b82603e737d0854ff2a2e3d3ae7c48465c277f03
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
210 public function implicitGroupby();
213 * Returns true if this database does an implicit order by when the column has an index
214 * For example: SELECT page_title FROM page LIMIT 1
218 public function implicitOrderby();
221 * Return the last query that went through IDatabase::query()
224 public function lastQuery();
227 * Returns true if the connection may have been used for write queries.
228 * Should return true if unsure.
232 public function doneWrites();
235 * Returns the last time the connection may have been used for write queries.
236 * Should return a timestamp if unsure.
238 * @return int|float UNIX timestamp or false
241 public function lastDoneWrites();
244 * @return bool Whether there is a transaction open with possible write queries
247 public function writesPending();
250 * Returns true if there is a transaction open with possible write
251 * queries or transaction pre-commit/idle callbacks waiting on it to finish.
252 * This does *not* count recurring callbacks, e.g. from setTransactionListener().
256 public function writesOrCallbacksPending();
259 * Get the time spend running write queries for this transaction
261 * High times could be due to scanning, updates, locking, and such
263 * @param string $type IDatabase::ESTIMATE_* constant [default: ESTIMATE_ALL]
264 * @return float|bool Returns false if not transaction is active
267 public function pendingWriteQueryDuration( $type = self
::ESTIMATE_TOTAL
);
270 * Get the list of method names that did write queries for this transaction
275 public function pendingWriteCallers();
278 * Get the number of affected rows from pending write queries
283 public function pendingWriteRowsAffected();
286 * Is a connection to the database open?
289 public function isOpen();
292 * Set a flag for this connection
294 * @param int $flag DBO_* constants from Defines.php:
295 * - DBO_DEBUG: output some debug info (same as debug())
296 * - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
297 * - DBO_TRX: automatically start transactions
298 * - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
299 * and removes it in command line mode
300 * - DBO_PERSISTENT: use persistant database connection
301 * @param string $remember IDatabase::REMEMBER_* constant [default: REMEMBER_NOTHING]
303 public function setFlag( $flag, $remember = self
::REMEMBER_NOTHING
);
306 * Clear a flag for this connection
308 * @param int $flag DBO_* constants from Defines.php:
309 * - DBO_DEBUG: output some debug info (same as debug())
310 * - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
311 * - DBO_TRX: automatically start transactions
312 * - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
313 * and removes it in command line mode
314 * - DBO_PERSISTENT: use persistant database connection
315 * @param string $remember IDatabase::REMEMBER_* constant [default: REMEMBER_NOTHING]
317 public function clearFlag( $flag, $remember = self
::REMEMBER_NOTHING
);
320 * Restore the flags to their prior state before the last setFlag/clearFlag call
322 * @param string $state IDatabase::RESTORE_* constant. [default: RESTORE_PRIOR]
325 public function restoreFlags( $state = self
::RESTORE_PRIOR
);
328 * Returns a boolean whether the flag $flag is set for this connection
330 * @param int $flag DBO_* constants from Defines.php:
331 * - DBO_DEBUG: output some debug info (same as debug())
332 * - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
333 * - DBO_TRX: automatically start transactions
334 * - DBO_PERSISTENT: use persistant database connection
337 public function getFlag( $flag );
342 public function getDomainID();
345 * Alias for getDomainID()
349 public function getWikiID();
352 * Get the type of the DBMS, as it appears in $wgDBtype.
356 public function getType();
359 * Open a connection to the database. Usually aborts on failure
361 * @param string $server Database server host
362 * @param string $user Database user name
363 * @param string $password Database user password
364 * @param string $dbName Database name
366 * @throws DBConnectionError
368 public function open( $server, $user, $password, $dbName );
371 * Fetch the next row from the given result object, in object form.
372 * Fields can be retrieved with $row->fieldname, with fields acting like
374 * If no more rows are available, false is returned.
376 * @param IResultWrapper|stdClass $res Object as returned from IDatabase::query(), etc.
377 * @return stdClass|bool
378 * @throws DBUnexpectedError Thrown if the database returns an error
380 public function fetchObject( $res );
383 * Fetch the next row from the given result object, in associative array
384 * form. Fields are retrieved with $row['fieldname'].
385 * If no more rows are available, false is returned.
387 * @param IResultWrapper $res Result object as returned from IDatabase::query(), etc.
389 * @throws DBUnexpectedError Thrown if the database returns an error
391 public function fetchRow( $res );
394 * Get the number of rows in a result object
396 * @param mixed $res A SQL result
399 public function numRows( $res );
402 * Get the number of fields in a result object
403 * @see https://secure.php.net/mysql_num_fields
405 * @param mixed $res A SQL result
408 public function numFields( $res );
411 * Get a field name in a result object
412 * @see https://secure.php.net/mysql_field_name
414 * @param mixed $res A SQL result
418 public function fieldName( $res, $n );
421 * Get the inserted value of an auto-increment row
423 * The value inserted should be fetched from nextSequenceValue()
426 * $id = $dbw->nextSequenceValue( 'page_page_id_seq' );
427 * $dbw->insert( 'page', [ 'page_id' => $id ] );
428 * $id = $dbw->insertId();
432 public function insertId();
435 * Change the position of the cursor in a result object
436 * @see https://secure.php.net/mysql_data_seek
438 * @param mixed $res A SQL result
441 public function dataSeek( $res, $row );
444 * Get the last error number
445 * @see https://secure.php.net/mysql_errno
449 public function lastErrno();
452 * Get a description of the last error
453 * @see https://secure.php.net/mysql_error
457 public function lastError();
460 * mysql_fetch_field() wrapper
461 * Returns false if the field doesn't exist
463 * @param string $table Table name
464 * @param string $field Field name
468 public function fieldInfo( $table, $field );
471 * Get the number of rows affected by the last write query
472 * @see https://secure.php.net/mysql_affected_rows
476 public function affectedRows();
479 * Returns a wikitext link to the DB's website, e.g.,
480 * return "[https://www.mysql.com/ MySQL]";
481 * Should at least contain plain text, if for some reason
482 * your database has no website.
