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 * All of the table names given here are automatically run through
624 * Database::tableName(), which causes the table prefix (if any) to be
625 * added, and various other table name mappings to be performed.
627 * Do not use untrusted user input as a table name. Alias names should
628 * not have characters outside of the Basic multilingual plane.
630 * @param string|array $vars
632 * May be either a field name or an array of field names. The field names
633 * can be complete fragments of SQL, for direct inclusion into the SELECT
634 * query. If an array is given, field aliases can be specified, for example:
636 * [ 'maxrev' => 'MAX(rev_id)' ]
638 * This includes an expression with the alias "maxrev" in the query.
640 * If an expression is given, care must be taken to ensure that it is
643 * Untrusted user input must not be passed to this parameter.
645 * @param string|array $conds
647 * May be either a string containing a single condition, or an array of
648 * conditions. If an array is given, the conditions constructed from each
649 * element are combined with AND.
651 * Array elements may take one of two forms:
653 * - Elements with a numeric key are interpreted as raw SQL fragments.
654 * - Elements with a string key are interpreted as equality conditions,
655 * where the key is the field name.
656 * - If the value of such an array element is a scalar (such as a
657 * string), it will be treated as data and thus quoted appropriately.
658 * If it is null, an IS NULL clause will be added.
659 * - If the value is an array, an IN (...) clause will be constructed
660 * from its non-null elements, and an IS NULL clause will be added
661 * if null is present, such that the field may match any of the
662 * elements in the array. The non-null elements will be quoted.
664 * Note that expressions are often DBMS-dependent in their syntax.
665 * DBMS-independent wrappers are provided for constructing several types of
666 * expression commonly used in condition queries. See:
667 * - IDatabase::buildLike()
668 * - IDatabase::conditional()
670 * Untrusted user input is safe in the values of string keys, however untrusted
671 * input must not be used in the array key names or in the values of numeric keys.
672 * Escaping of untrusted input used in values of numeric keys should be done via
673 * IDatabase::addQuotes()
675 * @param string|array $options
677 * Optional: Array of query options. Boolean options are specified by
678 * including them in the array as a string value with a numeric key, for
683 * The supported options are:
685 * - OFFSET: Skip this many rows at the start of the result set. OFFSET
686 * with LIMIT can theoretically be used for paging through a result set,
687 * but this is discouraged for performance reasons.
689 * - LIMIT: Integer: return at most this many rows. The rows are sorted
690 * and then the first rows are taken until the limit is reached. LIMIT
691 * is applied to a result set after OFFSET.
693 * - FOR UPDATE: Boolean: lock the returned rows so that they can't be
694 * changed until the next COMMIT.
696 * - DISTINCT: Boolean: return only unique result rows.
698 * - GROUP BY: May be either an SQL fragment string naming a field or
699 * expression to group by, or an array of such SQL fragments.
701 * - HAVING: May be either an string containing a HAVING clause or an array of
702 * conditions building the HAVING clause. If an array is given, the conditions
703 * constructed from each element are combined with AND.
705 * - ORDER BY: May be either an SQL fragment giving a field name or
706 * expression to order by, or an array of such SQL fragments.
708 * - USE INDEX: This may be either a string giving the index name to use
709 * for the query, or an array. If it is an associative array, each key
710 * gives the table name (or alias), each value gives the index name to
711 * use for that table. All strings are SQL fragments and so should be
712 * validated by the caller.
714 * - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
717 * And also the following boolean MySQL extensions, see the MySQL manual
720 * - LOCK IN SHARE MODE
724 * - SQL_BUFFER_RESULT
726 * - SQL_CALC_FOUND_ROWS
731 * @param string|array $join_conds
733 * Optional associative array of table-specific join conditions. In the
734 * most common case, this is unnecessary, since the join condition can be
735 * in $conds. However, it is useful for doing a LEFT JOIN.
737 * The key of the array contains the table name or alias. The value is an
738 * array with two elements, numbered 0 and 1. The first gives the type of
739 * join, the second is the same as the $conds parameter. Thus it can be
740 * an SQL fragment, or an array where the string keys are equality and the
741 * numeric keys are SQL fragments all AND'd together. For example:
743 * [ 'page' => [ 'LEFT JOIN', 'page_latest=rev_id' ] ]
745 * @return IResultWrapper|bool If the query returned no rows, a IResultWrapper
746 * with no rows in it will be returned. If there was a query error, a
747 * DBQueryError exception will be thrown, except if the "ignore errors"
748 * option was set, in which case false will be returned.
