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
;
31 use UnexpectedValueException
;
35 * Basic database interface for live and lazy-loaded relation database handles
37 * @note: IDatabase and DBConnRef should be updated to reflect any changes
41 /** @var int Callback triggered immediately due to no active transaction */
42 const TRIGGER_IDLE
= 1;
43 /** @var int Callback triggered by COMMIT */
44 const TRIGGER_COMMIT
= 2;
45 /** @var int Callback triggered by ROLLBACK */
46 const TRIGGER_ROLLBACK
= 3;
48 /** @var string Transaction is requested by regular caller outside of the DB layer */
49 const TRANSACTION_EXPLICIT
= '';
50 /** @var string Transaction is requested internally via DBO_TRX/startAtomic() */
51 const TRANSACTION_INTERNAL
= 'implicit';
53 /** @var string Transaction operation comes from service managing all DBs */
54 const FLUSHING_ALL_PEERS
= 'flush';
55 /** @var string Transaction operation comes from the database class internally */
56 const FLUSHING_INTERNAL
= 'flush';
58 /** @var string Do not remember the prior flags */
59 const REMEMBER_NOTHING
= '';
60 /** @var string Remember the prior flags */
61 const REMEMBER_PRIOR
= 'remember';
62 /** @var string Restore to the prior flag state */
63 const RESTORE_PRIOR
= 'prior';
64 /** @var string Restore to the initial flag state */
65 const RESTORE_INITIAL
= 'initial';
67 /** @var string Estimate total time (RTT, scanning, waiting on locks, applying) */
68 const ESTIMATE_TOTAL
= 'total';
69 /** @var string Estimate time to apply (scanning, applying) */
70 const ESTIMATE_DB_APPLY
= 'apply';
72 /** @var int Combine list with comma delimeters */
74 /** @var int Combine list with AND clauses */
76 /** @var int Convert map into a SET clause */
78 /** @var int Treat as field name and do not apply value escaping */
80 /** @var int Combine list with OR clauses */
83 /** @var int Enable debug logging */
85 /** @var int Disable query buffering (only one result set can be iterated at a time) */
86 const DBO_NOBUFFER
= 2;
87 /** @var int Ignore query errors (internal use only!) */
89 /** @var int Autoatically start transaction on first query (work with ILoadBalancer rounds) */
91 /** @var int Use DBO_TRX in non-CLI mode */
92 const DBO_DEFAULT
= 16;
93 /** @var int Use DB persistent connections if possible */
94 const DBO_PERSISTENT
= 32;
95 /** @var int DBA session mode; mostly for Oracle */
96 const DBO_SYSDBA
= 64;
97 /** @var int Schema file mode; mostly for Oracle */
98 const DBO_DDLMODE
= 128;
99 /** @var int Enable SSL/TLS in connection protocol */
101 /** @var int Enable compression in connection protocol */
102 const DBO_COMPRESS
= 512;
105 * A string describing the current software version, and possibly
106 * other details in a user-friendly way. Will be listed on Special:Version, etc.
107 * Use getServerVersion() to get machine-friendly information.
109 * @return string Version information from the database server
111 public function getServerInfo();
114 * Turns buffering of SQL result sets on (true) or off (false). Default is "on".
116 * Unbuffered queries are very troublesome in MySQL:
118 * - If another query is executed while the first query is being read
119 * out, the first query is killed. This means you can't call normal
120 * Database functions while you are reading an unbuffered query result
121 * from a normal Database connection.
123 * - Unbuffered queries cause the MySQL server to use large amounts of
124 * memory and to hold broad locks which block other queries.
126 * If you want to limit client-side memory, it's almost always better to
127 * split up queries into batches using a LIMIT clause than to switch off
130 * @param null|bool $buffer
131 * @return null|bool The previous value of the flag
133 public function bufferResults( $buffer = null );
136 * Gets the current transaction level.
138 * Historically, transactions were allowed to be "nested". This is no
139 * longer supported, so this function really only returns a boolean.
141 * @return int The previous value
143 public function trxLevel();
146 * Get the UNIX timestamp of the time that the transaction was established
148 * This can be used to reason about the staleness of SELECT data
149 * in REPEATABLE-READ transaction isolation level.
151 * @return float|null Returns null if there is not active transaction
154 public function trxTimestamp();
157 * @return bool Whether an explicit transaction or atomic sections are still open
160 public function explicitTrxActive();
163 * Get/set the table prefix.
164 * @param string $prefix The table prefix to set, or omitted to leave it unchanged.
165 * @return string The previous table prefix.
167 public function tablePrefix( $prefix = null );
170 * Get/set the db schema.
171 * @param string $schema The database schema to set, or omitted to leave it unchanged.
172 * @return string The previous db schema.
174 public function dbSchema( $schema = null );
177 * Get properties passed down from the server info array of the load
180 * @param string $name The entry of the info array to get, or null to get the
183 * @return array|mixed|null
185 public function getLBInfo( $name = null );
188 * Set the LB info array, or a member of it. If called with one parameter,
189 * the LB info array is set to that parameter. If it is called with two
190 * parameters, the member with the given name is set to the given value.
192 * @param string $name
193 * @param array $value
195 public function setLBInfo( $name, $value = null );
198 * Set a lazy-connecting DB handle to the master DB (for replication status purposes)
200 * @param IDatabase $conn
203 public function setLazyMasterHandle( IDatabase
$conn );
206 * Returns true if this database does an implicit sort when doing GROUP BY
209 * @deprecated Since 1.30; only use grouped or aggregated fields in the SELECT
211 public function implicitGroupby();
214 * Returns true if this database does an implicit order by when the column has an index
215 * For example: SELECT page_title FROM page LIMIT 1
219 public function implicitOrderby();
222 * Return the last query that went through IDatabase::query()
225 public function lastQuery();
228 * Returns true if the connection may have been used for write queries.
229 * Should return true if unsure.
233 public function doneWrites();
236 * Returns the last time the connection may have been used for write queries.
237 * Should return a timestamp if unsure.
239 * @return int|float UNIX timestamp or false
242 public function lastDoneWrites();
245 * @return bool Whether there is a transaction open with possible write queries
248 public function writesPending();
251 * Returns true if there is a transaction open with possible write
252 * queries or transaction pre-commit/idle callbacks waiting on it to finish.
253 * This does *not* count recurring callbacks, e.g. from setTransactionListener().