484 * @return string Wikitext of a link to the server software's web site
486 public function getSoftwareLink();
489 * A string describing the current software version, like from
490 * mysql_get_server_info().
492 * @return string Version information from the database server.
494 public function getServerVersion();
497 * Closes a database connection.
498 * if it is open : commits any open transactions
501 * @return bool Operation success. true if already closed.
503 public function close();
506 * @param string $error Fallback error message, used if none is given by DB
507 * @throws DBConnectionError
509 public function reportConnectionError( $error = 'Unknown error' );
512 * Run an SQL query and return the result. Normally throws a DBQueryError
513 * on failure. If errors are ignored, returns false instead.
515 * In new code, the query wrappers select(), insert(), update(), delete(),
516 * etc. should be used where possible, since they give much better DBMS
517 * independence and automatically quote or validate user input in a variety
518 * of contexts. This function is generally only useful for queries which are
519 * explicitly DBMS-dependent and are unsupported by the query wrappers, such
522 * However, the query wrappers themselves should call this function.
524 * @param string $sql SQL query
525 * @param string $fname Name of the calling function, for profiling/SHOW PROCESSLIST
526 * comment (you can use __METHOD__ or add some extra info)
527 * @param bool $tempIgnore Whether to avoid throwing an exception on errors...
528 * maybe best to catch the exception instead?
530 * @return bool|IResultWrapper True for a successful write query, IResultWrapper object
531 * for a successful read query, or false on failure if $tempIgnore set
533 public function query( $sql, $fname = __METHOD__
, $tempIgnore = false );
536 * Report a query error. Log the error, and if neither the object ignore
537 * flag nor the $tempIgnore flag is set, throw a DBQueryError.
539 * @param string $error
542 * @param string $fname
543 * @param bool $tempIgnore
544 * @throws DBQueryError
546 public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false );
549 * Free a result object returned by query() or select(). It's usually not
550 * necessary to call this, just use unset() or let the variable holding
551 * the result object go out of scope.
553 * @param mixed $res A SQL result
555 public function freeResult( $res );
558 * A SELECT wrapper which returns a single field from a single result row.
560 * Usually throws a DBQueryError on failure. If errors are explicitly
561 * ignored, returns false on failure.
563 * If no result rows are returned from the query, false is returned.
565 * @param string|array $table Table name. See IDatabase::select() for details.
566 * @param string $var The field name to select. This must be a valid SQL
567 * fragment: do not use unvalidated user input.
568 * @param string|array $cond The condition array. See IDatabase::select() for details.
569 * @param string $fname The function name of the caller.
570 * @param string|array $options The query options. See IDatabase::select() for details.
571 * @param string|array $join_conds The query join conditions. See IDatabase::select() for details.
573 * @return bool|mixed The value from the field, or false on failure.
575 public function selectField(
576 $table, $var, $cond = '', $fname = __METHOD__
, $options = [], $join_conds = []
580 * A SELECT wrapper which returns a list of single field values from result rows.
582 * Usually throws a DBQueryError on failure. If errors are explicitly
583 * ignored, returns false on failure.
585 * If no result rows are returned from the query, false is returned.
587 * @param string|array $table Table name. See IDatabase::select() for details.
588 * @param string $var The field name to select. This must be a valid SQL
589 * fragment: do not use unvalidated user input.
590 * @param string|array $cond The condition array. See IDatabase::select() for details.
591 * @param string $fname The function name of the caller.
592 * @param string|array $options The query options. See IDatabase::select() for details.
593 * @param string|array $join_conds The query join conditions. See IDatabase::select() for details.
595 * @return bool|array The values from the field, or false on failure
598 public function selectFieldValues(
599 $table, $var, $cond = '', $fname = __METHOD__
, $options = [], $join_conds = []
603 * Execute a SELECT query constructed using the various parameters provided.
604 * See below for full details of the parameters.
606 * @param string|array $table Table name
607 * @param string|array $vars Field names
608 * @param string|array $conds Conditions
609 * @param string $fname Caller function name
610 * @param array $options Query options
611 * @param array $join_conds Join conditions
614 * @param string|array $table
616 * May be either an array of table names, or a single string holding a table
617 * name. If an array is given, table aliases can be specified, for example:
621 * This includes the user table in the query, with the alias "a" available
622 * for use in field names (e.g. a.user_name).
624 * All of the table names given here are automatically run through
625 * Database::tableName(), which causes the table prefix (if any) to be
626 * added, and various other table name mappings to be performed.
628 * Do not use untrusted user input as a table name. Alias names should
629 * not have characters outside of the Basic multilingual plane.
631 * @param string|array $vars
633 * May be either a field name or an array of field names. The field names
634 * can be complete fragments of SQL, for direct inclusion into the SELECT
635 * query. If an array is given, field aliases can be specified, for example:
637 * [ 'maxrev' => 'MAX(rev_id)' ]
639 * This includes an expression with the alias "maxrev" in the query.
641 * If an expression is given, care must be taken to ensure that it is
644 * Untrusted user input must not be passed to this parameter.
646 * @param string|array $conds
648 * May be either a string containing a single condition, or an array of
649 * conditions. If an array is given, the conditions constructed from each
650 * element are combined with AND.
652 * Array elements may take one of two forms:
654 * - Elements with a numeric key are interpreted as raw SQL fragments.
655 * - Elements with a string key are interpreted as equality conditions,
656 * where the key is the field name.
657 * - If the value of such an array element is a scalar (such as a
658 * string), it will be treated as data and thus quoted appropriately.
659 * If it is null, an IS NULL clause will be added.
660 * - If the value is an array, an IN (...) clause will be constructed
661 * from its non-null elements, and an IS NULL clause will be added
662 * if null is present, such that the field may match any of the
663 * elements in the array. The non-null elements will be quoted.