750 public function select(
751 $table, $vars, $conds = '', $fname = __METHOD__
,
752 $options = [], $join_conds = []
756 * The equivalent of IDatabase::select() except that the constructed SQL
757 * is returned, instead of being immediately executed. This can be useful for
758 * doing UNION queries, where the SQL text of each query is needed. In general,
759 * however, callers outside of Database classes should just use select().
761 * @param string|array $table Table name
762 * @param string|array $vars Field names
763 * @param string|array $conds Conditions
764 * @param string $fname Caller function name
765 * @param string|array $options Query options
766 * @param string|array $join_conds Join conditions
768 * @return string SQL query string.
769 * @see IDatabase::select()
771 public function selectSQLText(
772 $table, $vars, $conds = '', $fname = __METHOD__
,
773 $options = [], $join_conds = []
777 * Single row SELECT wrapper. Equivalent to IDatabase::select(), except
778 * that a single row object is returned. If the query returns no rows,
781 * @param string|array $table Table name
782 * @param string|array $vars Field names
783 * @param array $conds Conditions
784 * @param string $fname Caller function name
785 * @param string|array $options Query options
786 * @param array|string $join_conds Join conditions
788 * @return stdClass|bool
790 public function selectRow( $table, $vars, $conds, $fname = __METHOD__
,
791 $options = [], $join_conds = []
795 * Estimate the number of rows in dataset
797 * MySQL allows you to estimate the number of rows that would be returned
798 * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
799 * index cardinality statistics, and is notoriously inaccurate, especially
800 * when large numbers of rows have recently been added or deleted.
802 * For DBMSs that don't support fast result size estimation, this function
803 * will actually perform the SELECT COUNT(*).
805 * Takes the same arguments as IDatabase::select().
807 * @param string $table Table name
808 * @param string $vars Unused
809 * @param array|string $conds Filters on the table
810 * @param string $fname Function name for profiling
811 * @param array $options Options for select
812 * @return int Row count
814 public function estimateRowCount(
815 $table, $vars = '*', $conds = '', $fname = __METHOD__
, $options = []
819 * Get the number of rows in dataset
821 * This is useful when trying to do COUNT(*) but with a LIMIT for performance.
823 * Takes the same arguments as IDatabase::select().
825 * @since 1.27 Added $join_conds parameter
827 * @param array|string $tables Table names
828 * @param string $vars Unused
829 * @param array|string $conds Filters on the table
830 * @param string $fname Function name for profiling
831 * @param array $options Options for select
832 * @param array $join_conds Join conditions (since 1.27)
833 * @return int Row count
835 public function selectRowCount(
836 $tables, $vars = '*', $conds = '', $fname = __METHOD__
, $options = [], $join_conds = []
840 * Determines whether a field exists in a table
842 * @param string $table Table name
843 * @param string $field Filed to check on that table
844 * @param string $fname Calling function name (optional)
845 * @return bool Whether $table has filed $field
847 public function fieldExists( $table, $field, $fname = __METHOD__
);
850 * Determines whether an index exists
851 * Usually throws a DBQueryError on failure
852 * If errors are explicitly ignored, returns NULL on failure
854 * @param string $table
855 * @param string $index
856 * @param string $fname
859 public function indexExists( $table, $index, $fname = __METHOD__
);
862 * Query whether a given table exists
864 * @param string $table
865 * @param string $fname
868 public function tableExists( $table, $fname = __METHOD__
);
871 * Determines if a given index is unique
873 * @param string $table
874 * @param string $index
878 public function indexUnique( $table, $index );
881 * INSERT wrapper, inserts an array into a table.
885 * - A single associative array. The array keys are the field names, and
886 * the values are the values to insert. The values are treated as data
887 * and will be quoted appropriately. If NULL is inserted, this will be
888 * converted to a database NULL.
889 * - An array with numeric keys, holding a list of associative arrays.
890 * This causes a multi-row INSERT on DBMSs that support it. The keys in
891 * each subarray must be identical to each other, and in the same order.
893 * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
896 * $options is an array of options, with boolean options encoded as values
897 * with numeric keys, in the same style as $options in
898 * IDatabase::select(). Supported options are:
900 * - IGNORE: Boolean: if present, duplicate key errors are ignored, and
901 * any rows which cause duplicate key errors are not inserted. It's
902 * possible to determine how many rows were successfully inserted using
903 * IDatabase::affectedRows().
905 * @param string $table Table name. This will be passed through
906 * Database::tableName().
907 * @param array $a Array of rows to insert
908 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
909 * @param array $options Array of options
913 public function insert( $table, $a, $fname = __METHOD__
, $options = [] );
916 * UPDATE wrapper. Takes a condition array and a SET array.
918 * @param string $table Name of the table to UPDATE. This will be passed through
919 * Database::tableName().
