includes/libs/rdbms/database/IDatabase.php

   1 <?php
   2
   3 /**
   4  * @defgroup Database Database
   5  *
   6  * This file deals with database interface functions
   7  * and query specifics/optimisations.
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License along
  20  * with this program; if not, write to the Free Software Foundation, Inc.,
  21  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  22  * http://www.gnu.org/copyleft/gpl.html
  23  *
  24  * @file
  25  * @ingroup Database
  26  */
  27
  28 /**
  29  * Basic database interface for live and lazy-loaded DB handles
  30  *
  31  * @note: IDatabase and DBConnRef should be updated to reflect any changes
  32  * @ingroup Database
  33  */
  34 interface IDatabase {
  35         /** @var int Callback triggered immediately due to no active transaction */
  36         const TRIGGER_IDLE = 1;
  37         /** @var int Callback triggered by COMMIT */
  38         const TRIGGER_COMMIT = 2;
  39         /** @var int Callback triggered by ROLLBACK */
  40         const TRIGGER_ROLLBACK = 3;
  41
  42         /** @var string Transaction is requested by regular caller outside of the DB layer */
  43         const TRANSACTION_EXPLICIT = '';
  44         /** @var string Transaction is requested internally via DBO_TRX/startAtomic() */
  45         const TRANSACTION_INTERNAL = 'implicit';
  46
  47         /** @var string Transaction operation comes from service managing all DBs */
  48         const FLUSHING_ALL_PEERS = 'flush';
  49         /** @var string Transaction operation comes from the database class internally */
  50         const FLUSHING_INTERNAL = 'flush';
  51
  52         /** @var string Do not remember the prior flags */
  53         const REMEMBER_NOTHING = '';
  54         /** @var string Remember the prior flags */
  55         const REMEMBER_PRIOR = 'remember';
  56         /** @var string Restore to the prior flag state */
  57         const RESTORE_PRIOR = 'prior';
  58         /** @var string Restore to the initial flag state */
  59         const RESTORE_INITIAL = 'initial';
  60
  61         /** @var string Estimate total time (RTT, scanning, waiting on locks, applying) */
  62         const ESTIMATE_TOTAL = 'total';
  63         /** @var string Estimate time to apply (scanning, applying) */
  64         const ESTIMATE_DB_APPLY = 'apply';
  65
  66         /** @var int Combine list with comma delimeters */
  67         const LIST_COMMA = 0;
  68         /** @var int Combine list with AND clauses */
  69         const LIST_AND = 1;
  70         /** @var int Convert map into a SET clause */
  71         const LIST_SET = 2;
  72         /** @var int Treat as field name and do not apply value escaping */
  73         const LIST_NAMES = 3;
  74         /** @var int Combine list with OR clauses */
  75         const LIST_OR = 4;
  76
  77         /**
  78          * A string describing the current software version, and possibly
  79          * other details in a user-friendly way. Will be listed on Special:Version, etc.
  80          * Use getServerVersion() to get machine-friendly information.
  81          *
  82          * @return string Version information from the database server
  83          */
  84         public function getServerInfo();
  85
  86         /**
  87          * Turns buffering of SQL result sets on (true) or off (false). Default is
  88          * "on".
  89          *
  90          * Unbuffered queries are very troublesome in MySQL:
  91          *
  92          *   - If another query is executed while the first query is being read
  93          *     out, the first query is killed. This means you can't call normal
  94          *     MediaWiki functions while you are reading an unbuffered query result
  95          *     from a normal wfGetDB() connection.
  96          *
  97          *   - Unbuffered queries cause the MySQL server to use large amounts of
  98          *     memory and to hold broad locks which block other queries.
  99          *
 100          * If you want to limit client-side memory, it's almost always better to
 101          * split up queries into batches using a LIMIT clause than to switch off
 102          * buffering.
 103          *
 104          * @param null|bool $buffer
 105          * @return null|bool The previous value of the flag
 106          */
 107         public function bufferResults( $buffer = null );
 108
 109         /**
 110          * Gets the current transaction level.
 111          *
 112          * Historically, transactions were allowed to be "nested". This is no
 113          * longer supported, so this function really only returns a boolean.
 114          *
 115          * @return int The previous value
 116          */
 117         public function trxLevel();
 118
 119         /**
 120          * Get the UNIX timestamp of the time that the transaction was established
 121          *
 122          * This can be used to reason about the staleness of SELECT data
 123          * in REPEATABLE-READ transaction isolation level.
 124          *
 125          * @return float|null Returns null if there is not active transaction
 126          * @since 1.25
 127          */
 128         public function trxTimestamp();
 129
 130         /**
 131          * @return bool Whether an explicit transaction or atomic sections are still open
 132          * @since 1.28
 133          */
 134         public function explicitTrxActive();
 135
 136         /**
 137          * Get/set the table prefix.
 138          * @param string $prefix The table prefix to set, or omitted to leave it unchanged.
 139          * @return string The previous table prefix.
 140          */
 141         public function tablePrefix( $prefix = null );
 142
 143         /**
 144          * Get/set the db schema.
 145          * @param string $schema The database schema to set, or omitted to leave it unchanged.
 146          * @return string The previous db schema.
 147          */
 148         public function dbSchema( $schema = null );
 149
 150         /**
 151          * Get properties passed down from the server info array of the load
 152          * balancer.
 153          *
 154          * @param string $name The entry of the info array to get, or null to get the
 155          *   whole array
 156          *
 157          * @return array|mixed|null
 158          */
 159         public function getLBInfo( $name = null );
 160
 161         /**
 162          * Set the LB info array, or a member of it. If called with one parameter,
 163          * the LB info array is set to that parameter. If it is called with two
 164          * parameters, the member with the given name is set to the given value.
 165          *
 166          * @param string $name
 167          * @param array $value
 168          */
 169         public function setLBInfo( $name, $value = null );
 170
 171         /**
 172          * Set a lazy-connecting DB handle to the master DB (for replication status purposes)
 173          *
 174          * @param IDatabase $conn
 175          * @since 1.27
 176          */
 177         public function setLazyMasterHandle( IDatabase $conn );
 178
 179         /**
 180          * Returns true if this database does an implicit sort when doing GROUP BY
 181          *
 182          * @return bool
 183          */
 184         public function implicitGroupby();
 185
 186         /**
 187          * Returns true if this database does an implicit order by when the column has an index
 188          * For example: SELECT page_title FROM page LIMIT 1
 189          *
 190          * @return bool
 191          */
 192         public function implicitOrderby();
 193
 194         /**
 195          * Return the last query that went through IDatabase::query()
 196          * @return string
 197          */
 198         public function lastQuery();
 199
 200         /**
 201          * Returns true if the connection may have been used for write queries.
 202          * Should return true if unsure.
 203          *
 204          * @return bool
 205          */
 206         public function doneWrites();
 207
 208         /**
 209          * Returns the last time the connection may have been used for write queries.
 210          * Should return a timestamp if unsure.
 211          *
 212          * @return int|float UNIX timestamp or false
 213          * @since 1.24
 214          */
 215         public function lastDoneWrites();
 216
 217         /**
 218          * @return bool Whether there is a transaction open with possible write queries
 219          * @since 1.27
 220          */
 221         public function writesPending();
 222
 223         /**
 224          * Returns true if there is a transaction open with possible write
 225          * queries or transaction pre-commit/idle callbacks waiting on it to finish.
 226          * This does *not* count recurring callbacks, e.g. from setTransactionListener().
