IDatabase.php
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IDatabase.php
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	<?php
	/**
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License along
	* with this program; if not, write to the Free Software Foundation, Inc.,
	* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
	* http://www.gnu.org/copyleft/gpl.html
	*
	* @file
	*/
	namespace Wikimedia\Rdbms;

	use Exception;
	use Wikimedia\ScopedCallback;

	/**
	* @defgroup Database Database
	* This group deals with database interface functions
	* and query specifics/optimisations.
	*/

	// Very long type annotations :(
	// phpcs:disable Generic.Files.LineLength

	/**
	* Interface to a relational database
	*
	* This is used for both primary databases and replicas, and used for both concrete
	* connections, as well as wrappers around shared connections, like DBConnRef.
	*
	* As such, callers should not assume that the object represents a live connection
	* (when using DBConnRef, the object may lazily defer the connection to the first query),
	* and should not assume that they have complete control over the connection
	* (when using DBConnRef, multiple objects may automatically share and reuse the same
	* underlying connection).
	*
	* @ingroup Database
	*/
	interface IDatabase extends IReadableDatabase {
	/** Callback triggered immediately due to no active transaction */
	public const TRIGGER_IDLE = 1;
	/** Callback triggered by COMMIT */
	public const TRIGGER_COMMIT = 2;
	/** Callback triggered by ROLLBACK */
	public const TRIGGER_ROLLBACK = 3;
	/** Callback triggered by atomic section cancel (ROLLBACK TO SAVEPOINT) */
	public const TRIGGER_CANCEL = 4;

	/** Transaction is requested by regular caller outside of the DB layer */
	public const TRANSACTION_EXPLICIT = '';
	/** Transaction is requested internally via DBO_TRX/startAtomic() */
	public const TRANSACTION_INTERNAL = 'implicit';

	/** Atomic section is not cancelable */
	public const ATOMIC_NOT_CANCELABLE = '';
	/** Atomic section is cancelable */
	public const ATOMIC_CANCELABLE = 'cancelable';

	/** Commit/rollback is from outside the IDatabase handle and connection manager */
	public const FLUSHING_ONE = '';
	/**
	* Commit/rollback is from the owning connection manager for the IDatabase handle
	* @internal Only for use within the rdbms library
	*/
	public const FLUSHING_ALL_PEERS = 'flush';
	/**
	* Commit/rollback is from the IDatabase handle internally
	* @internal Only for use within the rdbms library
	*/
	public const FLUSHING_INTERNAL = 'flush-internal';

	/** Estimate total time (RTT, scanning, waiting on locks, applying) */
	public const ESTIMATE_TOTAL = 'total';
	/** Estimate time to apply (scanning, applying) */
	public const ESTIMATE_DB_APPLY = 'apply';

	/** Flag to return the lock acquisition timestamp (null if not acquired) */
	public const LOCK_TIMESTAMP = 1;

	/** Field for getLBInfo()/setLBInfo() */
	public const LB_TRX_ROUND_ID = 'trxRoundId';
	/** Field for getLBInfo()/setLBInfo() */
	public const LB_READ_ONLY_REASON = 'readOnlyReason';

	/** Primary server than can stream writes to replica servers */
	public const ROLE_STREAMING_MASTER = 'streaming-master';
	/** Replica server that receives writes from a primary server */
	public const ROLE_STREAMING_REPLICA = 'streaming-replica';
	/** Replica server within a static dataset */
	public const ROLE_STATIC_CLONE = 'static-clone';
	/** Server with unknown topology role */
	public const ROLE_UNKNOWN = 'unknown';

	/**
	* Gets the current transaction level.
	*
	* Historically, transactions were allowed to be "nested". This is no
	* longer supported, so this function really only returns a boolean.
	*
	* @return int The previous value
	*/
	public function trxLevel();

	/**
	* Get the UNIX timestamp of the time that the transaction was established
	*
	* This can be used to reason about the staleness of SELECT data in REPEATABLE-READ
	* transaction isolation level. Callers can assume that if a view-snapshot isolation
	* is used, then the data read by SQL queries is at least up to date to that point
	* (possibly more up-to-date since the first SELECT defines the snapshot).
	*
	* @return float\|null Returns null if there is not active transaction
	* @since 1.25
	*/
	public function trxTimestamp();

	/**
	* Check whether there is a transaction open at the specific request of a caller
	*
	* Explicit transactions are spawned by begin(), startAtomic(), and doAtomicSection().
	* Note that explicit transactions should not be confused with explicit transaction rounds.
	*
	* @return bool
	* @since 1.28
	*/
	public function explicitTrxActive();

	/**
	* Get properties passed down from the server info array of the load balancer
	*
	* @internal should not be called outside of rdbms library.
	*
	* @param string\|null $name The entry of the info array to get, or null to get the whole array
	* @return array\|mixed\|null
	*/
	public function getLBInfo( $name = null );

	/**
	* Get the sequence-based ID assigned by the last query method call
	*
	* This method should only be called when all the following hold true:
	* - (a) A method call was made to insert(), upsert(), replace(), or insertSelect()
	* - (b) The method call attempts to insert exactly one row
	* - (c) The method call omits the value of exactly one auto-increment column
	* - (d) The method call succeeded
	* - (e) No subsequent method calls were made, with the exception of affectedRows(),
	* lastErrno(), lastError(), and getType()
	*
	* In all other cases, the return value is unspecified.
	*
	* When the query method is either insert() with "IGNORE", upsert(), or insertSelect(),
	* callers should first check affectedRows() before calling this method, making sure that
	* the query method actually created a row. Otherwise, an ID from a previous insert might
	* be incorrectly assumed to belong to last insert.
	*
	* @return int
	*/
	public function insertId();

