6047fb033dbc3008791e4b08774e144d9b631bb7
3 * @defgroup Database Database
5 * This file deals with database interface functions
6 * and query specifics/optimisations.
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
18 * You should have received a copy of the GNU General Public License along
19 * with this program; if not, write to the Free Software Foundation, Inc.,
20 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
21 * http://www.gnu.org/copyleft/gpl.html
26 namespace Wikimedia\Rdbms
;
28 use Wikimedia\ScopedCallback
;
30 use UnexpectedValueException
;
34 * Basic database interface for live and lazy-loaded relation database handles
36 * @note: IDatabase and DBConnRef should be updated to reflect any changes
40 /** @var int Callback triggered immediately due to no active transaction */
41 const TRIGGER_IDLE
= 1;
42 /** @var int Callback triggered by COMMIT */
43 const TRIGGER_COMMIT
= 2;
44 /** @var int Callback triggered by ROLLBACK */
45 const TRIGGER_ROLLBACK
= 3;
47 /** @var string Transaction is requested by regular caller outside of the DB layer */
48 const TRANSACTION_EXPLICIT
= '';
49 /** @var string Transaction is requested internally via DBO_TRX/startAtomic() */
50 const TRANSACTION_INTERNAL
= 'implicit';
52 /** @var string Transaction operation comes from service managing all DBs */
53 const FLUSHING_ALL_PEERS
= 'flush';
54 /** @var string Transaction operation comes from the database class internally */
55 const FLUSHING_INTERNAL
= 'flush';
57 /** @var string Do not remember the prior flags */
58 const REMEMBER_NOTHING
= '';
59 /** @var string Remember the prior flags */
60 const REMEMBER_PRIOR
= 'remember';
61 /** @var string Restore to the prior flag state */
62 const RESTORE_PRIOR
= 'prior';
63 /** @var string Restore to the initial flag state */
64 const RESTORE_INITIAL
= 'initial';
66 /** @var string Estimate total time (RTT, scanning, waiting on locks, applying) */
67 const ESTIMATE_TOTAL
= 'total';
68 /** @var string Estimate time to apply (scanning, applying) */
69 const ESTIMATE_DB_APPLY
= 'apply';
71 /** @var int Combine list with comma delimeters */
73 /** @var int Combine list with AND clauses */
75 /** @var int Convert map into a SET clause */
77 /** @var int Treat as field name and do not apply value escaping */
79 /** @var int Combine list with OR clauses */
82 /** @var int Enable debug logging */
84 /** @var int Disable query buffering (only one result set can be iterated at a time) */
85 const DBO_NOBUFFER
= 2;
86 /** @var int Ignore query errors (internal use only!) */
88 /** @var int Autoatically start transaction on first query (work with ILoadBalancer rounds) */
90 /** @var int Use DBO_TRX in non-CLI mode */
91 const DBO_DEFAULT
= 16;
92 /** @var int Use DB persistent connections if possible */
93 const DBO_PERSISTENT
= 32;
94 /** @var int DBA session mode; mostly for Oracle */
95 const DBO_SYSDBA
= 64;
96 /** @var int Schema file mode; mostly for Oracle */
97 const DBO_DDLMODE
= 128;
98 /** @var int Enable SSL/TLS in connection protocol */
100 /** @var int Enable compression in connection protocol */
101 const DBO_COMPRESS
= 512;
104 * A string describing the current software version, and possibly
105 * other details in a user-friendly way. Will be listed on Special:Version, etc.
106 * Use getServerVersion() to get machine-friendly information.
108 * @return string Version information from the database server
110 public function getServerInfo();
113 * Turns buffering of SQL result sets on (true) or off (false). Default is "on".
115 * Unbuffered queries are very troublesome in MySQL:
117 * - If another query is executed while the first query is being read
118 * out, the first query is killed. This means you can't call normal
119 * Database functions while you are reading an unbuffered query result
120 * from a normal Database connection.
122 * - Unbuffered queries cause the MySQL server to use large amounts of
123 * memory and to hold broad locks which block other queries.
125 * If you want to limit client-side memory, it's almost always better to
126 * split up queries into batches using a LIMIT clause than to switch off
129 * @param null|bool $buffer
130 * @return null|bool The previous value of the flag
132 public function bufferResults( $buffer = null );
135 * Gets the current transaction level.
137 * Historically, transactions were allowed to be "nested". This is no
138 * longer supported, so this function really only returns a boolean.
140 * @return int The previous value
142 public function trxLevel();
145 * Get the UNIX timestamp of the time that the transaction was established
147 * This can be used to reason about the staleness of SELECT data
148 * in REPEATABLE-READ transaction isolation level.
150 * @return float|null Returns null if there is not active transaction
153 public function trxTimestamp();
156 * @return bool Whether an explicit transaction or atomic sections are still open
159 public function explicitTrxActive();
162 * Get/set the table prefix.
163 * @param string $prefix The table prefix to set, or omitted to leave it unchanged.
164 * @return string The previous table prefix.
166 public function tablePrefix( $prefix = null );
169 * Get/set the db schema.
170 * @param string $schema The database schema to set, or omitted to leave it unchanged.
171 * @return string The previous db schema.
173 public function dbSchema( $schema = null );
176 * Get properties passed down from the server info array of the load
179 * @param string $name The entry of the info array to get, or null to get the
182 * @return array|mixed|null
184 public function getLBInfo( $name = null );
187 * Set the LB info array, or a member of it. If called with one parameter,
188 * the LB info array is set to that parameter. If it is called with two
189 * parameters, the member with the given name is set to the given value.
191 * @param string $name
192 * @param array $value
194 public function setLBInfo( $name, $value = null );
197 * Set a lazy-connecting DB handle to the master DB (for replication status purposes)
199 * @param IDatabase $conn
202 public function setLazyMasterHandle( IDatabase
$conn );
205 * Returns true if this database does an implicit sort when doing GROUP BY
208 * @deprecated Since 1.30; only use grouped or aggregated fields in the SELECT
210 public function implicitGroupby();
213 * Returns true if this database does an implicit order by when the column has an index
214 * For example: SELECT page_title FROM page LIMIT 1
218 public function implicitOrderby();
221 * Return the last query that went through IDatabase::query()
224 public function lastQuery();
227 * Returns true if the connection may have been used for write queries.
228 * Should return true if unsure.
232 public function doneWrites();
235 * Returns the last time the connection may have been used for write queries.
236 * Should return a timestamp if unsure.
238 * @return int|float UNIX timestamp or false
241 public function lastDoneWrites();
244 * @return bool Whether there is a transaction open with possible write queries
247 public function writesPending();
250 * Returns true if there is a transaction open with possible write
251 * queries or transaction pre-commit/idle callbacks waiting on it to finish.