 227          *
 228          * @return bool
 229          */
 230         public function writesOrCallbacksPending();
 231
 232         /**
 233          * Get the time spend running write queries for this transaction
 234          *
 235          * High times could be due to scanning, updates, locking, and such
 236          *
 237          * @param string $type IDatabase::ESTIMATE_* constant [default: ESTIMATE_ALL]
 238          * @return float|bool Returns false if not transaction is active
 239          * @since 1.26
 240          */
 241         public function pendingWriteQueryDuration( $type = self::ESTIMATE_TOTAL );
 242
 243         /**
 244          * Get the list of method names that did write queries for this transaction
 245          *
 246          * @return array
 247          * @since 1.27
 248          */
 249         public function pendingWriteCallers();
 250
 251         /**
 252          * Is a connection to the database open?
 253          * @return bool
 254          */
 255         public function isOpen();
 256
 257         /**
 258          * Set a flag for this connection
 259          *
 260          * @param int $flag DBO_* constants from Defines.php:
 261          *   - DBO_DEBUG: output some debug info (same as debug())
 262          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 263          *   - DBO_TRX: automatically start transactions
 264          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 265          *       and removes it in command line mode
 266          *   - DBO_PERSISTENT: use persistant database connection
 267          * @param string $remember IDatabase::REMEMBER_* constant [default: REMEMBER_NOTHING]
 268          */
 269         public function setFlag( $flag, $remember = self::REMEMBER_NOTHING );
 270
 271         /**
 272          * Clear a flag for this connection
 273          *
 274          * @param int $flag DBO_* constants from Defines.php:
 275          *   - DBO_DEBUG: output some debug info (same as debug())
 276          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 277          *   - DBO_TRX: automatically start transactions
 278          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 279          *       and removes it in command line mode
 280          *   - DBO_PERSISTENT: use persistant database connection
 281          * @param string $remember IDatabase::REMEMBER_* constant [default: REMEMBER_NOTHING]
 282          */
 283         public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING );
 284
 285         /**
 286          * Restore the flags to their prior state before the last setFlag/clearFlag call
 287          *
 288          * @param string $state IDatabase::RESTORE_* constant. [default: RESTORE_PRIOR]
 289          * @since 1.28
 290          */
 291         public function restoreFlags( $state = self::RESTORE_PRIOR );
 292
 293         /**
 294          * Returns a boolean whether the flag $flag is set for this connection
 295          *
 296          * @param int $flag DBO_* constants from Defines.php:
 297          *   - DBO_DEBUG: output some debug info (same as debug())
 298          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 299          *   - DBO_TRX: automatically start transactions
 300          *   - DBO_PERSISTENT: use persistant database connection
 301          * @return bool
 302          */
 303         public function getFlag( $flag );
 304
 305         /**
 306          * General read-only accessor
 307          *
 308          * @param string $name
 309          * @return string
 310          */
 311         public function getProperty( $name );
 312
 313         /**
 314          * @return string
 315          */
 316         public function getDomainID();
 317
 318         /**
 319          * Alias for getDomainID()
 320          *
 321          * @return string
 322          */
 323         public function getWikiID();
 324
 325         /**
 326          * Get the type of the DBMS, as it appears in $wgDBtype.
 327          *
 328          * @return string
 329          */
 330         public function getType();
 331
 332         /**
 333          * Open a connection to the database. Usually aborts on failure
 334          *
 335          * @param string $server Database server host
 336          * @param string $user Database user name
 337          * @param string $password Database user password
 338          * @param string $dbName Database name
 339          * @return bool
 340          * @throws DBConnectionError
 341          */
 342         public function open( $server, $user, $password, $dbName );
 343
 344         /**
 345          * Fetch the next row from the given result object, in object form.
 346          * Fields can be retrieved with $row->fieldname, with fields acting like
 347          * member variables.
 348          * If no more rows are available, false is returned.
 349          *
 350          * @param ResultWrapper|stdClass $res Object as returned from IDatabase::query(), etc.
 351          * @return stdClass|bool
 352          * @throws DBUnexpectedError Thrown if the database returns an error
 353          */
 354         public function fetchObject( $res );
 355
 356         /**
 357          * Fetch the next row from the given result object, in associative array
 358          * form. Fields are retrieved with $row['fieldname'].
 359          * If no more rows are available, false is returned.
 360          *
 361          * @param ResultWrapper $res Result object as returned from IDatabase::query(), etc.
 362          * @return array|bool
 363          * @throws DBUnexpectedError Thrown if the database returns an error
 364          */
 365         public function fetchRow( $res );
 366
 367         /**
 368          * Get the number of rows in a result object
 369          *
 370          * @param mixed $res A SQL result
 371          * @return int
 372          */
 373         public function numRows( $res );
 374
 375         /**
 376          * Get the number of fields in a result object
 377          * @see http://www.php.net/mysql_num_fields
 378          *
 379          * @param mixed $res A SQL result
 380          * @return int
 381          */
 382         public function numFields( $res );
 383
 384         /**
 385          * Get a field name in a result object
 386          * @see http://www.php.net/mysql_field_name
 387          *
 388          * @param mixed $res A SQL result
 389          * @param int $n
 390          * @return string
 391          */
 392         public function fieldName( $res, $n );
 393
 394         /**
 395          * Get the inserted value of an auto-increment row
 396          *
 397          * The value inserted should be fetched from nextSequenceValue()
 398          *
 399          * Example:
 400          * $id = $dbw->nextSequenceValue( 'page_page_id_seq' );
 401          * $dbw->insert( 'page', [ 'page_id' => $id ] );
 402          * $id = $dbw->insertId();
 403          *
 404          * @return int
 405          */
 406         public function insertId();
 407
 408         /**
 409          * Change the position of the cursor in a result object
 410          * @see http://www.php.net/mysql_data_seek
 411          *
 412          * @param mixed $res A SQL result
 413          * @param int $row
 414          */
 415         public function dataSeek( $res, $row );
 416
 417         /**
 418          * Get the last error number
 419          * @see http://www.php.net/mysql_errno
 420          *
 421          * @return int
 422          */
 423         public function lastErrno();
 424
 425         /**
 426          * Get a description of the last error
 427          * @see http://www.php.net/mysql_error
 428          *
 429          * @return string
 430          */
 431         public function lastError();
 432
 433         /**
 434          * mysql_fetch_field() wrapper
 435          * Returns false if the field doesn't exist
 436          *
 437          * @param string $table Table name
 438          * @param string $field Field name
 439          *
 440          * @return Field
 441          */
 442         public function fieldInfo( $table, $field );
 443
 444         /**
 445          * Get the number of rows affected by the last write query
 446          * @see http://www.php.net/mysql_affected_rows
 447          *
 448          * @return int
 449          */
 450         public function affectedRows();
 451
 452         /**
 453          * Returns a wikitext link to the DB's website, e.g.,
 454          *   return "[http://www.mysql.com/ MySQL]";
 455          * Should at least contain plain text, if for some reason
 456          * your database has no website.
 457          *
 458          * @return string Wikitext of a link to the server software's web site
 459          */
 460         public function getSoftwareLink();
 461
 462         /**
 463          * A string describing the current software version, like from
 464          * mysql_get_server_info().
 465          *
 466          * @return string Version information from the database server.
 467          */
 468         public function getServerVersion();
 469
 470         /**
 471          * Closes a database connection.
 472          * if it is open : commits any open transactions
 473          *
 474          * @throws DBError
 475          * @return bool Operation success. true if already closed.
 476          */
 477         public function close();
 478
 479         /**
 480          * @param string $error Fallback error message, used if none is given by DB
 481          * @throws DBConnectionError
 482          */
 483         public function reportConnectionError( $error = 'Unknown error' );
 484
 485         /**
 486          * Run an SQL query and return the result. Normally throws a DBQueryError
 487          * on failure. If errors are ignored, returns false instead.