	/**
	* Get the number of rows affected by the last query method call
	*
	* This method should only be called when all the following hold true:
	* - (a) A method call was made to insert(), upsert(), replace(), update(), delete(),
	* insertSelect(), query() with a non-SELECT statement, or queryMulti() with a
	* non-SELECT terminal statement
	* - (b) The method call succeeded
	* - (c) No subsequent method calls were made, with the exception of affectedRows(),
	* lastErrno(), lastError(), and getType()
	*
	* In all other cases, the return value is unspecified.
	*
	* UPDATE queries consider rows affected even when all their new column values match
	* the previous values. Such rows can be excluded from the count by changing the WHERE
	* clause to filter them out.
	*
	* If the last query method call was to query() or queryMulti(), then the results
	* are based on the (last) statement provided to that call and are driver-specific.
	*
	* @return int
	*/
	public function affectedRows();

	/**
	* Run an SQL query statement and return the result
	*
	* If a connection loss is detected, then an attempt to reconnect will be made.
	* For queries that involve no larger transactions or locks, they will be re-issued
	* for convenience, provided the connection was re-established.
	*
	* In new code, the query wrappers select(), insert(), update(), delete(),
	* etc. should be used where possible, since they give much better DBMS
	* independence and automatically quote or validate user input in a variety
	* of contexts. This function is generally only useful for queries which are
	* explicitly DBMS-dependent and are unsupported by the query wrappers, such
	* as CREATE TABLE.
	*
	* However, the query wrappers themselves should call this function.
	*
	* Callers should avoid the use of statements like BEGIN, COMMIT, and ROLLBACK.
	* Methods like startAtomic(), endAtomic(), and cancelAtomic() can be used instead.
	*
	* @param string\|Query $sql Single-statement SQL query
	* @param-taint $sql exec_sql
	* @param string $fname Caller name; used for profiling/SHOW PROCESSLIST comments @phan-mandatory-param
	* @param int $flags Bit field of ISQLPlatform::QUERY_* constants
	* @return bool\|IResultWrapper True for a successful write query, IResultWrapper object
	* for a successful read query, or false on failure if QUERY_SILENCE_ERRORS is set
	* @return-taint tainted
	* @throws DBQueryError If the query is issued, fails, and QUERY_SILENCE_ERRORS is not set
	* @throws DBExpectedError If the query is not, and cannot, be issued yet (non-DBQueryError)
	* @throws DBError If the query is inherently not allowed (non-DBExpectedError)
	*/
	public function query( $sql, $fname = __METHOD__, $flags = 0 );

	/**
	* Get an UpdateQueryBuilder bound to this connection. This is overridden by
	* DBConnRef.
	*
	* @note A new query builder must be created per query. Query builders
	* should not be reused since this uses a fluent interface and the state of
	* the builder changes during the query which may cause unexpected results.
	*
	* @return UpdateQueryBuilder
	*/
	public function newUpdateQueryBuilder(): UpdateQueryBuilder;

	/**
	* Get an DeleteQueryBuilder bound to this connection. This is overridden by
	* DBConnRef.
	*
	* @note A new query builder must be created per query. Query builders
	* should not be reused since this uses a fluent interface and the state of
	* the builder changes during the query which may cause unexpected results.
	*
	* @return DeleteQueryBuilder
	*/
	public function newDeleteQueryBuilder(): DeleteQueryBuilder;

	/**
	* Get an InsertQueryBuilder bound to this connection. This is overridden by
	* DBConnRef.
	*
	* @note A new query builder must be created per query. Query builders
	* should not be reused since this uses a fluent interface and the state of
	* the builder changes during the query which may cause unexpected results.
	*
	* @return InsertQueryBuilder
	*/
	public function newInsertQueryBuilder(): InsertQueryBuilder;

	/**
	* Get an ReplaceQueryBuilder bound to this connection. This is overridden by
	* DBConnRef.
	*
	* @note A new query builder must be created per query. Query builders
	* should not be reused since this uses a fluent interface and the state of
	* the builder changes during the query which may cause unexpected results.
	*
	* @return ReplaceQueryBuilder
	*/
	public function newReplaceQueryBuilder(): ReplaceQueryBuilder;

	/**
	* Lock all rows meeting the given conditions/options FOR UPDATE
	*
	* @param string\|string[] $table The unqualified name of table(s) (use an array for a join)
	* @param string\|IExpression\|array<string,?scalar\|non-empty-array<int,?scalar>\|RawSQLValue>\|array<int,string\|IExpression> $conds
	* Condition in the format of IDatabase::select() conditions
	* @param string $fname Function name for profiling @phan-mandatory-param
	* @param array $options Options for select ("FOR UPDATE" is added automatically)
	* @param array $join_conds Join conditions
	* @return int Number of matching rows found (and locked)
	* @throws DBError If an error occurs, {@see query}
	* @since 1.32
	* @deprecated since 1.43; Use SelectQueryBuilder::acquireRowLocks
	*/
	public function lockForUpdate(
	$table, $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
	);

