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()
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?
528 * @return bool|IResultWrapper True for a successful write query, IResultWrapper object
529 * 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 bool|mixed The value from the field, or false on failure.
573 public function selectField(
574 $table, $var, $cond = '', $fname = __METHOD__
, $options = [], $join_conds = []
578 * A SELECT wrapper which returns a list of single field values from result rows.
580 * Usually throws a DBQueryError on failure. If errors are explicitly
581 * ignored, returns false on failure.
583 * If no result rows are returned from the query, false is returned.
585 * @param string|array $table Table name. See IDatabase::select() for details.
586 * @param string $var The field name to select. This must be a valid SQL
587 * fragment: do not use unvalidated user input.
588 * @param string|array $cond The condition array. See IDatabase::select() for details.
589 * @param string $fname The function name of the caller.
590 * @param string|array $options The query options. See IDatabase::select() for details.
591 * @param string|array $join_conds The query join conditions. See IDatabase::select() for details.
593 * @return bool|array The values from the field, or false on failure
596 public function selectFieldValues(
597 $table, $var, $cond = '', $fname = __METHOD__
, $options = [], $join_conds = []
601 * Execute a SELECT query constructed using the various parameters provided.
602 * See below for full details of the parameters.
604 * @param string|array $table Table name
605 * @param string|array $vars Field names
606 * @param string|array $conds Conditions
607 * @param string $fname Caller function name
608 * @param array $options Query options
609 * @param array $join_conds Join conditions
612 * @param string|array $table
614 * May be either an array of table names, or a single string holding a table
615 * name. If an array is given, table aliases can be specified, for example:
619 * This includes the user table in the query, with the alias "a" available
620 * for use in field names (e.g. a.user_name).
622 * All of the table names given here are automatically run through
623 * Database::tableName(), which causes the table prefix (if any) to be
624 * added, and various other table name mappings to be performed.
626 * Do not use untrusted user input as a table name. Alias names should
627 * not have characters outside of the Basic multilingual plane.
629 * @param string|array $vars
631 * May be either a field name or an array of field names. The field names
632 * can be complete fragments of SQL, for direct inclusion into the SELECT
633 * query. If an array is given, field aliases can be specified, for example:
635 * [ 'maxrev' => 'MAX(rev_id)' ]
637 * This includes an expression with the alias "maxrev" in the query.
639 * If an expression is given, care must be taken to ensure that it is
642 * Untrusted user input must not be passed to this parameter.
644 * @param string|array $conds
646 * May be either a string containing a single condition, or an array of
647 * conditions. If an array is given, the conditions constructed from each
648 * element are combined with AND.
650 * Array elements may take one of two forms:
652 * - Elements with a numeric key are interpreted as raw SQL fragments.
653 * - Elements with a string key are interpreted as equality conditions,
654 * where the key is the field name.
655 * - If the value of such an array element is a scalar (such as a
656 * string), it will be treated as data and thus quoted appropriately.
657 * If it is null, an IS NULL clause will be added.
658 * - If the value is an array, an IN (...) clause will be constructed
659 * from its non-null elements, and an IS NULL clause will be added
660 * if null is present, such that the field may match any of the
661 * elements in the array. The non-null elements will be quoted.
663 * Note that expressions are often DBMS-dependent in their syntax.
664 * DBMS-independent wrappers are provided for constructing several types of
665 * expression commonly used in condition queries. See:
666 * - IDatabase::buildLike()
667 * - IDatabase::conditional()
669 * Untrusted user input is safe in the values of string keys, however untrusted
670 * input must not be used in the array key names or in the values of numeric keys.
671 * Escaping of untrusted input used in values of numeric keys should be done via
672 * IDatabase::addQuotes()
674 * @param string|array $options
676 * Optional: Array of query options. Boolean options are specified by
677 * including them in the array as a string value with a numeric key, for
682 * The supported options are:
684 * - OFFSET: Skip this many rows at the start of the result set. OFFSET
685 * with LIMIT can theoretically be used for paging through a result set,
686 * but this is discouraged for performance reasons.
688 * - LIMIT: Integer: return at most this many rows. The rows are sorted
689 * and then the first rows are taken until the limit is reached. LIMIT
690 * is applied to a result set after OFFSET.
692 * - FOR UPDATE: Boolean: lock the returned rows so that they can't be
693 * changed until the next COMMIT.
695 * - DISTINCT: Boolean: return only unique result rows.
697 * - GROUP BY: May be either an SQL fragment string naming a field or
698 * expression to group by, or an array of such SQL fragments.
700 * - HAVING: May be either an string containing a HAVING clause or an array of
701 * conditions building the HAVING clause. If an array is given, the conditions
702 * constructed from each element are combined with AND.
704 * - ORDER BY: May be either an SQL fragment giving a field name or
705 * expression to order by, or an array of such SQL fragments.