 488          *
 489          * In new code, the query wrappers select(), insert(), update(), delete(),
 490          * etc. should be used where possible, since they give much better DBMS
 491          * independence and automatically quote or validate user input in a variety
 492          * of contexts. This function is generally only useful for queries which are
 493          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 494          * as CREATE TABLE.
 495          *
 496          * However, the query wrappers themselves should call this function.
 497          *
 498          * @param string $sql SQL query
 499          * @param string $fname Name of the calling function, for profiling/SHOW PROCESSLIST
 500          *     comment (you can use __METHOD__ or add some extra info)
 501          * @param bool $tempIgnore Whether to avoid throwing an exception on errors...
 502          *     maybe best to catch the exception instead?
 503          * @throws DBError
 504          * @return bool|ResultWrapper True for a successful write query, ResultWrapper object
 505          *     for a successful read query, or false on failure if $tempIgnore set
 506          */
 507         public function query( $sql, $fname = __METHOD__, $tempIgnore = false );
 508
 509         /**
 510          * Report a query error. Log the error, and if neither the object ignore
 511          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
 512          *
 513          * @param string $error
 514          * @param int $errno
 515          * @param string $sql
 516          * @param string $fname
 517          * @param bool $tempIgnore
 518          * @throws DBQueryError
 519          */
 520         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false );
 521
 522         /**
 523          * Free a result object returned by query() or select(). It's usually not
 524          * necessary to call this, just use unset() or let the variable holding
 525          * the result object go out of scope.
 526          *
 527          * @param mixed $res A SQL result
 528          */
 529         public function freeResult( $res );
 530
 531         /**
 532          * A SELECT wrapper which returns a single field from a single result row.
 533          *
 534          * Usually throws a DBQueryError on failure. If errors are explicitly
 535          * ignored, returns false on failure.
 536          *
 537          * If no result rows are returned from the query, false is returned.
 538          *
 539          * @param string|array $table Table name. See IDatabase::select() for details.
 540          * @param string $var The field name to select. This must be a valid SQL
 541          *   fragment: do not use unvalidated user input.
 542          * @param string|array $cond The condition array. See IDatabase::select() for details.
 543          * @param string $fname The function name of the caller.
 544          * @param string|array $options The query options. See IDatabase::select() for details.
 545          *
 546          * @return bool|mixed The value from the field, or false on failure.
 547          */
 548         public function selectField(
 549                 $table, $var, $cond = '', $fname = __METHOD__, $options = []
 550         );
 551
 552         /**
 553          * A SELECT wrapper which returns a list of single field values from result rows.
 554          *
 555          * Usually throws a DBQueryError on failure. If errors are explicitly
 556          * ignored, returns false on failure.
 557          *
 558          * If no result rows are returned from the query, false is returned.
 559          *
 560          * @param string|array $table Table name. See IDatabase::select() for details.
 561          * @param string $var The field name to select. This must be a valid SQL
 562          *   fragment: do not use unvalidated user input.
 563          * @param string|array $cond The condition array. See IDatabase::select() for details.
 564          * @param string $fname The function name of the caller.
 565          * @param string|array $options The query options. See IDatabase::select() for details.
 566          *
 567          * @return bool|array The values from the field, or false on failure
 568          * @since 1.25
 569          */
 570         public function selectFieldValues(
 571                 $table, $var, $cond = '', $fname = __METHOD__, $options = []
 572         );
 573
 574         /**
 575          * Execute a SELECT query constructed using the various parameters provided.
 576          * See below for full details of the parameters.
 577          *
 578          * @param string|array $table Table name
 579          * @param string|array $vars Field names
 580          * @param string|array $conds Conditions
 581          * @param string $fname Caller function name
 582          * @param array $options Query options
 583          * @param array $join_conds Join conditions
 584          *
 585          *
 586          * @param string|array $table
 587          *
 588          * May be either an array of table names, or a single string holding a table
 589          * name. If an array is given, table aliases can be specified, for example:
 590          *
 591          *    [ 'a' => 'user' ]
 592          *
 593          * This includes the user table in the query, with the alias "a" available
 594          * for use in field names (e.g. a.user_name).
 595          *
 596          * All of the table names given here are automatically run through
 597          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
 598          * added, and various other table name mappings to be performed.
 599          *
 600          * Do not use untrusted user input as a table name. Alias names should
 601          * not have characters outside of the Basic multilingual plane.
 602          *
 603          * @param string|array $vars
 604          *
 605          * May be either a field name or an array of field names. The field names
 606          * can be complete fragments of SQL, for direct inclusion into the SELECT
 607          * query. If an array is given, field aliases can be specified, for example:
 608          *
 609          *   [ 'maxrev' => 'MAX(rev_id)' ]
 610          *
 611          * This includes an expression with the alias "maxrev" in the query.
 612          *
 613          * If an expression is given, care must be taken to ensure that it is
 614          * DBMS-independent.
 615          *
 616          * Untrusted user input must not be passed to this parameter.
 617          *
 618          * @param string|array $conds
 619          *
 620          * May be either a string containing a single condition, or an array of
 621          * conditions. If an array is given, the conditions constructed from each
 622          * element are combined with AND.
 623          *
 624          * Array elements may take one of two forms:
 625          *
 626          *   - Elements with a numeric key are interpreted as raw SQL fragments.
 627          *   - Elements with a string key are interpreted as equality conditions,
 628          *     where the key is the field name.
 629          *     - If the value of such an array element is a scalar (such as a
 630          *       string), it will be treated as data and thus quoted appropriately.
 631          *       If it is null, an IS NULL clause will be added.
 632          *     - If the value is an array, an IN (...) clause will be constructed
 633          *       from its non-null elements, and an IS NULL clause will be added
 634          *       if null is present, such that the field may match any of the
 635          *       elements in the array. The non-null elements will be quoted.
 636          *
 637          * Note that expressions are often DBMS-dependent in their syntax.
 638          * DBMS-independent wrappers are provided for constructing several types of
 639          * expression commonly used in condition queries. See:
 640          *    - IDatabase::buildLike()
 641          *    - IDatabase::conditional()
 642          *
 643          * Untrusted user input is safe in the values of string keys, however untrusted
 644          * input must not be used in the array key names or in the values of numeric keys.
 645          * Escaping of untrusted input used in values of numeric keys should be done via
 646          * IDatabase::addQuotes()
 647          *
 648          * @param string|array $options
 649          *
 650          * Optional: Array of query options. Boolean options are specified by
 651          * including them in the array as a string value with a numeric key, for
 652          * example:
 653          *
 654          *    [ 'FOR UPDATE' ]
 655          *
 656          * The supported options are:
 657          *
 658          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
 659          *     with LIMIT can theoretically be used for paging through a result set,
 660          *     but this is discouraged in MediaWiki for performance reasons.
 661          *
 662          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
 663          *     and then the first rows are taken until the limit is reached. LIMIT
 664          *     is applied to a result set after OFFSET.
 665          *
 666          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
 667          *     changed until the next COMMIT.
 668          *
 669          *   - DISTINCT: Boolean: return only unique result rows.
 670          *
 671          *   - GROUP BY: May be either an SQL fragment string naming a field or
 672          *     expression to group by, or an array of such SQL fragments.
 673          *
 674          *   - HAVING: May be either an string containing a HAVING clause or an array of
 675          *     conditions building the HAVING clause. If an array is given, the conditions
 676          *     constructed from each element are combined with AND.
 677          *
 678          *   - ORDER BY: May be either an SQL fragment giving a field name or
 679          *     expression to order by, or an array of such SQL fragments.
 680          *
 681          *   - USE INDEX: This may be either a string giving the index name to use
 682          *     for the query, or an array. If it is an associative array, each key
 683          *     gives the table name (or alias), each value gives the index name to
 684          *     use for that table. All strings are SQL fragments and so should be
 685          *     validated by the caller.
