";
                }

                return "'" . pg_escape_string( $conn, (string)$s ) . "'";
        }

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

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

        public function doLockIsFree( string $lockName, string $method ) {
                $query = new Query(
                        $this->platform->lockIsFreeSQLText( $lockName ),
                        self::QUERY_CHANGE_LOCKS,
                        'SELECT'
                );
                $res = $this->query( $query, $method );
                $row = $res->fetchObject();

                return (bool)$row->unlocked;
        }

        public function doLock( string $lockName, string $method, int $timeout ) {
                $query = new Query(
                        $this->platform->lockSQLText( $lockName, $timeout ),
                        self::QUERY_CHANGE_LOCKS,
                        'SELECT'
                );

                $acquired = null;
                $loop = new WaitConditionLoop(
                        function () use ( $query, $method, &$acquired ) {
                                $res = $this->query( $query, $method );
                                $row = $res->fetchObject();

                                if ( $row->acquired !== null ) {
                                        $acquired = (float)$row->acquired;

                                        return WaitConditionLoop::CONDITION_REACHED;
                                }

                                return WaitConditionLoop::CONDITION_CONTINUE;
                        },
                        $timeout
                );
                $loop->invoke();

                return $acquired;
        }

        public function doUnlock( string $lockName, string $method ) {
                $query = new Query(
                        $this->platform->unlockSQLText( $lockName ),
                        self::QUERY_CHANGE_LOCKS,
                        'SELECT'
                );
                $result = $this->query( $query, $method );
                $row = $result->fetchObject();

                return (bool)$row->released;
        }

        protected function doFlushSession( $fname ) {
                $flags = self::QUERY_CHANGE_LOCKS | self::QUERY_NO_RETRY;

                // https://www.postgresql.org/docs/9.1/functions-admin.html
                $sql = "SELECT pg_advisory_unlock_all()";
                $query = new Query( $sql, $flags, 'UNLOCK' );
                $qs = $this->executeQuery( $query, __METHOD__, $flags );
                if ( $qs->res === false ) {
                        $this->reportQueryError( $qs->message, $qs->code, $sql, $fname, true );
                }
        }

        public function serverIsReadOnly() {
                $query = new Query(
                        "SHOW default_transaction_read_only",
                        self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
                        'SHOW'
                );
                $res = $this->query( $query, __METHOD__ );
                $row = $res->fetchObject();

                return $row && strtolower( $row->default_transaction_read_only ) === 'on';
        }

        protected function getInsertIdColumnForUpsert( $table ) {
                $column = null;

                $flags = self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE;
                $components = $this->platform->qualifiedTableComponents( $table );
                $encTable = $this->addQuotes( end( $components ) );
                foreach ( $this->getCoreSchemas() as $schema ) {
                        $encSchema = $this->addQuotes( $schema );
                        $query = new Query(
                                "SELECT column_name,data_type,column_default " .
                                        "FROM information_schema.columns " .
                                        "WHERE table_name = $encTable AND table_schema = $encSchema",
                                self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
                                'SELECT'
                        );
                        $res = $this->query( $query, __METHOD__ );
                        if ( $res->numRows() ) {
                                foreach ( $res as $row ) {
                                        if (
                                                $row->column_default !== null &&
                                                str_starts_with( $row->column_default, "nextval(" ) &&
                                                in_array( $row->data_type, [ 'integer', 'bigint' ], true )
                                        ) {
                                                $column = $row->column_name;
                                        }
                                }
                                break;
                        }
                }

                return $column;
        }

        public static function getAttributes() {
                return [ self::ATTR_SCHEMAS_AS_TABLE_GROUPS => true ];
        }
}