252 * This does *not* count recurring callbacks, e.g. from setTransactionListener().
256 public function writesOrCallbacksPending();
259 * Get the time spend running write queries for this transaction
261 * High times could be due to scanning, updates, locking, and such
263 * @param string $type IDatabase::ESTIMATE_* constant [default: ESTIMATE_ALL]
264 * @return float|bool Returns false if not transaction is active
267 public function pendingWriteQueryDuration( $type = self
::ESTIMATE_TOTAL
);
270 * Get the list of method names that did write queries for this transaction
275 public function pendingWriteCallers();
278 * Get the number of affected rows from pending write queries
283 public function pendingWriteRowsAffected();
286 * Is a connection to the database open?
289 public function isOpen();
292 * Set a flag for this connection
294 * @param int $flag DBO_* constants from Defines.php:
295 * - DBO_DEBUG: output some debug info (same as debug())
296 * - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
297 * - DBO_TRX: automatically start transactions
298 * - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
299 * and removes it in command line mode
300 * - DBO_PERSISTENT: use persistant database connection
301 * @param string $remember IDatabase::REMEMBER_* constant [default: REMEMBER_NOTHING]
303 public function setFlag( $flag, $remember = self
::REMEMBER_NOTHING
);
306 * Clear a flag for this connection
308 * @param int $flag DBO_* constants from Defines.php:
309 * - DBO_DEBUG: output some debug info (same as debug())
310 * - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
311 * - DBO_TRX: automatically start transactions
312 * - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
313 * and removes it in command line mode
314 * - DBO_PERSISTENT: use persistant database connection
315 * @param string $remember IDatabase::REMEMBER_* constant [default: REMEMBER_NOTHING]
317 public function clearFlag( $flag, $remember = self
::REMEMBER_NOTHING
);
320 * Restore the flags to their prior state before the last setFlag/clearFlag call
322 * @param string $state IDatabase::RESTORE_* constant. [default: RESTORE_PRIOR]
325 public function restoreFlags( $state = self
::RESTORE_PRIOR
);
328 * Returns a boolean whether the flag $flag is set for this connection
330 * @param int $flag DBO_* constants from Defines.php:
331 * - DBO_DEBUG: output some debug info (same as debug())
332 * - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
333 * - DBO_TRX: automatically start transactions
334 * - DBO_PERSISTENT: use persistant database connection
337 public function getFlag( $flag );
342 public function getDomainID();
345 * Alias for getDomainID()
350 public function getWikiID();
353 * Get the type of the DBMS, as it appears in $wgDBtype.
357 public function getType();
360 * Open a connection to the database. Usually aborts on failure
362 * @param string $server Database server host
363 * @param string $user Database user name
364 * @param string $password Database user password
365 * @param string $dbName Database name
367 * @throws DBConnectionError
369 public function open( $server, $user, $password, $dbName );
372 * Fetch the next row from the given result object, in object form.
373 * Fields can be retrieved with $row->fieldname, with fields acting like
375 * If no more rows are available, false is returned.
377 * @param IResultWrapper|stdClass $res Object as returned from IDatabase::query(), etc.
378 * @return stdClass|bool
379 * @throws DBUnexpectedError Thrown if the database returns an error
381 public function fetchObject( $res );
384 * Fetch the next row from the given result object, in associative array
385 * form. Fields are retrieved with $row['fieldname'].
386 * If no more rows are available, false is returned.
388 * @param IResultWrapper $res Result object as returned from IDatabase::query(), etc.
390 * @throws DBUnexpectedError Thrown if the database returns an error
392 public function fetchRow( $res );
395 * Get the number of rows in a result object
397 * @param mixed $res A SQL result
400 public function numRows( $res );
403 * Get the number of fields in a result object
404 * @see https://secure.php.net/mysql_num_fields
406 * @param mixed $res A SQL result
409 public function numFields( $res );
412 * Get a field name in a result object
413 * @see https://secure.php.net/mysql_field_name
415 * @param mixed $res A SQL result
419 public function fieldName( $res, $n );
422 * Get the inserted value of an auto-increment row
424 * This should only be called after an insert that used an auto-incremented
425 * value. If no such insert was previously done in the current database
426 * session, the return value is undefined.
430 public function insertId();
433 * Change the position of the cursor in a result object
434 * @see https://secure.php.net/mysql_data_seek
436 * @param mixed $res A SQL result
439 public function dataSeek( $res, $row );
442 * Get the last error number
443 * @see https://secure.php.net/mysql_errno
447 public function lastErrno();
450 * Get a description of the last error
451 * @see https://secure.php.net/mysql_error
455 public function lastError();
458 * mysql_fetch_field() wrapper
459 * Returns false if the field doesn't exist
461 * @param string $table Table name
462 * @param string $field Field name
466 public function fieldInfo( $table, $field );
469 * Get the number of rows affected by the last write query
470 * @see https://secure.php.net/mysql_affected_rows
474 public function affectedRows();
477 * Returns a wikitext link to the DB's website, e.g.,
478 * return "[https://www.mysql.com/ MySQL]";
479 * Should at least contain plain text, if for some reason
480 * your database has no website.
482 * @return string Wikitext of a link to the server software's web site
484 public function getSoftwareLink();
487 * A string describing the current software version, like from
488 * mysql_get_server_info().
490 * @return string Version information from the database server.
492 public function getServerVersion();
495 * Closes a database connection.
496 * if it is open : commits any open transactions
499 * @return bool Operation success. true if already closed.
501 public function close();
504 * @param string $error Fallback error message, used if none is given by DB
505 * @throws DBConnectionError
507 public function reportConnectionError( $error = 'Unknown error' );
510 * Run an SQL query and return the result. Normally throws a DBQueryError
511 * on failure. If errors are ignored, returns false instead.
513 * In new code, the query wrappers select(), insert(), update(), delete(),
514 * etc. should be used where possible, since they give much better DBMS
515 * independence and automatically quote or validate user input in a variety
516 * of contexts. This function is generally only useful for queries which are
517 * explicitly DBMS-dependent and are unsupported by the query wrappers, such
520 * However, the query wrappers themselves should call this function.
522 * @param string $sql SQL query
523 * @param string $fname Name of the calling function, for profiling/SHOW PROCESSLIST
524 * comment (you can use __METHOD__ or add some extra info)
525 * @param bool $tempIgnore Whether to avoid throwing an exception on errors...
526 * maybe best to catch the exception instead?
527 * @return bool|IResultWrapper True for a successful write query, IResultWrapper object
528 * for a successful read query, or false on failure if $tempIgnore set
531 public function query( $sql, $fname = __METHOD__
, $tempIgnore = false );
534 * Report a query error. Log the error, and if neither the object ignore
535 * flag nor the $tempIgnore flag is set, throw a DBQueryError.