665 * Note that expressions are often DBMS-dependent in their syntax.
666 * DBMS-independent wrappers are provided for constructing several types of
667 * expression commonly used in condition queries. See:
668 * - IDatabase::buildLike()
669 * - IDatabase::conditional()
671 * Untrusted user input is safe in the values of string keys, however untrusted
672 * input must not be used in the array key names or in the values of numeric keys.
673 * Escaping of untrusted input used in values of numeric keys should be done via
674 * IDatabase::addQuotes()
676 * @param string|array $options
678 * Optional: Array of query options. Boolean options are specified by
679 * including them in the array as a string value with a numeric key, for
684 * The supported options are:
686 * - OFFSET: Skip this many rows at the start of the result set. OFFSET
687 * with LIMIT can theoretically be used for paging through a result set,
688 * but this is discouraged for performance reasons.
690 * - LIMIT: Integer: return at most this many rows. The rows are sorted
691 * and then the first rows are taken until the limit is reached. LIMIT
692 * is applied to a result set after OFFSET.
694 * - FOR UPDATE: Boolean: lock the returned rows so that they can't be
695 * changed until the next COMMIT.
697 * - DISTINCT: Boolean: return only unique result rows.
699 * - GROUP BY: May be either an SQL fragment string naming a field or
700 * expression to group by, or an array of such SQL fragments.
702 * - HAVING: May be either an string containing a HAVING clause or an array of
703 * conditions building the HAVING clause. If an array is given, the conditions
704 * constructed from each element are combined with AND.
706 * - ORDER BY: May be either an SQL fragment giving a field name or
707 * expression to order by, or an array of such SQL fragments.
709 * - USE INDEX: This may be either a string giving the index name to use
710 * for the query, or an array. If it is an associative array, each key
711 * gives the table name (or alias), each value gives the index name to
712 * use for that table. All strings are SQL fragments and so should be
713 * validated by the caller.
715 * - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
718 * And also the following boolean MySQL extensions, see the MySQL manual
721 * - LOCK IN SHARE MODE
725 * - SQL_BUFFER_RESULT
727 * - SQL_CALC_FOUND_ROWS
732 * @param string|array $join_conds
734 * Optional associative array of table-specific join conditions. In the
735 * most common case, this is unnecessary, since the join condition can be
736 * in $conds. However, it is useful for doing a LEFT JOIN.
738 * The key of the array contains the table name or alias. The value is an
739 * array with two elements, numbered 0 and 1. The first gives the type of
740 * join, the second is the same as the $conds parameter. Thus it can be
741 * an SQL fragment, or an array where the string keys are equality and the
742 * numeric keys are SQL fragments all AND'd together. For example:
744 * [ 'page' => [ 'LEFT JOIN', 'page_latest=rev_id' ] ]
746 * @return IResultWrapper|bool If the query returned no rows, a IResultWrapper
747 * with no rows in it will be returned. If there was a query error, a
748 * DBQueryError exception will be thrown, except if the "ignore errors"
749 * option was set, in which case false will be returned.
751 public function select(
752 $table, $vars, $conds = '', $fname = __METHOD__
,
753 $options = [], $join_conds = []
757 * The equivalent of IDatabase::select() except that the constructed SQL
758 * is returned, instead of being immediately executed. This can be useful for
759 * doing UNION queries, where the SQL text of each query is needed. In general,
760 * however, callers outside of Database classes should just use select().
762 * @param string|array $table Table name
763 * @param string|array $vars Field names
764 * @param string|array $conds Conditions
765 * @param string $fname Caller function name
766 * @param string|array $options Query options
767 * @param string|array $join_conds Join conditions
769 * @return string SQL query string.
770 * @see IDatabase::select()
772 public function selectSQLText(
773 $table, $vars, $conds = '', $fname = __METHOD__
,
774 $options = [], $join_conds = []
778 * Single row SELECT wrapper. Equivalent to IDatabase::select(), except
779 * that a single row object is returned. If the query returns no rows,
782 * @param string|array $table Table name
783 * @param string|array $vars Field names
784 * @param array $conds Conditions
785 * @param string $fname Caller function name
786 * @param string|array $options Query options
787 * @param array|string $join_conds Join conditions
789 * @return stdClass|bool
791 public function selectRow( $table, $vars, $conds, $fname = __METHOD__
,
792 $options = [], $join_conds = []
796 * Estimate the number of rows in dataset
798 * MySQL allows you to estimate the number of rows that would be returned
799 * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
800 * index cardinality statistics, and is notoriously inaccurate, especially
801 * when large numbers of rows have recently been added or deleted.
803 * For DBMSs that don't support fast result size estimation, this function
804 * will actually perform the SELECT COUNT(*).
806 * Takes the same arguments as IDatabase::select().
808 * @param string $table Table name
809 * @param string $vars Unused
810 * @param array|string $conds Filters on the table
811 * @param string $fname Function name for profiling
812 * @param array $options Options for select
813 * @return int Row count
815 public function estimateRowCount(
816 $table, $vars = '*', $conds = '', $fname = __METHOD__
, $options = []
820 * Get the number of rows in dataset
822 * This is useful when trying to do COUNT(*) but with a LIMIT for performance.
824 * Takes the same arguments as IDatabase::select().