257 public function writesOrCallbacksPending();
260 * Get the time spend running write queries for this transaction
262 * High times could be due to scanning, updates, locking, and such
264 * @param string $type IDatabase::ESTIMATE_* constant [default: ESTIMATE_ALL]
265 * @return float|bool Returns false if not transaction is active
268 public function pendingWriteQueryDuration( $type = self
::ESTIMATE_TOTAL
);
271 * Get the list of method names that did write queries for this transaction
276 public function pendingWriteCallers();
279 * Get the number of affected rows from pending write queries
284 public function pendingWriteRowsAffected();
287 * Is a connection to the database open?
290 public function isOpen();
293 * Set a flag for this connection
295 * @param int $flag DBO_* constants from Defines.php:
296 * - DBO_DEBUG: output some debug info (same as debug())
297 * - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
298 * - DBO_TRX: automatically start transactions
299 * - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
300 * and removes it in command line mode
301 * - DBO_PERSISTENT: use persistant database connection
302 * @param string $remember IDatabase::REMEMBER_* constant [default: REMEMBER_NOTHING]
304 public function setFlag( $flag, $remember = self
::REMEMBER_NOTHING
);
307 * Clear a flag for this connection
309 * @param int $flag DBO_* constants from Defines.php:
310 * - DBO_DEBUG: output some debug info (same as debug())
311 * - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
312 * - DBO_TRX: automatically start transactions
313 * - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
314 * and removes it in command line mode
315 * - DBO_PERSISTENT: use persistant database connection
316 * @param string $remember IDatabase::REMEMBER_* constant [default: REMEMBER_NOTHING]
318 public function clearFlag( $flag, $remember = self
::REMEMBER_NOTHING
);
321 * Restore the flags to their prior state before the last setFlag/clearFlag call
323 * @param string $state IDatabase::RESTORE_* constant. [default: RESTORE_PRIOR]
326 public function restoreFlags( $state = self
::RESTORE_PRIOR
);
329 * Returns a boolean whether the flag $flag is set for this connection
331 * @param int $flag DBO_* constants from Defines.php:
332 * - DBO_DEBUG: output some debug info (same as debug())
333 * - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
334 * - DBO_TRX: automatically start transactions
335 * - DBO_PERSISTENT: use persistant database connection
338 public function getFlag( $flag );
343 public function getDomainID();
346 * Alias for getDomainID()
351 public function getWikiID();
354 * Get the type of the DBMS, as it appears in $wgDBtype.
358 public function getType();
361 * Open a connection to the database. Usually aborts on failure
363 * @param string $server Database server host
364 * @param string $user Database user name
365 * @param string $password Database user password
366 * @param string $dbName Database name
368 * @throws DBConnectionError
370 public function open( $server, $user, $password, $dbName );
373 * Fetch the next row from the given result object, in object form.
374 * Fields can be retrieved with $row->fieldname, with fields acting like
376 * If no more rows are available, false is returned.
378 * @param IResultWrapper|stdClass $res Object as returned from IDatabase::query(), etc.
379 * @return stdClass|bool
380 * @throws DBUnexpectedError Thrown if the database returns an error
382 public function fetchObject( $res );
385 * Fetch the next row from the given result object, in associative array
386 * form. Fields are retrieved with $row['fieldname'].
387 * If no more rows are available, false is returned.
389 * @param IResultWrapper $res Result object as returned from IDatabase::query(), etc.
391 * @throws DBUnexpectedError Thrown if the database returns an error
393 public function fetchRow( $res );
396 * Get the number of rows in a result object
398 * @param mixed $res A SQL result
401 public function numRows( $res );
404 * Get the number of fields in a result object
405 * @see https://secure.php.net/mysql_num_fields
407 * @param mixed $res A SQL result
410 public function numFields( $res );
413 * Get a field name in a result object
414 * @see https://secure.php.net/mysql_field_name
416 * @param mixed $res A SQL result
420 public function fieldName( $res, $n );
423 * Get the inserted value of an auto-increment row
425 * This should only be called after an insert that used an auto-incremented
426 * value. If no such insert was previously done in the current database
427 * session, the return value is undefined.
431 public function insertId();
434 * Change the position of the cursor in a result object
435 * @see https://secure.php.net/mysql_data_seek
437 * @param mixed $res A SQL result
440 public function dataSeek( $res, $row );
443 * Get the last error number
444 * @see https://secure.php.net/mysql_errno
448 public function lastErrno();
451 * Get a description of the last error
452 * @see https://secure.php.net/mysql_error
456 public function lastError();
459 * mysql_fetch_field() wrapper
460 * Returns false if the field doesn't exist
462 * @param string $table Table name
463 * @param string $field Field name
467 public function fieldInfo( $table, $field );
470 * Get the number of rows affected by the last write query
471 * @see https://secure.php.net/mysql_affected_rows
475 public function affectedRows();
478 * Returns a wikitext link to the DB's website, e.g.,
479 * return "[https://www.mysql.com/ MySQL]";
480 * Should at least contain plain text, if for some reason
481 * your database has no website.
483 * @return string Wikitext of a link to the server software's web site
485 public function getSoftwareLink();
488 * A string describing the current software version, like from
489 * mysql_get_server_info().
491 * @return string Version information from the database server.
493 public function getServerVersion();
496 * Closes a database connection.
497 * if it is open : commits any open transactions
500 * @return bool Operation success. true if already closed.
502 public function close();
505 * @param string $error Fallback error message, used if none is given by DB
506 * @throws DBConnectionError
508 public function reportConnectionError( $error = 'Unknown error' );
511 * Run an SQL query and return the result. Normally throws a DBQueryError
512 * on failure. If errors are ignored, returns false instead.
514 * In new code, the query wrappers select(), insert(), update(), delete(),
515 * etc. should be used where possible, since they give much better DBMS
516 * independence and automatically quote or validate user input in a variety
517 * of contexts. This function is generally only useful for queries which are
518 * explicitly DBMS-dependent and are unsupported by the query wrappers, such
521 * However, the query wrappers themselves should call this function.
523 * @param string $sql SQL query
524 * @param string $fname Name of the calling function, for profiling/SHOW PROCESSLIST
525 * comment (you can use __METHOD__ or add some extra info)
526 * @param bool $tempIgnore Whether to avoid throwing an exception on errors...
527 * maybe best to catch the exception instead?
529 * @return bool|IResultWrapper True for a successful write query, IResultWrapper object
530 * for a successful read query, or false on failure if $tempIgnore set
532 public function query( $sql, $fname = __METHOD__
, $tempIgnore = false );
535 * Report a query error. Log the error, and if neither the object ignore
536 * flag nor the $tempIgnore flag is set, throw a DBQueryError.