920 * @param array $values An array of values to SET. For each array element,
921 * the key gives the field name, and the value gives the data to set
922 * that field to. The data will be quoted by IDatabase::addQuotes().
923 * Values with integer keys form unquoted SET statements, which can be used for
924 * things like "field = field + 1" or similar computed values.
925 * @param array $conds An array of conditions (WHERE). See
926 * IDatabase::select() for the details of the format of condition
927 * arrays. Use '*' to update all rows.
928 * @param string $fname The function name of the caller (from __METHOD__),
929 * for logging and profiling.
930 * @param array $options An array of UPDATE options, can be:
931 * - IGNORE: Ignore unique key conflicts
932 * - LOW_PRIORITY: MySQL-specific, see MySQL manual.
935 public function update( $table, $values, $conds, $fname = __METHOD__
, $options = [] );
938 * Makes an encoded list of strings from an array
940 * These can be used to make conjunctions or disjunctions on SQL condition strings
941 * derived from an array (see IDatabase::select() $conds documentation).
945 * $sql = $db->makeList( [
947 * $db->makeList( [ 'rev_minor' => 1, 'rev_len' < 500 ], $db::LIST_OR ] )
948 * ], $db::LIST_AND );
950 * This would set $sql to "rev_user = '$id' AND (rev_minor = '1' OR rev_len < '500')"
952 * @param array $a Containing the data
953 * @param int $mode IDatabase class constant:
954 * - IDatabase::LIST_COMMA: Comma separated, no field names
955 * - IDatabase::LIST_AND: ANDed WHERE clause (without the WHERE).
956 * - IDatabase::LIST_OR: ORed WHERE clause (without the WHERE)
957 * - IDatabase::LIST_SET: Comma separated with field names, like a SET clause
958 * - IDatabase::LIST_NAMES: Comma separated field names
962 public function makeList( $a, $mode = self
::LIST_COMMA
);
965 * Build a partial where clause from a 2-d array such as used for LinkBatch.
966 * The keys on each level may be either integers or strings.
968 * @param array $data Organized as 2-d
969 * [ baseKeyVal => [ subKeyVal => [ignored], ... ], ... ]
970 * @param string $baseKey Field name to match the base-level keys to (eg 'pl_namespace')
971 * @param string $subKey Field name to match the sub-level keys to (eg 'pl_title')
972 * @return string|bool SQL fragment, or false if no items in array
974 public function makeWhereFrom2d( $data, $baseKey, $subKey );
977 * Return aggregated value alias
979 * @param array $valuedata
980 * @param string $valuename
984 public function aggregateValue( $valuedata, $valuename = 'value' );
987 * @param string $field
990 public function bitNot( $field );
993 * @param string $fieldLeft
994 * @param string $fieldRight
997 public function bitAnd( $fieldLeft, $fieldRight );
1000 * @param string $fieldLeft
1001 * @param string $fieldRight
1004 public function bitOr( $fieldLeft, $fieldRight );
1007 * Build a concatenation list to feed into a SQL query
1008 * @param array $stringList List of raw SQL expressions; caller is
1009 * responsible for any quoting
1012 public function buildConcat( $stringList );
1015 * Build a GROUP_CONCAT or equivalent statement for a query.
1017 * This is useful for combining a field for several rows into a single string.
1018 * NULL values will not appear in the output, duplicated values will appear,
1019 * and the resulting delimiter-separated values have no defined sort order.
1020 * Code using the results may need to use the PHP unique() or sort() methods.
1022 * @param string $delim Glue to bind the results together
1023 * @param string|array $table Table name
1024 * @param string $field Field name
1025 * @param string|array $conds Conditions
1026 * @param string|array $join_conds Join conditions
1027 * @return string SQL text
1030 public function buildGroupConcatField(
1031 $delim, $table, $field, $conds = '', $join_conds = []
1035 * @param string $field Field or column to cast
1039 public function buildStringCast( $field );
1042 * Returns true if DBs are assumed to be on potentially different servers
1044 * In systems like mysql/mariadb, different databases can easily be referenced on a single
1045 * connection merely by name, even in a single query via JOIN. On the other hand, Postgres
1046 * treats databases as fully separate, only allowing mechanisms like postgres_fdw to
1047 * effectively "mount" foreign DBs. This is true even among DBs on the same server.
1052 public function databasesAreIndependent();
1055 * Change the current database
1058 * @return bool Success or failure
1059 * @throws DBConnectionError If databasesAreIndependent() is true and an error occurs
1061 public function selectDB( $db );
1064 * Get the current DB name
1067 public function getDBname();
1070 * Get the server hostname or IP address
1073 public function getServer();
1076 * Adds quotes and backslashes.