826 * @since 1.27 Added $join_conds parameter
828 * @param array|string $tables Table names
829 * @param string $vars Unused
830 * @param array|string $conds Filters on the table
831 * @param string $fname Function name for profiling
832 * @param array $options Options for select
833 * @param array $join_conds Join conditions (since 1.27)
834 * @return int Row count
836 public function selectRowCount(
837 $tables, $vars = '*', $conds = '', $fname = __METHOD__
, $options = [], $join_conds = []
841 * Determines whether a field exists in a table
843 * @param string $table Table name
844 * @param string $field Filed to check on that table
845 * @param string $fname Calling function name (optional)
846 * @return bool Whether $table has filed $field
848 public function fieldExists( $table, $field, $fname = __METHOD__
);
851 * Determines whether an index exists
852 * Usually throws a DBQueryError on failure
853 * If errors are explicitly ignored, returns NULL on failure
855 * @param string $table
856 * @param string $index
857 * @param string $fname
860 public function indexExists( $table, $index, $fname = __METHOD__
);
863 * Query whether a given table exists
865 * @param string $table
866 * @param string $fname
869 public function tableExists( $table, $fname = __METHOD__
);
872 * Determines if a given index is unique
874 * @param string $table
875 * @param string $index
879 public function indexUnique( $table, $index );
882 * INSERT wrapper, inserts an array into a table.
886 * - A single associative array. The array keys are the field names, and
887 * the values are the values to insert. The values are treated as data
888 * and will be quoted appropriately. If NULL is inserted, this will be
889 * converted to a database NULL.
890 * - An array with numeric keys, holding a list of associative arrays.
891 * This causes a multi-row INSERT on DBMSs that support it. The keys in
892 * each subarray must be identical to each other, and in the same order.
894 * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
897 * $options is an array of options, with boolean options encoded as values
898 * with numeric keys, in the same style as $options in
899 * IDatabase::select(). Supported options are:
901 * - IGNORE: Boolean: if present, duplicate key errors are ignored, and
902 * any rows which cause duplicate key errors are not inserted. It's
903 * possible to determine how many rows were successfully inserted using
904 * IDatabase::affectedRows().
906 * @param string $table Table name. This will be passed through
907 * Database::tableName().
908 * @param array $a Array of rows to insert
909 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
910 * @param array $options Array of options
914 public function insert( $table, $a, $fname = __METHOD__
, $options = [] );
917 * UPDATE wrapper. Takes a condition array and a SET array.
919 * @param string $table Name of the table to UPDATE. This will be passed through
920 * Database::tableName().
921 * @param array $values An array of values to SET. For each array element,
922 * the key gives the field name, and the value gives the data to set
923 * that field to. The data will be quoted by IDatabase::addQuotes().
924 * Values with integer keys form unquoted SET statements, which can be used for
925 * things like "field = field + 1" or similar computed values.
926 * @param array $conds An array of conditions (WHERE). See
927 * IDatabase::select() for the details of the format of condition
928 * arrays. Use '*' to update all rows.
929 * @param string $fname The function name of the caller (from __METHOD__),
930 * for logging and profiling.
931 * @param array $options An array of UPDATE options, can be:
932 * - IGNORE: Ignore unique key conflicts
933 * - LOW_PRIORITY: MySQL-specific, see MySQL manual.
936 public function update( $table, $values, $conds, $fname = __METHOD__
, $options = [] );
939 * Makes an encoded list of strings from an array
941 * These can be used to make conjunctions or disjunctions on SQL condition strings
942 * derived from an array (see IDatabase::select() $conds documentation).
946 * $sql = $db->makeList( [
948 * $db->makeList( [ 'rev_minor' => 1, 'rev_len' < 500 ], $db::LIST_OR ] )
949 * ], $db::LIST_AND );
951 * This would set $sql to "rev_user = '$id' AND (rev_minor = '1' OR rev_len < '500')"
953 * @param array $a Containing the data
954 * @param int $mode IDatabase class constant:
955 * - IDatabase::LIST_COMMA: Comma separated, no field names
956 * - IDatabase::LIST_AND: ANDed WHERE clause (without the WHERE).
957 * - IDatabase::LIST_OR: ORed WHERE clause (without the WHERE)
958 * - IDatabase::LIST_SET: Comma separated with field names, like a SET clause
959 * - IDatabase::LIST_NAMES: Comma separated field names
963 public function makeList( $a, $mode = self
::LIST_COMMA
);
966 * Build a partial where clause from a 2-d array such as used for LinkBatch.
967 * The keys on each level may be either integers or strings.
969 * @param array $data Organized as 2-d
970 * [ baseKeyVal => [ subKeyVal => [ignored], ... ], ... ]
971 * @param string $baseKey Field name to match the base-level keys to (eg 'pl_namespace')
972 * @param string $subKey Field name to match the sub-level keys to (eg 'pl_title')
973 * @return string|bool SQL fragment, or false if no items in array
975 public function makeWhereFrom2d( $data, $baseKey, $subKey );
978 * Return aggregated value alias
980 * @param array $valuedata
981 * @param string $valuename
985 public function aggregateValue( $valuedata, $valuename = 'value' );
988 * @param string $field
991 public function bitNot( $field );
994 * @param string $fieldLeft
995 * @param string $fieldRight
998 public function bitAnd( $fieldLeft, $fieldRight );
1001 * @param string $fieldLeft
1002 * @param string $fieldRight
1005 public function bitOr( $fieldLeft, $fieldRight );
1008 * Build a concatenation list to feed into a SQL query
1009 * @param array $stringList List of raw SQL expressions; caller is
1010 * responsible for any quoting
1013 public function buildConcat( $stringList );
1016 * Build a GROUP_CONCAT or equivalent statement for a query.
1018 * This is useful for combining a field for several rows into a single string.
1019 * NULL values will not appear in the output, duplicated values will appear,
1020 * and the resulting delimiter-separated values have no defined sort order.
1021 * Code using the results may need to use the PHP unique() or sort() methods.
1023 * @param string $delim Glue to bind the results together
1024 * @param string|array $table Table name
1025 * @param string $field Field name
1026 * @param string|array $conds Conditions
1027 * @param string|array $join_conds Join conditions
1028 * @return string SQL text
1031 public function buildGroupConcatField(
1032 $delim, $table, $field, $conds = '', $join_conds = []
1036 * @param string $field Field or column to cast
1040 public function buildStringCast( $field );
1043 * Returns true if DBs are assumed to be on potentially different servers
1045 * In systems like mysql/mariadb, different databases can easily be referenced on a single
1046 * connection merely by name, even in a single query via JOIN. On the other hand, Postgres
1047 * treats databases as fully separate, only allowing mechanisms like postgres_fdw to
1048 * effectively "mount" foreign DBs. This is true even among DBs on the same server.