707 * - USE INDEX: This may be either a string giving the index name to use
708 * for the query, or an array. If it is an associative array, each key
709 * gives the table name (or alias), each value gives the index name to
710 * use for that table. All strings are SQL fragments and so should be
711 * validated by the caller.
713 * - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
716 * And also the following boolean MySQL extensions, see the MySQL manual
719 * - LOCK IN SHARE MODE
723 * - SQL_BUFFER_RESULT
725 * - SQL_CALC_FOUND_ROWS
730 * @param string|array $join_conds
732 * Optional associative array of table-specific join conditions. In the
733 * most common case, this is unnecessary, since the join condition can be
734 * in $conds. However, it is useful for doing a LEFT JOIN.
736 * The key of the array contains the table name or alias. The value is an
737 * array with two elements, numbered 0 and 1. The first gives the type of
738 * join, the second is the same as the $conds parameter. Thus it can be
739 * an SQL fragment, or an array where the string keys are equality and the
740 * numeric keys are SQL fragments all AND'd together. For example:
742 * [ 'page' => [ 'LEFT JOIN', 'page_latest=rev_id' ] ]
744 * @return IResultWrapper|bool If the query returned no rows, a IResultWrapper
745 * with no rows in it will be returned. If there was a query error, a
746 * DBQueryError exception will be thrown, except if the "ignore errors"
747 * option was set, in which case false will be returned.
749 public function select(
750 $table, $vars, $conds = '', $fname = __METHOD__
,
751 $options = [], $join_conds = []
755 * The equivalent of IDatabase::select() except that the constructed SQL
756 * is returned, instead of being immediately executed. This can be useful for
757 * doing UNION queries, where the SQL text of each query is needed. In general,
758 * however, callers outside of Database classes should just use select().
760 * @param string|array $table Table name
761 * @param string|array $vars Field names
762 * @param string|array $conds Conditions
763 * @param string $fname Caller function name
764 * @param string|array $options Query options
765 * @param string|array $join_conds Join conditions
767 * @return string SQL query string.
768 * @see IDatabase::select()
770 public function selectSQLText(
771 $table, $vars, $conds = '', $fname = __METHOD__
,
772 $options = [], $join_conds = []
776 * Single row SELECT wrapper. Equivalent to IDatabase::select(), except
777 * that a single row object is returned. If the query returns no rows,
780 * @param string|array $table Table name
781 * @param string|array $vars Field names
782 * @param array $conds Conditions
783 * @param string $fname Caller function name
784 * @param string|array $options Query options
785 * @param array|string $join_conds Join conditions
787 * @return stdClass|bool
789 public function selectRow( $table, $vars, $conds, $fname = __METHOD__
,
790 $options = [], $join_conds = []
794 * Estimate the number of rows in dataset
796 * MySQL allows you to estimate the number of rows that would be returned
797 * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
798 * index cardinality statistics, and is notoriously inaccurate, especially
799 * when large numbers of rows have recently been added or deleted.
801 * For DBMSs that don't support fast result size estimation, this function
802 * will actually perform the SELECT COUNT(*).
804 * Takes the same arguments as IDatabase::select().
806 * @param string $table Table name
807 * @param string $vars Unused
808 * @param array|string $conds Filters on the table
809 * @param string $fname Function name for profiling
810 * @param array $options Options for select
811 * @return int Row count
813 public function estimateRowCount(
814 $table, $vars = '*', $conds = '', $fname = __METHOD__
, $options = []
818 * Get the number of rows in dataset
820 * This is useful when trying to do COUNT(*) but with a LIMIT for performance.
822 * Takes the same arguments as IDatabase::select().
824 * @since 1.27 Added $join_conds parameter
826 * @param array|string $tables Table names
827 * @param string $vars Unused
828 * @param array|string $conds Filters on the table
829 * @param string $fname Function name for profiling
830 * @param array $options Options for select
831 * @param array $join_conds Join conditions (since 1.27)
832 * @return int Row count
834 public function selectRowCount(
835 $tables, $vars = '*', $conds = '', $fname = __METHOD__
, $options = [], $join_conds = []
839 * Determines whether a field exists in a table
841 * @param string $table Table name
842 * @param string $field Filed to check on that table
843 * @param string $fname Calling function name (optional)
844 * @return bool Whether $table has filed $field
846 public function fieldExists( $table, $field, $fname = __METHOD__
);
849 * Determines whether an index exists
850 * Usually throws a DBQueryError on failure
851 * If errors are explicitly ignored, returns NULL on failure
853 * @param string $table
854 * @param string $index
855 * @param string $fname
858 public function indexExists( $table, $index, $fname = __METHOD__
);
861 * Query whether a given table exists
863 * @param string $table
864 * @param string $fname
867 public function tableExists( $table, $fname = __METHOD__
);
870 * Determines if a given index is unique
872 * @param string $table
873 * @param string $index
877 public function indexUnique( $table, $index );
880 * INSERT wrapper, inserts an array into a table.