537 * @param string $error
540 * @param string $fname
541 * @param bool $tempIgnore
542 * @throws DBQueryError
544 public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false );
547 * Free a result object returned by query() or select(). It's usually not
548 * necessary to call this, just use unset() or let the variable holding
549 * the result object go out of scope.
551 * @param mixed $res A SQL result
553 public function freeResult( $res );
556 * A SELECT wrapper which returns a single field from a single result row.
558 * Usually throws a DBQueryError on failure. If errors are explicitly
559 * ignored, returns false on failure.
561 * If no result rows are returned from the query, false is returned.
563 * @param string|array $table Table name. See IDatabase::select() for details.
564 * @param string $var The field name to select. This must be a valid SQL
565 * fragment: do not use unvalidated user input.
566 * @param string|array $cond The condition array. See IDatabase::select() for details.
567 * @param string $fname The function name of the caller.
568 * @param string|array $options The query options. See IDatabase::select() for details.
569 * @param string|array $join_conds The query join conditions. See IDatabase::select() for details.
571 * @return mixed The value from the field
574 public function selectField(
575 $table, $var, $cond = '', $fname = __METHOD__
, $options = [], $join_conds = []
579 * A SELECT wrapper which returns a list of single field values from result rows.
581 * Usually throws a DBQueryError on failure. If errors are explicitly
582 * ignored, returns false on failure.
584 * If no result rows are returned from the query, false is returned.
586 * @param string|array $table Table name. See IDatabase::select() for details.
587 * @param string $var The field name to select. This must be a valid SQL
588 * fragment: do not use unvalidated user input.
589 * @param string|array $cond The condition array. See IDatabase::select() for details.
590 * @param string $fname The function name of the caller.
591 * @param string|array $options The query options. See IDatabase::select() for details.
592 * @param string|array $join_conds The query join conditions. See IDatabase::select() for details.
594 * @return array The values from the field
598 public function selectFieldValues(
599 $table, $var, $cond = '', $fname = __METHOD__
, $options = [], $join_conds = []
603 * Execute a SELECT query constructed using the various parameters provided.
604 * See below for full details of the parameters.
606 * @param string|array $table Table name
607 * @param string|array $vars Field names
608 * @param string|array $conds Conditions
609 * @param string $fname Caller function name
610 * @param array $options Query options
611 * @param array $join_conds Join conditions
614 * @param string|array $table
616 * May be either an array of table names, or a single string holding a table
617 * name. If an array is given, table aliases can be specified, for example:
621 * This includes the user table in the query, with the alias "a" available
622 * for use in field names (e.g. a.user_name).
624 * Joins using parentheses for grouping (since MediaWiki 1.31) may be
625 * constructed using nested arrays. For example,
627 * [ 'tableA', 'nestedB' => [ 'tableB', 'b2' => 'tableB2' ] ]
629 * along with `$join_conds` like
631 * [ 'b2' => [ 'JOIN', 'b_id = b2_id' ], 'nestedB' => [ 'LEFT JOIN', 'b_a = a_id' ] ]
633 * will produce SQL something like
635 * FROM tableA LEFT JOIN (tableB JOIN tableB2 AS b2 ON (b_id = b2_id)) ON (b_a = a_id)
637 * All of the table names given here are automatically run through
638 * Database::tableName(), which causes the table prefix (if any) to be
639 * added, and various other table name mappings to be performed.
641 * Do not use untrusted user input as a table name. Alias names should
642 * not have characters outside of the Basic multilingual plane.
644 * @param string|array $vars
646 * May be either a field name or an array of field names. The field names
647 * can be complete fragments of SQL, for direct inclusion into the SELECT
648 * query. If an array is given, field aliases can be specified, for example:
650 * [ 'maxrev' => 'MAX(rev_id)' ]
652 * This includes an expression with the alias "maxrev" in the query.
654 * If an expression is given, care must be taken to ensure that it is
657 * Untrusted user input must not be passed to this parameter.
659 * @param string|array $conds
661 * May be either a string containing a single condition, or an array of
662 * conditions. If an array is given, the conditions constructed from each
663 * element are combined with AND.
665 * Array elements may take one of two forms:
667 * - Elements with a numeric key are interpreted as raw SQL fragments.
668 * - Elements with a string key are interpreted as equality conditions,
669 * where the key is the field name.
670 * - If the value of such an array element is a scalar (such as a
671 * string), it will be treated as data and thus quoted appropriately.
672 * If it is null, an IS NULL clause will be added.
673 * - If the value is an array, an IN (...) clause will be constructed
674 * from its non-null elements, and an IS NULL clause will be added
675 * if null is present, such that the field may match any of the
676 * elements in the array. The non-null elements will be quoted.
678 * Note that expressions are often DBMS-dependent in their syntax.
679 * DBMS-independent wrappers are provided for constructing several types of
680 * expression commonly used in condition queries. See:
681 * - IDatabase::buildLike()
682 * - IDatabase::conditional()
684 * Untrusted user input is safe in the values of string keys, however untrusted
685 * input must not be used in the array key names or in the values of numeric keys.
686 * Escaping of untrusted input used in values of numeric keys should be done via
687 * IDatabase::addQuotes()
689 * @param string|array $options
691 * Optional: Array of query options. Boolean options are specified by
692 * including them in the array as a string value with a numeric key, for
697 * The supported options are:
699 * - OFFSET: Skip this many rows at the start of the result set. OFFSET
700 * with LIMIT can theoretically be used for paging through a result set,
701 * but this is discouraged for performance reasons.
703 * - LIMIT: Integer: return at most this many rows. The rows are sorted
704 * and then the first rows are taken until the limit is reached. LIMIT
705 * is applied to a result set after OFFSET.
707 * - FOR UPDATE: Boolean: lock the returned rows so that they can't be
708 * changed until the next COMMIT.
710 * - DISTINCT: Boolean: return only unique result rows.
712 * - GROUP BY: May be either an SQL fragment string naming a field or
713 * expression to group by, or an array of such SQL fragments.
715 * - HAVING: May be either an string containing a HAVING clause or an array of
716 * conditions building the HAVING clause. If an array is given, the conditions
717 * constructed from each element are combined with AND.
719 * - ORDER BY: May be either an SQL fragment giving a field name or
720 * expression to order by, or an array of such SQL fragments.
722 * - USE INDEX: This may be either a string giving the index name to use
723 * for the query, or an array. If it is an associative array, each key
724 * gives the table name (or alias), each value gives the index name to
725 * use for that table. All strings are SQL fragments and so should be
726 * validated by the caller.