1053 public function databasesAreIndependent();
1056 * Change the current database
1059 * @return bool Success or failure
1060 * @throws DBConnectionError If databasesAreIndependent() is true and an error occurs
1062 public function selectDB( $db );
1065 * Get the current DB name
1068 public function getDBname();
1071 * Get the server hostname or IP address
1074 public function getServer();
1077 * Adds quotes and backslashes.
1079 * @param string|int|null|bool|Blob $s
1080 * @return string|int
1082 public function addQuotes( $s );
1085 * LIKE statement wrapper, receives a variable-length argument list with
1086 * parts of pattern to match containing either string literals that will be
1087 * escaped or tokens returned by anyChar() or anyString(). Alternatively,
1088 * the function could be provided with an array of aforementioned
1091 * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns
1092 * a LIKE clause that searches for subpages of 'My page title'.
1094 * $pattern = [ 'My_page_title/', $dbr->anyString() ];
1095 * $query .= $dbr->buildLike( $pattern );
1098 * @return string Fully built LIKE statement
1100 public function buildLike();
1103 * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
1107 public function anyChar();
1110 * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
1114 public function anyString();
1117 * Returns an appropriately quoted sequence value for inserting a new row.
1118 * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
1119 * subclass will return an integer, and save the value for insertId()
1121 * Any implementation of this function should *not* involve reusing
1122 * sequence numbers created for rolled-back transactions.
1123 * See https://bugs.mysql.com/bug.php?id=30767 for details.
1124 * @param string $seqName
1127 public function nextSequenceValue( $seqName );
1130 * REPLACE query wrapper.
1132 * REPLACE is a very handy MySQL extension, which functions like an INSERT
1133 * except that when there is a duplicate key error, the old row is deleted
1134 * and the new row is inserted in its place.
1136 * We simulate this with standard SQL with a DELETE followed by INSERT. To
1137 * perform the delete, we need to know what the unique indexes are so that
1138 * we know how to find the conflicting rows.
1140 * It may be more efficient to leave off unique indexes which are unlikely
1141 * to collide. However if you do this, you run the risk of encountering
1142 * errors which wouldn't have occurred in MySQL.
1144 * @param string $table The table to replace the row(s) in.
1145 * @param array $uniqueIndexes Is an array of indexes. Each element may be either
1146 * a field name or an array of field names
1147 * @param array $rows Can be either a single row to insert, or multiple rows,
1148 * in the same format as for IDatabase::insert()
1149 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1151 public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__
);
1154 * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
1156 * This updates any conflicting rows (according to the unique indexes) using
1157 * the provided SET clause and inserts any remaining (non-conflicted) rows.
1159 * $rows may be either:
1160 * - A single associative array. The array keys are the field names, and
1161 * the values are the values to insert. The values are treated as data
1162 * and will be quoted appropriately. If NULL is inserted, this will be
1163 * converted to a database NULL.
1164 * - An array with numeric keys, holding a list of associative arrays.
1165 * This causes a multi-row INSERT on DBMSs that support it. The keys in
1166 * each subarray must be identical to each other, and in the same order.
1168 * It may be more efficient to leave off unique indexes which are unlikely
1169 * to collide. However if you do this, you run the risk of encountering
1170 * errors which wouldn't have occurred in MySQL.
1172 * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1177 * @param string $table Table name. This will be passed through Database::tableName().
1178 * @param array $rows A single row or list of rows to insert
1179 * @param array $uniqueIndexes List of single field names or field name tuples
1180 * @param array $set An array of values to SET. For each array element, the
1181 * key gives the field name, and the value gives the data to set that
1182 * field to. The data will be quoted by IDatabase::addQuotes().
1183 * Values with integer keys form unquoted SET statements, which can be used for
1184 * things like "field = field + 1" or similar computed values.
1185 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1189 public function upsert(
1190 $table, array $rows, array $uniqueIndexes, array $set, $fname = __METHOD__
1194 * DELETE where the condition is a join.
1196 * MySQL overrides this to use a multi-table DELETE syntax, in other databases
1197 * we use sub-selects
1199 * For safety, an empty $conds will not delete everything. If you want to
1200 * delete all rows where the join condition matches, set $conds='*'.
1202 * DO NOT put the join condition in $conds.
1204 * @param string $delTable The table to delete from.
1205 * @param string $joinTable The other table.
1206 * @param string $delVar The variable to join on, in the first table.
1207 * @param string $joinVar The variable to join on, in the second table.
1208 * @param array $conds Condition array of field names mapped to variables,
1209 * ANDed together in the WHERE clause
1210 * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1211 * @throws DBUnexpectedError
1213 public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
1218 * DELETE query wrapper.
1220 * @param string $table Table name
1221 * @param string|array $conds Array of conditions. See $conds in IDatabase::select()
1222 * for the format. Use $conds == "*" to delete all rows
1223 * @param string $fname Name of the calling function
1224 * @throws DBUnexpectedError
1225 * @return bool|IResultWrapper
1227 public function delete( $table, $conds, $fname = __METHOD__
);
1230 * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
1231 * into another table.
1233 * @param string $destTable The table name to insert into
1234 * @param string|array $srcTable May be either a table name, or an array of table names
1235 * to include in a join.
1237 * @param array $varMap Must be an associative array of the form
1238 * [ 'dest1' => 'source1', ... ]. Source items may be literals
1239 * rather than field names, but strings should be quoted with
1240 * IDatabase::addQuotes()
1242 * @param array $conds Condition array. See $conds in IDatabase::select() for
1243 * the details of the format of condition arrays. May be "*" to copy the
1246 * @param string $fname The function name of the caller, from __METHOD__
1248 * @param array $insertOptions Options for the INSERT part of the query, see
1249 * IDatabase::insert() for details.