538 * @param string $error
541 * @param string $fname
542 * @param bool $tempIgnore
543 * @throws DBQueryError
545 public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false );
548 * Free a result object returned by query() or select(). It's usually not
549 * necessary to call this, just use unset() or let the variable holding
550 * the result object go out of scope.
552 * @param mixed $res A SQL result
554 public function freeResult( $res );
557 * A SELECT wrapper which returns a single field from a single result row.
559 * Usually throws a DBQueryError on failure. If errors are explicitly
560 * ignored, returns false on failure.
562 * If no result rows are returned from the query, false is returned.
564 * @param string|array $table Table name. See IDatabase::select() for details.
565 * @param string $var The field name to select. This must be a valid SQL
566 * fragment: do not use unvalidated user input.
567 * @param string|array $cond The condition array. See IDatabase::select() for details.
568 * @param string $fname The function name of the caller.
569 * @param string|array $options The query options. See IDatabase::select() for details.
570 * @param string|array $join_conds The query join conditions. See IDatabase::select() for details.
572 * @return bool|mixed The value from the field, or false on failure.
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 bool|array The values from the field, or false on failure
597 public function selectFieldValues(
598 $table, $var, $cond = '', $fname = __METHOD__
, $options = [], $join_conds = []
602 * Execute a SELECT query constructed using the various parameters provided.
603 * See below for full details of the parameters.
605 * @param string|array $table Table name
606 * @param string|array $vars Field names
607 * @param string|array $conds Conditions
608 * @param string $fname Caller function name
609 * @param array $options Query options
610 * @param array $join_conds Join conditions
613 * @param string|array $table
615 * May be either an array of table names, or a single string holding a table
616 * name. If an array is given, table aliases can be specified, for example:
620 * This includes the user table in the query, with the alias "a" available
621 * for use in field names (e.g. a.user_name).
623 * Joins using parentheses for grouping (since MediaWiki 1.31) may be
624 * constructed using nested arrays. For example,
626 * [ 'tableA', 'nestedB' => [ 'tableB', 'b2' => 'tableB2' ] ]
628 * along with `$join_conds` like
630 * [ 'b2' => [ 'JOIN', 'b_id = b2_id' ], 'nestedB' => [ 'LEFT JOIN', 'b_a = a_id' ] ]
632 * will produce SQL something like
634 * FROM tableA LEFT JOIN (tableB JOIN tableB2 AS b2 ON (b_id = b2_id)) ON (b_a = a_id)
636 * All of the table names given here are automatically run through
637 * Database::tableName(), which causes the table prefix (if any) to be
638 * added, and various other table name mappings to be performed.
640 * Do not use untrusted user input as a table name. Alias names should
641 * not have characters outside of the Basic multilingual plane.
643 * @param string|array $vars
645 * May be either a field name or an array of field names. The field names
646 * can be complete fragments of SQL, for direct inclusion into the SELECT
647 * query. If an array is given, field aliases can be specified, for example:
649 * [ 'maxrev' => 'MAX(rev_id)' ]
651 * This includes an expression with the alias "maxrev" in the query.
653 * If an expression is given, care must be taken to ensure that it is
656 * Untrusted user input must not be passed to this parameter.
658 * @param string|array $conds
660 * May be either a string containing a single condition, or an array of
661 * conditions. If an array is given, the conditions constructed from each
662 * element are combined with AND.
664 * Array elements may take one of two forms:
666 * - Elements with a numeric key are interpreted as raw SQL fragments.
667 * - Elements with a string key are interpreted as equality conditions,
668 * where the key is the field name.
669 * - If the value of such an array element is a scalar (such as a
670 * string), it will be treated as data and thus quoted appropriately.
671 * If it is null, an IS NULL clause will be added.
672 * - If the value is an array, an IN (...) clause will be constructed
673 * from its non-null elements, and an IS NULL clause will be added
674 * if null is present, such that the field may match any of the
675 * elements in the array. The non-null elements will be quoted.
677 * Note that expressions are often DBMS-dependent in their syntax.
678 * DBMS-independent wrappers are provided for constructing several types of
679 * expression commonly used in condition queries. See:
680 * - IDatabase::buildLike()
681 * - IDatabase::conditional()
683 * Untrusted user input is safe in the values of string keys, however untrusted
684 * input must not be used in the array key names or in the values of numeric keys.
685 * Escaping of untrusted input used in values of numeric keys should be done via
686 * IDatabase::addQuotes()
688 * @param string|array $options
690 * Optional: Array of query options. Boolean options are specified by
691 * including them in the array as a string value with a numeric key, for
696 * The supported options are:
698 * - OFFSET: Skip this many rows at the start of the result set. OFFSET
699 * with LIMIT can theoretically be used for paging through a result set,
700 * but this is discouraged for performance reasons.
702 * - LIMIT: Integer: return at most this many rows. The rows are sorted
703 * and then the first rows are taken until the limit is reached. LIMIT
704 * is applied to a result set after OFFSET.
706 * - FOR UPDATE: Boolean: lock the returned rows so that they can't be
707 * changed until the next COMMIT.
709 * - DISTINCT: Boolean: return only unique result rows.
711 * - GROUP BY: May be either an SQL fragment string naming a field or
712 * expression to group by, or an array of such SQL fragments.
714 * - HAVING: May be either an string containing a HAVING clause or an array of
715 * conditions building the HAVING clause. If an array is given, the conditions
716 * constructed from each element are combined with AND.
718 * - ORDER BY: May be either an SQL fragment giving a field name or
719 * expression to order by, or an array of such SQL fragments.
721 * - USE INDEX: This may be either a string giving the index name to use
722 * for the query, or an array. If it is an associative array, each key
723 * gives the table name (or alias), each value gives the index name to
724 * use for that table. All strings are SQL fragments and so should be
725 * validated by the caller.
727 * - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
730 * And also the following boolean MySQL extensions, see the MySQL manual
733 * - LOCK IN SHARE MODE
737 * - SQL_BUFFER_RESULT
739 * - SQL_CALC_FOUND_ROWS
744 * @param string|array $join_conds
746 * Optional associative array of table-specific join conditions. In the
747 * most common case, this is unnecessary, since the join condition can be
748 * in $conds. However, it is useful for doing a LEFT JOIN.
