3 * This program is free software; you can redistribute it and/or modify
4 * it under the terms of the GNU General Public License as published by
5 * the Free Software Foundation; either version 2 of the License, or
6 * (at your option) any later version.
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU General Public License for more details.
13 * You should have received a copy of the GNU General Public License along
14 * with this program; if not, write to the Free Software Foundation, Inc.,
15 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
16 * http://www.gnu.org/copyleft/gpl.html
20 namespace Wikimedia\Rdbms
;
22 use InvalidArgumentException
;
23 use Wikimedia\ScopedCallback
;
28 * @defgroup Database Database
29 * This group deals with database interface functions
30 * and query specifics/optimisations.
33 * Basic database interface for live and lazy-loaded relation database handles
35 * @note IDatabase and DBConnRef should be updated to reflect any changes
39 /** @var int Callback triggered immediately due to no active transaction */
40 const TRIGGER_IDLE
= 1;
41 /** @var int Callback triggered by COMMIT */
42 const TRIGGER_COMMIT
= 2;
43 /** @var int Callback triggered by ROLLBACK */
44 const TRIGGER_ROLLBACK
= 3;
46 /** @var string Transaction is requested by regular caller outside of the DB layer */
47 const TRANSACTION_EXPLICIT
= '';
48 /** @var string Transaction is requested internally via DBO_TRX/startAtomic() */
49 const TRANSACTION_INTERNAL
= 'implicit';
51 /** @var string Atomic section is not cancelable */
52 const ATOMIC_NOT_CANCELABLE
= '';
53 /** @var string Atomic section is cancelable */
54 const ATOMIC_CANCELABLE
= 'cancelable';
56 /** @var string Commit/rollback is from outside the IDatabase handle and connection manager */
57 const FLUSHING_ONE
= '';
58 /** @var string Commit/rollback is from the connection manager for the IDatabase handle */
59 const FLUSHING_ALL_PEERS
= 'flush';
60 /** @var string Commit/rollback is from the IDatabase handle internally */
61 const FLUSHING_INTERNAL
= 'flush-internal';
63 /** @var string Do not remember the prior flags */
64 const REMEMBER_NOTHING
= '';
65 /** @var string Remember the prior flags */
66 const REMEMBER_PRIOR
= 'remember';
67 /** @var string Restore to the prior flag state */
68 const RESTORE_PRIOR
= 'prior';
69 /** @var string Restore to the initial flag state */
70 const RESTORE_INITIAL
= 'initial';
72 /** @var string Estimate total time (RTT, scanning, waiting on locks, applying) */
73 const ESTIMATE_TOTAL
= 'total';
74 /** @var string Estimate time to apply (scanning, applying) */
75 const ESTIMATE_DB_APPLY
= 'apply';
77 /** @var int Combine list with comma delimeters */
79 /** @var int Combine list with AND clauses */
81 /** @var int Convert map into a SET clause */
83 /** @var int Treat as field name and do not apply value escaping */
85 /** @var int Combine list with OR clauses */
88 /** @var int Enable debug logging */
90 /** @var int Disable query buffering (only one result set can be iterated at a time) */
91 const DBO_NOBUFFER
= 2;
92 /** @var int Ignore query errors (internal use only!) */
94 /** @var int Automatically start a transaction before running a query if none is active */
96 /** @var int Use DBO_TRX in non-CLI mode */
97 const DBO_DEFAULT
= 16;
98 /** @var int Use DB persistent connections if possible */
99 const DBO_PERSISTENT
= 32;
100 /** @var int DBA session mode; mostly for Oracle */
101 const DBO_SYSDBA
= 64;
102 /** @var int Schema file mode; mostly for Oracle */
103 const DBO_DDLMODE
= 128;
104 /** @var int Enable SSL/TLS in connection protocol */
106 /** @var int Enable compression in connection protocol */
107 const DBO_COMPRESS
= 512;
109 /** @var int Ignore query errors and return false when they happen */
110 const QUERY_SILENCE_ERRORS
= 1; // b/c for 1.32 query() argument; note that (int)true = 1
112 * @var int Treat the TEMPORARY table from the given CREATE query as if it is
113 * permanent as far as write tracking is concerned. This is useful for testing.
115 const QUERY_PSEUDO_PERMANENT
= 2;
116 /** @var int Enforce that a query does not make effective writes */
117 const QUERY_REPLICA_ROLE
= 4;
119 /** @var bool Parameter to unionQueries() for UNION ALL */
120 const UNION_ALL
= true;
121 /** @var bool Parameter to unionQueries() for UNION DISTINCT */
122 const UNION_DISTINCT
= false;
125 * A string describing the current software version, and possibly
126 * other details in a user-friendly way. Will be listed on Special:Version, etc.
127 * Use getServerVersion() to get machine-friendly information.
129 * @return string Version information from the database server
131 public function getServerInfo();
134 * Turns buffering of SQL result sets on (true) or off (false). Default is "on".
136 * Unbuffered queries are very troublesome in MySQL:
138 * - If another query is executed while the first query is being read
139 * out, the first query is killed. This means you can't call normal
140 * Database functions while you are reading an unbuffered query result
141 * from a normal Database connection.
143 * - Unbuffered queries cause the MySQL server to use large amounts of
144 * memory and to hold broad locks which block other queries.
146 * If you want to limit client-side memory, it's almost always better to
147 * split up queries into batches using a LIMIT clause than to switch off
150 * @param null|bool $buffer
151 * @return null|bool The previous value of the flag
153 public function bufferResults( $buffer = null );
156 * Gets the current transaction level.
158 * Historically, transactions were allowed to be "nested". This is no
159 * longer supported, so this function really only returns a boolean.
161 * @return int The previous value
163 public function trxLevel();
166 * Get the UNIX timestamp of the time that the transaction was established
168 * This can be used to reason about the staleness of SELECT data
169 * in REPEATABLE-READ transaction isolation level.
171 * @return float|null Returns null if there is not active transaction
174 public function trxTimestamp();
177 * @return bool Whether an explicit transaction or atomic sections are still open
180 public function explicitTrxActive();
183 * Assert that all explicit transactions or atomic sections have been closed.
184 * @throws DBTransactionError
187 public function assertNoOpenTransactions();
190 * Get/set the table prefix.
191 * @param string|null $prefix The table prefix to set, or omitted to leave it unchanged.
192 * @return string The previous table prefix
193 * @throws DBUnexpectedError
195 public function tablePrefix( $prefix = null );
198 * Get/set the db schema.
199 * @param string|null $schema The database schema to set, or omitted to leave it unchanged.
200 * @return string The previous db schema
202 public function dbSchema( $schema = null );
205 * Get properties passed down from the server info array of the load
208 * @param string|null $name The entry of the info array to get, or null to get the
211 * @return array|mixed|null
213 public function getLBInfo( $name = null );
216 * Set the LB info array, or a member of it. If called with one parameter,
217 * the LB info array is set to that parameter. If it is called with two
218 * parameters, the member with the given name is set to the given value.
220 * @param string $name
221 * @param array|null $value
223 public function setLBInfo( $name, $value = null );
226 * Set a lazy-connecting DB handle to the master DB (for replication status purposes)
228 * @param IDatabase $conn
231 public function setLazyMasterHandle( IDatabase
$conn );
234 * Returns true if this database does an implicit sort when doing GROUP BY
237 * @deprecated Since 1.30; only use grouped or aggregated fields in the SELECT
239 public function implicitGroupby();
242 * Returns true if this database does an implicit order by when the column has an index
243 * For example: SELECT page_title FROM page LIMIT 1
247 public function implicitOrderby();
250 * Return the last query that sent on account of IDatabase::query()
251 * @return string SQL text or empty string if there was no such query
253 public function lastQuery();
256 * Returns true if the connection may have been used for write queries.
257 * Should return true if unsure.
260 * @deprecated Since 1.31; use lastDoneWrites()
262 public function doneWrites();
265 * Returns the last time the connection may have been used for write queries.
266 * Should return a timestamp if unsure.
268 * @return int|float UNIX timestamp or false
271 public function lastDoneWrites();
274 * @return bool Whether there is a transaction open with possible write queries
277 public function writesPending();
280 * @return bool Whether there is a transaction open with pre-commit callbacks pending
283 public function preCommitCallbacksPending();
286 * Whether there is a transaction open with either possible write queries
287 * or unresolved pre-commit/commit/resolution callbacks pending
289 * This does *not* count recurring callbacks, e.g. from setTransactionListener().