 686          *
 687          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
 688          *     instead of SELECT.
 689          *
 690          * And also the following boolean MySQL extensions, see the MySQL manual
 691          * for documentation:
 692          *
 693          *    - LOCK IN SHARE MODE
 694          *    - STRAIGHT_JOIN
 695          *    - HIGH_PRIORITY
 696          *    - SQL_BIG_RESULT
 697          *    - SQL_BUFFER_RESULT
 698          *    - SQL_SMALL_RESULT
 699          *    - SQL_CALC_FOUND_ROWS
 700          *    - SQL_CACHE
 701          *    - SQL_NO_CACHE
 702          *
 703          *
 704          * @param string|array $join_conds
 705          *
 706          * Optional associative array of table-specific join conditions. In the
 707          * most common case, this is unnecessary, since the join condition can be
 708          * in $conds. However, it is useful for doing a LEFT JOIN.
 709          *
 710          * The key of the array contains the table name or alias. The value is an
 711          * array with two elements, numbered 0 and 1. The first gives the type of
 712          * join, the second is the same as the $conds parameter. Thus it can be
 713          * an SQL fragment, or an array where the string keys are equality and the
 714          * numeric keys are SQL fragments all AND'd together. For example:
 715          *
 716          *    [ 'page' => [ 'LEFT JOIN', 'page_latest=rev_id' ] ]
 717          *
 718          * @return ResultWrapper|bool If the query returned no rows, a ResultWrapper
 719          *   with no rows in it will be returned. If there was a query error, a
 720          *   DBQueryError exception will be thrown, except if the "ignore errors"
 721          *   option was set, in which case false will be returned.
 722          */
 723         public function select(
 724                 $table, $vars, $conds = '', $fname = __METHOD__,
 725                 $options = [], $join_conds = []
 726         );
 727
 728         /**
 729          * The equivalent of IDatabase::select() except that the constructed SQL
 730          * is returned, instead of being immediately executed. This can be useful for
 731          * doing UNION queries, where the SQL text of each query is needed. In general,
 732          * however, callers outside of Database classes should just use select().
 733          *
 734          * @param string|array $table Table name
 735          * @param string|array $vars Field names
 736          * @param string|array $conds Conditions
 737          * @param string $fname Caller function name
 738          * @param string|array $options Query options
 739          * @param string|array $join_conds Join conditions
 740          *
 741          * @return string SQL query string.
 742          * @see IDatabase::select()
 743          */
 744         public function selectSQLText(
 745                 $table, $vars, $conds = '', $fname = __METHOD__,
 746                 $options = [], $join_conds = []
 747         );
 748
 749         /**
 750          * Single row SELECT wrapper. Equivalent to IDatabase::select(), except
 751          * that a single row object is returned. If the query returns no rows,
 752          * false is returned.
 753          *
 754          * @param string|array $table Table name
 755          * @param string|array $vars Field names
 756          * @param array $conds Conditions
 757          * @param string $fname Caller function name
 758          * @param string|array $options Query options
 759          * @param array|string $join_conds Join conditions
 760          *
 761          * @return stdClass|bool
 762          */
 763         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
 764                 $options = [], $join_conds = []
 765         );
 766
 767         /**
 768          * Estimate the number of rows in dataset
 769          *
 770          * MySQL allows you to estimate the number of rows that would be returned
 771          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
 772          * index cardinality statistics, and is notoriously inaccurate, especially
 773          * when large numbers of rows have recently been added or deleted.
 774          *
 775          * For DBMSs that don't support fast result size estimation, this function
 776          * will actually perform the SELECT COUNT(*).
 777          *
 778          * Takes the same arguments as IDatabase::select().
 779          *
 780          * @param string $table Table name
 781          * @param string $vars Unused
 782          * @param array|string $conds Filters on the table
 783          * @param string $fname Function name for profiling
 784          * @param array $options Options for select
 785          * @return int Row count
 786          */
 787         public function estimateRowCount(
 788                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = []
 789         );
 790
 791         /**
 792          * Get the number of rows in dataset
 793          *
 794          * This is useful when trying to do COUNT(*) but with a LIMIT for performance.
 795          *
 796          * Takes the same arguments as IDatabase::select().
 797          *
 798          * @since 1.27 Added $join_conds parameter
 799          *
 800          * @param array|string $tables Table names
 801          * @param string $vars Unused
 802          * @param array|string $conds Filters on the table
 803          * @param string $fname Function name for profiling
 804          * @param array $options Options for select
 805          * @param array $join_conds Join conditions (since 1.27)
 806          * @return int Row count
 807          */
 808         public function selectRowCount(
 809                 $tables, $vars = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
 810         );
 811
 812         /**
 813          * Determines whether a field exists in a table
 814          *
 815          * @param string $table Table name
 816          * @param string $field Filed to check on that table
 817          * @param string $fname Calling function name (optional)
 818          * @return bool Whether $table has filed $field
 819          */
 820         public function fieldExists( $table, $field, $fname = __METHOD__ );
 821
 822         /**
 823          * Determines whether an index exists
 824          * Usually throws a DBQueryError on failure
 825          * If errors are explicitly ignored, returns NULL on failure
 826          *
 827          * @param string $table
 828          * @param string $index
 829          * @param string $fname
 830          * @return bool|null
 831          */
 832         public function indexExists( $table, $index, $fname = __METHOD__ );
 833
 834         /**
 835          * Query whether a given table exists
 836          *
 837          * @param string $table
 838          * @param string $fname
 839          * @return bool
 840          */
 841         public function tableExists( $table, $fname = __METHOD__ );
 842
 843         /**
 844          * Determines if a given index is unique
 845          *
 846          * @param string $table
 847          * @param string $index
 848          *
 849          * @return bool
 850          */
 851         public function indexUnique( $table, $index );
 852
 853         /**
 854          * INSERT wrapper, inserts an array into a table.
 855          *
 856          * $a may be either:
 857          *
 858          *   - A single associative array. The array keys are the field names, and
 859          *     the values are the values to insert. The values are treated as data
 860          *     and will be quoted appropriately. If NULL is inserted, this will be
 861          *     converted to a database NULL.
 862          *   - An array with numeric keys, holding a list of associative arrays.
 863          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
 864          *     each subarray must be identical to each other, and in the same order.
 865          *
 866          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
 867          * returns success.
 868          *
 869          * $options is an array of options, with boolean options encoded as values
 870          * with numeric keys, in the same style as $options in
 871          * IDatabase::select(). Supported options are:
 872          *
 873          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
 874          *     any rows which cause duplicate key errors are not inserted. It's
 875          *     possible to determine how many rows were successfully inserted using
 876          *     IDatabase::affectedRows().
 877          *
 878          * @param string $table Table name. This will be passed through
 879          *   DatabaseBase::tableName().
 880          * @param array $a Array of rows to insert
 881          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
 882          * @param array $options Array of options
 883          *
 884          * @return bool
 885          */
 886         public function insert( $table, $a, $fname = __METHOD__, $options = [] );
 887
 888         /**
 889          * UPDATE wrapper. Takes a condition array and a SET array.
 890          *
 891          * @param string $table Name of the table to UPDATE. This will be passed through
 892          *   DatabaseBase::tableName().
 893          * @param array $values An array of values to SET. For each array element,
 894          *   the key gives the field name, and the value gives the data to set
 895          *   that field to. The data will be quoted by IDatabase::addQuotes().
 896          * @param array $conds An array of conditions (WHERE). See
 897          *   IDatabase::select() for the details of the format of condition
 898          *   arrays. Use '*' to update all rows.