728 * - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
731 * And also the following boolean MySQL extensions, see the MySQL manual
734 * - LOCK IN SHARE MODE
738 * - SQL_BUFFER_RESULT
740 * - SQL_CALC_FOUND_ROWS
745 * @param string|array $join_conds
747 * Optional associative array of table-specific join conditions. In the
748 * most common case, this is unnecessary, since the join condition can be
749 * in $conds. However, it is useful for doing a LEFT JOIN.
751 * The key of the array contains the table name or alias. The value is an
752 * array with two elements, numbered 0 and 1. The first gives the type of
753 * join, the second is the same as the $conds parameter. Thus it can be
754 * an SQL fragment, or an array where the string keys are equality and the
755 * numeric keys are SQL fragments all AND'd together. For example:
757 * [ 'page' => [ 'LEFT JOIN', 'page_latest=rev_id' ] ]
759 * @return IResultWrapper Resulting rows
762 public function select(
763 $table, $vars, $conds = '', $fname = __METHOD__
,
764 $options = [], $join_conds = []
768 * The equivalent of IDatabase::select() except that the constructed SQL
769 * is returned, instead of being immediately executed. This can be useful for
770 * doing UNION queries, where the SQL text of each query is needed. In general,
771 * however, callers outside of Database classes should just use select().
773 * @param string|array $table Table name
774 * @param string|array $vars Field names
775 * @param string|array $conds Conditions
776 * @param string $fname Caller function name
777 * @param string|array $options Query options
778 * @param string|array $join_conds Join conditions
780 * @return string SQL query string.
781 * @see IDatabase::select()
783 public function selectSQLText(
784 $table, $vars, $conds = '', $fname = __METHOD__
,
785 $options = [], $join_conds = []
789 * Single row SELECT wrapper. Equivalent to IDatabase::select(), except
790 * that a single row object is returned. If the query returns no rows,
793 * @param string|array $table Table name
794 * @param string|array $vars Field names
795 * @param array $conds Conditions
796 * @param string $fname Caller function name
797 * @param string|array $options Query options
798 * @param array|string $join_conds Join conditions
800 * @return stdClass|bool
803 public function selectRow( $table, $vars, $conds, $fname = __METHOD__
,
804 $options = [], $join_conds = []
808 * Estimate the number of rows in dataset
810 * MySQL allows you to estimate the number of rows that would be returned
811 * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
812 * index cardinality statistics, and is notoriously inaccurate, especially
813 * when large numbers of rows have recently been added or deleted.
815 * For DBMSs that don't support fast result size estimation, this function
816 * will actually perform the SELECT COUNT(*).
818 * Takes the same arguments as IDatabase::select().
820 * @param string $table Table name
821 * @param string $vars Unused
822 * @param array|string $conds Filters on the table
823 * @param string $fname Function name for profiling
824 * @param array $options Options for select
825 * @return int Row count
828 public function estimateRowCount(
829 $table, $vars = '*', $conds = '', $fname = __METHOD__
, $options = []
833 * Get the number of rows in dataset
835 * This is useful when trying to do COUNT(*) but with a LIMIT for performance.
837 * Takes the same arguments as IDatabase::select().
839 * @since 1.27 Added $join_conds parameter
841 * @param array|string $tables Table names
842 * @param string $vars Unused
843 * @param array|string $conds Filters on the table
844 * @param string $fname Function name for profiling
845 * @param array $options Options for select
846 * @param array $join_conds Join conditions (since 1.27)
847 * @return int Row count
850 public function selectRowCount(
851 $tables, $vars = '*', $conds = '', $fname = __METHOD__
, $options = [], $join_conds = []
855 * Determines whether a field exists in a table
857 * @param string $table Table name
858 * @param string $field Filed to check on that table
859 * @param string $fname Calling function name (optional)
860 * @return bool Whether $table has filed $field
863 public function fieldExists( $table, $field, $fname = __METHOD__
);
866 * Determines whether an index exists
867 * Usually throws a DBQueryError on failure
868 * If errors are explicitly ignored, returns NULL on failure
870 * @param string $table
871 * @param string $index
872 * @param string $fname
876 public function indexExists( $table, $index, $fname = __METHOD__
);
879 * Query whether a given table exists
881 * @param string $table
882 * @param string $fname
886 public function tableExists( $table, $fname = __METHOD__
);
889 * Determines if a given index is unique
891 * @param string $table
892 * @param string $index
896 public function indexUnique( $table, $index );
899 * INSERT wrapper, inserts an array into a table.
903 * - A single associative array. The array keys are the field names, and
904 * the values are the values to insert. The values are treated as data
905 * and will be quoted appropriately. If NULL is inserted, this will be
906 * converted to a database NULL.
907 * - An array with numeric keys, holding a list of associative arrays.
908 * This causes a multi-row INSERT on DBMSs that support it. The keys in
909 * each subarray must be identical to each other, and in the same order.
911 * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
914 * $options is an array of options, with boolean options encoded as values
915 * with numeric keys, in the same style as $options in
916 * IDatabase::select(). Supported options are:
918 * - IGNORE: Boolean: if present, duplicate key errors are ignored, and
919 * any rows which cause duplicate key errors are not inserted. It's
920 * possible to determine how many rows were successfully inserted using
921 * IDatabase::affectedRows().
923 * @param string $table Table name. This will be passed through
924 * Database::tableName().
925 * @param array $a Array of rows to insert
926 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
927 * @param array $options Array of options
932 public function insert( $table, $a, $fname = __METHOD__
, $options = [] );
935 * UPDATE wrapper. Takes a condition array and a SET array.
937 * @param string $table Name of the table to UPDATE. This will be passed through
938 * Database::tableName().
939 * @param array $values An array of values to SET. For each array element,
940 * the key gives the field name, and the value gives the data to set
941 * that field to. The data will be quoted by IDatabase::addQuotes().
942 * Values with integer keys form unquoted SET statements, which can be used for
943 * things like "field = field + 1" or similar computed values.
944 * @param array $conds An array of conditions (WHERE). See
945 * IDatabase::select() for the details of the format of condition
946 * arrays. Use '*' to update all rows.
947 * @param string $fname The function name of the caller (from __METHOD__),
948 * for logging and profiling.
949 * @param array $options An array of UPDATE options, can be:
950 * - IGNORE: Ignore unique key conflicts
951 * - LOW_PRIORITY: MySQL-specific, see MySQL manual.
955 public function update( $table, $values, $conds, $fname = __METHOD__
, $options = [] );
958 * Makes an encoded list of strings from an array
960 * These can be used to make conjunctions or disjunctions on SQL condition strings
961 * derived from an array (see IDatabase::select() $conds documentation).