293 public function writesOrCallbacksPending();
296 * Get the time spend running write queries for this transaction
298 * High times could be due to scanning, updates, locking, and such
300 * @param string $type IDatabase::ESTIMATE_* constant [default: ESTIMATE_ALL]
301 * @return float|bool Returns false if not transaction is active
304 public function pendingWriteQueryDuration( $type = self
::ESTIMATE_TOTAL
);
307 * Get the list of method names that did write queries for this transaction
312 public function pendingWriteCallers();
315 * Get the number of affected rows from pending write queries
320 public function pendingWriteRowsAffected();
323 * Is a connection to the database open?
326 public function isOpen();
329 * Set a flag 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_DEFAULT: automatically sets DBO_TRX if not in command line mode
336 * and removes it in command line mode
337 * - DBO_PERSISTENT: use persistant database connection
338 * @param string $remember IDatabase::REMEMBER_* constant [default: REMEMBER_NOTHING]
340 public function setFlag( $flag, $remember = self
::REMEMBER_NOTHING
);
343 * Clear a flag for this connection
345 * @param int $flag DBO_* constants from Defines.php:
346 * - DBO_DEBUG: output some debug info (same as debug())
347 * - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
348 * - DBO_TRX: automatically start transactions
349 * - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
350 * and removes it in command line mode
351 * - DBO_PERSISTENT: use persistant database connection
352 * @param string $remember IDatabase::REMEMBER_* constant [default: REMEMBER_NOTHING]
354 public function clearFlag( $flag, $remember = self
::REMEMBER_NOTHING
);
357 * Restore the flags to their prior state before the last setFlag/clearFlag call
359 * @param string $state IDatabase::RESTORE_* constant. [default: RESTORE_PRIOR]
362 public function restoreFlags( $state = self
::RESTORE_PRIOR
);
365 * Returns a boolean whether the flag $flag is set for this connection
367 * @param int $flag DBO_* constants from Defines.php:
368 * - DBO_DEBUG: output some debug info (same as debug())
369 * - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
370 * - DBO_TRX: automatically start transactions
371 * - DBO_PERSISTENT: use persistant database connection
374 public function getFlag( $flag );
377 * Return the currently selected domain ID
379 * Null components (database/schema) might change once a connection is established
383 public function getDomainID();
386 * Alias for getDomainID()
391 public function getWikiID();
394 * Get the type of the DBMS, as it appears in $wgDBtype.
398 public function getType();
401 * Fetch the next row from the given result object, in object form.
402 * Fields can be retrieved with $row->fieldname, with fields acting like
404 * If no more rows are available, false is returned.
406 * @param IResultWrapper|stdClass $res Object as returned from IDatabase::query(), etc.
407 * @return stdClass|bool
408 * @throws DBUnexpectedError Thrown if the database returns an error
410 public function fetchObject( $res );
413 * Fetch the next row from the given result object, in associative array
414 * form. Fields are retrieved with $row['fieldname'].
415 * If no more rows are available, false is returned.
417 * @param IResultWrapper $res Result object as returned from IDatabase::query(), etc.
419 * @throws DBUnexpectedError Thrown if the database returns an error
421 public function fetchRow( $res );
424 * Get the number of rows in a query result. If the query did not return
425 * any rows (for example, if it was a write query), this returns zero.
427 * @param mixed $res A SQL result
430 public function numRows( $res );
433 * Get the number of fields in a result object
434 * @see https://www.php.net/mysql_num_fields
436 * @param mixed $res A SQL result
439 public function numFields( $res );
442 * Get a field name in a result object
443 * @see https://www.php.net/mysql_field_name
445 * @param mixed $res A SQL result
449 public function fieldName( $res, $n );
452 * Get the inserted value of an auto-increment row
454 * This should only be called after an insert that used an auto-incremented
455 * value. If no such insert was previously done in the current database
456 * session, the return value is undefined.
460 public function insertId();
463 * Change the position of the cursor in a result object
464 * @see https://www.php.net/mysql_data_seek
466 * @param mixed $res A SQL result
469 public function dataSeek( $res, $row );
472 * Get the last error number
473 * @see https://www.php.net/mysql_errno
477 public function lastErrno();
480 * Get a description of the last error
481 * @see https://www.php.net/mysql_error
485 public function lastError();
488 * Get the number of rows affected by the last write query
489 * @see https://www.php.net/mysql_affected_rows
493 public function affectedRows();
496 * Returns a wikitext link to the DB's website, e.g.,
497 * return "[https://www.mysql.com/ MySQL]";
498 * Should at least contain plain text, if for some reason
499 * your database has no website.
501 * @return string Wikitext of a link to the server software's web site
503 public function getSoftwareLink();
506 * A string describing the current software version, like from
507 * mysql_get_server_info().
509 * @return string Version information from the database server.
511 public function getServerVersion();
514 * Close the database connection
516 * This should only be called after any transactions have been resolved,
517 * aside from read-only automatic transactions (assuming no callbacks are registered).
518 * If a transaction is still open anyway, it will be rolled back.
521 * @return bool Operation success. true if already closed.
523 public function close();
526 * Run an SQL query and return the result. Normally throws a DBQueryError
527 * on failure. If errors are ignored, returns false instead.
529 * If a connection loss is detected, then an attempt to reconnect will be made.
530 * For queries that involve no larger transactions or locks, they will be re-issued
531 * for convenience, provided the connection was re-established.
533 * In new code, the query wrappers select(), insert(), update(), delete(),
534 * etc. should be used where possible, since they give much better DBMS
535 * independence and automatically quote or validate user input in a variety
536 * of contexts. This function is generally only useful for queries which are
537 * explicitly DBMS-dependent and are unsupported by the query wrappers, such
540 * However, the query wrappers themselves should call this function.
542 * @param string $sql SQL query
543 * @param string $fname Name of the calling function, for profiling/SHOW PROCESSLIST
544 * comment (you can use __METHOD__ or add some extra info)
545 * @param int $flags Bitfield of IDatabase::QUERY_* constants. Note that suppression
546 * of errors is best handled by try/catch rather than using one of these flags.
547 * @return bool|IResultWrapper True for a successful write query, IResultWrapper object
548 * for a successful read query, or false on failure if QUERY_SILENCE_ERRORS is set.
551 public function query( $sql, $fname = __METHOD__
, $flags = 0 );
554 * Free a result object returned by query() or select(). It's usually not
555 * necessary to call this, just use unset() or let the variable holding
556 * the result object go out of scope.
558 * @param mixed $res A SQL result
560 public function freeResult( $res );
563 * A SELECT wrapper which returns a single field from a single result row.
565 * Usually throws a DBQueryError on failure. If errors are explicitly
566 * ignored, returns false on failure.
568 * If no result rows are returned from the query, false is returned.
570 * @param string|array $table Table name. See IDatabase::select() for details.
571 * @param string $var The field name to select. This must be a valid SQL
572 * fragment: do not use unvalidated user input.
573 * @param string|array $cond The condition array. See IDatabase::select() for details.
574 * @param string $fname The function name of the caller.
575 * @param string|array $options The query options. See IDatabase::select() for details.
576 * @param string|array $join_conds The query join conditions. See IDatabase::select() for details.
578 * @return mixed The value from the field
581 public function selectField(
582 $table, $var, $cond = '', $fname = __METHOD__
, $options = [], $join_conds = []
586 * A SELECT wrapper which returns a list of single field values from result rows.
588 * Usually throws a DBQueryError on failure. If errors are explicitly
589 * ignored, returns false on failure.
591 * If no result rows are returned from the query, false is returned.
593 * @param string|array $table Table name. See IDatabase::select() for details.
594 * @param string $var The field name to select. This must be a valid SQL
595 * fragment: do not use unvalidated user input.
596 * @param string|array $cond The condition array. See IDatabase::select() for details.
597 * @param string $fname The function name of the caller.
598 * @param string|array $options The query options. See IDatabase::select() for details.
599 * @param string|array $join_conds The query join conditions. See IDatabase::select() for details.
601 * @return array The values from the field in the order they were returned from the DB
605 public function selectFieldValues(
606 $table, $var, $cond = '', $fname = __METHOD__
, $options = [], $join_conds = []
610 * Execute a SELECT query constructed using the various parameters provided.
611 * See below for full details of the parameters.