 899          * @param string $fname The function name of the caller (from __METHOD__),
 900          *   for logging and profiling.
 901          * @param array $options An array of UPDATE options, can be:
 902          *   - IGNORE: Ignore unique key conflicts
 903          *   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
 904          * @return bool
 905          */
 906         public function update( $table, $values, $conds, $fname = __METHOD__, $options = [] );
 907
 908         /**
 909          * Makes an encoded list of strings from an array
 910          *
 911          * These can be used to make conjunctions or disjunctions on SQL condition strings
 912          * derived from an array (see IDatabase::select() $conds documentation).
 913          *
 914          * Example usage:
 915          * @code
 916          *     $sql = $db->makeList( [
 917          *         'rev_user' => $id,
 918          *         $db->makeList( [ 'rev_minor' => 1, 'rev_len' < 500 ], $db::LIST_OR ] )
 919          *     ], $db::LIST_AND );
 920          * @endcode
 921          * This would set $sql to "rev_user = '$id' AND (rev_minor = '1' OR rev_len < '500')"
 922          *
 923          * @param array $a Containing the data
 924          * @param int $mode IDatabase class constant:
 925          *    - IDatabase::LIST_COMMA: Comma separated, no field names
 926          *    - IDatabase::LIST_AND:   ANDed WHERE clause (without the WHERE).
 927          *    - IDatabase::LIST_OR:    ORed WHERE clause (without the WHERE)
 928          *    - IDatabase::LIST_SET:   Comma separated with field names, like a SET clause
 929          *    - IDatabase::LIST_NAMES: Comma separated field names
 930          * @throws DBError
 931          * @return string
 932          */
 933         public function makeList( $a, $mode = self::LIST_COMMA );
 934
 935         /**
 936          * Build a partial where clause from a 2-d array such as used for LinkBatch.
 937          * The keys on each level may be either integers or strings.
 938          *
 939          * @param array $data Organized as 2-d
 940          *    [ baseKeyVal => [ subKeyVal => [ignored], ... ], ... ]
 941          * @param string $baseKey Field name to match the base-level keys to (eg 'pl_namespace')
 942          * @param string $subKey Field name to match the sub-level keys to (eg 'pl_title')
 943          * @return string|bool SQL fragment, or false if no items in array
 944          */
 945         public function makeWhereFrom2d( $data, $baseKey, $subKey );
 946
 947         /**
 948          * @param string $field
 949          * @return string
 950          */
 951         public function bitNot( $field );
 952
 953         /**
 954          * @param string $fieldLeft
 955          * @param string $fieldRight
 956          * @return string
 957          */
 958         public function bitAnd( $fieldLeft, $fieldRight );
 959
 960         /**
 961          * @param string $fieldLeft
 962          * @param string $fieldRight
 963          * @return string
 964          */
 965         public function bitOr( $fieldLeft, $fieldRight );
 966
 967         /**
 968          * Build a concatenation list to feed into a SQL query
 969          * @param array $stringList List of raw SQL expressions; caller is
 970          *   responsible for any quoting
 971          * @return string
 972          */
 973         public function buildConcat( $stringList );
 974
 975         /**
 976          * Build a GROUP_CONCAT or equivalent statement for a query.
 977          *
 978          * This is useful for combining a field for several rows into a single string.
 979          * NULL values will not appear in the output, duplicated values will appear,
 980          * and the resulting delimiter-separated values have no defined sort order.
 981          * Code using the results may need to use the PHP unique() or sort() methods.
 982          *
 983          * @param string $delim Glue to bind the results together
 984          * @param string|array $table Table name
 985          * @param string $field Field name
 986          * @param string|array $conds Conditions
 987          * @param string|array $join_conds Join conditions
 988          * @return string SQL text
 989          * @since 1.23
 990          */
 991         public function buildGroupConcatField(
 992                 $delim, $table, $field, $conds = '', $join_conds = []
 993         );
 994
 995         /**
 996          * Change the current database
 997          *
 998          * @param string $db
 999          * @return bool Success or failure
1000          */
1001         public function selectDB( $db );
1002
1003         /**
1004          * Get the current DB name
1005          * @return string
1006          */
1007         public function getDBname();
1008
1009         /**
1010          * Get the server hostname or IP address
1011          * @return string
1012          */
1013         public function getServer();
1014
1015         /**
1016          * Adds quotes and backslashes.
1017          *
1018          * @param string|Blob $s
1019          * @return string
1020          */
1021         public function addQuotes( $s );
1022
1023         /**
1024          * LIKE statement wrapper, receives a variable-length argument list with
1025          * parts of pattern to match containing either string literals that will be
1026          * escaped or tokens returned by anyChar() or anyString(). Alternatively,
1027          * the function could be provided with an array of aforementioned
1028          * parameters.
1029          *
1030          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns
1031          * a LIKE clause that searches for subpages of 'My page title'.
1032          * Alternatively:
1033          *   $pattern = [ 'My_page_title/', $dbr->anyString() ];
1034          *   $query .= $dbr->buildLike( $pattern );
1035          *
1036          * @since 1.16
1037          * @return string Fully built LIKE statement
1038          */
1039         public function buildLike();
1040
1041         /**
1042          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
1043          *
1044          * @return LikeMatch
1045          */
1046         public function anyChar();
1047
1048         /**
1049          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
1050          *
1051          * @return LikeMatch
1052          */
1053         public function anyString();
1054
1055         /**
1056          * Returns an appropriately quoted sequence value for inserting a new row.
1057          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
1058          * subclass will return an integer, and save the value for insertId()
1059          *
1060          * Any implementation of this function should *not* involve reusing
1061          * sequence numbers created for rolled-back transactions.
1062          * See http://bugs.mysql.com/bug.php?id=30767 for details.
1063          * @param string $seqName
1064          * @return null|int
1065          */
1066         public function nextSequenceValue( $seqName );
1067
1068         /**
1069          * REPLACE query wrapper.
1070          *
1071          * REPLACE is a very handy MySQL extension, which functions like an INSERT
1072          * except that when there is a duplicate key error, the old row is deleted
1073          * and the new row is inserted in its place.
1074          *
1075          * We simulate this with standard SQL with a DELETE followed by INSERT. To
1076          * perform the delete, we need to know what the unique indexes are so that
1077          * we know how to find the conflicting rows.
1078          *
1079          * It may be more efficient to leave off unique indexes which are unlikely
1080          * to collide. However if you do this, you run the risk of encountering
1081          * errors which wouldn't have occurred in MySQL.
1082          *
1083          * @param string $table The table to replace the row(s) in.
1084          * @param array $uniqueIndexes Is an array of indexes. Each element may be either
1085          *    a field name or an array of field names
1086          * @param array $rows Can be either a single row to insert, or multiple rows,
1087          *    in the same format as for IDatabase::insert()
1088          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1089          */
1090         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ );
1091
1092         /**
1093          * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
1094          *
1095          * This updates any conflicting rows (according to the unique indexes) using
1096          * the provided SET clause and inserts any remaining (non-conflicted) rows.
1097          *
1098          * $rows may be either:
1099          *   - A single associative array. The array keys are the field names, and
1100          *     the values are the values to insert. The values are treated as data
1101          *     and will be quoted appropriately. If NULL is inserted, this will be
1102          *     converted to a database NULL.
1103          *   - An array with numeric keys, holding a list of associative arrays.
1104          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1105          *     each subarray must be identical to each other, and in the same order.
1106          *
1107          * It may be more efficient to leave off unique indexes which are unlikely
1108          * to collide. However if you do this, you run the risk of encountering
1109          * errors which wouldn't have occurred in MySQL.
1110          *
1111          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1112          * returns success.