884 * - A single associative array. The array keys are the field names, and
885 * the values are the values to insert. The values are treated as data
886 * and will be quoted appropriately. If NULL is inserted, this will be
887 * converted to a database NULL.
888 * - An array with numeric keys, holding a list of associative arrays.
889 * This causes a multi-row INSERT on DBMSs that support it. The keys in
890 * each subarray must be identical to each other, and in the same order.
892 * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
895 * $options is an array of options, with boolean options encoded as values
896 * with numeric keys, in the same style as $options in
897 * IDatabase::select(). Supported options are:
899 * - IGNORE: Boolean: if present, duplicate key errors are ignored, and
900 * any rows which cause duplicate key errors are not inserted. It's
901 * possible to determine how many rows were successfully inserted using
902 * IDatabase::affectedRows().
904 * @param string $table Table name. This will be passed through
905 * Database::tableName().
906 * @param array $a Array of rows to insert
907 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
908 * @param array $options Array of options
912 public function insert( $table, $a, $fname = __METHOD__
, $options = [] );
915 * UPDATE wrapper. Takes a condition array and a SET array.
917 * @param string $table Name of the table to UPDATE. This will be passed through
918 * Database::tableName().
919 * @param array $values An array of values to SET. For each array element,
920 * the key gives the field name, and the value gives the data to set
921 * that field to. The data will be quoted by IDatabase::addQuotes().
922 * Values with integer keys form unquoted SET statements, which can be used for
923 * things like "field = field + 1" or similar computed values.
924 * @param array $conds An array of conditions (WHERE). See
925 * IDatabase::select() for the details of the format of condition
926 * arrays. Use '*' to update all rows.
927 * @param string $fname The function name of the caller (from __METHOD__),
928 * for logging and profiling.
929 * @param array $options An array of UPDATE options, can be:
930 * - IGNORE: Ignore unique key conflicts
931 * - LOW_PRIORITY: MySQL-specific, see MySQL manual.
934 public function update( $table, $values, $conds, $fname = __METHOD__
, $options = [] );
937 * Makes an encoded list of strings from an array
939 * These can be used to make conjunctions or disjunctions on SQL condition strings
940 * derived from an array (see IDatabase::select() $conds documentation).
944 * $sql = $db->makeList( [
946 * $db->makeList( [ 'rev_minor' => 1, 'rev_len' < 500 ], $db::LIST_OR ] )
947 * ], $db::LIST_AND );
949 * This would set $sql to "rev_user = '$id' AND (rev_minor = '1' OR rev_len < '500')"
951 * @param array $a Containing the data
952 * @param int $mode IDatabase class constant:
953 * - IDatabase::LIST_COMMA: Comma separated, no field names
954 * - IDatabase::LIST_AND: ANDed WHERE clause (without the WHERE).
955 * - IDatabase::LIST_OR: ORed WHERE clause (without the WHERE)
956 * - IDatabase::LIST_SET: Comma separated with field names, like a SET clause
957 * - IDatabase::LIST_NAMES: Comma separated field names
961 public function makeList( $a, $mode = self
::LIST_COMMA
);
964 * Build a partial where clause from a 2-d array such as used for LinkBatch.
965 * The keys on each level may be either integers or strings.
967 * @param array $data Organized as 2-d
968 * [ baseKeyVal => [ subKeyVal => [ignored], ... ], ... ]
969 * @param string $baseKey Field name to match the base-level keys to (eg 'pl_namespace')
970 * @param string $subKey Field name to match the sub-level keys to (eg 'pl_title')
971 * @return string|bool SQL fragment, or false if no items in array
973 public function makeWhereFrom2d( $data, $baseKey, $subKey );
976 * Return aggregated value alias
978 * @param array $valuedata
979 * @param string $valuename
983 public function aggregateValue( $valuedata, $valuename = 'value' );
986 * @param string $field
989 public function bitNot( $field );
992 * @param string $fieldLeft
993 * @param string $fieldRight
996 public function bitAnd( $fieldLeft, $fieldRight );
999 * @param string $fieldLeft
1000 * @param string $fieldRight
1003 public function bitOr( $fieldLeft, $fieldRight );
1006 * Build a concatenation list to feed into a SQL query
1007 * @param array $stringList List of raw SQL expressions; caller is
1008 * responsible for any quoting
1011 public function buildConcat( $stringList );
1014 * Build a GROUP_CONCAT or equivalent statement for a query.
1016 * This is useful for combining a field for several rows into a single string.
1017 * NULL values will not appear in the output, duplicated values will appear,
1018 * and the resulting delimiter-separated values have no defined sort order.
1019 * Code using the results may need to use the PHP unique() or sort() methods.