613 * @param string|array $table Table name(s)
615 * May be either an array of table names, or a single string holding a table
616 * name. If an array is given, table aliases can be specified, for example:
620 * This includes the user table in the query, with the alias "a" available
621 * for use in field names (e.g. a.user_name).
623 * A derived table, defined by the result of selectSQLText(), requires an alias
624 * key and a Subquery instance value which wraps the SQL query, for example:
626 * [ 'c' => new Subquery( 'SELECT ...' ) ]
628 * Joins using parentheses for grouping (since MediaWiki 1.31) may be
629 * constructed using nested arrays. For example,
631 * [ 'tableA', 'nestedB' => [ 'tableB', 'b2' => 'tableB2' ] ]
633 * along with `$join_conds` like
635 * [ 'b2' => [ 'JOIN', 'b_id = b2_id' ], 'nestedB' => [ 'LEFT JOIN', 'b_a = a_id' ] ]
637 * will produce SQL something like
639 * FROM tableA LEFT JOIN (tableB JOIN tableB2 AS b2 ON (b_id = b2_id)) ON (b_a = a_id)
641 * All of the table names given here are automatically run through
642 * Database::tableName(), which causes the table prefix (if any) to be
643 * added, and various other table name mappings to be performed.
645 * Do not use untrusted user input as a table name. Alias names should
646 * not have characters outside of the Basic multilingual plane.
648 * @param string|array $vars Field name(s)
650 * May be either a field name or an array of field names. The field names
651 * can be complete fragments of SQL, for direct inclusion into the SELECT
652 * query. If an array is given, field aliases can be specified, for example:
654 * [ 'maxrev' => 'MAX(rev_id)' ]
656 * This includes an expression with the alias "maxrev" in the query.
658 * If an expression is given, care must be taken to ensure that it is
661 * Untrusted user input must not be passed to this parameter.
663 * @param string|array $conds
665 * May be either a string containing a single condition, or an array of
666 * conditions. If an array is given, the conditions constructed from each
667 * element are combined with AND.
669 * Array elements may take one of two forms:
671 * - Elements with a numeric key are interpreted as raw SQL fragments.
672 * - Elements with a string key are interpreted as equality conditions,
673 * where the key is the field name.
674 * - If the value of such an array element is a scalar (such as a
675 * string), it will be treated as data and thus quoted appropriately.
676 * If it is null, an IS NULL clause will be added.
677 * - If the value is an array, an IN (...) clause will be constructed
678 * from its non-null elements, and an IS NULL clause will be added
679 * if null is present, such that the field may match any of the
680 * elements in the array. The non-null elements will be quoted.
682 * Note that expressions are often DBMS-dependent in their syntax.
683 * DBMS-independent wrappers are provided for constructing several types of
684 * expression commonly used in condition queries. See:
685 * - IDatabase::buildLike()
686 * - IDatabase::conditional()
688 * Untrusted user input is safe in the values of string keys, however untrusted
689 * input must not be used in the array key names or in the values of numeric keys.
690 * Escaping of untrusted input used in values of numeric keys should be done via
691 * IDatabase::addQuotes()
693 * Use an empty array, string, or '*' to update all rows.
695 * @param string $fname Caller function name
697 * @param string|array $options Query options
699 * Optional: Array of query options. Boolean options are specified by
700 * including them in the array as a string value with a numeric key, for
705 * The supported options are:
707 * - OFFSET: Skip this many rows at the start of the result set. OFFSET
708 * with LIMIT can theoretically be used for paging through a result set,
709 * but this is discouraged for performance reasons.
711 * - LIMIT: Integer: return at most this many rows. The rows are sorted
712 * and then the first rows are taken until the limit is reached. LIMIT
713 * is applied to a result set after OFFSET.
715 * - FOR UPDATE: Boolean: lock the returned rows so that they can't be
716 * changed until the next COMMIT. Cannot be used with aggregate functions
717 * (COUNT, MAX, etc., but also DISTINCT).
719 * - DISTINCT: Boolean: return only unique result rows.
721 * - GROUP BY: May be either an SQL fragment string naming a field or
722 * expression to group by, or an array of such SQL fragments.
724 * - HAVING: May be either an string containing a HAVING clause or an array of
725 * conditions building the HAVING clause. If an array is given, the conditions
726 * constructed from each element are combined with AND.
728 * - ORDER BY: May be either an SQL fragment giving a field name or
729 * expression to order by, or an array of such SQL fragments.
731 * - USE INDEX: This may be either a string giving the index name to use
732 * for the query, or an array. If it is an associative array, each key
733 * gives the table name (or alias), each value gives the index name to
734 * use for that table. All strings are SQL fragments and so should be
735 * validated by the caller.
737 * - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
740 * And also the following boolean MySQL extensions, see the MySQL manual
743 * - LOCK IN SHARE MODE
747 * - SQL_BUFFER_RESULT
749 * - SQL_CALC_FOUND_ROWS
754 * @param string|array $join_conds Join conditions
756 * Optional associative array of table-specific join conditions. In the
757 * most common case, this is unnecessary, since the join condition can be
758 * in $conds. However, it is useful for doing a LEFT JOIN.
760 * The key of the array contains the table name or alias. The value is an
761 * array with two elements, numbered 0 and 1. The first gives the type of
762 * join, the second is the same as the $conds parameter. Thus it can be
763 * an SQL fragment, or an array where the string keys are equality and the
764 * numeric keys are SQL fragments all AND'd together. For example:
766 * [ 'page' => [ 'LEFT JOIN', 'page_latest=rev_id' ] ]
768 * @return IResultWrapper Resulting rows
771 public function select(
772 $table, $vars, $conds = '', $fname = __METHOD__
,
773 $options = [], $join_conds = []
777 * The equivalent of IDatabase::select() except that the constructed SQL
778 * is returned, instead of being immediately executed. This can be useful for
779 * doing UNION queries, where the SQL text of each query is needed. In general,
780 * however, callers outside of Database classes should just use select().
782 * @see IDatabase::select()
784 * @param string|array $table Table name
785 * @param string|array $vars Field names
786 * @param string|array $conds Conditions
787 * @param string $fname Caller function name
788 * @param string|array $options Query options
789 * @param string|array $join_conds Join conditions
790 * @return string SQL query string
792 public function selectSQLText(
793 $table, $vars, $conds = '', $fname = __METHOD__
,
794 $options = [], $join_conds = []
798 * Single row SELECT wrapper. Equivalent to IDatabase::select(), except
799 * that a single row object is returned. If the query returns no rows,
802 * @param string|array $table Table name
803 * @param string|array $vars Field names
804 * @param array $conds Conditions
805 * @param string $fname Caller function name
806 * @param string|array $options Query options
807 * @param array|string $join_conds Join conditions
809 * @return stdClass|bool
812 public function selectRow( $table, $vars, $conds, $fname = __METHOD__
,
813 $options = [], $join_conds = []
817 * Estimate the number of rows in dataset
819 * MySQL allows you to estimate the number of rows that would be returned
820 * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
821 * index cardinality statistics, and is notoriously inaccurate, especially
822 * when large numbers of rows have recently been added or deleted.
824 * For DBMSs that don't support fast result size estimation, this function
825 * will actually perform the SELECT COUNT(*).
827 * Takes the same arguments as IDatabase::select().
829 * @param string $table Table name
830 * @param string $var Column for which NULL values are not counted [default "*"]
831 * @param array|string $conds Filters on the table
832 * @param string $fname Function name for profiling
833 * @param array $options Options for select
834 * @param array|string $join_conds Join conditions
835 * @return int Row count
838 public function estimateRowCount(
839 $table, $var = '*', $conds = '', $fname = __METHOD__
, $options = [], $join_conds = []
843 * Get the number of rows in dataset
845 * This is useful when trying to do COUNT(*) but with a LIMIT for performance.
847 * Takes the same arguments as IDatabase::select().