1078 * @param string|int|null|bool|Blob $s
1079 * @return string|int
1081 public function addQuotes( $s );
1084 * LIKE statement wrapper, receives a variable-length argument list with
1085 * parts of pattern to match containing either string literals that will be
1086 * escaped or tokens returned by anyChar() or anyString(). Alternatively,
1087 * the function could be provided with an array of aforementioned
1090 * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns
1091 * a LIKE clause that searches for subpages of 'My page title'.
1093 * $pattern = [ 'My_page_title/', $dbr->anyString() ];
1094 * $query .= $dbr->buildLike( $pattern );
1097 * @return string Fully built LIKE statement
1099 public function buildLike();
1102 * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
1106 public function anyChar();
1109 * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
1113 public function anyString();
1116 * Deprecated method, calls should be removed.
1118 * This was formerly used for PostgreSQL and Oracle to handle
1119 * self::insertId() auto-incrementing fields. It is no longer necessary
1120 * since DatabasePostgres::insertId() has been reimplemented using
1121 * `lastval()` and Oracle has been reimplemented using triggers.
1123 * Implementations should return null if inserting `NULL` into an
1124 * auto-incrementing field works, otherwise it should return an instance of
1125 * NextSequenceValue and filter it on calls to relevant methods.
1127 * @deprecated since 1.30, no longer needed
1128 * @param string $seqName
1129 * @return null|NextSequenceValue
1131 public function nextSequenceValue( $seqName );
1134 * REPLACE query wrapper.
1136 * REPLACE is a very handy MySQL extension, which functions like an INSERT
1137 * except that when there is a duplicate key error, the old row is deleted
1138 * and the new row is inserted in its place.
1140 * We simulate this with standard SQL with a DELETE followed by INSERT. To
1141 * perform the delete, we need to know what the unique indexes are so that
1142 * we know how to find the conflicting rows.
1144 * It may be more efficient to leave off unique indexes which are unlikely
1145 * to collide. However if you do this, you run the risk of encountering
1146 * errors which wouldn't have occurred in MySQL.
1148 * @param string $table The table to replace the row(s) in.
1149 * @param array $uniqueIndexes Is an array of indexes. Each element may be either
1150 * a field name or an array of field names
1151 * @param array $rows Can be either a single row to insert, or multiple rows,
1152 * in the same format as for IDatabase::insert()
1153 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1155 public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__
);
1158 * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
1160 * This updates any conflicting rows (according to the unique indexes) using
1161 * the provided SET clause and inserts any remaining (non-conflicted) rows.
1163 * $rows may be either:
1164 * - A single associative array. The array keys are the field names, and
1165 * the values are the values to insert. The values are treated as data
1166 * and will be quoted appropriately. If NULL is inserted, this will be
1167 * converted to a database NULL.
1168 * - An array with numeric keys, holding a list of associative arrays.
1169 * This causes a multi-row INSERT on DBMSs that support it. The keys in
1170 * each subarray must be identical to each other, and in the same order.
1172 * It may be more efficient to leave off unique indexes which are unlikely
1173 * to collide. However if you do this, you run the risk of encountering
1174 * errors which wouldn't have occurred in MySQL.
1176 * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1181 * @param string $table Table name. This will be passed through Database::tableName().
1182 * @param array $rows A single row or list of rows to insert
1183 * @param array $uniqueIndexes List of single field names or field name tuples
1184 * @param array $set An array of values to SET. For each array element, the
1185 * key gives the field name, and the value gives the data to set that
1186 * field to. The data will be quoted by IDatabase::addQuotes().
1187 * Values with integer keys form unquoted SET statements, which can be used for
1188 * things like "field = field + 1" or similar computed values.
1189 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1193 public function upsert(
1194 $table, array $rows, array $uniqueIndexes, array $set, $fname = __METHOD__
1198 * DELETE where the condition is a join.
1200 * MySQL overrides this to use a multi-table DELETE syntax, in other databases
1201 * we use sub-selects
1203 * For safety, an empty $conds will not delete everything. If you want to
1204 * delete all rows where the join condition matches, set $conds='*'.
1206 * DO NOT put the join condition in $conds.
1208 * @param string $delTable The table to delete from.
1209 * @param string $joinTable The other table.
1210 * @param string $delVar The variable to join on, in the first table.
1211 * @param string $joinVar The variable to join on, in the second table.
1212 * @param array $conds Condition array of field names mapped to variables,
1213 * ANDed together in the WHERE clause
1214 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1215 * @throws DBUnexpectedError
1217 public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
1222 * DELETE query wrapper.