1250 * @param array $selectOptions Options for the SELECT part of the query, see
1251 * IDatabase::select() for details.
1252 * @param array $selectJoinConds Join conditions for the SELECT part of the query, see
1253 * IDatabase::select() for details.
1257 public function insertSelect( $destTable, $srcTable, $varMap, $conds,
1258 $fname = __METHOD__
,
1259 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
1263 * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
1264 * within the UNION construct.
1267 public function unionSupportsOrderAndLimit();
1270 * Construct a UNION query
1271 * This is used for providing overload point for other DB abstractions
1272 * not compatible with the MySQL syntax.
1273 * @param array $sqls SQL statements to combine
1274 * @param bool $all Use UNION ALL
1275 * @return string SQL fragment
1277 public function unionQueries( $sqls, $all );
1280 * Construct a UNION query for permutations of conditions
1282 * Databases sometimes have trouble with queries that have multiple values
1283 * for multiple condition parameters combined with limits and ordering.
1284 * This method constructs queries for the Cartesian product of the
1285 * conditions and unions them all together.
1287 * @see IDatabase::select()
1289 * @param string|array $table Table name
1290 * @param string|array $vars Field names
1291 * @param array $permute_conds Conditions for the Cartesian product. Keys
1292 * are field names, values are arrays of the possible values for that
1294 * @param string|array $extra_conds Additional conditions to include in the
1296 * @param string $fname Caller function name
1297 * @param string|array $options Query options. In addition to the options
1298 * recognized by IDatabase::select(), the following may be used:
1299 * - NOTALL: Set to use UNION instead of UNION ALL.
1300 * - INNER ORDER BY: If specified and supported, subqueries will use this
1301 * instead of ORDER BY.
1302 * @param string|array $join_conds Join conditions
1303 * @return string SQL query string.
1305 public function unionConditionPermutations(
1306 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__
,
1307 $options = [], $join_conds = []
1311 * Returns an SQL expression for a simple conditional. This doesn't need
1312 * to be overridden unless CASE isn't supported in your DBMS.
1314 * @param string|array $cond SQL expression which will result in a boolean value
1315 * @param string $trueVal SQL expression to return if true
1316 * @param string $falseVal SQL expression to return if false
1317 * @return string SQL fragment
1319 public function conditional( $cond, $trueVal, $falseVal );
1322 * Returns a command for str_replace function in SQL query.
1323 * Uses REPLACE() in MySQL
1325 * @param string $orig Column to modify
1326 * @param string $old Column to seek
1327 * @param string $new Column to replace with
1331 public function strreplace( $orig, $old, $new );
1334 * Determines how long the server has been up
1338 public function getServerUptime();
1341 * Determines if the last failure was due to a deadlock
1345 public function wasDeadlock();
1348 * Determines if the last failure was due to a lock timeout
1352 public function wasLockTimeout();
1355 * Determines if the last query error was due to a dropped connection and should
1356 * be dealt with by pinging the connection and reissuing the query.
1360 public function wasErrorReissuable();
1363 * Determines if the last failure was due to the database being read-only.
1367 public function wasReadOnlyError();
1370 * Wait for the replica DB to catch up to a given master position
1372 * @param DBMasterPos $pos
1373 * @param int $timeout The maximum number of seconds to wait for synchronisation
1374 * @return int|null Zero if the replica DB was past that position already,
1375 * greater than zero if we waited for some period of time, less than
1376 * zero if it timed out, and null on error
1378 public function masterPosWait( DBMasterPos
$pos, $timeout );
1381 * Get the replication position of this replica DB
1383 * @return DBMasterPos|bool False if this is not a replica DB.
1385 public function getReplicaPos();
1388 * Get the position of this master
1390 * @return DBMasterPos|bool False if this is not a master
1392 public function getMasterPos();
1395 * @return bool Whether the DB is marked as read-only server-side
1398 public function serverIsReadOnly();
1401 * Run a callback as soon as the current transaction commits or rolls back.
1402 * An error is thrown if no transaction is pending. Queries in the function will run in
1403 * AUTO-COMMIT mode unless there are begin() calls. Callbacks must commit any transactions
1406 * This is useful for combining cooperative locks and DB transactions.
1408 * The callback takes one argument:
1409 * - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK)
1411 * @param callable $callback
1412 * @param string $fname Caller name
1416 public function onTransactionResolution( callable
$callback, $fname = __METHOD__
);
1419 * Run a callback as soon as there is no transaction pending.
1420 * If there is a transaction and it is rolled back, then the callback is cancelled.
1421 * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
1422 * Callbacks must commit any transactions that they begin.
1424 * This is useful for updates to different systems or when separate transactions are needed.
1425 * For example, one might want to enqueue jobs into a system outside the database, but only
1426 * after the database is updated so that the jobs will see the data when they actually run.
1427 * It can also be used for updates that easily cause deadlocks if locks are held too long.
1429 * Updates will execute in the order they were enqueued.
1431 * The callback takes one argument:
1432 * - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_IDLE)
1434 * @param callable $callback
1435 * @param string $fname Caller name
1438 public function onTransactionIdle( callable
$callback, $fname = __METHOD__
);
1441 * Run a callback before the current transaction commits or now if there is none.
1442 * If there is a transaction and it is rolled back, then the callback is cancelled.
1443 * Callbacks must not start nor commit any transactions. If no transaction is active,
1444 * then a transaction will wrap the callback.
1446 * This is useful for updates that easily cause deadlocks if locks are held too long
1447 * but where atomicity is strongly desired for these updates and some related updates.
1449 * Updates will execute in the order they were enqueued.
1451 * @param callable $callback
1452 * @param string $fname Caller name
1455 public function onTransactionPreCommitOrIdle( callable
$callback, $fname = __METHOD__
);
1458 * Run a callback each time any transaction commits or rolls back
1460 * The callback takes two arguments:
1461 * - IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK
1462 * - This IDatabase object
1463 * Callbacks must commit any transactions that they begin.