849 * @since 1.27 Added $join_conds parameter
851 * @param array|string $tables Table names
852 * @param string $var Column for which NULL values are not counted [default "*"]
853 * @param array|string $conds Filters on the table
854 * @param string $fname Function name for profiling
855 * @param array $options Options for select
856 * @param array $join_conds Join conditions (since 1.27)
857 * @return int Row count
860 public function selectRowCount(
861 $tables, $var = '*', $conds = '', $fname = __METHOD__
, $options = [], $join_conds = []
865 * Lock all rows meeting the given conditions/options FOR UPDATE
867 * @param array|string $table Table names
868 * @param array|string $conds Filters on the table
869 * @param string $fname Function name for profiling
870 * @param array $options Options for select ("FOR UPDATE" is added automatically)
871 * @param array $join_conds Join conditions
872 * @return int Number of matching rows found (and locked)
875 public function lockForUpdate(
876 $table, $conds = '', $fname = __METHOD__
, $options = [], $join_conds = []
880 * Determines whether a field exists in a table
882 * @param string $table Table name
883 * @param string $field Filed to check on that table
884 * @param string $fname Calling function name (optional)
885 * @return bool Whether $table has filed $field
888 public function fieldExists( $table, $field, $fname = __METHOD__
);
891 * Determines whether an index exists
892 * Usually throws a DBQueryError on failure
893 * If errors are explicitly ignored, returns NULL on failure
895 * @param string $table
896 * @param string $index
897 * @param string $fname
901 public function indexExists( $table, $index, $fname = __METHOD__
);
904 * Query whether a given table exists
906 * @param string $table
907 * @param string $fname
911 public function tableExists( $table, $fname = __METHOD__
);
914 * INSERT wrapper, inserts an array into a table.
918 * - A single associative array. The array keys are the field names, and
919 * the values are the values to insert. The values are treated as data
920 * and will be quoted appropriately. If NULL is inserted, this will be
921 * converted to a database NULL.
922 * - An array with numeric keys, holding a list of associative arrays.
923 * This causes a multi-row INSERT on DBMSs that support it. The keys in
924 * each subarray must be identical to each other, and in the same order.
926 * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
929 * $options is an array of options, with boolean options encoded as values
930 * with numeric keys, in the same style as $options in
931 * IDatabase::select(). Supported options are:
933 * - IGNORE: Boolean: if present, duplicate key errors are ignored, and
934 * any rows which cause duplicate key errors are not inserted. It's
935 * possible to determine how many rows were successfully inserted using
936 * IDatabase::affectedRows().
938 * @param string $table Table name. This will be passed through
939 * Database::tableName().
940 * @param array $a Array of rows to insert
941 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
942 * @param array $options Array of options
943 * @return bool Return true if no exception was thrown (deprecated since 1.33)
946 public function insert( $table, $a, $fname = __METHOD__
, $options = [] );
949 * UPDATE wrapper. Takes a condition array and a SET array.
951 * @param string $table Name of the table to UPDATE. This will be passed through
952 * Database::tableName().
953 * @param array $values An array of values to SET. For each array element,
954 * the key gives the field name, and the value gives the data to set
955 * that field to. The data will be quoted by IDatabase::addQuotes().
956 * Values with integer keys form unquoted SET statements, which can be used for
957 * things like "field = field + 1" or similar computed values.
958 * @param array $conds An array of conditions (WHERE). See
959 * IDatabase::select() for the details of the format of condition
960 * arrays. Use '*' to update all rows.
961 * @param string $fname The function name of the caller (from __METHOD__),
962 * for logging and profiling.
963 * @param array $options An array of UPDATE options, can be:
964 * - IGNORE: Ignore unique key conflicts
965 * - LOW_PRIORITY: MySQL-specific, see MySQL manual.
966 * @return bool Return true if no exception was thrown (deprecated since 1.33)
969 public function update( $table, $values, $conds, $fname = __METHOD__
, $options = [] );
972 * Makes an encoded list of strings from an array
974 * These can be used to make conjunctions or disjunctions on SQL condition strings
975 * derived from an array (see IDatabase::select() $conds documentation).
979 * $sql = $db->makeList( [
981 * $db->makeList( [ 'rev_minor' => 1, 'rev_len' < 500 ], $db::LIST_OR ] )
982 * ], $db::LIST_AND );
984 * This would set $sql to "rev_page = '$id' AND (rev_minor = '1' OR rev_len < '500')"
986 * @param array $a Containing the data
987 * @param int $mode IDatabase class constant:
988 * - IDatabase::LIST_COMMA: Comma separated, no field names
989 * - IDatabase::LIST_AND: ANDed WHERE clause (without the WHERE).
990 * - IDatabase::LIST_OR: ORed WHERE clause (without the WHERE)
991 * - IDatabase::LIST_SET: Comma separated with field names, like a SET clause
992 * - IDatabase::LIST_NAMES: Comma separated field names
996 public function makeList( $a, $mode = self
::LIST_COMMA
);
999 * Build a partial where clause from a 2-d array such as used for LinkBatch.
1000 * The keys on each level may be either integers or strings.
1002 * @param array $data Organized as 2-d
1003 * [ baseKeyVal => [ subKeyVal => [ignored], ... ], ... ]
1004 * @param string $baseKey Field name to match the base-level keys to (eg 'pl_namespace')
1005 * @param string $subKey Field name to match the sub-level keys to (eg 'pl_title')
1006 * @return string|bool SQL fragment, or false if no items in array
1008 public function makeWhereFrom2d( $data, $baseKey, $subKey );
1011 * Return aggregated value alias
1013 * @param array $valuedata
1014 * @param string $valuename
1017 * @deprecated Since 1.33
1019 public function aggregateValue( $valuedata, $valuename = 'value' );
1022 * @param string $field
1025 public function bitNot( $field );
1028 * @param string $fieldLeft
1029 * @param string $fieldRight
1032 public function bitAnd( $fieldLeft, $fieldRight );
1035 * @param string $fieldLeft
1036 * @param string $fieldRight
1039 public function bitOr( $fieldLeft, $fieldRight );
1042 * Build a concatenation list to feed into a SQL query
1043 * @param array $stringList List of raw SQL expressions; caller is
1044 * responsible for any quoting
1047 public function buildConcat( $stringList );
1050 * Build a GROUP_CONCAT or equivalent statement for a query.
1052 * This is useful for combining a field for several rows into a single string.
1053 * NULL values will not appear in the output, duplicated values will appear,
1054 * and the resulting delimiter-separated values have no defined sort order.
1055 * Code using the results may need to use the PHP unique() or sort() methods.
1057 * @param string $delim Glue to bind the results together
1058 * @param string|array $table Table name
1059 * @param string $field Field name
1060 * @param string|array $conds Conditions
1061 * @param string|array $join_conds Join conditions
1062 * @return string SQL text
1065 public function buildGroupConcatField(
1066 $delim, $table, $field, $conds = '', $join_conds = []
1070 * Build a SUBSTRING function.
1072 * Behavior for non-ASCII values is undefined.
1074 * @param string $input Field name
1075 * @param int $startPosition Positive integer
1076 * @param int|null $length Non-negative integer length or null for no limit
1077 * @throws InvalidArgumentException
1078 * @return string SQL text
1081 public function buildSubString( $input, $startPosition, $length = null );
1084 * @param string $field Field or column to cast
1088 public function buildStringCast( $field );
1091 * @param string $field Field or column to cast
1095 public function buildIntegerCast( $field );
1098 * Equivalent to IDatabase::selectSQLText() except wraps the result in Subqyery
1100 * @see IDatabase::selectSQLText()
1102 * @param string|array $table Table name
1103 * @param string|array $vars Field names
1104 * @param string|array $conds Conditions
1105 * @param string $fname Caller function name
1106 * @param string|array $options Query options
1107 * @param string|array $join_conds Join conditions
1111 public function buildSelectSubquery(
1112 $table, $vars, $conds = '', $fname = __METHOD__
,
1113 $options = [], $join_conds = []
1117 * Construct a LIMIT query with optional offset. This is used for query
1118 * pages. The SQL should be adjusted so that only the first $limit rows
1119 * are returned. If $offset is provided as well, then the first $offset
1120 * rows should be discarded, and the next $limit rows should be returned.
1121 * If the result of the query is not ordered, then the rows to be returned
1122 * are theoretically arbitrary.
1124 * $sql is expected to be a SELECT, if that makes a difference.
1126 * @param string $sql SQL query we will append the limit too
1127 * @param int $limit The SQL limit
1128 * @param int|bool $offset The SQL offset (default false)
1129 * @throws DBUnexpectedError
1133 public function limitResult( $sql, $limit, $offset = false );
1136 * Returns true if DBs are assumed to be on potentially different servers
1138 * In systems like mysql/mariadb, different databases can easily be referenced on a single
1139 * connection merely by name, even in a single query via JOIN. On the other hand, Postgres
1140 * treats databases as fully separate, only allowing mechanisms like postgres_fdw to
1141 * effectively "mount" foreign DBs. This is true even among DBs on the same server.