1224 * @param string $table Table name
1225 * @param string|array $conds Array of conditions. See $conds in IDatabase::select()
1226 * for the format. Use $conds == "*" to delete all rows
1227 * @param string $fname Name of the calling function
1228 * @throws DBUnexpectedError
1229 * @return bool|IResultWrapper
1231 public function delete( $table, $conds, $fname = __METHOD__
);
1234 * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
1235 * into another table.
1237 * @param string $destTable The table name to insert into
1238 * @param string|array $srcTable May be either a table name, or an array of table names
1239 * to include in a join.
1241 * @param array $varMap Must be an associative array of the form
1242 * [ 'dest1' => 'source1', ... ]. Source items may be literals
1243 * rather than field names, but strings should be quoted with
1244 * IDatabase::addQuotes()
1246 * @param array $conds Condition array. See $conds in IDatabase::select() for
1247 * the details of the format of condition arrays. May be "*" to copy the
1250 * @param string $fname The function name of the caller, from __METHOD__
1252 * @param array $insertOptions Options for the INSERT part of the query, see
1253 * IDatabase::insert() for details.
1254 * @param array $selectOptions Options for the SELECT part of the query, see
1255 * IDatabase::select() for details.
1256 * @param array $selectJoinConds Join conditions for the SELECT part of the query, see
1257 * IDatabase::select() for details.
1261 public function insertSelect( $destTable, $srcTable, $varMap, $conds,
1262 $fname = __METHOD__
,
1263 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
1267 * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
1268 * within the UNION construct.
1271 public function unionSupportsOrderAndLimit();
1274 * Construct a UNION query
1275 * This is used for providing overload point for other DB abstractions
1276 * not compatible with the MySQL syntax.
1277 * @param array $sqls SQL statements to combine
1278 * @param bool $all Use UNION ALL
1279 * @return string SQL fragment
1281 public function unionQueries( $sqls, $all );
1284 * Construct a UNION query for permutations of conditions
1286 * Databases sometimes have trouble with queries that have multiple values
1287 * for multiple condition parameters combined with limits and ordering.
1288 * This method constructs queries for the Cartesian product of the
1289 * conditions and unions them all together.
1291 * @see IDatabase::select()
1293 * @param string|array $table Table name
1294 * @param string|array $vars Field names
1295 * @param array $permute_conds Conditions for the Cartesian product. Keys
1296 * are field names, values are arrays of the possible values for that
1298 * @param string|array $extra_conds Additional conditions to include in the
1300 * @param string $fname Caller function name
1301 * @param string|array $options Query options. In addition to the options
1302 * recognized by IDatabase::select(), the following may be used:
1303 * - NOTALL: Set to use UNION instead of UNION ALL.
1304 * - INNER ORDER BY: If specified and supported, subqueries will use this
1305 * instead of ORDER BY.
1306 * @param string|array $join_conds Join conditions
1307 * @return string SQL query string.
1309 public function unionConditionPermutations(
1310 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__
,
1311 $options = [], $join_conds = []
1315 * Returns an SQL expression for a simple conditional. This doesn't need
1316 * to be overridden unless CASE isn't supported in your DBMS.
1318 * @param string|array $cond SQL expression which will result in a boolean value
1319 * @param string $trueVal SQL expression to return if true
1320 * @param string $falseVal SQL expression to return if false
1321 * @return string SQL fragment
1323 public function conditional( $cond, $trueVal, $falseVal );
1326 * Returns a command for str_replace function in SQL query.
1327 * Uses REPLACE() in MySQL
1329 * @param string $orig Column to modify
1330 * @param string $old Column to seek
1331 * @param string $new Column to replace with
1335 public function strreplace( $orig, $old, $new );
1338 * Determines how long the server has been up
1342 public function getServerUptime();
1345 * Determines if the last failure was due to a deadlock
1349 public function wasDeadlock();
1352 * Determines if the last failure was due to a lock timeout
1356 public function wasLockTimeout();
1359 * Determines if the last query error was due to a dropped connection and should
1360 * be dealt with by pinging the connection and reissuing the query.
1364 public function wasErrorReissuable();
1367 * Determines if the last failure was due to the database being read-only.
1371 public function wasReadOnlyError();
1374 * Wait for the replica DB to catch up to a given master position
1376 * @param DBMasterPos $pos
1377 * @param int $timeout The maximum number of seconds to wait for synchronisation
1378 * @return int|null Zero if the replica DB was past that position already,
1379 * greater than zero if we waited for some period of time, less than
1380 * zero if it timed out, and null on error
1382 public function masterPosWait( DBMasterPos
$pos, $timeout );
1385 * Get the replication position of this replica DB
1387 * @return DBMasterPos|bool False if this is not a replica DB.