750 * The key of the array contains the table name or alias. The value is an
751 * array with two elements, numbered 0 and 1. The first gives the type of
752 * join, the second is the same as the $conds parameter. Thus it can be
753 * an SQL fragment, or an array where the string keys are equality and the
754 * numeric keys are SQL fragments all AND'd together. For example:
756 * [ 'page' => [ 'LEFT JOIN', 'page_latest=rev_id' ] ]
758 * @return IResultWrapper|bool If the query returned no rows, a IResultWrapper
759 * with no rows in it will be returned. If there was a query error, a
760 * DBQueryError exception will be thrown, except if the "ignore errors"
761 * option was set, in which case false will be returned.
763 public function select(
764 $table, $vars, $conds = '', $fname = __METHOD__
,
765 $options = [], $join_conds = []
769 * The equivalent of IDatabase::select() except that the constructed SQL
770 * is returned, instead of being immediately executed. This can be useful for
771 * doing UNION queries, where the SQL text of each query is needed. In general,
772 * however, callers outside of Database classes should just use select().
774 * @param string|array $table Table name
775 * @param string|array $vars Field names
776 * @param string|array $conds Conditions
777 * @param string $fname Caller function name
778 * @param string|array $options Query options
779 * @param string|array $join_conds Join conditions
781 * @return string SQL query string.
782 * @see IDatabase::select()
784 public function selectSQLText(
785 $table, $vars, $conds = '', $fname = __METHOD__
,
786 $options = [], $join_conds = []
790 * Single row SELECT wrapper. Equivalent to IDatabase::select(), except
791 * that a single row object is returned. If the query returns no rows,
794 * @param string|array $table Table name
795 * @param string|array $vars Field names
796 * @param array $conds Conditions
797 * @param string $fname Caller function name
798 * @param string|array $options Query options
799 * @param array|string $join_conds Join conditions
801 * @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
827 public function estimateRowCount(
828 $table, $vars = '*', $conds = '', $fname = __METHOD__
, $options = []
832 * Get the number of rows in dataset
834 * This is useful when trying to do COUNT(*) but with a LIMIT for performance.
836 * Takes the same arguments as IDatabase::select().
838 * @since 1.27 Added $join_conds parameter
840 * @param array|string $tables Table names
841 * @param string $vars Unused
842 * @param array|string $conds Filters on the table
843 * @param string $fname Function name for profiling
844 * @param array $options Options for select
845 * @param array $join_conds Join conditions (since 1.27)
846 * @return int Row count
848 public function selectRowCount(
849 $tables, $vars = '*', $conds = '', $fname = __METHOD__
, $options = [], $join_conds = []
853 * Determines whether a field exists in a table
855 * @param string $table Table name
856 * @param string $field Filed to check on that table
857 * @param string $fname Calling function name (optional)
858 * @return bool Whether $table has filed $field
860 public function fieldExists( $table, $field, $fname = __METHOD__
);
863 * Determines whether an index exists
864 * Usually throws a DBQueryError on failure
865 * If errors are explicitly ignored, returns NULL on failure
867 * @param string $table
868 * @param string $index
869 * @param string $fname
872 public function indexExists( $table, $index, $fname = __METHOD__
);
875 * Query whether a given table exists
877 * @param string $table
878 * @param string $fname
881 public function tableExists( $table, $fname = __METHOD__
);
884 * Determines if a given index is unique
886 * @param string $table
887 * @param string $index
891 public function indexUnique( $table, $index );
894 * INSERT wrapper, inserts an array into a table.
898 * - A single associative array. The array keys are the field names, and
899 * the values are the values to insert. The values are treated as data
900 * and will be quoted appropriately. If NULL is inserted, this will be
901 * converted to a database NULL.
902 * - An array with numeric keys, holding a list of associative arrays.
903 * This causes a multi-row INSERT on DBMSs that support it. The keys in
904 * each subarray must be identical to each other, and in the same order.
906 * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
909 * $options is an array of options, with boolean options encoded as values
910 * with numeric keys, in the same style as $options in
911 * IDatabase::select(). Supported options are:
913 * - IGNORE: Boolean: if present, duplicate key errors are ignored, and
914 * any rows which cause duplicate key errors are not inserted. It's
915 * possible to determine how many rows were successfully inserted using
916 * IDatabase::affectedRows().
918 * @param string $table Table name. This will be passed through
919 * Database::tableName().
920 * @param array $a Array of rows to insert
921 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
922 * @param array $options Array of options
926 public function insert( $table, $a, $fname = __METHOD__
, $options = [] );
929 * UPDATE wrapper. Takes a condition array and a SET array.
931 * @param string $table Name of the table to UPDATE. This will be passed through
932 * Database::tableName().
933 * @param array $values An array of values to SET. For each array element,
934 * the key gives the field name, and the value gives the data to set
935 * that field to. The data will be quoted by IDatabase::addQuotes().
936 * Values with integer keys form unquoted SET statements, which can be used for
937 * things like "field = field + 1" or similar computed values.
938 * @param array $conds An array of conditions (WHERE). See
939 * IDatabase::select() for the details of the format of condition
940 * arrays. Use '*' to update all rows.
941 * @param string $fname The function name of the caller (from __METHOD__),
942 * for logging and profiling.
943 * @param array $options An array of UPDATE options, can be:
944 * - IGNORE: Ignore unique key conflicts
945 * - LOW_PRIORITY: MySQL-specific, see MySQL manual.
948 public function update( $table, $values, $conds, $fname = __METHOD__
, $options = [] );
951 * Makes an encoded list of strings from an array
953 * These can be used to make conjunctions or disjunctions on SQL condition strings
954 * derived from an array (see IDatabase::select() $conds documentation).
958 * $sql = $db->makeList( [
960 * $db->makeList( [ 'rev_minor' => 1, 'rev_len' < 500 ], $db::LIST_OR ] )
961 * ], $db::LIST_AND );
963 * This would set $sql to "rev_user = '$id' AND (rev_minor = '1' OR rev_len < '500')"
965 * @param array $a Containing the data
966 * @param int $mode IDatabase class constant:
967 * - IDatabase::LIST_COMMA: Comma separated, no field names
968 * - IDatabase::LIST_AND: ANDed WHERE clause (without the WHERE).
969 * - IDatabase::LIST_OR: ORed WHERE clause (without the WHERE)
970 * - IDatabase::LIST_SET: Comma separated with field names, like a SET clause
971 * - IDatabase::LIST_NAMES: Comma separated field names
975 public function makeList( $a, $mode = self
::LIST_COMMA
);
978 * Build a partial where clause from a 2-d array such as used for LinkBatch.