1021 * @param string $delim Glue to bind the results together
1022 * @param string|array $table Table name
1023 * @param string $field Field name
1024 * @param string|array $conds Conditions
1025 * @param string|array $join_conds Join conditions
1026 * @return string SQL text
1029 public function buildGroupConcatField(
1030 $delim, $table, $field, $conds = '', $join_conds = []
1034 * @param string $field Field or column to cast
1038 public function buildStringCast( $field );
1041 * Returns true if DBs are assumed to be on potentially different servers
1043 * In systems like mysql/mariadb, different databases can easily be referenced on a single
1044 * connection merely by name, even in a single query via JOIN. On the other hand, Postgres
1045 * treats databases as fully separate, only allowing mechanisms like postgres_fdw to
1046 * effectively "mount" foreign DBs. This is true even among DBs on the same server.
1051 public function databasesAreIndependent();
1054 * Change the current database
1057 * @return bool Success or failure
1058 * @throws DBConnectionError If databasesAreIndependent() is true and an error occurs
1060 public function selectDB( $db );
1063 * Get the current DB name
1066 public function getDBname();
1069 * Get the server hostname or IP address
1072 public function getServer();
1075 * Adds quotes and backslashes.
1077 * @param string|int|null|bool|Blob $s
1078 * @return string|int
1080 public function addQuotes( $s );
1083 * LIKE statement wrapper, receives a variable-length argument list with
1084 * parts of pattern to match containing either string literals that will be
1085 * escaped or tokens returned by anyChar() or anyString(). Alternatively,
1086 * the function could be provided with an array of aforementioned
1089 * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns
1090 * a LIKE clause that searches for subpages of 'My page title'.
1092 * $pattern = [ 'My_page_title/', $dbr->anyString() ];
1093 * $query .= $dbr->buildLike( $pattern );
1096 * @return string Fully built LIKE statement
1098 public function buildLike();
1101 * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
1105 public function anyChar();
1108 * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
1112 public function anyString();
1115 * Deprecated method, calls should be removed.
1117 * This was formerly used for PostgreSQL and Oracle to handle
1118 * self::insertId() auto-incrementing fields. It is no longer necessary
1119 * since DatabasePostgres::insertId() has been reimplemented using
1120 * `lastval()` and Oracle has been reimplemented using triggers.
1122 * Implementations should return null if inserting `NULL` into an
1123 * auto-incrementing field works, otherwise it should return an instance of
1124 * NextSequenceValue and filter it on calls to relevant methods.
1126 * @deprecated since 1.30, no longer needed
1127 * @param string $seqName
1128 * @return null|NextSequenceValue
1130 public function nextSequenceValue( $seqName );
1133 * REPLACE query wrapper.
1135 * REPLACE is a very handy MySQL extension, which functions like an INSERT
1136 * except that when there is a duplicate key error, the old row is deleted
1137 * and the new row is inserted in its place.
1139 * We simulate this with standard SQL with a DELETE followed by INSERT. To
1140 * perform the delete, we need to know what the unique indexes are so that
1141 * we know how to find the conflicting rows.
1143 * It may be more efficient to leave off unique indexes which are unlikely
1144 * to collide. However if you do this, you run the risk of encountering
1145 * errors which wouldn't have occurred in MySQL.
1147 * @param string $table The table to replace the row(s) in.
1148 * @param array $uniqueIndexes Is an array of indexes. Each element may be either
1149 * a field name or an array of field names
1150 * @param array $rows Can be either a single row to insert, or multiple rows,
1151 * in the same format as for IDatabase::insert()
1152 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1154 public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__
);
1157 * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
1159 * This updates any conflicting rows (according to the unique indexes) using
1160 * the provided SET clause and inserts any remaining (non-conflicted) rows.
1162 * $rows may be either:
1163 * - A single associative array. The array keys are the field names, and
1164 * the values are the values to insert. The values are treated as data
1165 * and will be quoted appropriately. If NULL is inserted, this will be
1166 * converted to a database NULL.
1167 * - An array with numeric keys, holding a list of associative arrays.
1168 * This causes a multi-row INSERT on DBMSs that support it. The keys in
1169 * each subarray must be identical to each other, and in the same order.
1171 * It may be more efficient to leave off unique indexes which are unlikely
1172 * to collide. However if you do this, you run the risk of encountering
1173 * errors which wouldn't have occurred in MySQL.
1175 * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1180 * @param string $table Table name. This will be passed through Database::tableName().
1181 * @param array $rows A single row or list of rows to insert
1182 * @param array $uniqueIndexes List of single field names or field name tuples
1183 * @param array $set An array of values to SET. For each array element, the
1184 * key gives the field name, and the value gives the data to set that
1185 * field to. The data will be quoted by IDatabase::addQuotes().
1186 * Values with integer keys form unquoted SET statements, which can be used for
1187 * things like "field = field + 1" or similar computed values.
1188 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1192 public function upsert(
1193 $table, array $rows, array $uniqueIndexes, array $set, $fname = __METHOD__
1197 * DELETE where the condition is a join.