	/**
	* Insert row(s) into a table, in the provided order
	*
	* This operation will be seen by affectedRows()/insertId() as one query statement,
	* regardless of how many statements are actually sent by the class implementation.
	*
	* @internal callers outside of rdbms library should use InsertQueryBuilder instead.
	*
	* @param string $table The unqualified name of a table
	* @param array\|array[] $rows Row(s) to insert, as either:
	* - A string-keyed map of (column name => value) defining a new row. Values are
	* treated as literals and quoted appropriately; null is interpreted as NULL.
	* - An integer-keyed list of such string-keyed maps, defining a list of new rows.
	* The keys in each map must be identical to each other and in the same order.
	* The rows must not collide with each other.
	* @param string $fname Calling function name (use __METHOD__) for logs/profiling @phan-mandatory-param
	* @param string\|array $options Combination map/list where each string-keyed entry maps
	* a non-boolean option to the option parameters and each integer-keyed value is the
	* name of a boolean option. Supported options are:
	* - IGNORE: Boolean: skip insertion of rows that would cause unique key conflicts.
	* IDatabase::affectedRows() can be used to determine how many rows were inserted.
	* @return bool Return true if no exception was thrown (deprecated since 1.33)
	* @throws DBError If an error occurs, {@see query}
	*/
	public function insert( $table, $rows, $fname = __METHOD__, $options = [] );

	/**
	* Update all rows in a table that match a given condition
	*
	* This operation will be seen by affectedRows()/insertId() as one query statement,
	* regardless of how many statements are actually sent by the class implementation.
	*
	* @internal callers outside of rdbms library should use UpdateQueryBuilder instead.
	*
	* @param string $table The unqualified name of a table
	* @param-taint $table exec_sql
	* @param array<string,?scalar\|RawSQLValue>\|array<int,string> $set
	* Combination map/list where each string-keyed entry maps a column
	* to a literal assigned value and each integer-keyed value is a SQL expression in the
	* format of a column assignment within UPDATE...SET. The (column => value) entries are
	* convenient due to automatic value quoting and conversion of null to NULL. The SQL
	* assignment format is useful for updates like "column = column + X". All assignments
	* have no defined execution order, so they should not depend on each other. Do not
	* modify AUTOINCREMENT or UUID columns in assignments.
	* @param-taint $set exec_sql_numkey
	* @param string\|IExpression\|array<string,?scalar\|non-empty-array<int,?scalar>\|RawSQLValue>\|array<int,string\|IExpression> $conds
	* Condition in the format of IDatabase::select() conditions.
	* In order to prevent possible performance or replication issues or damaging a data
	* accidentally, an empty condition for 'update' queries isn't allowed.
	* IDatabase::ALL_ROWS should be passed explicitly in order to update all rows.
	* @param-taint $conds exec_sql_numkey
	* @param string $fname Calling function name (use __METHOD__) for logs/profiling @phan-mandatory-param
	* @param-taint $fname exec_sql
	* @param string\|array $options Combination map/list where each string-keyed entry maps
	* a non-boolean option to the option parameters and each integer-keyed value is the
	* name of a boolean option. Supported options are:
	* - IGNORE: Boolean: skip update of rows that would cause unique key conflicts.
	* IDatabase::affectedRows() includes all matching rows,
	* that includes also rows not updated due to key conflict.
	* @param-taint $options none
	* @return bool Return true if no exception was thrown (deprecated since 1.33)
	* @return-taint none
	* @throws DBError If an error occurs, {@see query}
	*/
	public function update( $table, $set, $conds, $fname = __METHOD__, $options = [] );

	/**
	* Insert row(s) into a table, in the provided order, while deleting conflicting rows
	*
	* Conflicts are determined by the provided unique indexes. Note that it is possible
	* for the provided rows to conflict even among themselves; it is preferable for the
	* caller to de-duplicate such input beforehand.
	*
	* Note some important implications of the deletion semantics:
	* - If the table has an AUTOINCREMENT column and $rows omit that column, then any
	* conflicting existing rows will be replaced with newer having higher values for
	* that column, even if nothing else changed.
	* - There might be worse contention than upsert() due to the use of gap-locking.
	* This does not apply to RDBMS types that use predicate locking nor those that
	* just lock the whole table or databases anyway.
	*
	* This operation will be seen by affectedRows()/insertId() as one query statement,
	* regardless of how many statements are actually sent by the class implementation.
	*
	* @internal callers outside of rdbms library should use ReplaceQueryBuilder instead.
	*
	* @param string $table The unqualified name of a table
	* @param string\|string[]\|string[][] $uniqueKeys Column name or non-empty list of column
	* name lists that define all applicable unique keys on the table. There must only be
	* one such key. Each unique key on the table is "applicable" unless either:
	* - It involves an AUTOINCREMENT column for which no values are assigned in $rows
	* - It involves a UUID column for which newly generated UUIDs are assigned in $rows
	* @param array\|array[] $rows Row(s) to insert, in the form of either:
	* - A string-keyed map of (column name => value) defining a new row. Values are
	* treated as literals and quoted appropriately; null is interpreted as NULL.
	* Columns belonging to a key in $uniqueKeys must be defined here and non-null.
	* - An integer-keyed list of such string-keyed maps, defining a list of new rows.
	* The keys in each map must be identical to each other and in the same order.
	* The rows must not collide with each other.
	* @param string $fname Calling function name (use __METHOD__) for logs/profiling @phan-mandatory-param
	* @throws DBError If an error occurs, {@see query}
	*/
	public function replace( $table, $uniqueKeys, $rows, $fname = __METHOD__ );