1389 public function getReplicaPos();
1392 * Get the position of this master
1394 * @return DBMasterPos|bool False if this is not a master
1396 public function getMasterPos();
1399 * @return bool Whether the DB is marked as read-only server-side
1402 public function serverIsReadOnly();
1405 * Run a callback as soon as the current transaction commits or rolls back.
1406 * An error is thrown if no transaction is pending. Queries in the function will run in
1407 * AUTO-COMMIT mode unless there are begin() calls. Callbacks must commit any transactions
1410 * This is useful for combining cooperative locks and DB transactions.
1412 * The callback takes one argument:
1413 * - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK)
1415 * @param callable $callback
1416 * @param string $fname Caller name
1420 public function onTransactionResolution( callable
$callback, $fname = __METHOD__
);
1423 * Run a callback as soon as there is no transaction pending.
1424 * If there is a transaction and it is rolled back, then the callback is cancelled.
1425 * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
1426 * Callbacks must commit any transactions that they begin.
1428 * This is useful for updates to different systems or when separate transactions are needed.
1429 * For example, one might want to enqueue jobs into a system outside the database, but only
1430 * after the database is updated so that the jobs will see the data when they actually run.
1431 * It can also be used for updates that easily cause deadlocks if locks are held too long.
1433 * Updates will execute in the order they were enqueued.
1435 * The callback takes one argument:
1436 * - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_IDLE)
1438 * @param callable $callback
1439 * @param string $fname Caller name
1442 public function onTransactionIdle( callable
$callback, $fname = __METHOD__
);
1445 * Run a callback before the current transaction commits or now if there is none.
1446 * If there is a transaction and it is rolled back, then the callback is cancelled.
1447 * Callbacks must not start nor commit any transactions. If no transaction is active,
1448 * then a transaction will wrap the callback.
1450 * This is useful for updates that easily cause deadlocks if locks are held too long
1451 * but where atomicity is strongly desired for these updates and some related updates.
1453 * Updates will execute in the order they were enqueued.
1455 * @param callable $callback
1456 * @param string $fname Caller name
1459 public function onTransactionPreCommitOrIdle( callable
$callback, $fname = __METHOD__
);
1462 * Run a callback each time any transaction commits or rolls back
1464 * The callback takes two arguments:
1465 * - IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK
1466 * - This IDatabase object
1467 * Callbacks must commit any transactions that they begin.
1469 * Registering a callback here will not affect writesOrCallbacks() pending
1471 * @param string $name Callback name
1472 * @param callable|null $callback Use null to unset a listener
1476 public function setTransactionListener( $name, callable
$callback = null );
1479 * Begin an atomic section of statements
1481 * If a transaction has been started already, just keep track of the given
1482 * section name to make sure the transaction is not committed pre-maturely.
1483 * This function can be used in layers (with sub-sections), so use a stack
1484 * to keep track of the different atomic sections. If there is no transaction,
1485 * start one implicitly.
1487 * The goal of this function is to create an atomic section of SQL queries
1488 * without having to start a new transaction if it already exists.
1490 * All atomic levels *must* be explicitly closed using IDatabase::endAtomic(),
1491 * and any database transactions cannot be began or committed until all atomic
1492 * levels are closed. There is no such thing as implicitly opening or closing
1493 * an atomic section.
1496 * @param string $fname
1499 public function startAtomic( $fname = __METHOD__
);
1502 * Ends an atomic section of SQL statements
1504 * Ends the next section of atomic SQL statements and commits the transaction
1508 * @see IDatabase::startAtomic
1509 * @param string $fname
1512 public function endAtomic( $fname = __METHOD__
);
1515 * Run a callback to do an atomic set of updates for this database
1517 * The $callback takes the following arguments:
1518 * - This database object
1519 * - The value of $fname
1521 * If any exception occurs in the callback, then rollback() will be called and the error will
1522 * be re-thrown. It may also be that the rollback itself fails with an exception before then.
1523 * In any case, such errors are expected to terminate the request, without any outside caller
1524 * attempting to catch errors and commit anyway. Note that any rollback undoes all prior
1525 * atomic section and uncommitted updates, which trashes the current request, requiring an
1526 * error to be displayed.
1528 * This can be an alternative to explicit startAtomic()/endAtomic() calls.
1530 * @see Database::startAtomic
1531 * @see Database::endAtomic
1533 * @param string $fname Caller name (usually __METHOD__)
1534 * @param callable $callback Callback that issues DB updates
1535 * @return mixed $res Result of the callback (since 1.28)
1537 * @throws RuntimeException
1538 * @throws UnexpectedValueException
1541 public function doAtomicSection( $fname, callable
$callback );
1544 * Begin a transaction. If a transaction is already in progress,
1545 * that transaction will be committed before the new transaction is started.