965 * $sql = $db->makeList( [
967 * $db->makeList( [ 'rev_minor' => 1, 'rev_len' < 500 ], $db::LIST_OR ] )
968 * ], $db::LIST_AND );
970 * This would set $sql to "rev_user = '$id' AND (rev_minor = '1' OR rev_len < '500')"
972 * @param array $a Containing the data
973 * @param int $mode IDatabase class constant:
974 * - IDatabase::LIST_COMMA: Comma separated, no field names
975 * - IDatabase::LIST_AND: ANDed WHERE clause (without the WHERE).
976 * - IDatabase::LIST_OR: ORed WHERE clause (without the WHERE)
977 * - IDatabase::LIST_SET: Comma separated with field names, like a SET clause
978 * - IDatabase::LIST_NAMES: Comma separated field names
982 public function makeList( $a, $mode = self
::LIST_COMMA
);
985 * Build a partial where clause from a 2-d array such as used for LinkBatch.
986 * The keys on each level may be either integers or strings.
988 * @param array $data Organized as 2-d
989 * [ baseKeyVal => [ subKeyVal => [ignored], ... ], ... ]
990 * @param string $baseKey Field name to match the base-level keys to (eg 'pl_namespace')
991 * @param string $subKey Field name to match the sub-level keys to (eg 'pl_title')
992 * @return string|bool SQL fragment, or false if no items in array
994 public function makeWhereFrom2d( $data, $baseKey, $subKey );
997 * Return aggregated value alias
999 * @param array $valuedata
1000 * @param string $valuename
1004 public function aggregateValue( $valuedata, $valuename = 'value' );
1007 * @param string $field
1010 public function bitNot( $field );
1013 * @param string $fieldLeft
1014 * @param string $fieldRight
1017 public function bitAnd( $fieldLeft, $fieldRight );
1020 * @param string $fieldLeft
1021 * @param string $fieldRight
1024 public function bitOr( $fieldLeft, $fieldRight );
1027 * Build a concatenation list to feed into a SQL query
1028 * @param array $stringList List of raw SQL expressions; caller is
1029 * responsible for any quoting
1032 public function buildConcat( $stringList );
1035 * Build a GROUP_CONCAT or equivalent statement for a query.
1037 * This is useful for combining a field for several rows into a single string.
1038 * NULL values will not appear in the output, duplicated values will appear,
1039 * and the resulting delimiter-separated values have no defined sort order.
1040 * Code using the results may need to use the PHP unique() or sort() methods.
1042 * @param string $delim Glue to bind the results together
1043 * @param string|array $table Table name
1044 * @param string $field Field name
1045 * @param string|array $conds Conditions
1046 * @param string|array $join_conds Join conditions
1047 * @return string SQL text
1050 public function buildGroupConcatField(
1051 $delim, $table, $field, $conds = '', $join_conds = []
1055 * @param string $field Field or column to cast
1059 public function buildStringCast( $field );
1062 * Returns true if DBs are assumed to be on potentially different servers
1064 * In systems like mysql/mariadb, different databases can easily be referenced on a single
1065 * connection merely by name, even in a single query via JOIN. On the other hand, Postgres
1066 * treats databases as fully separate, only allowing mechanisms like postgres_fdw to
1067 * effectively "mount" foreign DBs. This is true even among DBs on the same server.
1072 public function databasesAreIndependent();
1075 * Change the current database
1078 * @return bool Success or failure
1079 * @throws DBConnectionError If databasesAreIndependent() is true and an error occurs
1081 public function selectDB( $db );
1084 * Get the current DB name
1087 public function getDBname();
1090 * Get the server hostname or IP address
1093 public function getServer();
1096 * Adds quotes and backslashes.
1098 * @param string|int|null|bool|Blob $s
1099 * @return string|int
1101 public function addQuotes( $s );
1104 * LIKE statement wrapper, receives a variable-length argument list with
1105 * parts of pattern to match containing either string literals that will be
1106 * escaped or tokens returned by anyChar() or anyString(). Alternatively,
1107 * the function could be provided with an array of aforementioned
1110 * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns
1111 * a LIKE clause that searches for subpages of 'My page title'.
1113 * $pattern = [ 'My_page_title/', $dbr->anyString() ];
1114 * $query .= $dbr->buildLike( $pattern );
1117 * @return string Fully built LIKE statement
1119 public function buildLike();
1122 * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
1126 public function anyChar();
1129 * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
1133 public function anyString();
1136 * Deprecated method, calls should be removed.
1138 * This was formerly used for PostgreSQL and Oracle to handle
1139 * self::insertId() auto-incrementing fields. It is no longer necessary
1140 * since DatabasePostgres::insertId() has been reimplemented using
1141 * `lastval()` and Oracle has been reimplemented using triggers.
1143 * Implementations should return null if inserting `NULL` into an
1144 * auto-incrementing field works, otherwise it should return an instance of
1145 * NextSequenceValue and filter it on calls to relevant methods.
1147 * @deprecated since 1.30, no longer needed
1148 * @param string $seqName
1149 * @return null|NextSequenceValue
1151 public function nextSequenceValue( $seqName );
1154 * REPLACE query wrapper.
1156 * REPLACE is a very handy MySQL extension, which functions like an INSERT
1157 * except that when there is a duplicate key error, the old row is deleted
1158 * and the new row is inserted in its place.
1160 * We simulate this with standard SQL with a DELETE followed by INSERT. To
1161 * perform the delete, we need to know what the unique indexes are so that
1162 * we know how to find the conflicting rows.
1164 * It may be more efficient to leave off unique indexes which are unlikely
1165 * to collide. However if you do this, you run the risk of encountering
1166 * errors which wouldn't have occurred in MySQL.
1168 * @param string $table The table to replace the row(s) in.
1169 * @param array $uniqueIndexes Is an array of indexes. Each element may be either
1170 * a field name or an array of field names
1171 * @param array $rows Can be either a single row to insert, or multiple rows,
1172 * in the same format as for IDatabase::insert()
1173 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1176 public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__
);
1179 * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
1181 * This updates any conflicting rows (according to the unique indexes) using
1182 * the provided SET clause and inserts any remaining (non-conflicted) rows.
1184 * $rows may be either:
1185 * - A single associative array. The array keys are the field names, and
1186 * the values are the values to insert. The values are treated as data
1187 * and will be quoted appropriately. If NULL is inserted, this will be
1188 * converted to a database NULL.
1189 * - An array with numeric keys, holding a list of associative arrays.
1190 * This causes a multi-row INSERT on DBMSs that support it. The keys in
1191 * each subarray must be identical to each other, and in the same order.