	/**
	* Upsert row(s) into a table, in the provided order, while updating conflicting rows
	*
	* Conflicts are determined by the provided unique indexes. Note that it is possible
	* for the provided rows to conflict even among themselves; it is preferable for the
	* caller to de-duplicate such input beforehand.
	*
	* This operation will be seen by affectedRows()/insertId() as one query statement,
	* regardless of how many statements are actually sent by the class implementation.
	*
	* @internal callers outside of rdbms library should use InsertQueryBuilder instead.
	*
	* @param string $table The unqualified name of a table
	* @param array\|array[] $rows Row(s) to insert, in the form of either:
	* - A string-keyed map of (column name => value) defining a new row. Values are
	* treated as literals and quoted appropriately; null is interpreted as NULL.
	* Columns belonging to a key in $uniqueKeys must be defined here and non-null.
	* - An integer-keyed list of such string-keyed maps, defining a list of new rows.
	* The keys in each map must be identical to each other and in the same order.
	* The rows must not collide with each other.
	* @param string\|string[]\|string[][] $uniqueKeys Column name or non-empty list of column
	* name lists that define all applicable unique keys on the table. There must only be
	* one such key. Each unique key on the table is "applicable" unless either:
	* - It involves an AUTOINCREMENT column for which no values are assigned in $rows
	* - It involves a UUID column for which newly generated UUIDs are assigned in $rows
	* @param array<string,?scalar\|RawSQLValue>\|array<int,string> $set
	* Combination map/list where each string-keyed entry maps a column
	* to a literal assigned value and each integer-keyed value is a SQL assignment expression
	* of the form "<unquoted alphanumeric column> = <SQL expression>". The (column => value)
	* entries are convenient due to automatic value quoting and conversion of null to NULL.
	* The SQL assignment entries are useful for updates like "column = column + X". All of
	* the assignments have no defined execution order, so callers should make sure that they
	* not depend on each other. Do not modify AUTOINCREMENT or UUID columns in assignments,
	* even if they are just "secondary" unique keys. For multi-row upserts, use
	* buildExcludedValue() to reference the value of a column from the corresponding row
	* in $rows that conflicts with the current row.
	* @param string $fname Calling function name (use __METHOD__) for logs/profiling @phan-mandatory-param
	* @throws DBError If an error occurs, {@see query}
	* @since 1.22
	*/
	public function upsert(
	$table, array $rows, $uniqueKeys, array $set, $fname = __METHOD__
	);

	/**
	* Delete all rows in a table that match a condition which includes a join
	*
	* For safety, an empty $conds will not delete everything. If you want to
	* delete all rows where the join condition matches, set $conds=IDatabase::ALL_ROWS.
	*
	* DO NOT put the join condition in $conds.
	*
	* This operation will be seen by affectedRows()/insertId() as one query statement,
	* regardless of how many statements are actually sent by the class implementation.
	*
	* @param string $delTable The unqualified name of the table to delete rows from.
	* @param string $joinTable The unqualified name of the reference table to join on.
	* @param string $delVar The variable to join on, in the first table.
	* @param string $joinVar The variable to join on, in the second table.
	* @param string\|IExpression\|array<string,?scalar\|non-empty-array<int,?scalar>\|RawSQLValue>\|array<int,string\|IExpression> $conds
	* Condition array of field names mapped to variables,
	* ANDed together in the WHERE clause
	* @param string $fname Calling function name (use __METHOD__) for logs/profiling @phan-mandatory-param
	* @throws DBError If an error occurs, {@see query}
	*/
	public function deleteJoin(
	$delTable,
	$joinTable,
	$delVar,
	$joinVar,
	$conds,
	$fname = __METHOD__
	);

	/**
	* Delete all rows in a table that match a condition
	*
	* This operation will be seen by affectedRows()/insertId() as one query statement,
	* regardless of how many statements are actually sent by the class implementation.
	*
	* @internal callers outside of rdbms library should use DeleteQueryBuilder instead.
	*
	* @param string $table The unqualified name of a table
	* @param-taint $table exec_sql
	* @param string\|IExpression\|array<string,?scalar\|non-empty-array<int,?scalar>\|RawSQLValue>\|array<int,string\|IExpression> $conds
	* Array of conditions. See $conds in IDatabase::select()
	* In order to prevent possible performance or replication issues or damaging a data
	* accidentally, an empty condition for 'delete' queries isn't allowed.
	* IDatabase::ALL_ROWS should be passed explicitly in order to delete all rows.
	* @param-taint $conds exec_sql_numkey
	* @param string $fname Name of the calling function @phan-mandatory-param
	* @param-taint $fname exec_sql
	* @return bool Return true if no exception was thrown (deprecated since 1.33)
	* @return-taint none
	* @throws DBError If an error occurs, {@see query}
	*/
	public function delete( $table, $conds, $fname = __METHOD__ );