1199 * MySQL overrides this to use a multi-table DELETE syntax, in other databases
1200 * we use sub-selects
1202 * For safety, an empty $conds will not delete everything. If you want to
1203 * delete all rows where the join condition matches, set $conds='*'.
1205 * DO NOT put the join condition in $conds.
1207 * @param string $delTable The table to delete from.
1208 * @param string $joinTable The other table.
1209 * @param string $delVar The variable to join on, in the first table.
1210 * @param string $joinVar The variable to join on, in the second table.
1211 * @param array $conds Condition array of field names mapped to variables,
1212 * ANDed together in the WHERE clause
1213 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1214 * @throws DBUnexpectedError
1216 public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
1221 * DELETE query wrapper.
1223 * @param string $table Table name
1224 * @param string|array $conds Array of conditions. See $conds in IDatabase::select()
1225 * for the format. Use $conds == "*" to delete all rows
1226 * @param string $fname Name of the calling function
1227 * @throws DBUnexpectedError
1228 * @return bool|IResultWrapper
1230 public function delete( $table, $conds, $fname = __METHOD__
);
1233 * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
1234 * into another table.
1236 * @param string $destTable The table name to insert into
1237 * @param string|array $srcTable May be either a table name, or an array of table names
1238 * to include in a join.
1240 * @param array $varMap Must be an associative array of the form
1241 * [ 'dest1' => 'source1', ... ]. Source items may be literals
1242 * rather than field names, but strings should be quoted with
1243 * IDatabase::addQuotes()
1245 * @param array $conds Condition array. See $conds in IDatabase::select() for
1246 * the details of the format of condition arrays. May be "*" to copy the
1249 * @param string $fname The function name of the caller, from __METHOD__
1251 * @param array $insertOptions Options for the INSERT part of the query, see
1252 * IDatabase::insert() for details.
1253 * @param array $selectOptions Options for the SELECT part of the query, see
1254 * IDatabase::select() for details.
1255 * @param array $selectJoinConds Join conditions for the SELECT part of the query, see
1256 * IDatabase::select() for details.
1260 public function insertSelect( $destTable, $srcTable, $varMap, $conds,
1261 $fname = __METHOD__
,
1262 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
1266 * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
1267 * within the UNION construct.
1270 public function unionSupportsOrderAndLimit();
1273 * Construct a UNION query
1274 * This is used for providing overload point for other DB abstractions
1275 * not compatible with the MySQL syntax.
1276 * @param array $sqls SQL statements to combine
1277 * @param bool $all Use UNION ALL
1278 * @return string SQL fragment
1280 public function unionQueries( $sqls, $all );
1283 * Construct a UNION query for permutations of conditions
1285 * Databases sometimes have trouble with queries that have multiple values
1286 * for multiple condition parameters combined with limits and ordering.
1287 * This method constructs queries for the Cartesian product of the
1288 * conditions and unions them all together.
1290 * @see IDatabase::select()
1292 * @param string|array $table Table name
1293 * @param string|array $vars Field names
1294 * @param array $permute_conds Conditions for the Cartesian product. Keys
1295 * are field names, values are arrays of the possible values for that
1297 * @param string|array $extra_conds Additional conditions to include in the
1299 * @param string $fname Caller function name
1300 * @param string|array $options Query options. In addition to the options
1301 * recognized by IDatabase::select(), the following may be used:
1302 * - NOTALL: Set to use UNION instead of UNION ALL.
1303 * - INNER ORDER BY: If specified and supported, subqueries will use this
1304 * instead of ORDER BY.
1305 * @param string|array $join_conds Join conditions
1306 * @return string SQL query string.
1308 public function unionConditionPermutations(
1309 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__
,
1310 $options = [], $join_conds = []
1314 * Returns an SQL expression for a simple conditional. This doesn't need
1315 * to be overridden unless CASE isn't supported in your DBMS.
1317 * @param string|array $cond SQL expression which will result in a boolean value
1318 * @param string $trueVal SQL expression to return if true
1319 * @param string $falseVal SQL expression to return if false
1320 * @return string SQL fragment
1322 public function conditional( $cond, $trueVal, $falseVal );
1325 * Returns a command for str_replace function in SQL query.
1326 * Uses REPLACE() in MySQL
1328 * @param string $orig Column to modify
1329 * @param string $old Column to seek
1330 * @param string $new Column to replace with
1334 public function strreplace( $orig, $old, $new );
1337 * Determines how long the server has been up
1341 public function getServerUptime();
1344 * Determines if the last failure was due to a deadlock
1348 public function wasDeadlock();
1351 * Determines if the last failure was due to a lock timeout
1355 public function wasLockTimeout();
1358 * Determines if the last query error was due to a dropped connection and should
1359 * be dealt with by pinging the connection and reissuing the query.
1363 public function wasErrorReissuable();
1366 * Determines if the last failure was due to the database being read-only.