1193 * It may be more efficient to leave off unique indexes which are unlikely
1194 * to collide. However if you do this, you run the risk of encountering
1195 * errors which wouldn't have occurred in MySQL.
1197 * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1202 * @param string $table Table name. This will be passed through Database::tableName().
1203 * @param array $rows A single row or list of rows to insert
1204 * @param array $uniqueIndexes List of single field names or field name tuples
1205 * @param array $set An array of values to SET. For each array element, the
1206 * key gives the field name, and the value gives the data to set that
1207 * field to. The data will be quoted by IDatabase::addQuotes().
1208 * Values with integer keys form unquoted SET statements, which can be used for
1209 * things like "field = field + 1" or similar computed values.
1210 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1214 public function upsert(
1215 $table, array $rows, array $uniqueIndexes, array $set, $fname = __METHOD__
1219 * DELETE where the condition is a join.
1221 * MySQL overrides this to use a multi-table DELETE syntax, in other databases
1222 * we use sub-selects
1224 * For safety, an empty $conds will not delete everything. If you want to
1225 * delete all rows where the join condition matches, set $conds='*'.
1227 * DO NOT put the join condition in $conds.
1229 * @param string $delTable The table to delete from.
1230 * @param string $joinTable The other table.
1231 * @param string $delVar The variable to join on, in the first table.
1232 * @param string $joinVar The variable to join on, in the second table.
1233 * @param array $conds Condition array of field names mapped to variables,
1234 * ANDed together in the WHERE clause
1235 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1238 public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
1243 * DELETE query wrapper.
1245 * @param string $table Table name
1246 * @param string|array $conds Array of conditions. See $conds in IDatabase::select()
1247 * for the format. Use $conds == "*" to delete all rows
1248 * @param string $fname Name of the calling function
1249 * @throws DBUnexpectedError
1250 * @return bool|IResultWrapper
1253 public function delete( $table, $conds, $fname = __METHOD__
);
1256 * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
1257 * into another table.
1259 * @param string $destTable The table name to insert into
1260 * @param string|array $srcTable May be either a table name, or an array of table names
1261 * to include in a join.
1263 * @param array $varMap Must be an associative array of the form
1264 * [ 'dest1' => 'source1', ... ]. Source items may be literals
1265 * rather than field names, but strings should be quoted with
1266 * IDatabase::addQuotes()
1268 * @param array $conds Condition array. See $conds in IDatabase::select() for
1269 * the details of the format of condition arrays. May be "*" to copy the
1272 * @param string $fname The function name of the caller, from __METHOD__
1274 * @param array $insertOptions Options for the INSERT part of the query, see
1275 * IDatabase::insert() for details.
1276 * @param array $selectOptions Options for the SELECT part of the query, see
1277 * IDatabase::select() for details.
1278 * @param array $selectJoinConds Join conditions for the SELECT part of the query, see
1279 * IDatabase::select() for details.
1284 public function insertSelect( $destTable, $srcTable, $varMap, $conds,
1285 $fname = __METHOD__
,
1286 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
1290 * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
1291 * within the UNION construct.
1294 public function unionSupportsOrderAndLimit();
1297 * Construct a UNION query
1298 * This is used for providing overload point for other DB abstractions
1299 * not compatible with the MySQL syntax.
1300 * @param array $sqls SQL statements to combine
1301 * @param bool $all Use UNION ALL
1302 * @return string SQL fragment
1304 public function unionQueries( $sqls, $all );
1307 * Construct a UNION query for permutations of conditions
1309 * Databases sometimes have trouble with queries that have multiple values
1310 * for multiple condition parameters combined with limits and ordering.
1311 * This method constructs queries for the Cartesian product of the
1312 * conditions and unions them all together.
1314 * @see IDatabase::select()
1316 * @param string|array $table Table name
1317 * @param string|array $vars Field names
1318 * @param array $permute_conds Conditions for the Cartesian product. Keys
1319 * are field names, values are arrays of the possible values for that
1321 * @param string|array $extra_conds Additional conditions to include in the
1323 * @param string $fname Caller function name
1324 * @param string|array $options Query options. In addition to the options
1325 * recognized by IDatabase::select(), the following may be used:
1326 * - NOTALL: Set to use UNION instead of UNION ALL.
1327 * - INNER ORDER BY: If specified and supported, subqueries will use this
1328 * instead of ORDER BY.
1329 * @param string|array $join_conds Join conditions
1330 * @return string SQL query string.
1332 public function unionConditionPermutations(
1333 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__
,
1334 $options = [], $join_conds = []
1338 * Returns an SQL expression for a simple conditional. This doesn't need
1339 * to be overridden unless CASE isn't supported in your DBMS.
1341 * @param string|array $cond SQL expression which will result in a boolean value
1342 * @param string $trueVal SQL expression to return if true
1343 * @param string $falseVal SQL expression to return if false
1344 * @return string SQL fragment
1346 public function conditional( $cond, $trueVal, $falseVal );
1349 * Returns a command for str_replace function in SQL query.
1350 * Uses REPLACE() in MySQL
1352 * @param string $orig Column to modify
1353 * @param string $old Column to seek
1354 * @param string $new Column to replace with
1358 public function strreplace( $orig, $old, $new );
1361 * Determines how long the server has been up
1366 public function getServerUptime();
1369 * Determines if the last failure was due to a deadlock
1373 public function wasDeadlock();
1376 * Determines if the last failure was due to a lock timeout
1380 public function wasLockTimeout();
1383 * Determines if the last query error was due to a dropped connection and should
1384 * be dealt with by pinging the connection and reissuing the query.
1388 public function wasErrorReissuable();
1391 * Determines if the last failure was due to the database being read-only.
1395 public function wasReadOnlyError();
1398 * Wait for the replica DB to catch up to a given master position
1400 * @param DBMasterPos $pos
1401 * @param int $timeout The maximum number of seconds to wait for synchronisation
1402 * @return int|null Zero if the replica DB was past that position already,
1403 * greater than zero if we waited for some period of time, less than
1404 * zero if it timed out, and null on error
1407 public function masterPosWait( DBMasterPos
$pos, $timeout );
1410 * Get the replication position of this replica DB
1412 * @return DBMasterPos|bool False if this is not a replica DB
1415 public function getReplicaPos();
1418 * Get the position of this master
1420 * @return DBMasterPos|bool False if this is not a master
1423 public function getMasterPos();
1426 * @return bool Whether the DB is marked as read-only server-side
1429 public function serverIsReadOnly();
1432 * Run a callback as soon as the current transaction commits or rolls back.
1433 * An error is thrown if no transaction is pending. Queries in the function will run in
1434 * AUTO-COMMIT mode unless there are begin() calls. Callbacks must commit any transactions
1437 * This is useful for combining cooperative locks and DB transactions.