1146 public function databasesAreIndependent();
1149 * Change the current database
1151 * This should not be called outside LoadBalancer for connections managed by a LoadBalancer
1154 * @return bool True unless an exception was thrown
1155 * @throws DBConnectionError If databasesAreIndependent() is true and an error occurs
1157 * @deprecated Since 1.32 Use selectDomain() instead
1159 public function selectDB( $db );
1162 * Set the current domain (database, schema, and table prefix)
1164 * This will throw an error for some database types if the database unspecified
1166 * This should not be called outside LoadBalancer for connections managed by a LoadBalancer
1168 * @param string|DatabaseDomain $domain
1170 * @throws DBConnectionError
1172 public function selectDomain( $domain );
1175 * Get the current DB name
1176 * @return string|null
1178 public function getDBname();
1181 * Get the server hostname or IP address
1184 public function getServer();
1187 * Adds quotes and backslashes.
1189 * @param string|int|null|bool|Blob $s
1190 * @return string|int
1192 public function addQuotes( $s );
1195 * Quotes an identifier, in order to make user controlled input safe
1197 * Depending on the database this will either be `backticks` or "double quotes"
1203 public function addIdentifierQuotes( $s );
1206 * LIKE statement wrapper, receives a variable-length argument list with
1207 * parts of pattern to match containing either string literals that will be
1208 * escaped or tokens returned by anyChar() or anyString(). Alternatively,
1209 * the function could be provided with an array of aforementioned
1212 * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns
1213 * a LIKE clause that searches for subpages of 'My page title'.
1215 * $pattern = [ 'My_page_title/', $dbr->anyString() ];
1216 * $query .= $dbr->buildLike( $pattern );
1219 * @return string Fully built LIKE statement
1221 public function buildLike();
1224 * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
1228 public function anyChar();
1231 * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
1235 public function anyString();
1238 * Deprecated method, calls should be removed.
1240 * This was formerly used for PostgreSQL and Oracle to handle
1241 * self::insertId() auto-incrementing fields. It is no longer necessary
1242 * since DatabasePostgres::insertId() has been reimplemented using
1243 * `lastval()` and Oracle has been reimplemented using triggers.
1245 * Implementations should return null if inserting `NULL` into an
1246 * auto-incrementing field works, otherwise it should return an instance of
1247 * NextSequenceValue and filter it on calls to relevant methods.
1249 * @deprecated since 1.30, no longer needed
1250 * @param string $seqName
1251 * @return null|NextSequenceValue
1253 public function nextSequenceValue( $seqName );
1256 * REPLACE query wrapper.
1258 * REPLACE is a very handy MySQL extension, which functions like an INSERT
1259 * except that when there is a duplicate key error, the old row is deleted
1260 * and the new row is inserted in its place.
1262 * We simulate this with standard SQL with a DELETE followed by INSERT. To
1263 * perform the delete, we need to know what the unique indexes are so that
1264 * we know how to find the conflicting rows.
1266 * It may be more efficient to leave off unique indexes which are unlikely
1267 * to collide. However if you do this, you run the risk of encountering
1268 * errors which wouldn't have occurred in MySQL.
1270 * @param string $table The table to replace the row(s) in.
1271 * @param array[]|string[]|string $uniqueIndexes All unique indexes. One of the following:
1272 * a) the one unique field in the table (when no composite unique key exist)
1273 * b) a list of all unique fields in the table (when no composite unique key exist)
1274 * c) a list of all unique indexes in the table (each as a list of the indexed fields)
1275 * @param array $rows Can be either a single row to insert, or multiple rows,
1276 * in the same format as for IDatabase::insert()
1277 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1280 public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__
);
1283 * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
1285 * This updates any conflicting rows (according to the unique indexes) using
1286 * the provided SET clause and inserts any remaining (non-conflicted) rows.
1288 * $rows may be either:
1289 * - A single associative array. The array keys are the field names, and
1290 * the values are the values to insert. The values are treated as data
1291 * and will be quoted appropriately. If NULL is inserted, this will be
1292 * converted to a database NULL.
1293 * - An array with numeric keys, holding a list of associative arrays.
1294 * This causes a multi-row INSERT on DBMSs that support it. The keys in
1295 * each subarray must be identical to each other, and in the same order.
1297 * It may be more efficient to leave off unique indexes which are unlikely
1298 * to collide. However if you do this, you run the risk of encountering
1299 * errors which wouldn't have occurred in MySQL.
1301 * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1306 * @param string $table Table name. This will be passed through Database::tableName().
1307 * @param array $rows A single row or list of rows to insert
1308 * @param array[]|string[]|string $uniqueIndexes All unique indexes. One of the following:
1309 * a) the one unique field in the table (when no composite unique key exist)
1310 * b) a list of all unique fields in the table (when no composite unique key exist)
1311 * c) a list of all unique indexes in the table (each as a list of the indexed fields)
1312 * @param array $set An array of values to SET. For each array element, the
1313 * key gives the field name, and the value gives the data to set that
1314 * field to. The data will be quoted by IDatabase::addQuotes().
1315 * Values with integer keys form unquoted SET statements, which can be used for
1316 * things like "field = field + 1" or similar computed values.
1317 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1319 * @return bool Return true if no exception was thrown (deprecated since 1.33)
1321 public function upsert(
1322 $table, array $rows, $uniqueIndexes, array $set, $fname = __METHOD__
1326 * DELETE where the condition is a join.
1328 * MySQL overrides this to use a multi-table DELETE syntax, in other databases
1329 * we use sub-selects
1331 * For safety, an empty $conds will not delete everything. If you want to
1332 * delete all rows where the join condition matches, set $conds='*'.
1334 * DO NOT put the join condition in $conds.
1336 * @param string $delTable The table to delete from.
1337 * @param string $joinTable The other table.
1338 * @param string $delVar The variable to join on, in the first table.
1339 * @param string $joinVar The variable to join on, in the second table.
1340 * @param array $conds Condition array of field names mapped to variables,
1341 * ANDed together in the WHERE clause
1342 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1345 public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
1350 * DELETE query wrapper.
1352 * @param string $table Table name
1353 * @param string|array $conds Array of conditions. See $conds in IDatabase::select()
1354 * for the format. Use $conds == "*" to delete all rows
1355 * @param string $fname Name of the calling function
1356 * @throws DBUnexpectedError
1357 * @return bool Return true if no exception was thrown (deprecated since 1.33)
1360 public function delete( $table, $conds, $fname = __METHOD__
);
1363 * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
1364 * into another table.
1366 * @warning If the insert will use an auto-increment or sequence to
1367 * determine the value of a column, this may break replication on
1368 * databases using statement-based replication if the SELECT is not
1369 * deterministically ordered.
1371 * @param string $destTable The table name to insert into
1372 * @param string|array $srcTable May be either a table name, or an array of table names
1373 * to include in a join.
1375 * @param array $varMap Must be an associative array of the form
1376 * [ 'dest1' => 'source1', ... ]. Source items may be literals
1377 * rather than field names, but strings should be quoted with
1378 * IDatabase::addQuotes()
1380 * @param array $conds Condition array. See $conds in IDatabase::select() for
1381 * the details of the format of condition arrays. May be "*" to copy the
1384 * @param string $fname The function name of the caller, from __METHOD__
1386 * @param array $insertOptions Options for the INSERT part of the query, see
1387 * IDatabase::insert() for details. Also, one additional option is
1388 * available: pass 'NO_AUTO_COLUMNS' to hint that the query does not use
1389 * an auto-increment or sequence to determine any column values.
1390 * @param array $selectOptions Options for the SELECT part of the query, see
1391 * IDatabase::select() for details.
1392 * @param array $selectJoinConds Join conditions for the SELECT part of the query, see
1393 * IDatabase::select() for details.
1395 * @return bool Return true if no exception was thrown (deprecated since 1.33)
1398 public function insertSelect( $destTable, $srcTable, $varMap, $conds,
1399 $fname = __METHOD__
,
1400 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
1404 * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
1405 * within the UNION construct.
1408 public function unionSupportsOrderAndLimit();
1411 * Construct a UNION query
1412 * This is used for providing overload point for other DB abstractions
1413 * not compatible with the MySQL syntax.