979 * The keys on each level may be either integers or strings.
981 * @param array $data Organized as 2-d
982 * [ baseKeyVal => [ subKeyVal => [ignored], ... ], ... ]
983 * @param string $baseKey Field name to match the base-level keys to (eg 'pl_namespace')
984 * @param string $subKey Field name to match the sub-level keys to (eg 'pl_title')
985 * @return string|bool SQL fragment, or false if no items in array
987 public function makeWhereFrom2d( $data, $baseKey, $subKey );
990 * Return aggregated value alias
992 * @param array $valuedata
993 * @param string $valuename
997 public function aggregateValue( $valuedata, $valuename = 'value' );
1000 * @param string $field
1003 public function bitNot( $field );
1006 * @param string $fieldLeft
1007 * @param string $fieldRight
1010 public function bitAnd( $fieldLeft, $fieldRight );
1013 * @param string $fieldLeft
1014 * @param string $fieldRight
1017 public function bitOr( $fieldLeft, $fieldRight );
1020 * Build a concatenation list to feed into a SQL query
1021 * @param array $stringList List of raw SQL expressions; caller is
1022 * responsible for any quoting
1025 public function buildConcat( $stringList );
1028 * Build a GROUP_CONCAT or equivalent statement for a query.
1030 * This is useful for combining a field for several rows into a single string.
1031 * NULL values will not appear in the output, duplicated values will appear,
1032 * and the resulting delimiter-separated values have no defined sort order.
1033 * Code using the results may need to use the PHP unique() or sort() methods.
1035 * @param string $delim Glue to bind the results together
1036 * @param string|array $table Table name
1037 * @param string $field Field name
1038 * @param string|array $conds Conditions
1039 * @param string|array $join_conds Join conditions
1040 * @return string SQL text
1043 public function buildGroupConcatField(
1044 $delim, $table, $field, $conds = '', $join_conds = []
1048 * @param string $field Field or column to cast
1052 public function buildStringCast( $field );
1055 * Returns true if DBs are assumed to be on potentially different servers
1057 * In systems like mysql/mariadb, different databases can easily be referenced on a single
1058 * connection merely by name, even in a single query via JOIN. On the other hand, Postgres
1059 * treats databases as fully separate, only allowing mechanisms like postgres_fdw to
1060 * effectively "mount" foreign DBs. This is true even among DBs on the same server.
1065 public function databasesAreIndependent();
1068 * Change the current database
1071 * @return bool Success or failure
1072 * @throws DBConnectionError If databasesAreIndependent() is true and an error occurs
1074 public function selectDB( $db );
1077 * Get the current DB name
1080 public function getDBname();
1083 * Get the server hostname or IP address
1086 public function getServer();
1089 * Adds quotes and backslashes.
1091 * @param string|int|null|bool|Blob $s
1092 * @return string|int
1094 public function addQuotes( $s );
1097 * LIKE statement wrapper, receives a variable-length argument list with
1098 * parts of pattern to match containing either string literals that will be
1099 * escaped or tokens returned by anyChar() or anyString(). Alternatively,
1100 * the function could be provided with an array of aforementioned
1103 * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns
1104 * a LIKE clause that searches for subpages of 'My page title'.
1106 * $pattern = [ 'My_page_title/', $dbr->anyString() ];
1107 * $query .= $dbr->buildLike( $pattern );
1110 * @return string Fully built LIKE statement
1112 public function buildLike();
1115 * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
1119 public function anyChar();
1122 * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
1126 public function anyString();
1129 * Deprecated method, calls should be removed.
1131 * This was formerly used for PostgreSQL and Oracle to handle
1132 * self::insertId() auto-incrementing fields. It is no longer necessary
1133 * since DatabasePostgres::insertId() has been reimplemented using
1134 * `lastval()` and Oracle has been reimplemented using triggers.
1136 * Implementations should return null if inserting `NULL` into an
1137 * auto-incrementing field works, otherwise it should return an instance of
1138 * NextSequenceValue and filter it on calls to relevant methods.
1140 * @deprecated since 1.30, no longer needed
1141 * @param string $seqName
1142 * @return null|NextSequenceValue
1144 public function nextSequenceValue( $seqName );
1147 * REPLACE query wrapper.
1149 * REPLACE is a very handy MySQL extension, which functions like an INSERT
1150 * except that when there is a duplicate key error, the old row is deleted
1151 * and the new row is inserted in its place.
1153 * We simulate this with standard SQL with a DELETE followed by INSERT. To
1154 * perform the delete, we need to know what the unique indexes are so that
1155 * we know how to find the conflicting rows.
1157 * It may be more efficient to leave off unique indexes which are unlikely
1158 * to collide. However if you do this, you run the risk of encountering
1159 * errors which wouldn't have occurred in MySQL.
1161 * @param string $table The table to replace the row(s) in.
1162 * @param array $uniqueIndexes Is an array of indexes. Each element may be either
1163 * a field name or an array of field names
1164 * @param array $rows Can be either a single row to insert, or multiple rows,
1165 * in the same format as for IDatabase::insert()
1166 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1168 public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__
);
1171 * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
1173 * This updates any conflicting rows (according to the unique indexes) using
1174 * the provided SET clause and inserts any remaining (non-conflicted) rows.
1176 * $rows may be either:
1177 * - A single associative array. The array keys are the field names, and
1178 * the values are the values to insert. The values are treated as data
1179 * and will be quoted appropriately. If NULL is inserted, this will be
1180 * converted to a database NULL.
1181 * - An array with numeric keys, holding a list of associative arrays.
1182 * This causes a multi-row INSERT on DBMSs that support it. The keys in
1183 * each subarray must be identical to each other, and in the same order.
1185 * It may be more efficient to leave off unique indexes which are unlikely
1186 * to collide. However if you do this, you run the risk of encountering
1187 * errors which wouldn't have occurred in MySQL.
1189 * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1194 * @param string $table Table name. This will be passed through Database::tableName().
1195 * @param array $rows A single row or list of rows to insert
1196 * @param array $uniqueIndexes List of single field names or field name tuples
1197 * @param array $set An array of values to SET. For each array element, the
1198 * key gives the field name, and the value gives the data to set that
1199 * field to. The data will be quoted by IDatabase::addQuotes().
1200 * Values with integer keys form unquoted SET statements, which can be used for
1201 * things like "field = field + 1" or similar computed values.
1202 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1206 public function upsert(
1207 $table, array $rows, array $uniqueIndexes, array $set, $fname = __METHOD__
1211 * DELETE where the condition is a join.