1547 * Only call this from code with outer transcation scope.
1548 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1549 * Nesting of transactions is not supported.
1551 * Note that when the DBO_TRX flag is set (which is usually the case for web
1552 * requests, but not for maintenance scripts), any previous database query
1553 * will have started a transaction automatically.
1555 * Nesting of transactions is not supported. Attempts to nest transactions
1556 * will cause a warning, unless the current transaction was started
1557 * automatically because of the DBO_TRX flag.
1559 * @param string $fname Calling function name
1560 * @param string $mode A situationally valid IDatabase::TRANSACTION_* constant [optional]
1563 public function begin( $fname = __METHOD__
, $mode = self
::TRANSACTION_EXPLICIT
);
1566 * Commits a transaction previously started using begin().
1567 * If no transaction is in progress, a warning is issued.
1569 * Only call this from code with outer transcation scope.
1570 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1571 * Nesting of transactions is not supported.
1573 * @param string $fname
1574 * @param string $flush Flush flag, set to situationally valid IDatabase::FLUSHING_*
1575 * constant to disable warnings about explicitly committing implicit transactions,
1576 * or calling commit when no transaction is in progress.
1578 * This will trigger an exception if there is an ongoing explicit transaction.
1580 * Only set the flush flag if you are sure that these warnings are not applicable,
1581 * and no explicit transactions are open.
1583 * @throws DBUnexpectedError
1585 public function commit( $fname = __METHOD__
, $flush = '' );
1588 * Rollback a transaction previously started using begin().
1589 * If no transaction is in progress, a warning is issued.
1591 * Only call this from code with outer transcation scope.
1592 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1593 * Nesting of transactions is not supported. If a serious unexpected error occurs,
1594 * throwing an Exception is preferrable, using a pre-installed error handler to trigger
1595 * rollback (in any case, failure to issue COMMIT will cause rollback server-side).
1597 * Query, connection, and onTransaction* callback errors will be suppressed and logged.
1599 * @param string $fname Calling function name
1600 * @param string $flush Flush flag, set to a situationally valid IDatabase::FLUSHING_*
1601 * constant to disable warnings about calling rollback when no transaction is in
1602 * progress. This will silently break any ongoing explicit transaction. Only set the
1603 * flush flag if you are sure that it is safe to ignore these warnings in your context.
1604 * @throws DBUnexpectedError
1605 * @since 1.23 Added $flush parameter
1607 public function rollback( $fname = __METHOD__
, $flush = '' );
1610 * Commit any transaction but error out if writes or callbacks are pending
1612 * This is intended for clearing out REPEATABLE-READ snapshots so that callers can
1613 * see a new point-in-time of the database. This is useful when one of many transaction
1614 * rounds finished and significant time will pass in the script's lifetime. It is also
1615 * useful to call on a replica DB after waiting on replication to catch up to the master.
1617 * @param string $fname Calling function name
1618 * @throws DBUnexpectedError
1621 public function flushSnapshot( $fname = __METHOD__
);
1624 * List all tables on the database
1626 * @param string $prefix Only show tables with this prefix, e.g. mw_
1627 * @param string $fname Calling function name
1631 public function listTables( $prefix = null, $fname = __METHOD__
);
1634 * Convert a timestamp in one of the formats accepted by wfTimestamp()
1635 * to the format used for inserting into timestamp fields in this DBMS.
1637 * The result is unquoted, and needs to be passed through addQuotes()
1638 * before it can be included in raw SQL.
1640 * @param string|int $ts
1644 public function timestamp( $ts = 0 );
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. If
1649 * NULL is input, it is passed through, allowing NULL values to be inserted
1650 * into timestamp fields.
1652 * The result is unquoted, and needs to be passed through addQuotes()
1653 * before it can be included in raw SQL.
1655 * @param string|int $ts
1659 public function timestampOrNull( $ts = null );
1662 * Ping the server and try to reconnect if it there is no connection
1664 * @param float|null &$rtt Value to store the estimated RTT [optional]
1665 * @return bool Success or failure
1667 public function ping( &$rtt = null );
1670 * Get replica DB lag. Currently supported only by MySQL.
1672 * Note that this function will generate a fatal error on many
1673 * installations. Most callers should use LoadBalancer::safeGetLag()
1676 * @return int|bool Database replication lag in seconds or false on error
1678 public function getLag();
1681 * Get the replica DB lag when the current transaction started
1682 * or a general lag estimate if not transaction is active
1684 * This is useful when transactions might use snapshot isolation
1685 * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
1686 * is this lag plus transaction duration. If they don't, it is still
1687 * safe to be pessimistic. In AUTO-COMMIT mode, this still gives an
1688 * indication of the staleness of subsequent reads.