1414 * @param array $sqls SQL statements to combine
1415 * @param bool $all Either IDatabase::UNION_ALL or IDatabase::UNION_DISTINCT
1416 * @return string SQL fragment
1418 public function unionQueries( $sqls, $all );
1421 * Construct a UNION query for permutations of conditions
1423 * Databases sometimes have trouble with queries that have multiple values
1424 * for multiple condition parameters combined with limits and ordering.
1425 * This method constructs queries for the Cartesian product of the
1426 * conditions and unions them all together.
1428 * @see IDatabase::select()
1430 * @param string|array $table Table name
1431 * @param string|array $vars Field names
1432 * @param array $permute_conds Conditions for the Cartesian product. Keys
1433 * are field names, values are arrays of the possible values for that
1435 * @param string|array $extra_conds Additional conditions to include in the
1437 * @param string $fname Caller function name
1438 * @param string|array $options Query options. In addition to the options
1439 * recognized by IDatabase::select(), the following may be used:
1440 * - NOTALL: Set to use UNION instead of UNION ALL.
1441 * - INNER ORDER BY: If specified and supported, subqueries will use this
1442 * instead of ORDER BY.
1443 * @param string|array $join_conds Join conditions
1444 * @return string SQL query string.
1446 public function unionConditionPermutations(
1447 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__
,
1448 $options = [], $join_conds = []
1452 * Returns an SQL expression for a simple conditional. This doesn't need
1453 * to be overridden unless CASE isn't supported in your DBMS.
1455 * @param string|array $cond SQL expression which will result in a boolean value
1456 * @param string $trueVal SQL expression to return if true
1457 * @param string $falseVal SQL expression to return if false
1458 * @return string SQL fragment
1460 public function conditional( $cond, $trueVal, $falseVal );
1463 * Returns a command for str_replace function in SQL query.
1464 * Uses REPLACE() in MySQL
1466 * @param string $orig Column to modify
1467 * @param string $old Column to seek
1468 * @param string $new Column to replace with
1472 public function strreplace( $orig, $old, $new );
1475 * Determines how long the server has been up
1480 public function getServerUptime();
1483 * Determines if the last failure was due to a deadlock
1485 * Note that during a deadlock, the prior transaction will have been lost
1489 public function wasDeadlock();
1492 * Determines if the last failure was due to a lock timeout
1494 * Note that during a lock wait timeout, the prior transaction will have been lost
1498 public function wasLockTimeout();
1501 * Determines if the last query error was due to a dropped connection
1503 * Note that during a connection loss, the prior transaction will have been lost
1508 public function wasConnectionLoss();
1511 * Determines if the last failure was due to the database being read-only.
1515 public function wasReadOnlyError();
1518 * Determines if the last query error was due to something outside of the query itself
1520 * Note that the transaction may have been lost, discarding prior writes and results
1524 public function wasErrorReissuable();
1527 * Wait for the replica DB to catch up to a given master position
1529 * Note that this does not start any new transactions. If any existing transaction
1530 * is flushed, and this is called, then queries will reflect the point the DB was synced
1531 * up to (on success) without interference from REPEATABLE-READ snapshots.
1533 * @param DBMasterPos $pos
1534 * @param int $timeout The maximum number of seconds to wait for synchronisation
1535 * @return int|null Zero if the replica DB was past that position already,
1536 * greater than zero if we waited for some period of time, less than
1537 * zero if it timed out, and null on error
1540 public function masterPosWait( DBMasterPos
$pos, $timeout );
1543 * Get the replication position of this replica DB
1545 * @return DBMasterPos|bool False if this is not a replica DB
1548 public function getReplicaPos();
1551 * Get the position of this master
1553 * @return DBMasterPos|bool False if this is not a master
1556 public function getMasterPos();
1559 * @return bool Whether the DB is marked as read-only server-side
1562 public function serverIsReadOnly();
1565 * Run a callback as soon as the current transaction commits or rolls back.
1566 * An error is thrown if no transaction is pending. Queries in the function will run in
1567 * AUTOCOMMIT mode unless there are begin() calls. Callbacks must commit any transactions
1570 * This is useful for combining cooperative locks and DB transactions.
1572 * @note do not assume that *other* IDatabase instances will be AUTOCOMMIT mode
1574 * The callback takes the following arguments:
1575 * - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK)
1576 * - This IDatabase instance (since 1.32)
1578 * @param callable $callback
1579 * @param string $fname Caller name
1582 public function onTransactionResolution( callable
$callback, $fname = __METHOD__
);
1585 * Run a callback as soon as there is no transaction pending.
1586 * If there is a transaction and it is rolled back, then the callback is cancelled.
1588 * When transaction round mode (DBO_TRX) is set, the callback will run at the end
1589 * of the round, just after all peer transactions COMMIT. If the transaction round
1590 * is rolled back, then the callback is cancelled.
1592 * Queries in the function will run in AUTOCOMMIT mode unless there are begin() calls.
1593 * Callbacks must commit any transactions that they begin.
1595 * This is useful for updates to different systems or when separate transactions are needed.
1596 * For example, one might want to enqueue jobs into a system outside the database, but only
1597 * after the database is updated so that the jobs will see the data when they actually run.
1598 * It can also be used for updates that easily suffer from lock timeouts and deadlocks,
1599 * but where atomicity is not essential.
1601 * Avoid using IDatabase instances aside from this one in the callback, unless such instances
1602 * never have IDatabase::DBO_TRX set. This keeps callbacks from interfering with one another.
1604 * Updates will execute in the order they were enqueued.
1606 * @note do not assume that *other* IDatabase instances will be AUTOCOMMIT mode
1608 * The callback takes the following arguments:
1609 * - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_IDLE)
1610 * - This IDatabase instance (since 1.32)
1612 * @param callable $callback
1613 * @param string $fname Caller name
1616 public function onTransactionCommitOrIdle( callable
$callback, $fname = __METHOD__
);
1619 * Alias for onTransactionCommitOrIdle() for backwards-compatibility
1621 * @param callable $callback
1622 * @param string $fname
1624 * @deprecated Since 1.32
1626 public function onTransactionIdle( callable
$callback, $fname = __METHOD__
);
1629 * Run a callback before the current transaction commits or now if there is none.
1630 * If there is a transaction and it is rolled back, then the callback is cancelled.
1632 * When transaction round mode (DBO_TRX) is set, the callback will run at the end
1633 * of the round, just before all peer transactions COMMIT. If the transaction round
1634 * is rolled back, then the callback is cancelled.
1636 * Callbacks must not start nor commit any transactions. If no transaction is active,
1637 * then a transaction will wrap the callback.
1639 * This is useful for updates that easily suffer from lock timeouts and deadlocks,
1640 * but where atomicity is strongly desired for these updates and some related updates.
1642 * Updates will execute in the order they were enqueued.
1644 * The callback takes the one argument:
1645 * - This IDatabase instance (since 1.32)
1647 * @param callable $callback
1648 * @param string $fname Caller name
1651 public function onTransactionPreCommitOrIdle( callable
$callback, $fname = __METHOD__
);
1654 * Run a callback after each time any transaction commits or rolls back
1656 * The callback takes two arguments:
1657 * - IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK
1658 * - This IDatabase object
1659 * Callbacks must commit any transactions that they begin.
1661 * Registering a callback here will not affect writesOrCallbacks() pending.
1663 * Since callbacks from this or onTransactionCommitOrIdle() can start and end transactions,
1664 * a single call to IDatabase::commit might trigger multiple runs of the listener callbacks.
1666 * @param string $name Callback name
1667 * @param callable|null $callback Use null to unset a listener
1670 public function setTransactionListener( $name, callable
$callback = null );
1673 * Begin an atomic section of SQL statements
1675 * Start an implicit transaction if no transaction is already active, set a savepoint
1676 * (if $cancelable is ATOMIC_CANCELABLE), and track the given section name to enforce
1677 * that the transaction is not committed prematurely. The end of the section must be
1678 * signified exactly once, either by endAtomic() or cancelAtomic(). Sections can have
1679 * have layers of inner sections (sub-sections), but all sections must be ended in order
1680 * of innermost to outermost. Transactions cannot be started or committed until all
1681 * atomic sections are closed.