1113          *
1114          * @since 1.22
1115          *
1116          * @param string $table Table name. This will be passed through DatabaseBase::tableName().
1117          * @param array $rows A single row or list of rows to insert
1118          * @param array $uniqueIndexes List of single field names or field name tuples
1119          * @param array $set An array of values to SET. For each array element, the
1120          *   key gives the field name, and the value gives the data to set that
1121          *   field to. The data will be quoted by IDatabase::addQuotes().
1122          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1123          * @throws Exception
1124          * @return bool
1125          */
1126         public function upsert(
1127                 $table, array $rows, array $uniqueIndexes, array $set, $fname = __METHOD__
1128         );
1129
1130         /**
1131          * DELETE where the condition is a join.
1132          *
1133          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
1134          * we use sub-selects
1135          *
1136          * For safety, an empty $conds will not delete everything. If you want to
1137          * delete all rows where the join condition matches, set $conds='*'.
1138          *
1139          * DO NOT put the join condition in $conds.
1140          *
1141          * @param string $delTable The table to delete from.
1142          * @param string $joinTable The other table.
1143          * @param string $delVar The variable to join on, in the first table.
1144          * @param string $joinVar The variable to join on, in the second table.
1145          * @param array $conds Condition array of field names mapped to variables,
1146          *   ANDed together in the WHERE clause
1147          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1148          * @throws DBUnexpectedError
1149          */
1150         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
1151                 $fname = __METHOD__
1152         );
1153
1154         /**
1155          * DELETE query wrapper.
1156          *
1157          * @param array $table Table name
1158          * @param string|array $conds Array of conditions. See $conds in IDatabase::select()
1159          *   for the format. Use $conds == "*" to delete all rows
1160          * @param string $fname Name of the calling function
1161          * @throws DBUnexpectedError
1162          * @return bool|ResultWrapper
1163          */
1164         public function delete( $table, $conds, $fname = __METHOD__ );
1165
1166         /**
1167          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
1168          * into another table.
1169          *
1170          * @param string $destTable The table name to insert into
1171          * @param string|array $srcTable May be either a table name, or an array of table names
1172          *    to include in a join.
1173          *
1174          * @param array $varMap Must be an associative array of the form
1175          *    [ 'dest1' => 'source1', ... ]. Source items may be literals
1176          *    rather than field names, but strings should be quoted with
1177          *    IDatabase::addQuotes()
1178          *
1179          * @param array $conds Condition array. See $conds in IDatabase::select() for
1180          *    the details of the format of condition arrays. May be "*" to copy the
1181          *    whole table.
1182          *
1183          * @param string $fname The function name of the caller, from __METHOD__
1184          *
1185          * @param array $insertOptions Options for the INSERT part of the query, see
1186          *    IDatabase::insert() for details.
1187          * @param array $selectOptions Options for the SELECT part of the query, see
1188          *    IDatabase::select() for details.
1189          *
1190          * @return ResultWrapper
1191          */
1192         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
1193                 $fname = __METHOD__,
1194                 $insertOptions = [], $selectOptions = []
1195         );
1196
1197         /**
1198          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
1199          * within the UNION construct.
1200          * @return bool
1201          */
1202         public function unionSupportsOrderAndLimit();
1203
1204         /**
1205          * Construct a UNION query
1206          * This is used for providing overload point for other DB abstractions
1207          * not compatible with the MySQL syntax.
1208          * @param array $sqls SQL statements to combine
1209          * @param bool $all Use UNION ALL
1210          * @return string SQL fragment
1211          */
1212         public function unionQueries( $sqls, $all );
1213
1214         /**
1215          * Returns an SQL expression for a simple conditional. This doesn't need
1216          * to be overridden unless CASE isn't supported in your DBMS.
1217          *
1218          * @param string|array $cond SQL expression which will result in a boolean value
1219          * @param string $trueVal SQL expression to return if true
1220          * @param string $falseVal SQL expression to return if false
1221          * @return string SQL fragment
1222          */
1223         public function conditional( $cond, $trueVal, $falseVal );
1224
1225         /**
1226          * Returns a comand for str_replace function in SQL query.
1227          * Uses REPLACE() in MySQL
1228          *
1229          * @param string $orig Column to modify
1230          * @param string $old Column to seek
1231          * @param string $new Column to replace with
1232          *
1233          * @return string
1234          */
1235         public function strreplace( $orig, $old, $new );
1236
1237         /**
1238          * Determines how long the server has been up
1239          *
1240          * @return int
1241          */
1242         public function getServerUptime();
1243
1244         /**
1245          * Determines if the last failure was due to a deadlock
1246          *
1247          * @return bool
1248          */
1249         public function wasDeadlock();
1250
1251         /**
1252          * Determines if the last failure was due to a lock timeout
1253          *
1254          * @return bool
1255          */
1256         public function wasLockTimeout();
1257
1258         /**
1259          * Determines if the last query error was due to a dropped connection and should
1260          * be dealt with by pinging the connection and reissuing the query.
1261          *
1262          * @return bool
1263          */
1264         public function wasErrorReissuable();
1265
1266         /**
1267          * Determines if the last failure was due to the database being read-only.
1268          *
1269          * @return bool
1270          */
1271         public function wasReadOnlyError();
1272
1273         /**
1274          * Wait for the replica DB to catch up to a given master position
1275          *
1276          * @param DBMasterPos $pos
1277          * @param int $timeout The maximum number of seconds to wait for synchronisation
1278          * @return int|null Zero if the replica DB was past that position already,
1279          *   greater than zero if we waited for some period of time, less than
1280          *   zero if it timed out, and null on error
1281          */
1282         public function masterPosWait( DBMasterPos $pos, $timeout );
1283
1284         /**
1285          * Get the replication position of this replica DB
1286          *
1287          * @return DBMasterPos|bool False if this is not a replica DB.
1288          */
1289         public function getSlavePos();
1290
1291         /**
1292          * Get the position of this master
1293          *
1294          * @return DBMasterPos|bool False if this is not a master
1295          */
1296         public function getMasterPos();
1297
1298         /**
1299          * @return bool Whether the DB is marked as read-only server-side
1300          * @since 1.28
1301          */
1302         public function serverIsReadOnly();
1303
1304         /**
1305          * Run a callback as soon as the current transaction commits or rolls back.
1306          * An error is thrown if no transaction is pending. Queries in the function will run in
1307          * AUTO-COMMIT mode unless there are begin() calls. Callbacks must commit any transactions
1308          * that they begin.
1309          *
1310          * This is useful for combining cooperative locks and DB transactions.
1311          *
1312          * The callback takes one argument:
1313          *   - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK)
1314          *
1315          * @param callable $callback
1316          * @param string $fname Caller name
1317          * @return mixed
1318          * @since 1.28
1319          */
1320         public function onTransactionResolution( callable $callback, $fname = __METHOD__ );
1321
1322         /**
1323          * Run a callback as soon as there is no transaction pending.
1324          * If there is a transaction and it is rolled back, then the callback is cancelled.
1325          * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
1326          * Callbacks must commit any transactions that they begin.
1327          *
1328          * This is useful for updates to different systems or when separate transactions are needed.
1329          * For example, one might want to enqueue jobs into a system outside the database, but only
1330          * after the database is updated so that the jobs will see the data when they actually run.
1331          * It can also be used for updates that easily cause deadlocks if locks are held too long.
1332          *
1333          * Updates will execute in the order they were enqueued.
1334          *
1335          * The callback takes one argument:
1336          *   - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_IDLE)
1337          *
1338          * @param callable $callback
1339          * @param string $fname Caller name
1340          * @since 1.20
1341          */
1342         public function onTransactionIdle( callable $callback, $fname = __METHOD__ );
1343
1344         /**
1345          * Run a callback before the current transaction commits or now if there is none.