1439 * The callback takes one argument:
1440 * - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK)
1442 * @param callable $callback
1443 * @param string $fname Caller name
1447 public function onTransactionResolution( callable
$callback, $fname = __METHOD__
);
1450 * Run a callback as soon as there is no transaction pending.
1451 * If there is a transaction and it is rolled back, then the callback is cancelled.
1452 * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
1453 * Callbacks must commit any transactions that they begin.
1455 * This is useful for updates to different systems or when separate transactions are needed.
1456 * For example, one might want to enqueue jobs into a system outside the database, but only
1457 * after the database is updated so that the jobs will see the data when they actually run.
1458 * It can also be used for updates that easily cause deadlocks if locks are held too long.
1460 * Updates will execute in the order they were enqueued.
1462 * The callback takes one argument:
1463 * - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_IDLE)
1465 * @param callable $callback
1466 * @param string $fname Caller name
1469 public function onTransactionIdle( callable
$callback, $fname = __METHOD__
);
1472 * Run a callback before the current transaction commits or now if there is none.
1473 * If there is a transaction and it is rolled back, then the callback is cancelled.
1474 * Callbacks must not start nor commit any transactions. If no transaction is active,
1475 * then a transaction will wrap the callback.
1477 * This is useful for updates that easily cause deadlocks if locks are held too long
1478 * but where atomicity is strongly desired for these updates and some related updates.
1480 * Updates will execute in the order they were enqueued.
1482 * @param callable $callback
1483 * @param string $fname Caller name
1486 public function onTransactionPreCommitOrIdle( callable
$callback, $fname = __METHOD__
);
1489 * Run a callback each time any transaction commits or rolls back
1491 * The callback takes two arguments:
1492 * - IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK
1493 * - This IDatabase object
1494 * Callbacks must commit any transactions that they begin.
1496 * Registering a callback here will not affect writesOrCallbacks() pending
1498 * @param string $name Callback name
1499 * @param callable|null $callback Use null to unset a listener
1503 public function setTransactionListener( $name, callable
$callback = null );
1506 * Begin an atomic section of statements
1508 * If a transaction has been started already, just keep track of the given
1509 * section name to make sure the transaction is not committed pre-maturely.
1510 * This function can be used in layers (with sub-sections), so use a stack
1511 * to keep track of the different atomic sections. If there is no transaction,
1512 * start one implicitly.
1514 * The goal of this function is to create an atomic section of SQL queries
1515 * without having to start a new transaction if it already exists.
1517 * All atomic levels *must* be explicitly closed using IDatabase::endAtomic(),
1518 * and any database transactions cannot be began or committed until all atomic
1519 * levels are closed. There is no such thing as implicitly opening or closing
1520 * an atomic section.
1523 * @param string $fname
1526 public function startAtomic( $fname = __METHOD__
);
1529 * Ends an atomic section of SQL statements
1531 * Ends the next section of atomic SQL statements and commits the transaction
1535 * @see IDatabase::startAtomic
1536 * @param string $fname
1539 public function endAtomic( $fname = __METHOD__
);
1542 * Run a callback to do an atomic set of updates for this database
1544 * The $callback takes the following arguments:
1545 * - This database object
1546 * - The value of $fname
1548 * If any exception occurs in the callback, then rollback() will be called and the error will
1549 * be re-thrown. It may also be that the rollback itself fails with an exception before then.
1550 * In any case, such errors are expected to terminate the request, without any outside caller
1551 * attempting to catch errors and commit anyway. Note that any rollback undoes all prior
1552 * atomic section and uncommitted updates, which trashes the current request, requiring an
1553 * error to be displayed.
1555 * This can be an alternative to explicit startAtomic()/endAtomic() calls.
1557 * @see Database::startAtomic
1558 * @see Database::endAtomic
1560 * @param string $fname Caller name (usually __METHOD__)
1561 * @param callable $callback Callback that issues DB updates
1562 * @return mixed $res Result of the callback (since 1.28)
1564 * @throws RuntimeException
1565 * @throws UnexpectedValueException
1568 public function doAtomicSection( $fname, callable
$callback );
1571 * Begin a transaction. If a transaction is already in progress,
1572 * that transaction will be committed before the new transaction is started.
1574 * Only call this from code with outer transcation scope.
1575 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1576 * Nesting of transactions is not supported.
1578 * Note that when the DBO_TRX flag is set (which is usually the case for web
1579 * requests, but not for maintenance scripts), any previous database query
1580 * will have started a transaction automatically.
1582 * Nesting of transactions is not supported. Attempts to nest transactions
1583 * will cause a warning, unless the current transaction was started
1584 * automatically because of the DBO_TRX flag.
1586 * @param string $fname Calling function name
1587 * @param string $mode A situationally valid IDatabase::TRANSACTION_* constant [optional]
1590 public function begin( $fname = __METHOD__
, $mode = self
::TRANSACTION_EXPLICIT
);
1593 * Commits a transaction previously started using begin().
1594 * If no transaction is in progress, a warning is issued.
1596 * Only call this from code with outer transcation scope.
1597 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1598 * Nesting of transactions is not supported.
1600 * @param string $fname
1601 * @param string $flush Flush flag, set to situationally valid IDatabase::FLUSHING_*
1602 * constant to disable warnings about explicitly committing implicit transactions,
1603 * or calling commit when no transaction is in progress.
1605 * This will trigger an exception if there is an ongoing explicit transaction.
1607 * Only set the flush flag if you are sure that these warnings are not applicable,
1608 * and no explicit transactions are open.
1612 public function commit( $fname = __METHOD__
, $flush = '' );
1615 * Rollback a transaction previously started using begin().
1616 * If no transaction is in progress, a warning is issued.
1618 * Only call this from code with outer transcation scope.
1619 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1620 * Nesting of transactions is not supported. If a serious unexpected error occurs,
1621 * throwing an Exception is preferrable, using a pre-installed error handler to trigger
1622 * rollback (in any case, failure to issue COMMIT will cause rollback server-side).
1624 * Query, connection, and onTransaction* callback errors will be suppressed and logged.
1626 * @param string $fname Calling function name
1627 * @param string $flush Flush flag, set to a situationally valid IDatabase::FLUSHING_*
1628 * constant to disable warnings about calling rollback when no transaction is in
1629 * progress. This will silently break any ongoing explicit transaction. Only set the
1630 * flush flag if you are sure that it is safe to ignore these warnings in your context.