1683 * ATOMIC_CANCELABLE is useful when the caller needs to handle specific failure cases
1684 * by discarding the section's writes. This should not be used for failures when:
1685 * - upsert() could easily be used instead
1686 * - insert() with IGNORE could easily be used instead
1687 * - select() with FOR UPDATE could be checked before issuing writes instead
1688 * - The failure is from code that runs after the first write but doesn't need to
1689 * - The failures are from contention solvable via onTransactionPreCommitOrIdle()
1690 * - The failures are deadlocks; the RDBMs usually discard the whole transaction
1692 * @note callers must use additional measures for situations involving two or more
1693 * (peer) transactions (e.g. updating two database servers at once). The transaction
1694 * and savepoint logic of this method only applies to this specific IDatabase instance.
1698 * // Start a transaction if there isn't one already
1699 * $dbw->startAtomic( __METHOD__ );
1700 * // Serialize these thread table updates
1701 * $dbw->select( 'thread', '1', [ 'td_id' => $tid ], __METHOD__, 'FOR UPDATE' );
1702 * // Add a new comment for the thread
1703 * $dbw->insert( 'comment', $row, __METHOD__ );
1704 * $cid = $db->insertId();
1705 * // Update thread reference to last comment
1706 * $dbw->update( 'thread', [ 'td_latest' => $cid ], [ 'td_id' => $tid ], __METHOD__ );
1707 * // Demark the end of this conceptual unit of updates
1708 * $dbw->endAtomic( __METHOD__ );
1711 * Example usage (atomic changes that might have to be discarded):
1713 * // Start a transaction if there isn't one already
1714 * $sectionId = $dbw->startAtomic( __METHOD__, $dbw::ATOMIC_CANCELABLE );
1715 * // Create new record metadata row
1716 * $dbw->insert( 'records', $row, __METHOD__ );
1717 * // Figure out where to store the data based on the new row's ID
1718 * $path = $recordDirectory . '/' . $dbw->insertId();
1719 * // Write the record data to the storage system
1720 * $status = $fileBackend->create( [ 'dst' => $path, 'content' => $data ] );
1721 * if ( $status->isOK() ) {
1722 * // Try to cleanup files orphaned by transaction rollback
1723 * $dbw->onTransactionResolution(
1724 * function ( $type ) use ( $fileBackend, $path ) {
1725 * if ( $type === IDatabase::TRIGGER_ROLLBACK ) {
1726 * $fileBackend->delete( [ 'src' => $path ] );
1731 * // Demark the end of this conceptual unit of updates
1732 * $dbw->endAtomic( __METHOD__ );
1734 * // Discard these writes from the transaction (preserving prior writes)
1735 * $dbw->cancelAtomic( __METHOD__, $sectionId );
1740 * @param string $fname
1741 * @param string $cancelable Pass self::ATOMIC_CANCELABLE to use a
1742 * savepoint and enable self::cancelAtomic() for this section.
1743 * @return AtomicSectionIdentifier section ID token
1746 public function startAtomic( $fname = __METHOD__
, $cancelable = self
::ATOMIC_NOT_CANCELABLE
);
1749 * Ends an atomic section of SQL statements
1751 * Ends the next section of atomic SQL statements and commits the transaction
1755 * @see IDatabase::startAtomic
1756 * @param string $fname
1759 public function endAtomic( $fname = __METHOD__
);
1762 * Cancel an atomic section of SQL statements
1764 * This will roll back only the statements executed since the start of the
1765 * most recent atomic section, and close that section. If a transaction was
1766 * open before the corresponding startAtomic() call, any statements before
1767 * that call are *not* rolled back and the transaction remains open. If the
1768 * corresponding startAtomic() implicitly started a transaction, that
1769 * transaction is rolled back.
1771 * @note callers must use additional measures for situations involving two or more
1772 * (peer) transactions (e.g. updating two database servers at once). The transaction
1773 * and savepoint logic of startAtomic() are bound to specific IDatabase instances.
1775 * Note that a call to IDatabase::rollback() will also roll back any open atomic sections.
1777 * @note As a micro-optimization to save a few DB calls, this method may only
1778 * be called when startAtomic() was called with the ATOMIC_CANCELABLE flag.
1780 * @see IDatabase::startAtomic
1781 * @param string $fname
1782 * @param AtomicSectionIdentifier|null $sectionId Section ID from startAtomic();
1783 * passing this enables cancellation of unclosed nested sections [optional]
1786 public function cancelAtomic( $fname = __METHOD__
, AtomicSectionIdentifier
$sectionId = null );
1789 * Perform an atomic section of reversable SQL statements from a callback
1791 * The $callback takes the following arguments:
1792 * - This database object
1793 * - The value of $fname
1795 * This will execute the callback inside a pair of startAtomic()/endAtomic() calls.
1796 * If any exception occurs during execution of the callback, it will be handled as follows:
1797 * - If $cancelable is ATOMIC_CANCELABLE, cancelAtomic() will be called to back out any
1798 * (and only) statements executed during the atomic section. If that succeeds, then the
1799 * exception will be re-thrown; if it fails, then a different exception will be thrown
1800 * and any further query attempts will fail until rollback() is called.
1801 * - If $cancelable is ATOMIC_NOT_CANCELABLE, cancelAtomic() will be called to mark the
1802 * end of the section and the error will be re-thrown. Any further query attempts will
1803 * fail until rollback() is called.
1805 * This method is convenient for letting calls to the caller of this method be wrapped
1806 * in a try/catch blocks for exception types that imply that the caller failed but was
1807 * able to properly discard the changes it made in the transaction. This method can be
1808 * an alternative to explicit calls to startAtomic()/endAtomic()/cancelAtomic().
1810 * Example usage, "RecordStore::save" method:
1812 * $dbw->doAtomicSection( __METHOD__, function ( $dbw ) use ( $record ) {
1813 * // Create new record metadata row
1814 * $dbw->insert( 'records', $record->toArray(), __METHOD__ );
1815 * // Figure out where to store the data based on the new row's ID
1816 * $path = $this->recordDirectory . '/' . $dbw->insertId();
1817 * // Write the record data to the storage system;
1818 * // blob store throughs StoreFailureException on failure
1819 * $this->blobStore->create( $path, $record->getJSON() );
1820 * // Try to cleanup files orphaned by transaction rollback
1821 * $dbw->onTransactionResolution(
1822 * function ( $type ) use ( $path ) {
1823 * if ( $type === IDatabase::TRIGGER_ROLLBACK ) {
1824 * $this->blobStore->delete( $path );
1829 * }, $dbw::ATOMIC_CANCELABLE );
1832 * Example usage, caller of the "RecordStore::save" method:
1834 * $dbw->startAtomic( __METHOD__ );
1835 * // ...various SQL writes happen...
1837 * $recordStore->save( $record );
1838 * } catch ( StoreFailureException $e ) {
1839 * // ...various SQL writes happen...
1841 * // ...various SQL writes happen...
1842 * $dbw->endAtomic( __METHOD__ );
1845 * @see Database::startAtomic
1846 * @see Database::endAtomic
1847 * @see Database::cancelAtomic
1849 * @param string $fname Caller name (usually __METHOD__)
1850 * @param callable $callback Callback that issues DB updates
1851 * @param string $cancelable Pass self::ATOMIC_CANCELABLE to use a
1852 * savepoint and enable self::cancelAtomic() for this section.
1853 * @return mixed $res Result of the callback (since 1.28)
1855 * @throws RuntimeException
1856 * @since 1.27; prior to 1.31 this did a rollback() instead of
1857 * cancelAtomic(), and assumed no callers up the stack would ever try to
1858 * catch the exception.
1860 public function doAtomicSection(
1861 $fname, callable
$callback, $cancelable = self
::ATOMIC_NOT_CANCELABLE
1865 * Begin a transaction. If a transaction is already in progress,
1866 * that transaction will be committed before the new transaction is started.
1868 * Only call this from code with outer transcation scope.
1869 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1870 * Nesting of transactions is not supported.
1872 * Note that when the DBO_TRX flag is set (which is usually the case for web
1873 * requests, but not for maintenance scripts), any previous database query
1874 * will have started a transaction automatically.
1876 * Nesting of transactions is not supported. Attempts to nest transactions
1877 * will cause a warning, unless the current transaction was started
1878 * automatically because of the DBO_TRX flag.
1880 * @param string $fname Calling function name
1881 * @param string $mode A situationally valid IDatabase::TRANSACTION_* constant [optional]
1884 public function begin( $fname = __METHOD__
, $mode = self
::TRANSACTION_EXPLICIT
);
1887 * Commits a transaction previously started using begin().
1888 * If no transaction is in progress, a warning is issued.
1890 * Only call this from code with outer transcation scope.
1891 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1892 * Nesting of transactions is not supported.