	/**
	* INSERT SELECT wrapper
	*
	* @warning If the insert will use an auto-increment or sequence to
	* determine the value of a column, this may break replication on
	* databases using statement-based replication if the SELECT is not
	* deterministically ordered.
	*
	* This operation will be seen by affectedRows()/insertId() as one query statement,
	* regardless of how many statements are actually sent by the class implementation.
	*
	* @param string $destTable Unqualified name of destination table
	* @param string\|array $srcTable Unqualified name of source table(s) (use an array for a join)
	* @param array $varMap Must be an associative array of the form
	* [ 'dest1' => 'source1', ... ]. Source items may be literals
	* rather than field names, but strings should be quoted with
	* IDatabase::addQuotes()
	* @param string\|IExpression\|array<string,?scalar\|non-empty-array<int,?scalar>\|RawSQLValue>\|array<int,string\|IExpression> $conds
	* Condition array. See $conds in IDatabase::select() for
	* the details of the format of condition arrays. May be "*" to copy the
	* whole table.
	* @param string $fname The function name of the caller, from __METHOD__ @phan-mandatory-param
	* @param array $insertOptions Options for the INSERT part of the query, see
	* IDatabase::insert() for details. Also, one additional option is
	* available: pass 'NO_AUTO_COLUMNS' to hint that the query does not use
	* an auto-increment or sequence to determine any column values.
	* @param array $selectOptions Options for the SELECT part of the query, see
	* IDatabase::select() for details.
	* @param array $selectJoinConds Join conditions for the SELECT part of the query, see
	* IDatabase::select() for details.
	* @return bool Return true if no exception was thrown (deprecated since 1.33)
	* @throws DBError If an error occurs, {@see query}
	*/
	public function insertSelect(
	$destTable,
	$srcTable,
	$varMap,
	$conds,
	$fname = __METHOD__,
	$insertOptions = [],
	$selectOptions = [],
	$selectJoinConds = []
	);

	/**
	* Run a callback when the current transaction commits or rolls back
	*
	* An error is thrown if no transaction is pending.
	*
	* When transaction round mode (DBO_TRX) is set, the callback will run at the end
	* of the round, just after all peer transactions COMMIT/ROLLBACK.
	*
	* This IDatabase instance will start off in auto-commit mode when the callback starts.
	* The use of other IDatabase handles from the callback should be avoided unless they are
	* known to be in auto-commit mode. Callbacks that create transactions via begin() or
	* startAtomic() must have matching calls to commit()/endAtomic().
	*
	* Use this method only for the following purposes:
	* - (a) Release of cooperative locks on resources
	* - (b) Cancellation of in-process deferred tasks
	*
	* The callback takes the following arguments:
	* - How the current atomic section (if any) or overall transaction (otherwise) ended
	* (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK)
	* - This IDatabase instance (since 1.32)
	*
	* Callbacks will execute in the order they were enqueued.
	*
	* @note Use onAtomicSectionCancel() to take action as soon as an atomic section is cancelled
	*
	* @param callable $callback
	* @param string $fname Caller name @phan-mandatory-param
	* @throws DBError If an error occurs, {@see query}
	* @throws Exception If the callback runs immediately and an error occurs in it
	* @since 1.28
	*/
	public function onTransactionResolution( callable $callback, $fname = __METHOD__ );

	/**
	* Run a callback when the current transaction commits or now if there is none
	*
	* If there is a transaction and it is rolled back, then the callback is cancelled.
	*
	* When transaction round mode (DBO_TRX) is set, the callback will run at the end
	* of the round, just after all peer transactions COMMIT. If the transaction round
	* is rolled back, then the callback is cancelled.
	*
	* This IDatabase instance will start off in auto-commit mode when the callback starts.
	* The use of other IDatabase handles from the callback should be avoided unless they are
	* known to be in auto-commit mode. Callbacks that create transactions via begin() or
	* startAtomic() must have matching calls to commit()/endAtomic().
	*
	* Use this method only for the following purposes:
	* - (a) RDBMS updates, prone to lock timeouts/deadlocks, that do not require
	* atomicity with respect to the updates in the current transaction (if any)
	* - (b) Purges to lightweight cache services due to RDBMS updates
	* - (c) Updates to secondary DBs/stores that must only commit once the updates in
	* the current transaction (if any) are committed (e.g. insert user account row
	* to DB1, then, initialize corresponding LDAP account)
	*
	* The callback takes the following arguments:
	* - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_IDLE)
	* - This IDatabase instance (since 1.32)
	*
	* Callbacks will execute in the order they were enqueued.
	*
	* @param callable $callback
	* @param string $fname Caller name @phan-mandatory-param
	* @throws DBError If an error occurs, {@see query}
	* @throws Exception If the callback runs immediately and an error occurs in it
	* @since 1.32
	*/
	public function onTransactionCommitOrIdle( callable $callback, $fname = __METHOD__ );

	/**
	* Run a callback before the current transaction commits or now if there is none
	*
	* If there is a transaction and it is rolled back, then the callback is cancelled.
	*
	* When transaction round mode (DBO_TRX) is set, the callback will run at the end
	* of the round, just after all peer transactions COMMIT. If the transaction round
	* is rolled back, then the callback is cancelled.
	*
	* If there is no current transaction, one will be created to wrap the callback.
	* Callbacks cannot use begin()/commit() to manage transactions. The use of other
	* IDatabase handles from the callback should be avoided.
	*
	* Use this method only for the following purposes:
	* - a) RDBMS updates, prone to lock timeouts/deadlocks, that require atomicity
	* with respect to the updates in the current transaction (if any)
	* - b) Purges to lightweight cache services due to RDBMS updates
	*
	* The callback takes the one argument:
	* - This IDatabase instance (since 1.32)
	*
	* Callbacks will execute in the order they were enqueued.
	*
	* @param callable $callback
	* @param string $fname Caller name @phan-mandatory-param
	* @throws DBError If an error occurs, {@see query}
	* @throws Exception If the callback runs immediately and an error occurs in it
	* @since 1.22
	*/
	public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ );

	/**
	* Run a callback when the atomic section is cancelled
	*
	* The callback is run just after the current atomic section, any outer
	* atomic section, or the whole transaction is rolled back.
	*
	* An error is thrown if no atomic section is pending. The atomic section
	* need not have been created with the ATOMIC_CANCELABLE flag.
	*
	* Queries in the function may be running in the context of an outer
	* transaction or may be running in AUTOCOMMIT mode. The callback should
	* use atomic sections if necessary.
	*
	* @note do not assume that other IDatabase instances will be AUTOCOMMIT mode
	*
	* The callback takes the following arguments:
	* - IDatabase::TRIGGER_CANCEL or IDatabase::TRIGGER_ROLLBACK
	* - This IDatabase instance
	*
	* @param callable $callback
	* @param string $fname Caller name @phan-mandatory-param
	* @since 1.34
	*/
	public function onAtomicSectionCancel( callable $callback, $fname = __METHOD__ );

	/**
	* Begin an atomic section of SQL statements
	*
	* Start an implicit transaction if no transaction is already active, set a savepoint
	* (if $cancelable is ATOMIC_CANCELABLE), and track the given section name to enforce
	* that the transaction is not committed prematurely. The end of the section must be
	* signified exactly once, either by endAtomic() or cancelAtomic(). Sections can have
	* have layers of inner sections (sub-sections), but all sections must be ended in order
	* of innermost to outermost. Transactions cannot be started or committed until all
	* atomic sections are closed.
	*
	* ATOMIC_CANCELABLE is useful when the caller needs to handle specific failure cases
	* by discarding the section's writes. This should not be used for failures when:
	* - upsert() could easily be used instead
	* - insert() with IGNORE could easily be used instead
	* - select() with FOR UPDATE could be checked before issuing writes instead
	* - The failure is from code that runs after the first write but doesn't need to
	* - The failures are from contention solvable via onTransactionPreCommitOrIdle()
	* - The failures are deadlocks; the RDBMs usually discard the whole transaction
	*
	* @note callers must use additional measures for situations involving two or more
	* (peer) transactions (e.g. updating two database servers at once). The transaction
	* and savepoint logic of this method only applies to this specific IDatabase instance.
	*
	* Example usage:
	* @code
	* // Start a transaction if there isn't one already
	* $dbw->startAtomic( __METHOD__ );
	* // Serialize these thread table updates
	* $dbw->select( 'thread', '1', [ 'td_id' => $tid ], __METHOD__, 'FOR UPDATE' );
	* // Add a new comment for the thread
	* $dbw->insert( 'comment', $row, __METHOD__ );
	* $cid = $db->insertId();
	* // Update thread reference to last comment
	* $dbw->update( 'thread', [ 'td_latest' => $cid ], [ 'td_id' => $tid ], __METHOD__ );
	* // Demark the end of this conceptual unit of updates
	* $dbw->endAtomic( __METHOD__ );
	* @endcode
	*
	* Example usage (atomic changes that might have to be discarded):
	* @code
	* // Start a transaction if there isn't one already
	* $sectionId = $dbw->startAtomic( __METHOD__, $dbw::ATOMIC_CANCELABLE );
	* // Create new record metadata row
	* $dbw->insert( 'records', $row, __METHOD__ );
	* // Figure out where to store the data based on the new row's ID
	* $path = $recordDirectory . '/' . $dbw->insertId();
	* // Write the record data to the storage system
	* $status = $fileBackend->create( [ 'dst' => $path, 'content' => $data ] );
	* if ( $status->isOK() ) {
	* // Try to cleanup files orphaned by transaction rollback
	* $dbw->onTransactionResolution(
	* function ( $type ) use ( $fileBackend, $path ) {
	* if ( $type === IDatabase::TRIGGER_ROLLBACK ) {
	* $fileBackend->delete( [ 'src' => $path ] );
	* }
	* },
	* __METHOD__
	* );
	* // Demark the end of this conceptual unit of updates
	* $dbw->endAtomic( __METHOD__ );
	* } else {
	* // Discard these writes from the transaction (preserving prior writes)
	* $dbw->cancelAtomic( __METHOD__, $sectionId );
	* }
	* @endcode
	*
	* @since 1.23
	* @param string $fname @phan-mandatory-param
	* @param string $cancelable Pass self::ATOMIC_CANCELABLE to use a
	* savepoint and enable self::cancelAtomic() for this section.
	* @return AtomicSectionIdentifier section ID token
	* @throws DBError If an error occurs, {@see query}
	*/
	public function startAtomic( $fname = __METHOD__, $cancelable = self::ATOMIC_NOT_CANCELABLE );

	/**
	* Ends an atomic section of SQL statements
	*
	* Ends the next section of atomic SQL statements and commits the transaction
	* if necessary.
	*
	* @since 1.23
	* @see IDatabase::startAtomic
	* @param string $fname @phan-mandatory-param
	* @throws DBError If an error occurs, {@see query}
	*/
	public function endAtomic( $fname = __METHOD__ );