1632 * @since 1.23 Added $flush parameter
1634 public function rollback( $fname = __METHOD__
, $flush = '' );
1637 * Commit any transaction but error out if writes or callbacks are pending
1639 * This is intended for clearing out REPEATABLE-READ snapshots so that callers can
1640 * see a new point-in-time of the database. This is useful when one of many transaction
1641 * rounds finished and significant time will pass in the script's lifetime. It is also
1642 * useful to call on a replica DB after waiting on replication to catch up to the master.
1644 * @param string $fname Calling function name
1648 public function flushSnapshot( $fname = __METHOD__
);
1651 * List all tables on the database
1653 * @param string $prefix Only show tables with this prefix, e.g. mw_
1654 * @param string $fname Calling function name
1658 public function listTables( $prefix = null, $fname = __METHOD__
);
1661 * Convert a timestamp in one of the formats accepted by wfTimestamp()
1662 * to the format used for inserting into timestamp fields in this DBMS.
1664 * The result is unquoted, and needs to be passed through addQuotes()
1665 * before it can be included in raw SQL.
1667 * @param string|int $ts
1671 public function timestamp( $ts = 0 );
1674 * Convert a timestamp in one of the formats accepted by wfTimestamp()
1675 * to the format used for inserting into timestamp fields in this DBMS. If
1676 * NULL is input, it is passed through, allowing NULL values to be inserted
1677 * into timestamp fields.
1679 * The result is unquoted, and needs to be passed through addQuotes()
1680 * before it can be included in raw SQL.
1682 * @param string|int $ts
1686 public function timestampOrNull( $ts = null );
1689 * Ping the server and try to reconnect if it there is no connection
1691 * @param float|null &$rtt Value to store the estimated RTT [optional]
1692 * @return bool Success or failure
1694 public function ping( &$rtt = null );
1697 * Get replica DB lag. Currently supported only by MySQL.
1699 * Note that this function will generate a fatal error on many
1700 * installations. Most callers should use LoadBalancer::safeGetLag()
1703 * @return int|bool Database replication lag in seconds or false on error
1706 public function getLag();
1709 * Get the replica DB lag when the current transaction started
1710 * or a general lag estimate if not transaction is active
1712 * This is useful when transactions might use snapshot isolation
1713 * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
1714 * is this lag plus transaction duration. If they don't, it is still
1715 * safe to be pessimistic. In AUTO-COMMIT mode, this still gives an
1716 * indication of the staleness of subsequent reads.
1718 * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
1722 public function getSessionLagStatus();
1725 * Return the maximum number of items allowed in a list, or 0 for unlimited.
1729 public function maxListLen();
1732 * Some DBMSs have a special format for inserting into blob fields, they
1733 * don't allow simple quoted strings to be inserted. To insert into such
1734 * a field, pass the data through this function before passing it to
1735 * IDatabase::insert().
1738 * @return string|Blob
1740 public function encodeBlob( $b );
1743 * Some DBMSs return a special placeholder object representing blob fields
1744 * in result objects. Pass the object through this function to return the
1747 * @param string|Blob $b
1750 public function decodeBlob( $b );
1753 * Override database's default behavior. $options include:
1754 * 'connTimeout' : Set the connection timeout value in seconds.
1755 * May be useful for very long batch queries such as
1756 * full-wiki dumps, where a single query reads out over
1759 * @param array $options
1763 public function setSessionOptions( array $options );
1766 * Set variables to be used in sourceFile/sourceStream, in preference to the
1767 * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
1768 * all. If it's set to false, $GLOBALS will be used.
1770 * @param bool|array $vars Mapping variable name to value.
1772 public function setSchemaVars( $vars );
1775 * Check to see if a named lock is available (non-blocking)
1777 * @param string $lockName Name of lock to poll
1778 * @param string $method Name of method calling us
1783 public function lockIsFree( $lockName, $method );
1786 * Acquire a named lock
1788 * Named locks are not related to transactions
1790 * @param string $lockName Name of lock to aquire
1791 * @param string $method Name of the calling method
1792 * @param int $timeout Acquisition timeout in seconds
1796 public function lock( $lockName, $method, $timeout = 5 );
1801 * Named locks are not related to transactions
1803 * @param string $lockName Name of lock to release
1804 * @param string $method Name of the calling method
1806 * @return int Returns 1 if the lock was released, 0 if the lock was not established
1807 * by this thread (in which case the lock is not released), and NULL if the named lock
1812 public function unlock( $lockName, $method );
1815 * Acquire a named lock, flush any transaction, and return an RAII style unlocker object
1817 * Only call this from outer transcation scope and when only one DB will be affected.
1818 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1820 * This is suitiable for transactions that need to be serialized using cooperative locks,
1821 * where each transaction can see each others' changes. Any transaction is flushed to clear
1822 * out stale REPEATABLE-READ snapshot data. Once the returned object falls out of PHP scope,
1823 * the lock will be released unless a transaction is active. If one is active, then the lock
1824 * will be released when it either commits or rolls back.
1826 * If the lock acquisition failed, then no transaction flush happens, and null is returned.
1828 * @param string $lockKey Name of lock to release
1829 * @param string $fname Name of the calling method
1830 * @param int $timeout Acquisition timeout in seconds
1831 * @return ScopedCallback|null
1835 public function getScopedLockAndFlush( $lockKey, $fname, $timeout );
1838 * Check to see if a named lock used by lock() use blocking queues
1843 public function namedLocksEnqueue();
1846 * Find out when 'infinity' is. Most DBMSes support this. This is a special
1847 * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
1848 * because "i" sorts after all numbers.
1852 public function getInfinity();
1855 * Encode an expiry time into the DBMS dependent format
1857 * @param string $expiry Timestamp for expiry, or the 'infinity' string
1860 public function encodeExpiry( $expiry );
1863 * Decode an expiry time into a DBMS independent format
1865 * @param string $expiry DB timestamp field value for expiry
1866 * @param int $format TS_* constant, defaults to TS_MW
1869 public function decodeExpiry( $expiry, $format = TS_MW
);
1872 * Allow or deny "big selects" for this session only. This is done by setting
1873 * the sql_big_selects session variable.
1875 * This is a MySQL-specific feature.
1877 * @param bool|string $value True for allow, false for deny, or "default" to
1878 * restore the initial value
1880 public function setBigSelects( $value = true );
1883 * @return bool Whether this DB is read-only
1886 public function isReadOnly();
1889 * Make certain table names use their own database, schema, and table prefix
1890 * when passed into SQL queries pre-escaped and without a qualified database name
1892 * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
1893 * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
1895 * Calling this twice will completely clear any old table aliases. Also, note that
1896 * callers are responsible for making sure the schemas and databases actually exist.
1898 * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
1901 public function setTableAliases( array $aliases );
1904 class_alias( IDatabase
::class, 'IDatabase' );