1370 public function wasReadOnlyError();
1373 * Wait for the replica DB to catch up to a given master position
1375 * @param DBMasterPos $pos
1376 * @param int $timeout The maximum number of seconds to wait for synchronisation
1377 * @return int|null Zero if the replica DB was past that position already,
1378 * greater than zero if we waited for some period of time, less than
1379 * zero if it timed out, and null on error
1381 public function masterPosWait( DBMasterPos
$pos, $timeout );
1384 * Get the replication position of this replica DB
1386 * @return DBMasterPos|bool False if this is not a replica DB.
1388 public function getReplicaPos();
1391 * Get the position of this master
1393 * @return DBMasterPos|bool False if this is not a master
1395 public function getMasterPos();
1398 * @return bool Whether the DB is marked as read-only server-side
1401 public function serverIsReadOnly();
1404 * Run a callback as soon as the current transaction commits or rolls back.
1405 * An error is thrown if no transaction is pending. Queries in the function will run in
1406 * AUTO-COMMIT mode unless there are begin() calls. Callbacks must commit any transactions
1409 * This is useful for combining cooperative locks and DB transactions.
1411 * The callback takes one argument:
1412 * - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK)
1414 * @param callable $callback
1415 * @param string $fname Caller name
1419 public function onTransactionResolution( callable
$callback, $fname = __METHOD__
);
1422 * Run a callback as soon as there is no transaction pending.
1423 * If there is a transaction and it is rolled back, then the callback is cancelled.
1424 * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
1425 * Callbacks must commit any transactions that they begin.
1427 * This is useful for updates to different systems or when separate transactions are needed.
1428 * For example, one might want to enqueue jobs into a system outside the database, but only
1429 * after the database is updated so that the jobs will see the data when they actually run.
1430 * It can also be used for updates that easily cause deadlocks if locks are held too long.
1432 * Updates will execute in the order they were enqueued.
1434 * The callback takes one argument:
1435 * - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_IDLE)
1437 * @param callable $callback
1438 * @param string $fname Caller name
1441 public function onTransactionIdle( callable
$callback, $fname = __METHOD__
);
1444 * Run a callback before the current transaction commits or now if there is none.
1445 * If there is a transaction and it is rolled back, then the callback is cancelled.
1446 * Callbacks must not start nor commit any transactions. If no transaction is active,
1447 * then a transaction will wrap the callback.
1449 * This is useful for updates that easily cause deadlocks if locks are held too long
1450 * but where atomicity is strongly desired for these updates and some related updates.
1452 * Updates will execute in the order they were enqueued.
1454 * @param callable $callback
1455 * @param string $fname Caller name
1458 public function onTransactionPreCommitOrIdle( callable
$callback, $fname = __METHOD__
);
1461 * Run a callback each time any transaction commits or rolls back
1463 * The callback takes two arguments:
1464 * - IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK
1465 * - This IDatabase object
1466 * Callbacks must commit any transactions that they begin.
1468 * Registering a callback here will not affect writesOrCallbacks() pending
1470 * @param string $name Callback name
1471 * @param callable|null $callback Use null to unset a listener
1475 public function setTransactionListener( $name, callable
$callback = null );
1478 * Begin an atomic section of statements
1480 * If a transaction has been started already, just keep track of the given
1481 * section name to make sure the transaction is not committed pre-maturely.
1482 * This function can be used in layers (with sub-sections), so use a stack
1483 * to keep track of the different atomic sections. If there is no transaction,
1484 * start one implicitly.
1486 * The goal of this function is to create an atomic section of SQL queries
1487 * without having to start a new transaction if it already exists.
1489 * All atomic levels *must* be explicitly closed using IDatabase::endAtomic(),
1490 * and any database transactions cannot be began or committed until all atomic
1491 * levels are closed. There is no such thing as implicitly opening or closing
1492 * an atomic section.
1495 * @param string $fname
1498 public function startAtomic( $fname = __METHOD__
);
1501 * Ends an atomic section of SQL statements
1503 * Ends the next section of atomic SQL statements and commits the transaction
1507 * @see IDatabase::startAtomic
1508 * @param string $fname
1511 public function endAtomic( $fname = __METHOD__
);
1514 * Run a callback to do an atomic set of updates for this database
1516 * The $callback takes the following arguments:
1517 * - This database object
1518 * - The value of $fname
1520 * If any exception occurs in the callback, then rollback() will be called and the error will
1521 * be re-thrown. It may also be that the rollback itself fails with an exception before then.
1522 * In any case, such errors are expected to terminate the request, without any outside caller
1523 * attempting to catch errors and commit anyway. Note that any rollback undoes all prior
1524 * atomic section and uncommitted updates, which trashes the current request, requiring an
1525 * error to be displayed.
1527 * This can be an alternative to explicit startAtomic()/endAtomic() calls.