	/**
	* Cancel an atomic section of SQL statements
	*
	* This will roll back only the statements executed since the start of the
	* most recent atomic section, and close that section. If a transaction was
	* open before the corresponding startAtomic() call, any statements before
	* that call are not rolled back and the transaction remains open. If the
	* corresponding startAtomic() implicitly started a transaction, that
	* transaction is rolled back.
	*
	* @note callers must use additional measures for situations involving two or more
	* (peer) transactions (e.g. updating two database servers at once). The transaction
	* and savepoint logic of startAtomic() are bound to specific IDatabase instances.
	*
	* Note that a call to IDatabase::rollback() will also roll back any open atomic sections.
	*
	* @note As an optimization to save rountrips, this method may only be called
	* when startAtomic() was called with the ATOMIC_CANCELABLE flag.
	* @since 1.31
	* @see IDatabase::startAtomic
	* @param string $fname @phan-mandatory-param
	* @param AtomicSectionIdentifier\|null $sectionId Section ID from startAtomic();
	* passing this enables cancellation of unclosed nested sections [optional]
	* @throws DBError If an error occurs, {@see query}
	*/
	public function cancelAtomic( $fname = __METHOD__, ?AtomicSectionIdentifier $sectionId = null );

	/**
	* Perform an atomic section of reversible SQL statements from a callback
	*
	* The $callback takes the following arguments:
	* - This database object
	* - The value of $fname
	*
	* This will execute the callback inside a pair of startAtomic()/endAtomic() calls.
	* If any exception occurs during execution of the callback, it will be handled as follows:
	* - If $cancelable is ATOMIC_CANCELABLE, cancelAtomic() will be called to back out any
	* (and only) statements executed during the atomic section. If that succeeds, then the
	* exception will be re-thrown; if it fails, then a different exception will be thrown
	* and any further query attempts will fail until rollback() is called.
	* - If $cancelable is ATOMIC_NOT_CANCELABLE, cancelAtomic() will be called to mark the
	* end of the section and the error will be re-thrown. Any further query attempts will
	* fail until rollback() is called.
	*
	* This method is convenient for letting calls to the caller of this method be wrapped
	* in a try/catch blocks for exception types that imply that the caller failed but was
	* able to properly discard the changes it made in the transaction. This method can be
	* an alternative to explicit calls to startAtomic()/endAtomic()/cancelAtomic().
	*
	* Example usage, "RecordStore::save" method:
	* @code
	* $dbw->doAtomicSection( __METHOD__, function ( $dbw ) use ( $record ) {
	* // Create new record metadata row
	* $dbw->insert( 'records', $record->toArray(), __METHOD__ );
	* // Figure out where to store the data based on the new row's ID
	* $path = $this->recordDirectory . '/' . $dbw->insertId();
	* // Write the record data to the storage system;
	* // blob store throws StoreFailureException on failure
	* $this->blobStore->create( $path, $record->getJSON() );
	* // Try to cleanup files orphaned by transaction rollback
	* $dbw->onTransactionResolution(
	* function ( $type ) use ( $path ) {
	* if ( $type === IDatabase::TRIGGER_ROLLBACK ) {
	* $this->blobStore->delete( $path );
	* }
	* },
	* __METHOD__
	* );
	* }, $dbw::ATOMIC_CANCELABLE );
	* @endcode
	*
	* Example usage, caller of the "RecordStore::save" method:
	* @code
	* $dbw->startAtomic( __METHOD__ );
	* // ...various SQL writes happen...
	* try {
	* $recordStore->save( $record );
	* } catch ( StoreFailureException $e ) {
	* // ...various SQL writes happen...
	* }
	* // ...various SQL writes happen...
	* $dbw->endAtomic( __METHOD__ );
	* @endcode
	*
	* @see Database::startAtomic
	* @see Database::endAtomic
	* @see Database::cancelAtomic
	*
	* @param string $fname Caller name (usually __METHOD__) @phan-mandatory-param
	* @param callable $callback Callback that issues write queries
	* @param string $cancelable Pass self::ATOMIC_CANCELABLE to use a
	* savepoint and enable self::cancelAtomic() for this section.
	* @return mixed Result of the callback (since 1.28)
	* @throws DBError If an error occurs, {@see query}
	* @throws Exception If an error occurs in the callback
	* @since 1.27; prior to 1.31 this did a rollback() instead of
	* cancelAtomic(), and assumed no callers up the stack would ever try to
	* catch the exception.
	*/
	public function doAtomicSection(
	$fname, callable $callback, $cancelable = self::ATOMIC_NOT_CANCELABLE
	);

	/**
	* Begin a transaction
	*
	* Only call this from code with outer transaction scope.
	* See https://www.mediawiki.org/wiki/Database_transactions for details.
	* Nesting of transactions is not supported.
	*
	* Note that when the DBO_TRX flag is set (which is usually the case for web
	* requests, but not for maintenance scripts), any previous database query
	* will have started a transaction automatically.
	*
	* Nesting of transactions is not supported. Attempts to nest transactions
	* will cause a warning, unless the current transaction was started
	* automatically because of the DBO_TRX flag.
	*
	* @param string $fname Calling function name @phan-mandatory-param
	* @param string $mode A situationally valid IDatabase::TRANSACTION_* constant [optional]
	* @throws DBError If an error occurs, {@see query}
	*/
	public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT );

	/**
	* Commits a transaction previously started using begin()
	*
	* If no transaction is in progress, a warning is issued.
	*
	* Only call this from code with outer transaction scope.
	* See https://www.mediawiki.org/wiki/Database_transactions for details.
	* Nesting of transactions is not supported.
	*
	* @param string $fname @phan-mandatory-param
	* @param string $flush Flush flag, set to situationally valid IDatabase::FLUSHING_*
	* constant to disable warnings about explicitly committing implicit transactions,
	* or calling commit when no transaction is in progress.
	* This will trigger an exception if there is an ongoing explicit transaction.
	* Only set the flush flag if you are sure that these warnings are not applicable,
	* and no explicit transactions are open.
	* @throws DBError If an error occurs, {@see query}
	*/
	public function commit( $fname = __METHOD__, $flush = self::FLUSHING_ONE );