1346          * If there is a transaction and it is rolled back, then the callback is cancelled.
1347          * Callbacks must not start nor commit any transactions. If no transaction is active,
1348          * then a transaction will wrap the callback.
1349          *
1350          * This is useful for updates that easily cause deadlocks if locks are held too long
1351          * but where atomicity is strongly desired for these updates and some related updates.
1352          *
1353          * Updates will execute in the order they were enqueued.
1354          *
1355          * @param callable $callback
1356          * @param string $fname Caller name
1357          * @since 1.22
1358          */
1359         public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ );
1360
1361         /**
1362          * Run a callback each time any transaction commits or rolls back
1363          *
1364          * The callback takes two arguments:
1365          *   - IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK
1366          *   - This IDatabase object
1367          * Callbacks must commit any transactions that they begin.
1368          *
1369          * Registering a callback here will not affect writesOrCallbacks() pending
1370          *
1371          * @param string $name Callback name
1372          * @param callable|null $callback Use null to unset a listener
1373          * @return mixed
1374          * @since 1.28
1375          */
1376         public function setTransactionListener( $name, callable $callback = null );
1377
1378         /**
1379          * Begin an atomic section of statements
1380          *
1381          * If a transaction has been started already, just keep track of the given
1382          * section name to make sure the transaction is not committed pre-maturely.
1383          * This function can be used in layers (with sub-sections), so use a stack
1384          * to keep track of the different atomic sections. If there is no transaction,
1385          * start one implicitly.
1386          *
1387          * The goal of this function is to create an atomic section of SQL queries
1388          * without having to start a new transaction if it already exists.
1389          *
1390          * Atomic sections are more strict than transactions. With transactions,
1391          * attempting to begin a new transaction when one is already running results
1392          * in MediaWiki issuing a brief warning and doing an implicit commit. All
1393          * atomic levels *must* be explicitly closed using IDatabase::endAtomic(),
1394          * and any database transactions cannot be began or committed until all atomic
1395          * levels are closed. There is no such thing as implicitly opening or closing
1396          * an atomic section.
1397          *
1398          * @since 1.23
1399          * @param string $fname
1400          * @throws DBError
1401          */
1402         public function startAtomic( $fname = __METHOD__ );
1403
1404         /**
1405          * Ends an atomic section of SQL statements
1406          *
1407          * Ends the next section of atomic SQL statements and commits the transaction
1408          * if necessary.
1409          *
1410          * @since 1.23
1411          * @see IDatabase::startAtomic
1412          * @param string $fname
1413          * @throws DBError
1414          */
1415         public function endAtomic( $fname = __METHOD__ );
1416
1417         /**
1418          * Run a callback to do an atomic set of updates for this database
1419          *
1420          * The $callback takes the following arguments:
1421          *   - This database object
1422          *   - The value of $fname
1423          *
1424          * If any exception occurs in the callback, then rollback() will be called and the error will
1425          * be re-thrown. It may also be that the rollback itself fails with an exception before then.
1426          * In any case, such errors are expected to terminate the request, without any outside caller
1427          * attempting to catch errors and commit anyway. Note that any rollback undoes all prior
1428          * atomic section and uncommitted updates, which trashes the current request, requiring an
1429          * error to be displayed.
1430          *
1431          * This can be an alternative to explicit startAtomic()/endAtomic() calls.
1432          *
1433          * @see DatabaseBase::startAtomic
1434          * @see DatabaseBase::endAtomic
1435          *
1436          * @param string $fname Caller name (usually __METHOD__)
1437          * @param callable $callback Callback that issues DB updates
1438          * @return mixed $res Result of the callback (since 1.28)
1439          * @throws DBError
1440          * @throws RuntimeException
1441          * @throws UnexpectedValueException
1442          * @since 1.27
1443          */
1444         public function doAtomicSection( $fname, callable $callback );
1445
1446         /**
1447          * Begin a transaction. If a transaction is already in progress,
1448          * that transaction will be committed before the new transaction is started.
1449          *
1450          * Only call this from code with outer transcation scope.
1451          * See https://www.mediawiki.org/wiki/Database_transactions for details.
1452          * Nesting of transactions is not supported.
1453          *
1454          * Note that when the DBO_TRX flag is set (which is usually the case for web
1455          * requests, but not for maintenance scripts), any previous database query
1456          * will have started a transaction automatically.
1457          *
1458          * Nesting of transactions is not supported. Attempts to nest transactions
1459          * will cause a warning, unless the current transaction was started
1460          * automatically because of the DBO_TRX flag.
1461          *
1462          * @param string $fname Calling function name
1463          * @param string $mode A situationally valid IDatabase::TRANSACTION_* constant [optional]
1464          * @throws DBError
1465          */
1466         public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT );
1467
1468         /**
1469          * Commits a transaction previously started using begin().
1470          * If no transaction is in progress, a warning is issued.
1471          *
1472          * Only call this from code with outer transcation scope.
1473          * See https://www.mediawiki.org/wiki/Database_transactions for details.
1474          * Nesting of transactions is not supported.
1475          *
1476          * @param string $fname
1477          * @param string $flush Flush flag, set to situationally valid IDatabase::FLUSHING_*
1478          *   constant to disable warnings about explicitly committing implicit transactions,
1479          *   or calling commit when no transaction is in progress.
1480          *
1481          *   This will trigger an exception if there is an ongoing explicit transaction.
1482          *
1483          *   Only set the flush flag if you are sure that these warnings are not applicable,
1484          *   and no explicit transactions are open.
1485          *
1486          * @throws DBUnexpectedError
1487          */
1488         public function commit( $fname = __METHOD__, $flush = '' );
1489
1490         /**
1491          * Rollback a transaction previously started using begin().
1492          * If no transaction is in progress, a warning is issued.
1493          *
1494          * Only call this from code with outer transcation scope.
1495          * See https://www.mediawiki.org/wiki/Database_transactions for details.
1496          * Nesting of transactions is not supported. If a serious unexpected error occurs,
1497          * throwing an Exception is preferrable, using a pre-installed error handler to trigger
1498          * rollback (in any case, failure to issue COMMIT will cause rollback server-side).
1499          *
1500          * @param string $fname Calling function name
1501          * @param string $flush Flush flag, set to a situationally valid IDatabase::FLUSHING_*
1502          *   constant to disable warnings about calling rollback when no transaction is in
1503          *   progress. This will silently break any ongoing explicit transaction. Only set the
1504          *   flush flag if you are sure that it is safe to ignore these warnings in your context.
1505          * @throws DBUnexpectedError
1506          * @since 1.23 Added $flush parameter
1507          */
1508         public function rollback( $fname = __METHOD__, $flush = '' );
1509
1510         /**
1511          * Commit any transaction but error out if writes or callbacks are pending
1512          *
1513          * This is intended for clearing out REPEATABLE-READ snapshots so that callers can
1514          * see a new point-in-time of the database. This is useful when one of many transaction
1515          * rounds finished and significant time will pass in the script's lifetime. It is also
1516          * useful to call on a replica DB after waiting on replication to catch up to the master.
1517          *
1518          * @param string $fname Calling function name
1519          * @throws DBUnexpectedError
1520          * @since 1.28
1521          */
1522         public function flushSnapshot( $fname = __METHOD__ );
1523
1524         /**
1525          * List all tables on the database
1526          *
1527          * @param string $prefix Only show tables with this prefix, e.g. mw_
1528          * @param string $fname Calling function name
1529          * @throws DBError
1530          * @return array
1531          */
1532         public function listTables( $prefix = null, $fname = __METHOD__ );
1533
1534         /**
1535          * Convert a timestamp in one of the formats accepted by wfTimestamp()
1536          * to the format used for inserting into timestamp fields in this DBMS.