1529 * @see Database::startAtomic
1530 * @see Database::endAtomic
1532 * @param string $fname Caller name (usually __METHOD__)
1533 * @param callable $callback Callback that issues DB updates
1534 * @return mixed $res Result of the callback (since 1.28)
1536 * @throws RuntimeException
1537 * @throws UnexpectedValueException
1540 public function doAtomicSection( $fname, callable
$callback );
1543 * Begin a transaction. If a transaction is already in progress,
1544 * that transaction will be committed before the new transaction is started.
1546 * Only call this from code with outer transcation scope.
1547 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1548 * Nesting of transactions is not supported.
1550 * Note that when the DBO_TRX flag is set (which is usually the case for web
1551 * requests, but not for maintenance scripts), any previous database query
1552 * will have started a transaction automatically.
1554 * Nesting of transactions is not supported. Attempts to nest transactions
1555 * will cause a warning, unless the current transaction was started
1556 * automatically because of the DBO_TRX flag.
1558 * @param string $fname Calling function name
1559 * @param string $mode A situationally valid IDatabase::TRANSACTION_* constant [optional]
1562 public function begin( $fname = __METHOD__
, $mode = self
::TRANSACTION_EXPLICIT
);
1565 * Commits a transaction previously started using begin().
1566 * If no transaction is in progress, a warning is issued.
1568 * Only call this from code with outer transcation scope.
1569 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1570 * Nesting of transactions is not supported.
1572 * @param string $fname
1573 * @param string $flush Flush flag, set to situationally valid IDatabase::FLUSHING_*
1574 * constant to disable warnings about explicitly committing implicit transactions,
1575 * or calling commit when no transaction is in progress.
1577 * This will trigger an exception if there is an ongoing explicit transaction.
1579 * Only set the flush flag if you are sure that these warnings are not applicable,
1580 * and no explicit transactions are open.
1582 * @throws DBUnexpectedError
1584 public function commit( $fname = __METHOD__
, $flush = '' );
1587 * Rollback a transaction previously started using begin().
1588 * If no transaction is in progress, a warning is issued.
1590 * Only call this from code with outer transcation scope.
1591 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1592 * Nesting of transactions is not supported. If a serious unexpected error occurs,
1593 * throwing an Exception is preferrable, using a pre-installed error handler to trigger
1594 * rollback (in any case, failure to issue COMMIT will cause rollback server-side).
1596 * @param string $fname Calling function name
1597 * @param string $flush Flush flag, set to a situationally valid IDatabase::FLUSHING_*
1598 * constant to disable warnings about calling rollback when no transaction is in
1599 * progress. This will silently break any ongoing explicit transaction. Only set the
1600 * flush flag if you are sure that it is safe to ignore these warnings in your context.
1601 * @throws DBUnexpectedError
1602 * @since 1.23 Added $flush parameter
1604 public function rollback( $fname = __METHOD__
, $flush = '' );
1607 * Commit any transaction but error out if writes or callbacks are pending
1609 * This is intended for clearing out REPEATABLE-READ snapshots so that callers can
1610 * see a new point-in-time of the database. This is useful when one of many transaction
1611 * rounds finished and significant time will pass in the script's lifetime. It is also
1612 * useful to call on a replica DB after waiting on replication to catch up to the master.
1614 * @param string $fname Calling function name
1615 * @throws DBUnexpectedError
1618 public function flushSnapshot( $fname = __METHOD__
);
1621 * List all tables on the database
1623 * @param string $prefix Only show tables with this prefix, e.g. mw_
1624 * @param string $fname Calling function name
1628 public function listTables( $prefix = null, $fname = __METHOD__
);
1631 * Convert a timestamp in one of the formats accepted by wfTimestamp()
1632 * to the format used for inserting into timestamp fields in this DBMS.
1634 * The result is unquoted, and needs to be passed through addQuotes()
1635 * before it can be included in raw SQL.
1637 * @param string|int $ts
1641 public function timestamp( $ts = 0 );
1644 * Convert a timestamp in one of the formats accepted by wfTimestamp()
1645 * to the format used for inserting into timestamp fields in this DBMS. If
1646 * NULL is input, it is passed through, allowing NULL values to be inserted
1647 * into timestamp fields.
1649 * The result is unquoted, and needs to be passed through addQuotes()
1650 * before it can be included in raw SQL.
1652 * @param string|int $ts
1656 public function timestampOrNull( $ts = null );
1659 * Ping the server and try to reconnect if it there is no connection
1661 * @param float|null &$rtt Value to store the estimated RTT [optional]
1662 * @return bool Success or failure
1664 public function ping( &$rtt = null );
1667 * Get replica DB lag. Currently supported only by MySQL.