1213 * MySQL overrides this to use a multi-table DELETE syntax, in other databases
1214 * we use sub-selects
1216 * For safety, an empty $conds will not delete everything. If you want to
1217 * delete all rows where the join condition matches, set $conds='*'.
1219 * DO NOT put the join condition in $conds.
1221 * @param string $delTable The table to delete from.
1222 * @param string $joinTable The other table.
1223 * @param string $delVar The variable to join on, in the first table.
1224 * @param string $joinVar The variable to join on, in the second table.
1225 * @param array $conds Condition array of field names mapped to variables,
1226 * ANDed together in the WHERE clause
1227 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1228 * @throws DBUnexpectedError
1230 public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
1235 * DELETE query wrapper.
1237 * @param string $table Table name
1238 * @param string|array $conds Array of conditions. See $conds in IDatabase::select()
1239 * for the format. Use $conds == "*" to delete all rows
1240 * @param string $fname Name of the calling function
1241 * @throws DBUnexpectedError
1242 * @return bool|IResultWrapper
1244 public function delete( $table, $conds, $fname = __METHOD__
);
1247 * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
1248 * into another table.
1250 * @param string $destTable The table name to insert into
1251 * @param string|array $srcTable May be either a table name, or an array of table names
1252 * to include in a join.
1254 * @param array $varMap Must be an associative array of the form
1255 * [ 'dest1' => 'source1', ... ]. Source items may be literals
1256 * rather than field names, but strings should be quoted with
1257 * IDatabase::addQuotes()
1259 * @param array $conds Condition array. See $conds in IDatabase::select() for
1260 * the details of the format of condition arrays. May be "*" to copy the
1263 * @param string $fname The function name of the caller, from __METHOD__
1265 * @param array $insertOptions Options for the INSERT part of the query, see
1266 * IDatabase::insert() for details.
1267 * @param array $selectOptions Options for the SELECT part of the query, see
1268 * IDatabase::select() for details.
1269 * @param array $selectJoinConds Join conditions for the SELECT part of the query, see
1270 * IDatabase::select() for details.
1274 public function insertSelect( $destTable, $srcTable, $varMap, $conds,
1275 $fname = __METHOD__
,
1276 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
1280 * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
1281 * within the UNION construct.
1284 public function unionSupportsOrderAndLimit();
1287 * Construct a UNION query
1288 * This is used for providing overload point for other DB abstractions
1289 * not compatible with the MySQL syntax.
1290 * @param array $sqls SQL statements to combine
1291 * @param bool $all Use UNION ALL
1292 * @return string SQL fragment
1294 public function unionQueries( $sqls, $all );
1297 * Construct a UNION query for permutations of conditions
1299 * Databases sometimes have trouble with queries that have multiple values
1300 * for multiple condition parameters combined with limits and ordering.
1301 * This method constructs queries for the Cartesian product of the
1302 * conditions and unions them all together.
1304 * @see IDatabase::select()
1306 * @param string|array $table Table name
1307 * @param string|array $vars Field names
1308 * @param array $permute_conds Conditions for the Cartesian product. Keys
1309 * are field names, values are arrays of the possible values for that
1311 * @param string|array $extra_conds Additional conditions to include in the
1313 * @param string $fname Caller function name
1314 * @param string|array $options Query options. In addition to the options
1315 * recognized by IDatabase::select(), the following may be used:
1316 * - NOTALL: Set to use UNION instead of UNION ALL.
1317 * - INNER ORDER BY: If specified and supported, subqueries will use this
1318 * instead of ORDER BY.
1319 * @param string|array $join_conds Join conditions
1320 * @return string SQL query string.
1322 public function unionConditionPermutations(
1323 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__
,
1324 $options = [], $join_conds = []
1328 * Returns an SQL expression for a simple conditional. This doesn't need
1329 * to be overridden unless CASE isn't supported in your DBMS.
1331 * @param string|array $cond SQL expression which will result in a boolean value
1332 * @param string $trueVal SQL expression to return if true
1333 * @param string $falseVal SQL expression to return if false
1334 * @return string SQL fragment
1336 public function conditional( $cond, $trueVal, $falseVal );
1339 * Returns a command for str_replace function in SQL query.
1340 * Uses REPLACE() in MySQL
1342 * @param string $orig Column to modify
1343 * @param string $old Column to seek
1344 * @param string $new Column to replace with
1348 public function strreplace( $orig, $old, $new );
1351 * Determines how long the server has been up
1355 public function getServerUptime();
1358 * Determines if the last failure was due to a deadlock
1362 public function wasDeadlock();
1365 * Determines if the last failure was due to a lock timeout
1369 public function wasLockTimeout();
1372 * Determines if the last query error was due to a dropped connection and should
1373 * be dealt with by pinging the connection and reissuing the query.
1377 public function wasErrorReissuable();
1380 * Determines if the last failure was due to the database being read-only.
1384 public function wasReadOnlyError();
1387 * Wait for the replica DB to catch up to a given master position
1389 * @param DBMasterPos $pos
1390 * @param int $timeout The maximum number of seconds to wait for synchronisation
1391 * @return int|null Zero if the replica DB was past that position already,
1392 * greater than zero if we waited for some period of time, less than
1393 * zero if it timed out, and null on error
1395 public function masterPosWait( DBMasterPos
$pos, $timeout );
1398 * Get the replication position of this replica DB
1400 * @return DBMasterPos|bool False if this is not a replica DB.
1402 public function getReplicaPos();
1405 * Get the position of this master
1407 * @return DBMasterPos|bool False if this is not a master
1409 public function getMasterPos();
1412 * @return bool Whether the DB is marked as read-only server-side
1415 public function serverIsReadOnly();
1418 * Run a callback as soon as the current transaction commits or rolls back.
1419 * An error is thrown if no transaction is pending. Queries in the function will run in
1420 * AUTO-COMMIT mode unless there are begin() calls. Callbacks must commit any transactions
1423 * This is useful for combining cooperative locks and DB transactions.
1425 * The callback takes one argument:
1426 * - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK)
1428 * @param callable $callback
1429 * @param string $fname Caller name
1433 public function onTransactionResolution( callable
$callback, $fname = __METHOD__
);
1436 * Run a callback as soon as there is no transaction pending.
1437 * If there is a transaction and it is rolled back, then the callback is cancelled.
1438 * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
1439 * Callbacks must commit any transactions that they begin.
1441 * This is useful for updates to different systems or when separate transactions are needed.