1690 * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
1693 public function getSessionLagStatus();
1696 * Return the maximum number of items allowed in a list, or 0 for unlimited.
1700 public function maxListLen();
1703 * Some DBMSs have a special format for inserting into blob fields, they
1704 * don't allow simple quoted strings to be inserted. To insert into such
1705 * a field, pass the data through this function before passing it to
1706 * IDatabase::insert().
1709 * @return string|Blob
1711 public function encodeBlob( $b );
1714 * Some DBMSs return a special placeholder object representing blob fields
1715 * in result objects. Pass the object through this function to return the
1718 * @param string|Blob $b
1721 public function decodeBlob( $b );
1724 * Override database's default behavior. $options include:
1725 * 'connTimeout' : Set the connection timeout value in seconds.
1726 * May be useful for very long batch queries such as
1727 * full-wiki dumps, where a single query reads out over
1730 * @param array $options
1733 public function setSessionOptions( array $options );
1736 * Set variables to be used in sourceFile/sourceStream, in preference to the
1737 * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
1738 * all. If it's set to false, $GLOBALS will be used.
1740 * @param bool|array $vars Mapping variable name to value.
1742 public function setSchemaVars( $vars );
1745 * Check to see if a named lock is available (non-blocking)
1747 * @param string $lockName Name of lock to poll
1748 * @param string $method Name of method calling us
1752 public function lockIsFree( $lockName, $method );
1755 * Acquire a named lock
1757 * Named locks are not related to transactions
1759 * @param string $lockName Name of lock to aquire
1760 * @param string $method Name of the calling method
1761 * @param int $timeout Acquisition timeout in seconds
1764 public function lock( $lockName, $method, $timeout = 5 );
1769 * Named locks are not related to transactions
1771 * @param string $lockName Name of lock to release
1772 * @param string $method Name of the calling method
1774 * @return int Returns 1 if the lock was released, 0 if the lock was not established
1775 * by this thread (in which case the lock is not released), and NULL if the named
1776 * lock did not exist
1778 public function unlock( $lockName, $method );
1781 * Acquire a named lock, flush any transaction, and return an RAII style unlocker object
1783 * Only call this from outer transcation scope and when only one DB will be affected.
1784 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1786 * This is suitiable for transactions that need to be serialized using cooperative locks,
1787 * where each transaction can see each others' changes. Any transaction is flushed to clear
1788 * out stale REPEATABLE-READ snapshot data. Once the returned object falls out of PHP scope,
1789 * the lock will be released unless a transaction is active. If one is active, then the lock
1790 * will be released when it either commits or rolls back.
1792 * If the lock acquisition failed, then no transaction flush happens, and null is returned.
1794 * @param string $lockKey Name of lock to release
1795 * @param string $fname Name of the calling method
1796 * @param int $timeout Acquisition timeout in seconds
1797 * @return ScopedCallback|null
1798 * @throws DBUnexpectedError
1801 public function getScopedLockAndFlush( $lockKey, $fname, $timeout );
1804 * Check to see if a named lock used by lock() use blocking queues
1809 public function namedLocksEnqueue();
1812 * Find out when 'infinity' is. Most DBMSes support this. This is a special
1813 * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
1814 * because "i" sorts after all numbers.
1818 public function getInfinity();
1821 * Encode an expiry time into the DBMS dependent format
1823 * @param string $expiry Timestamp for expiry, or the 'infinity' string
1826 public function encodeExpiry( $expiry );
1829 * Decode an expiry time into a DBMS independent format
1831 * @param string $expiry DB timestamp field value for expiry
1832 * @param int $format TS_* constant, defaults to TS_MW
1835 public function decodeExpiry( $expiry, $format = TS_MW
);
1838 * Allow or deny "big selects" for this session only. This is done by setting
1839 * the sql_big_selects session variable.
1841 * This is a MySQL-specific feature.
1843 * @param bool|string $value True for allow, false for deny, or "default" to
1844 * restore the initial value
1846 public function setBigSelects( $value = true );
1849 * @return bool Whether this DB is read-only
1852 public function isReadOnly();
1855 * Make certain table names use their own database, schema, and table prefix
1856 * when passed into SQL queries pre-escaped and without a qualified database name
1858 * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
1859 * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
1861 * Calling this twice will completely clear any old table aliases. Also, note that
1862 * callers are responsible for making sure the schemas and databases actually exist.
1864 * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
1867 public function setTableAliases( array $aliases );
1870 class_alias( IDatabase
::class, 'IDatabase' );