1465 * Registering a callback here will not affect writesOrCallbacks() pending
1467 * @param string $name Callback name
1468 * @param callable|null $callback Use null to unset a listener
1472 public function setTransactionListener( $name, callable
$callback = null );
1475 * Begin an atomic section of statements
1477 * If a transaction has been started already, just keep track of the given
1478 * section name to make sure the transaction is not committed pre-maturely.
1479 * This function can be used in layers (with sub-sections), so use a stack
1480 * to keep track of the different atomic sections. If there is no transaction,
1481 * start one implicitly.
1483 * The goal of this function is to create an atomic section of SQL queries
1484 * without having to start a new transaction if it already exists.
1486 * All atomic levels *must* be explicitly closed using IDatabase::endAtomic(),
1487 * and any database transactions cannot be began or committed until all atomic
1488 * levels are closed. There is no such thing as implicitly opening or closing
1489 * an atomic section.
1492 * @param string $fname
1495 public function startAtomic( $fname = __METHOD__
);
1498 * Ends an atomic section of SQL statements
1500 * Ends the next section of atomic SQL statements and commits the transaction
1504 * @see IDatabase::startAtomic
1505 * @param string $fname
1508 public function endAtomic( $fname = __METHOD__
);
1511 * Run a callback to do an atomic set of updates for this database
1513 * The $callback takes the following arguments:
1514 * - This database object
1515 * - The value of $fname
1517 * If any exception occurs in the callback, then rollback() will be called and the error will
1518 * be re-thrown. It may also be that the rollback itself fails with an exception before then.
1519 * In any case, such errors are expected to terminate the request, without any outside caller
1520 * attempting to catch errors and commit anyway. Note that any rollback undoes all prior
1521 * atomic section and uncommitted updates, which trashes the current request, requiring an
1522 * error to be displayed.
1524 * This can be an alternative to explicit startAtomic()/endAtomic() calls.
1526 * @see Database::startAtomic
1527 * @see Database::endAtomic
1529 * @param string $fname Caller name (usually __METHOD__)
1530 * @param callable $callback Callback that issues DB updates
1531 * @return mixed $res Result of the callback (since 1.28)
1533 * @throws RuntimeException
1534 * @throws UnexpectedValueException
1537 public function doAtomicSection( $fname, callable
$callback );
1540 * Begin a transaction. If a transaction is already in progress,
1541 * that transaction will be committed before the new transaction is started.
1543 * Only call this from code with outer transcation scope.
1544 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1545 * Nesting of transactions is not supported.
1547 * Note that when the DBO_TRX flag is set (which is usually the case for web
1548 * requests, but not for maintenance scripts), any previous database query
1549 * will have started a transaction automatically.
1551 * Nesting of transactions is not supported. Attempts to nest transactions
1552 * will cause a warning, unless the current transaction was started
1553 * automatically because of the DBO_TRX flag.
1555 * @param string $fname Calling function name
1556 * @param string $mode A situationally valid IDatabase::TRANSACTION_* constant [optional]
1559 public function begin( $fname = __METHOD__
, $mode = self
::TRANSACTION_EXPLICIT
);
1562 * Commits a transaction previously started using begin().
1563 * If no transaction is in progress, a warning is issued.
1565 * Only call this from code with outer transcation scope.
1566 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1567 * Nesting of transactions is not supported.
1569 * @param string $fname
1570 * @param string $flush Flush flag, set to situationally valid IDatabase::FLUSHING_*
1571 * constant to disable warnings about explicitly committing implicit transactions,
1572 * or calling commit when no transaction is in progress.
1574 * This will trigger an exception if there is an ongoing explicit transaction.
1576 * Only set the flush flag if you are sure that these warnings are not applicable,
1577 * and no explicit transactions are open.
1579 * @throws DBUnexpectedError
1581 public function commit( $fname = __METHOD__
, $flush = '' );
1584 * Rollback a transaction previously started using begin().
1585 * If no transaction is in progress, a warning is issued.
1587 * Only call this from code with outer transcation scope.
1588 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1589 * Nesting of transactions is not supported. If a serious unexpected error occurs,
1590 * throwing an Exception is preferrable, using a pre-installed error handler to trigger
1591 * rollback (in any case, failure to issue COMMIT will cause rollback server-side).
1593 * @param string $fname Calling function name
1594 * @param string $flush Flush flag, set to a situationally valid IDatabase::FLUSHING_*
1595 * constant to disable warnings about calling rollback when no transaction is in
1596 * progress. This will silently break any ongoing explicit transaction. Only set the
1597 * flush flag if you are sure that it is safe to ignore these warnings in your context.
1598 * @throws DBUnexpectedError
1599 * @since 1.23 Added $flush parameter
1601 public function rollback( $fname = __METHOD__
, $flush = '' );
1604 * Commit any transaction but error out if writes or callbacks are pending
1606 * This is intended for clearing out REPEATABLE-READ snapshots so that callers can
1607 * see a new point-in-time of the database. This is useful when one of many transaction
1608 * rounds finished and significant time will pass in the script's lifetime. It is also
1609 * useful to call on a replica DB after waiting on replication to catch up to the master.
1611 * @param string $fname Calling function name
1612 * @throws DBUnexpectedError
1615 public function flushSnapshot( $fname = __METHOD__
);
1618 * List all tables on the database
1620 * @param string $prefix Only show tables with this prefix, e.g. mw_
1621 * @param string $fname Calling function name
1625 public function listTables( $prefix = null, $fname = __METHOD__
);
1628 * Convert a timestamp in one of the formats accepted by wfTimestamp()
1629 * to the format used for inserting into timestamp fields in this DBMS.
1631 * The result is unquoted, and needs to be passed through addQuotes()
1632 * before it can be included in raw SQL.