1669 * Note that this function will generate a fatal error on many
1670 * installations. Most callers should use LoadBalancer::safeGetLag()
1673 * @return int|bool Database replication lag in seconds or false on error
1675 public function getLag();
1678 * Get the replica DB lag when the current transaction started
1679 * or a general lag estimate if not transaction is active
1681 * This is useful when transactions might use snapshot isolation
1682 * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
1683 * is this lag plus transaction duration. If they don't, it is still
1684 * safe to be pessimistic. In AUTO-COMMIT mode, this still gives an
1685 * indication of the staleness of subsequent reads.
1687 * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
1690 public function getSessionLagStatus();
1693 * Return the maximum number of items allowed in a list, or 0 for unlimited.
1697 public function maxListLen();
1700 * Some DBMSs have a special format for inserting into blob fields, they
1701 * don't allow simple quoted strings to be inserted. To insert into such
1702 * a field, pass the data through this function before passing it to
1703 * IDatabase::insert().
1706 * @return string|Blob
1708 public function encodeBlob( $b );
1711 * Some DBMSs return a special placeholder object representing blob fields
1712 * in result objects. Pass the object through this function to return the
1715 * @param string|Blob $b
1718 public function decodeBlob( $b );
1721 * Override database's default behavior. $options include:
1722 * 'connTimeout' : Set the connection timeout value in seconds.
1723 * May be useful for very long batch queries such as
1724 * full-wiki dumps, where a single query reads out over
1727 * @param array $options
1730 public function setSessionOptions( array $options );
1733 * Set variables to be used in sourceFile/sourceStream, in preference to the
1734 * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
1735 * all. If it's set to false, $GLOBALS will be used.
1737 * @param bool|array $vars Mapping variable name to value.
1739 public function setSchemaVars( $vars );
1742 * Check to see if a named lock is available (non-blocking)
1744 * @param string $lockName Name of lock to poll
1745 * @param string $method Name of method calling us
1749 public function lockIsFree( $lockName, $method );
1752 * Acquire a named lock
1754 * Named locks are not related to transactions
1756 * @param string $lockName Name of lock to aquire
1757 * @param string $method Name of the calling method
1758 * @param int $timeout Acquisition timeout in seconds
1761 public function lock( $lockName, $method, $timeout = 5 );
1766 * Named locks are not related to transactions
1768 * @param string $lockName Name of lock to release
1769 * @param string $method Name of the calling method
1771 * @return int Returns 1 if the lock was released, 0 if the lock was not established
1772 * by this thread (in which case the lock is not released), and NULL if the named
1773 * lock did not exist
1775 public function unlock( $lockName, $method );
1778 * Acquire a named lock, flush any transaction, and return an RAII style unlocker object
1780 * Only call this from outer transcation scope and when only one DB will be affected.
1781 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1783 * This is suitiable for transactions that need to be serialized using cooperative locks,
1784 * where each transaction can see each others' changes. Any transaction is flushed to clear
1785 * out stale REPEATABLE-READ snapshot data. Once the returned object falls out of PHP scope,
1786 * the lock will be released unless a transaction is active. If one is active, then the lock
1787 * will be released when it either commits or rolls back.
1789 * If the lock acquisition failed, then no transaction flush happens, and null is returned.
1791 * @param string $lockKey Name of lock to release
1792 * @param string $fname Name of the calling method
1793 * @param int $timeout Acquisition timeout in seconds
1794 * @return ScopedCallback|null
1795 * @throws DBUnexpectedError
1798 public function getScopedLockAndFlush( $lockKey, $fname, $timeout );
1801 * Check to see if a named lock used by lock() use blocking queues
1806 public function namedLocksEnqueue();
1809 * Find out when 'infinity' is. Most DBMSes support this. This is a special
1810 * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
1811 * because "i" sorts after all numbers.
1815 public function getInfinity();
1818 * Encode an expiry time into the DBMS dependent format
1820 * @param string $expiry Timestamp for expiry, or the 'infinity' string
1823 public function encodeExpiry( $expiry );
1826 * Decode an expiry time into a DBMS independent format
1828 * @param string $expiry DB timestamp field value for expiry
1829 * @param int $format TS_* constant, defaults to TS_MW
1832 public function decodeExpiry( $expiry, $format = TS_MW
);
1835 * Allow or deny "big selects" for this session only. This is done by setting
1836 * the sql_big_selects session variable.
1838 * This is a MySQL-specific feature.
1840 * @param bool|string $value True for allow, false for deny, or "default" to
1841 * restore the initial value
1843 public function setBigSelects( $value = true );
1846 * @return bool Whether this DB is read-only
1849 public function isReadOnly();
1852 * Make certain table names use their own database, schema, and table prefix
1853 * when passed into SQL queries pre-escaped and without a qualified database name
1855 * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
1856 * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
1858 * Calling this twice will completely clear any old table aliases. Also, note that
1859 * callers are responsible for making sure the schemas and databases actually exist.
1861 * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
1864 public function setTableAliases( array $aliases );
1867 class_alias( IDatabase
::class, 'IDatabase' );