	/**
	* Rollback a transaction previously started using begin()
	*
	* Only call this from code with outer transaction scope.
	* See https://www.mediawiki.org/wiki/Database_transactions for details.
	* Nesting of transactions is not supported. If a serious unexpected error occurs,
	* throwing an Exception is preferable, using a pre-installed error handler to trigger
	* rollback (in any case, failure to issue COMMIT will cause rollback server-side).
	*
	* Query, connection, and onTransaction* callback errors will be suppressed and logged.
	*
	* @param string $fname Calling function name @phan-mandatory-param
	* @param string $flush Flush flag, set to a situationally valid IDatabase::FLUSHING_*
	* constant to disable warnings about explicitly rolling back implicit transactions.
	* This will silently break any ongoing explicit transaction. Only set the flush flag
	* if you are sure that it is safe to ignore these warnings in your context.
	* @throws DBError If an error occurs, {@see query}
	* @since 1.23 Added $flush parameter
	*/
	public function rollback( $fname = __METHOD__, $flush = self::FLUSHING_ONE );

	/**
	* Commit any transaction but error out if writes or callbacks are pending
	*
	* This is intended for clearing out REPEATABLE-READ snapshots so that callers can
	* see a new point-in-time of the database. This is useful when one of many transaction
	* rounds finished and significant time will pass in the script's lifetime. It is also
	* useful to call on a replica server after waiting on replication to catch up to the
	* primary server.
	*
	* @param string $fname Calling function name @phan-mandatory-param
	* @param string $flush Flush flag, set to situationally valid IDatabase::FLUSHING_*
	* constant to disable warnings about explicitly committing implicit transactions,
	* or calling commit when no transaction is in progress.
	* This will trigger an exception if there is an ongoing explicit transaction.
	* Only set the flush flag if you are sure that these warnings are not applicable,
	* and no explicit transactions are open.
	* @throws DBError If an error occurs, {@see query}
	* @since 1.28
	* @since 1.34 Added $flush parameter
	*/
	public function flushSnapshot( $fname = __METHOD__, $flush = self::FLUSHING_ONE );

	/**
	* Override database's default behavior.
	* Not all options are supported on all database backends;
	* unsupported options are silently ignored.
	*
	* $options include:
	* - 'connTimeout': Set the connection timeout value in seconds.
	* May be useful for very long batch queries such as full-wiki dumps,
	* where a single query reads out over hours or days.
	* Only supported on MySQL and MariaDB.
	* - 'groupConcatMaxLen': Maximum length of a GROUP_CONCAT() result.
	* Only supported on MySQL and MariaDB.
	*
	* @param array $options
	* @return void
	* @throws DBError If an error occurs, {@see query}
	*/
	public function setSessionOptions( array $options );

	/**
	* Check to see if a named lock is not locked by any thread (non-blocking)
	*
	* @param string $lockName Name of lock to poll
	* @param string $method Name of method calling us
	* @return bool
	* @throws DBError If an error occurs, {@see query}
	* @since 1.20
	*/
	public function lockIsFree( $lockName, $method );

	/**
	* Acquire a named lock
	*
	* Named locks are not related to transactions
	*
	* @param string $lockName Name of lock to acquire
	* @param string $method Name of the calling method
	* @param int $timeout Acquisition timeout in seconds (0 means non-blocking)
	* @param int $flags Bit field of IDatabase::LOCK_* constants
	* @return bool\|float\|null Success (bool); acquisition time (float/null) if LOCK_TIMESTAMP
	* @throws DBError If an error occurs, {@see query}
	*/
	public function lock( $lockName, $method, $timeout = 5, $flags = 0 );

	/**
	* Release a lock
	*
	* Named locks are not related to transactions
	*
	* @param string $lockName Name of lock to release
	* @param string $method Name of the calling method
	* @return bool Success
	* @throws DBError If an error occurs, {@see query}
	*/
	public function unlock( $lockName, $method );

	/**
	* Acquire a named lock, flush any transaction, and return an RAII style unlocker object
	*
	* Only call this from outer transaction scope and when only one DB server will be affected.
	* See https://www.mediawiki.org/wiki/Database_transactions for details.
	*
	* This is suitable for transactions that need to be serialized using cooperative locks,
	* where each transaction can see each others' changes. Any transaction is flushed to clear
	* out stale REPEATABLE-READ snapshot data. Once the returned object falls out of PHP scope,
	* the lock will be released unless a transaction is active. If one is active, then the lock
	* will be released when it either commits or rolls back.
	*
	* If the lock acquisition failed, then no transaction flush happens, and null is returned.
	*
	* @param string $lockKey Name of lock to release
	* @param string $fname Name of the calling method
	* @param int $timeout Acquisition timeout in seconds
	* @return ScopedCallback\|null
	* @throws DBError If an error occurs, {@see query}
	* @since 1.27
	*/
	public function getScopedLockAndFlush( $lockKey, $fname, $timeout );

	/**
	* Check if this DB server is marked as read-only according to load balancer info
	*
	* @note LoadBalancer checks serverIsReadOnly() when setting the load balancer info array
	*
	* @return bool
	* @since 1.27
	*/
	public function isReadOnly();
	}

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