1634 * @param string|int $ts
1638 public function timestamp( $ts = 0 );
1641 * Convert a timestamp in one of the formats accepted by wfTimestamp()
1642 * to the format used for inserting into timestamp fields in this DBMS. If
1643 * NULL is input, it is passed through, allowing NULL values to be inserted
1644 * into timestamp fields.
1646 * The result is unquoted, and needs to be passed through addQuotes()
1647 * before it can be included in raw SQL.
1649 * @param string|int $ts
1653 public function timestampOrNull( $ts = null );
1656 * Ping the server and try to reconnect if it there is no connection
1658 * @param float|null &$rtt Value to store the estimated RTT [optional]
1659 * @return bool Success or failure
1661 public function ping( &$rtt = null );
1664 * Get replica DB lag. Currently supported only by MySQL.
1666 * Note that this function will generate a fatal error on many
1667 * installations. Most callers should use LoadBalancer::safeGetLag()
1670 * @return int|bool Database replication lag in seconds or false on error
1672 public function getLag();
1675 * Get the replica DB lag when the current transaction started
1676 * or a general lag estimate if not transaction is active
1678 * This is useful when transactions might use snapshot isolation
1679 * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
1680 * is this lag plus transaction duration. If they don't, it is still
1681 * safe to be pessimistic. In AUTO-COMMIT mode, this still gives an
1682 * indication of the staleness of subsequent reads.
1684 * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
1687 public function getSessionLagStatus();
1690 * Return the maximum number of items allowed in a list, or 0 for unlimited.
1694 public function maxListLen();
1697 * Some DBMSs have a special format for inserting into blob fields, they
1698 * don't allow simple quoted strings to be inserted. To insert into such
1699 * a field, pass the data through this function before passing it to
1700 * IDatabase::insert().
1703 * @return string|Blob
1705 public function encodeBlob( $b );
1708 * Some DBMSs return a special placeholder object representing blob fields
1709 * in result objects. Pass the object through this function to return the
1712 * @param string|Blob $b
1715 public function decodeBlob( $b );
1718 * Override database's default behavior. $options include:
1719 * 'connTimeout' : Set the connection timeout value in seconds.
1720 * May be useful for very long batch queries such as
1721 * full-wiki dumps, where a single query reads out over
1724 * @param array $options
1727 public function setSessionOptions( array $options );
1730 * Set variables to be used in sourceFile/sourceStream, in preference to the
1731 * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
1732 * all. If it's set to false, $GLOBALS will be used.
1734 * @param bool|array $vars Mapping variable name to value.
1736 public function setSchemaVars( $vars );
1739 * Check to see if a named lock is available (non-blocking)
1741 * @param string $lockName Name of lock to poll
1742 * @param string $method Name of method calling us
1746 public function lockIsFree( $lockName, $method );
1749 * Acquire a named lock
1751 * Named locks are not related to transactions
1753 * @param string $lockName Name of lock to aquire
1754 * @param string $method Name of the calling method
1755 * @param int $timeout Acquisition timeout in seconds
1758 public function lock( $lockName, $method, $timeout = 5 );
1763 * Named locks are not related to transactions
1765 * @param string $lockName Name of lock to release
1766 * @param string $method Name of the calling method
1768 * @return int Returns 1 if the lock was released, 0 if the lock was not established
1769 * by this thread (in which case the lock is not released), and NULL if the named
1770 * lock did not exist
1772 public function unlock( $lockName, $method );
1775 * Acquire a named lock, flush any transaction, and return an RAII style unlocker object
1777 * Only call this from outer transcation scope and when only one DB will be affected.
1778 * See https://www.mediawiki.org/wiki/Database_transactions for details.
1780 * This is suitiable for transactions that need to be serialized using cooperative locks,
1781 * where each transaction can see each others' changes. Any transaction is flushed to clear
1782 * out stale REPEATABLE-READ snapshot data. Once the returned object falls out of PHP scope,
1783 * the lock will be released unless a transaction is active. If one is active, then the lock
1784 * will be released when it either commits or rolls back.
1786 * If the lock acquisition failed, then no transaction flush happens, and null is returned.
1788 * @param string $lockKey Name of lock to release
1789 * @param string $fname Name of the calling method
1790 * @param int $timeout Acquisition timeout in seconds
1791 * @return ScopedCallback|null
1792 * @throws DBUnexpectedError
1795 public function getScopedLockAndFlush( $lockKey, $fname, $timeout );
1798 * Check to see if a named lock used by lock() use blocking queues
1803 public function namedLocksEnqueue();
1806 * Find out when 'infinity' is. Most DBMSes support this. This is a special
1807 * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
1808 * because "i" sorts after all numbers.
1812 public function getInfinity();
1815 * Encode an expiry time into the DBMS dependent format
1817 * @param string $expiry Timestamp for expiry, or the 'infinity' string
1820 public function encodeExpiry( $expiry );
1823 * Decode an expiry time into a DBMS independent format
1825 * @param string $expiry DB timestamp field value for expiry
1826 * @param int $format TS_* constant, defaults to TS_MW
1829 public function decodeExpiry( $expiry, $format = TS_MW
);
1832 * Allow or deny "big selects" for this session only. This is done by setting
1833 * the sql_big_selects session variable.
1835 * This is a MySQL-specific feature.
1837 * @param bool|string $value True for allow, false for deny, or "default" to
1838 * restore the initial value
1840 public function setBigSelects( $value = true );
1843 * @return bool Whether this DB is read-only
1846 public function isReadOnly();
1849 * Make certain table names use their own database, schema, and table prefix
1850 * when passed into SQL queries pre-escaped and without a qualified database name
1852 * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
1853 * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
1855 * Calling this twice will completely clear any old table aliases. Also, note that
1856 * callers are responsible for making sure the schemas and databases actually exist.
1858 * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
1861 public function setTableAliases( array $aliases );
1864 class_alias( IDatabase
::class, 'IDatabase' );