1442 * For example, one might want to enqueue jobs into a system outside the database, but only
1443 * after the database is updated so that the jobs will see the data when they actually run.
1444 * It can also be used for updates that easily cause deadlocks if locks are held too long.
1446 * Updates will execute in the order they were enqueued.
1448 * The callback takes one argument:
1449 * - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_IDLE)
1451 * @param callable $callback
1452 * @param string $fname Caller name
1455 public function onTransactionIdle( callable
$callback, $fname = __METHOD__
);
1458 * Run a callback before the current transaction commits or now if there is none.
1459 * If there is a transaction and it is rolled back, then the callback is cancelled.
1460 * Callbacks must not start nor commit any transactions. If no transaction is active,
1461 * then a transaction will wrap the callback.
1463 * This is useful for updates that easily cause deadlocks if locks are held too long
1464 * but where atomicity is strongly desired for these updates and some related updates.
1466 * Updates will execute in the order they were enqueued.
1468 * @param callable $callback
1469 * @param string $fname Caller name
1472 public function onTransactionPreCommitOrIdle( callable
$callback, $fname = __METHOD__
);
1475 * Run a callback each time any transaction commits or rolls back
1477 * The callback takes two arguments:
1478 * - IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK
1479 * - This IDatabase object
1480 * Callbacks must commit any transactions that they begin.
1482 * Registering a callback here will not affect writesOrCallbacks() pending
1484 * @param string $name Callback name
1485 * @param callable|null $callback Use null to unset a listener
1489 public function setTransactionListener( $name, callable
$callback = null );
1492 * Begin an atomic section of statements
1494 * If a transaction has been started already, just keep track of the given
1495 * section name to make sure the transaction is not committed pre-maturely.
1496 * This function can be used in layers (with sub-sections), so use a stack
1497 * to keep track of the different atomic sections. If there is no transaction,
1498 * start one implicitly.
1500 * The goal of this function is to create an atomic section of SQL queries
1501 * without having to start a new transaction if it already exists.
1503 * All atomic levels *must* be explicitly closed using IDatabase::endAtomic(),
1504 * and any database transactions cannot be began or committed until all atomic
1505 * levels are closed. There is no such thing as implicitly opening or closing
1506 * an atomic section.
1509 * @param string $fname
1512 public function startAtomic( $fname = __METHOD__
);
1515 * Ends an atomic section of SQL statements
1517 * Ends the next section of atomic SQL statements and commits the transaction
1521 * @see IDatabase::startAtomic
1522 * @param string $fname
1525 public function endAtomic( $fname = __METHOD__
);
1528 * Run a callback to do an atomic set of updates for this database
1530 * The $callback takes the following arguments:
1531 * - This database object
1532 * - The value of $fname
1534 * If any exception occurs in the callback, then rollback() will be called and the error will
1535 * be re-thrown. It may also be that the rollback itself fails with an exception before then.
1536 * In any case, such errors are expected to terminate the request, without any outside caller
1537 * attempting to catch errors and commit anyway. Note that any rollback undoes all prior
1538 * atomic section and uncommitted updates, which trashes the current request, requiring an
1539 * error to be displayed.
1541 * This can be an alternative to explicit startAtomic()/endAtomic() calls.
1543 * @see Database::startAtomic
1544 * @see Database::endAtomic
1546 * @param string $fname Caller name (usually __METHOD__)
1547 * @param callable $callback Callback that issues DB updates
1548 * @return mixed $res Result of the callback (since 1.28)
1550 * @throws RuntimeException
1551 * @throws UnexpectedValueException
1554 public function doAtomicSection( $fname, callable
$callback );
1557 * Begin a transaction. If a transaction is already in progress,
1558 * that transaction will be committed before the new transaction is started.
1560 * Only call this from code with outer transcation scope.
1561 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1562 * Nesting of transactions is not supported.
1564 * Note that when the DBO_TRX flag is set (which is usually the case for web
1565 * requests, but not for maintenance scripts), any previous database query
1566 * will have started a transaction automatically.
1568 * Nesting of transactions is not supported. Attempts to nest transactions
1569 * will cause a warning, unless the current transaction was started
1570 * automatically because of the DBO_TRX flag.
1572 * @param string $fname Calling function name
1573 * @param string $mode A situationally valid IDatabase::TRANSACTION_* constant [optional]
1576 public function begin( $fname = __METHOD__
, $mode = self
::TRANSACTION_EXPLICIT
);
1579 * Commits a transaction previously started using begin().
1580 * If no transaction is in progress, a warning is issued.
1582 * Only call this from code with outer transcation scope.
1583 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1584 * Nesting of transactions is not supported.
1586 * @param string $fname
1587 * @param string $flush Flush flag, set to situationally valid IDatabase::FLUSHING_*
1588 * constant to disable warnings about explicitly committing implicit transactions,
1589 * or calling commit when no transaction is in progress.
1591 * This will trigger an exception if there is an ongoing explicit transaction.
1593 * Only set the flush flag if you are sure that these warnings are not applicable,
1594 * and no explicit transactions are open.
1596 * @throws DBUnexpectedError
1598 public function commit( $fname = __METHOD__
, $flush = '' );
1601 * Rollback a transaction previously started using begin().
1602 * If no transaction is in progress, a warning is issued.
1604 * Only call this from code with outer transcation scope.
1605 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1606 * Nesting of transactions is not supported. If a serious unexpected error occurs,
1607 * throwing an Exception is preferrable, using a pre-installed error handler to trigger
1608 * rollback (in any case, failure to issue COMMIT will cause rollback server-side).
1610 * Query, connection, and onTransaction* callback errors will be suppressed and logged.
1612 * @param string $fname Calling function name
1613 * @param string $flush Flush flag, set to a situationally valid IDatabase::FLUSHING_*
1614 * constant to disable warnings about calling rollback when no transaction is in
1615 * progress. This will silently break any ongoing explicit transaction. Only set the
1616 * flush flag if you are sure that it is safe to ignore these warnings in your context.
1617 * @throws DBUnexpectedError
1618 * @since 1.23 Added $flush parameter
1620 public function rollback( $fname = __METHOD__
, $flush = '' );
1623 * Commit any transaction but error out if writes or callbacks are pending
1625 * This is intended for clearing out REPEATABLE-READ snapshots so that callers can
1626 * see a new point-in-time of the database. This is useful when one of many transaction
1627 * rounds finished and significant time will pass in the script's lifetime. It is also
1628 * useful to call on a replica DB after waiting on replication to catch up to the master.