1894 * @param string $fname
1895 * @param string $flush Flush flag, set to situationally valid IDatabase::FLUSHING_*
1896 * constant to disable warnings about explicitly committing implicit transactions,
1897 * or calling commit when no transaction is in progress.
1899 * This will trigger an exception if there is an ongoing explicit transaction.
1901 * Only set the flush flag if you are sure that these warnings are not applicable,
1902 * and no explicit transactions are open.
1906 public function commit( $fname = __METHOD__
, $flush = '' );
1909 * Rollback a transaction previously started using begin().
1910 * If no transaction is in progress, a warning is issued.
1912 * Only call this from code with outer transcation scope.
1913 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1914 * Nesting of transactions is not supported. If a serious unexpected error occurs,
1915 * throwing an Exception is preferrable, using a pre-installed error handler to trigger
1916 * rollback (in any case, failure to issue COMMIT will cause rollback server-side).
1918 * Query, connection, and onTransaction* callback errors will be suppressed and logged.
1920 * @param string $fname Calling function name
1921 * @param string $flush Flush flag, set to a situationally valid IDatabase::FLUSHING_*
1922 * constant to disable warnings about calling rollback when no transaction is in
1923 * progress. This will silently break any ongoing explicit transaction. Only set the
1924 * flush flag if you are sure that it is safe to ignore these warnings in your context.
1926 * @since 1.23 Added $flush parameter
1928 public function rollback( $fname = __METHOD__
, $flush = '' );
1931 * Commit any transaction but error out if writes or callbacks are pending
1933 * This is intended for clearing out REPEATABLE-READ snapshots so that callers can
1934 * see a new point-in-time of the database. This is useful when one of many transaction
1935 * rounds finished and significant time will pass in the script's lifetime. It is also
1936 * useful to call on a replica DB after waiting on replication to catch up to the master.
1938 * @param string $fname Calling function name
1942 public function flushSnapshot( $fname = __METHOD__
);
1945 * Convert a timestamp in one of the formats accepted by wfTimestamp()
1946 * to the format used for inserting into timestamp fields in this DBMS.
1948 * The result is unquoted, and needs to be passed through addQuotes()
1949 * before it can be included in raw SQL.
1951 * @param string|int $ts
1955 public function timestamp( $ts = 0 );
1958 * Convert a timestamp in one of the formats accepted by wfTimestamp()
1959 * to the format used for inserting into timestamp fields in this DBMS. If
1960 * NULL is input, it is passed through, allowing NULL values to be inserted
1961 * into timestamp fields.
1963 * The result is unquoted, and needs to be passed through addQuotes()
1964 * before it can be included in raw SQL.
1966 * @param string|int|null $ts
1970 public function timestampOrNull( $ts = null );
1973 * Ping the server and try to reconnect if it there is no connection
1975 * @param float|null &$rtt Value to store the estimated RTT [optional]
1976 * @return bool Success or failure
1978 public function ping( &$rtt = null );
1981 * Get the amount of replication lag for this database server
1983 * Callers should avoid using this method while a transaction is active
1985 * @return int|bool Database replication lag in seconds or false on error
1988 public function getLag();
1991 * Get the replica DB lag when the current transaction started
1992 * or a general lag estimate if not transaction is active
1994 * This is useful when transactions might use snapshot isolation
1995 * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
1996 * is this lag plus transaction duration. If they don't, it is still
1997 * safe to be pessimistic. In AUTOCOMMIT mode, this still gives an
1998 * indication of the staleness of subsequent reads.
2000 * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
2004 public function getSessionLagStatus();
2007 * Return the maximum number of items allowed in a list, or 0 for unlimited.
2011 public function maxListLen();
2014 * Some DBMSs have a special format for inserting into blob fields, they
2015 * don't allow simple quoted strings to be inserted. To insert into such
2016 * a field, pass the data through this function before passing it to
2017 * IDatabase::insert().
2020 * @return string|Blob
2022 public function encodeBlob( $b );
2025 * Some DBMSs return a special placeholder object representing blob fields
2026 * in result objects. Pass the object through this function to return the
2029 * @param string|Blob $b
2032 public function decodeBlob( $b );
2035 * Override database's default behavior. $options include:
2036 * 'connTimeout' : Set the connection timeout value in seconds.
2037 * May be useful for very long batch queries such as
2038 * full-wiki dumps, where a single query reads out over
2041 * @param array $options
2045 public function setSessionOptions( array $options );
2048 * Set variables to be used in sourceFile/sourceStream, in preference to the
2049 * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
2050 * all. If it's set to false, $GLOBALS will be used.
2052 * @param bool|array $vars Mapping variable name to value.
2054 public function setSchemaVars( $vars );
2057 * Check to see if a named lock is not locked by any thread (non-blocking)
2059 * @param string $lockName Name of lock to poll
2060 * @param string $method Name of method calling us
2065 public function lockIsFree( $lockName, $method );
2068 * Acquire a named lock
2070 * Named locks are not related to transactions
2072 * @param string $lockName Name of lock to aquire
2073 * @param string $method Name of the calling method
2074 * @param int $timeout Acquisition timeout in seconds
2078 public function lock( $lockName, $method, $timeout = 5 );
2083 * Named locks are not related to transactions
2085 * @param string $lockName Name of lock to release
2086 * @param string $method Name of the calling method
2088 * @return int Returns 1 if the lock was released, 0 if the lock was not established
2089 * by this thread (in which case the lock is not released), and NULL if the named lock
2094 public function unlock( $lockName, $method );
2097 * Acquire a named lock, flush any transaction, and return an RAII style unlocker object
2099 * Only call this from outer transcation scope and when only one DB will be affected.
2100 * See https://www.mediawiki.org/wiki/Database_transactions for details.
2102 * This is suitiable for transactions that need to be serialized using cooperative locks,
2103 * where each transaction can see each others' changes. Any transaction is flushed to clear
2104 * out stale REPEATABLE-READ snapshot data. Once the returned object falls out of PHP scope,
2105 * the lock will be released unless a transaction is active. If one is active, then the lock
2106 * will be released when it either commits or rolls back.
2108 * If the lock acquisition failed, then no transaction flush happens, and null is returned.
2110 * @param string $lockKey Name of lock to release
2111 * @param string $fname Name of the calling method
2112 * @param int $timeout Acquisition timeout in seconds
2113 * @return ScopedCallback|null
2117 public function getScopedLockAndFlush( $lockKey, $fname, $timeout );
2120 * Check to see if a named lock used by lock() use blocking queues
2125 public function namedLocksEnqueue();
2128 * Find out when 'infinity' is. Most DBMSes support this. This is a special
2129 * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
2130 * because "i" sorts after all numbers.
2134 public function getInfinity();
2137 * Encode an expiry time into the DBMS dependent format
2139 * @param string $expiry Timestamp for expiry, or the 'infinity' string
2142 public function encodeExpiry( $expiry );
2145 * Decode an expiry time into a DBMS independent format
2147 * @param string $expiry DB timestamp field value for expiry
2148 * @param int $format TS_* constant, defaults to TS_MW
2151 public function decodeExpiry( $expiry, $format = TS_MW
);
2154 * Allow or deny "big selects" for this session only. This is done by setting
2155 * the sql_big_selects session variable.
2157 * This is a MySQL-specific feature.
2159 * @param bool|string $value True for allow, false for deny, or "default" to
2160 * restore the initial value
2162 public function setBigSelects( $value = true );
2165 * @return bool Whether this DB is read-only
2168 public function isReadOnly();
2171 * Make certain table names use their own database, schema, and table prefix
2172 * when passed into SQL queries pre-escaped and without a qualified database name
2174 * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
2175 * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
2177 * Calling this twice will completely clear any old table aliases. Also, note that
2178 * callers are responsible for making sure the schemas and databases actually exist.
2180 * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
2183 public function setTableAliases( array $aliases );
2186 * Convert certain index names to alternative names before querying the DB
2188 * Note that this applies to indexes regardless of the table they belong to.
2190 * This can be employed when an index was renamed X => Y in code, but the new Y-named
2191 * indexes were not yet built on all DBs. After all the Y-named ones are added by the DBA,
2192 * the aliases can be removed, and then the old X-named indexes dropped.
2194 * @param string[] $aliases
2197 public function setIndexAliases( array $aliases );
2201 * @deprecated since 1.29
2203 class_alias( IDatabase
::class, 'IDatabase' );