1537          *
1538          * The result is unquoted, and needs to be passed through addQuotes()
1539          * before it can be included in raw SQL.
1540          *
1541          * @param string|int $ts
1542          *
1543          * @return string
1544          */
1545         public function timestamp( $ts = 0 );
1546
1547         /**
1548          * Convert a timestamp in one of the formats accepted by wfTimestamp()
1549          * to the format used for inserting into timestamp fields in this DBMS. If
1550          * NULL is input, it is passed through, allowing NULL values to be inserted
1551          * into timestamp fields.
1552          *
1553          * The result is unquoted, and needs to be passed through addQuotes()
1554          * before it can be included in raw SQL.
1555          *
1556          * @param string|int $ts
1557          *
1558          * @return string
1559          */
1560         public function timestampOrNull( $ts = null );
1561
1562         /**
1563          * Ping the server and try to reconnect if it there is no connection
1564          *
1565          * @param float|null &$rtt Value to store the estimated RTT [optional]
1566          * @return bool Success or failure
1567          */
1568         public function ping( &$rtt = null );
1569
1570         /**
1571          * Get replica DB lag. Currently supported only by MySQL.
1572          *
1573          * Note that this function will generate a fatal error on many
1574          * installations. Most callers should use LoadBalancer::safeGetLag()
1575          * instead.
1576          *
1577          * @return int|bool Database replication lag in seconds or false on error
1578          */
1579         public function getLag();
1580
1581         /**
1582          * Get the replica DB lag when the current transaction started
1583          * or a general lag estimate if not transaction is active
1584          *
1585          * This is useful when transactions might use snapshot isolation
1586          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
1587          * is this lag plus transaction duration. If they don't, it is still
1588          * safe to be pessimistic. In AUTO-COMMIT mode, this still gives an
1589          * indication of the staleness of subsequent reads.
1590          *
1591          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
1592          * @since 1.27
1593          */
1594         public function getSessionLagStatus();
1595
1596         /**
1597          * Return the maximum number of items allowed in a list, or 0 for unlimited.
1598          *
1599          * @return int
1600          */
1601         public function maxListLen();
1602
1603         /**
1604          * Some DBMSs have a special format for inserting into blob fields, they
1605          * don't allow simple quoted strings to be inserted. To insert into such
1606          * a field, pass the data through this function before passing it to
1607          * IDatabase::insert().
1608          *
1609          * @param string $b
1610          * @return string
1611          */
1612         public function encodeBlob( $b );
1613
1614         /**
1615          * Some DBMSs return a special placeholder object representing blob fields
1616          * in result objects. Pass the object through this function to return the
1617          * original string.
1618          *
1619          * @param string|Blob $b
1620          * @return string
1621          */
1622         public function decodeBlob( $b );
1623
1624         /**
1625          * Override database's default behavior. $options include:
1626          *     'connTimeout' : Set the connection timeout value in seconds.
1627          *                     May be useful for very long batch queries such as
1628          *                     full-wiki dumps, where a single query reads out over
1629          *                     hours or days.
1630          *
1631          * @param array $options
1632          * @return void
1633          */
1634         public function setSessionOptions( array $options );
1635
1636         /**
1637          * Set variables to be used in sourceFile/sourceStream, in preference to the
1638          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
1639          * all. If it's set to false, $GLOBALS will be used.
1640          *
1641          * @param bool|array $vars Mapping variable name to value.
1642          */
1643         public function setSchemaVars( $vars );
1644
1645         /**
1646          * Check to see if a named lock is available (non-blocking)
1647          *
1648          * @param string $lockName Name of lock to poll
1649          * @param string $method Name of method calling us
1650          * @return bool
1651          * @since 1.20
1652          */
1653         public function lockIsFree( $lockName, $method );
1654
1655         /**
1656          * Acquire a named lock
1657          *
1658          * Named locks are not related to transactions
1659          *
1660          * @param string $lockName Name of lock to aquire
1661          * @param string $method Name of the calling method
1662          * @param int $timeout Acquisition timeout in seconds
1663          * @return bool
1664          */
1665         public function lock( $lockName, $method, $timeout = 5 );
1666
1667         /**
1668          * Release a lock
1669          *
1670          * Named locks are not related to transactions
1671          *
1672          * @param string $lockName Name of lock to release
1673          * @param string $method Name of the calling method
1674          *
1675          * @return int Returns 1 if the lock was released, 0 if the lock was not established
1676          * by this thread (in which case the lock is not released), and NULL if the named
1677          * lock did not exist
1678          */
1679         public function unlock( $lockName, $method );
1680
1681         /**
1682          * Acquire a named lock, flush any transaction, and return an RAII style unlocker object
1683          *
1684          * Only call this from outer transcation scope and when only one DB will be affected.
1685          * See https://www.mediawiki.org/wiki/Database_transactions for details.
1686          *
1687          * This is suitiable for transactions that need to be serialized using cooperative locks,
1688          * where each transaction can see each others' changes. Any transaction is flushed to clear
1689          * out stale REPEATABLE-READ snapshot data. Once the returned object falls out of PHP scope,
1690          * the lock will be released unless a transaction is active. If one is active, then the lock
1691          * will be released when it either commits or rolls back.
1692          *
1693          * If the lock acquisition failed, then no transaction flush happens, and null is returned.
1694          *
1695          * @param string $lockKey Name of lock to release
1696          * @param string $fname Name of the calling method
1697          * @param int $timeout Acquisition timeout in seconds
1698          * @return ScopedCallback|null
1699          * @throws DBUnexpectedError
1700          * @since 1.27
1701          */
1702         public function getScopedLockAndFlush( $lockKey, $fname, $timeout );
1703
1704         /**
1705          * Check to see if a named lock used by lock() use blocking queues
1706          *
1707          * @return bool
1708          * @since 1.26
1709          */
1710         public function namedLocksEnqueue();
1711
1712         /**
1713          * Find out when 'infinity' is. Most DBMSes support this. This is a special
1714          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
1715          * because "i" sorts after all numbers.
1716          *
1717          * @return string
1718          */
1719         public function getInfinity();
1720
1721         /**
1722          * Encode an expiry time into the DBMS dependent format
1723          *
1724          * @param string $expiry Timestamp for expiry, or the 'infinity' string
1725          * @return string
1726          */
1727         public function encodeExpiry( $expiry );
1728
1729         /**
1730          * Decode an expiry time into a DBMS independent format
1731          *
1732          * @param string $expiry DB timestamp field value for expiry
1733          * @param int $format TS_* constant, defaults to TS_MW
1734          * @return string
1735          */
1736         public function decodeExpiry( $expiry, $format = TS_MW );
1737
1738         /**
1739          * Allow or deny "big selects" for this session only. This is done by setting
1740          * the sql_big_selects session variable.
1741          *
1742          * This is a MySQL-specific feature.
1743          *
1744          * @param bool|string $value True for allow, false for deny, or "default" to
1745          *   restore the initial value
1746          */
1747         public function setBigSelects( $value = true );
1748
1749         /**
1750          * @return bool Whether this DB is read-only
1751          * @since 1.27
1752          */
1753         public function isReadOnly();
1754
1755         /**
1756          * Make certain table names use their own database, schema, and table prefix
1757          * when passed into SQL queries pre-escaped and without a qualified database name
1758          *
1759          * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
1760          * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
1761          *
1762          * Calling this twice will completely clear any old table aliases. Also, note that
1763          * callers are responsible for making sure the schemas and databases actually exist.
1764          *
1765          * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
1766          * @since 1.28
1767          */
1768         public function setTableAliases( array $aliases );
1769 }