1630 * @param string $fname Calling function name
1631 * @throws DBUnexpectedError
1634 public function flushSnapshot( $fname = __METHOD__
);
1637 * List all tables on the database
1639 * @param string $prefix Only show tables with this prefix, e.g. mw_
1640 * @param string $fname Calling function name
1644 public function listTables( $prefix = null, $fname = __METHOD__
);
1647 * Convert a timestamp in one of the formats accepted by wfTimestamp()
1648 * to the format used for inserting into timestamp fields in this DBMS.
1650 * The result is unquoted, and needs to be passed through addQuotes()
1651 * before it can be included in raw SQL.
1653 * @param string|int $ts
1657 public function timestamp( $ts = 0 );
1660 * Convert a timestamp in one of the formats accepted by wfTimestamp()
1661 * to the format used for inserting into timestamp fields in this DBMS. If
1662 * NULL is input, it is passed through, allowing NULL values to be inserted
1663 * into timestamp fields.
1665 * The result is unquoted, and needs to be passed through addQuotes()
1666 * before it can be included in raw SQL.
1668 * @param string|int $ts
1672 public function timestampOrNull( $ts = null );
1675 * Ping the server and try to reconnect if it there is no connection
1677 * @param float|null &$rtt Value to store the estimated RTT [optional]
1678 * @return bool Success or failure
1680 public function ping( &$rtt = null );
1683 * Get replica DB lag. Currently supported only by MySQL.
1685 * Note that this function will generate a fatal error on many
1686 * installations. Most callers should use LoadBalancer::safeGetLag()
1689 * @return int|bool Database replication lag in seconds or false on error
1691 public function getLag();
1694 * Get the replica DB lag when the current transaction started
1695 * or a general lag estimate if not transaction is active
1697 * This is useful when transactions might use snapshot isolation
1698 * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
1699 * is this lag plus transaction duration. If they don't, it is still
1700 * safe to be pessimistic. In AUTO-COMMIT mode, this still gives an
1701 * indication of the staleness of subsequent reads.
1703 * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
1706 public function getSessionLagStatus();
1709 * Return the maximum number of items allowed in a list, or 0 for unlimited.
1713 public function maxListLen();
1716 * Some DBMSs have a special format for inserting into blob fields, they
1717 * don't allow simple quoted strings to be inserted. To insert into such
1718 * a field, pass the data through this function before passing it to
1719 * IDatabase::insert().
1722 * @return string|Blob
1724 public function encodeBlob( $b );
1727 * Some DBMSs return a special placeholder object representing blob fields
1728 * in result objects. Pass the object through this function to return the
1731 * @param string|Blob $b
1734 public function decodeBlob( $b );
1737 * Override database's default behavior. $options include:
1738 * 'connTimeout' : Set the connection timeout value in seconds.
1739 * May be useful for very long batch queries such as
1740 * full-wiki dumps, where a single query reads out over
1743 * @param array $options
1746 public function setSessionOptions( array $options );
1749 * Set variables to be used in sourceFile/sourceStream, in preference to the
1750 * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
1751 * all. If it's set to false, $GLOBALS will be used.
1753 * @param bool|array $vars Mapping variable name to value.
1755 public function setSchemaVars( $vars );
1758 * Check to see if a named lock is available (non-blocking)
1760 * @param string $lockName Name of lock to poll
1761 * @param string $method Name of method calling us
1765 public function lockIsFree( $lockName, $method );
1768 * Acquire a named lock
1770 * Named locks are not related to transactions
1772 * @param string $lockName Name of lock to aquire
1773 * @param string $method Name of the calling method
1774 * @param int $timeout Acquisition timeout in seconds
1777 public function lock( $lockName, $method, $timeout = 5 );
1782 * Named locks are not related to transactions
1784 * @param string $lockName Name of lock to release
1785 * @param string $method Name of the calling method
1787 * @return int Returns 1 if the lock was released, 0 if the lock was not established
1788 * by this thread (in which case the lock is not released), and NULL if the named
1789 * lock did not exist
1791 public function unlock( $lockName, $method );
1794 * Acquire a named lock, flush any transaction, and return an RAII style unlocker object
1796 * Only call this from outer transcation scope and when only one DB will be affected.
1797 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1799 * This is suitiable for transactions that need to be serialized using cooperative locks,
1800 * where each transaction can see each others' changes. Any transaction is flushed to clear
1801 * out stale REPEATABLE-READ snapshot data. Once the returned object falls out of PHP scope,
1802 * the lock will be released unless a transaction is active. If one is active, then the lock
1803 * will be released when it either commits or rolls back.
1805 * If the lock acquisition failed, then no transaction flush happens, and null is returned.
1807 * @param string $lockKey Name of lock to release
1808 * @param string $fname Name of the calling method
1809 * @param int $timeout Acquisition timeout in seconds
1810 * @return ScopedCallback|null
1811 * @throws DBUnexpectedError
1814 public function getScopedLockAndFlush( $lockKey, $fname, $timeout );
1817 * Check to see if a named lock used by lock() use blocking queues
1822 public function namedLocksEnqueue();
1825 * Find out when 'infinity' is. Most DBMSes support this. This is a special
1826 * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
1827 * because "i" sorts after all numbers.
1831 public function getInfinity();
1834 * Encode an expiry time into the DBMS dependent format
1836 * @param string $expiry Timestamp for expiry, or the 'infinity' string
1839 public function encodeExpiry( $expiry );
1842 * Decode an expiry time into a DBMS independent format
1844 * @param string $expiry DB timestamp field value for expiry
1845 * @param int $format TS_* constant, defaults to TS_MW
1848 public function decodeExpiry( $expiry, $format = TS_MW
);
1851 * Allow or deny "big selects" for this session only. This is done by setting
1852 * the sql_big_selects session variable.
1854 * This is a MySQL-specific feature.
1856 * @param bool|string $value True for allow, false for deny, or "default" to
1857 * restore the initial value
1859 public function setBigSelects( $value = true );
1862 * @return bool Whether this DB is read-only
1865 public function isReadOnly();
1868 * Make certain table names use their own database, schema, and table prefix
1869 * when passed into SQL queries pre-escaped and without a qualified database name
1871 * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
1872 * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
1874 * Calling this twice will completely clear any old table aliases. Also, note that
1875 * callers are responsible for making sure the schemas and databases actually exist.
1877 * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
1880 public function setTableAliases( array $aliases );
1883 class_alias( IDatabase
::class, 'IDatabase' );