includes/libs/rdbms/database/IDatabase.php

   1 <?php
   2 /**
   3  * @defgroup Database Database
   4  *
   5  * This file deals with database interface functions
   6  * and query specifics/optimisations.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Database
  25  */
  26
  27 /**
  28  * Basic database interface for live and lazy-loaded relation database handles
  29  *
  30  * @note: IDatabase and DBConnRef should be updated to reflect any changes
  31  * @ingroup Database
  32  */
  33 interface IDatabase {
  34         /** @var int Callback triggered immediately due to no active transaction */
  35         const TRIGGER_IDLE = 1;
  36         /** @var int Callback triggered by COMMIT */
  37         const TRIGGER_COMMIT = 2;
  38         /** @var int Callback triggered by ROLLBACK */
  39         const TRIGGER_ROLLBACK = 3;
  40
  41         /** @var string Transaction is requested by regular caller outside of the DB layer */
  42         const TRANSACTION_EXPLICIT = '';
  43         /** @var string Transaction is requested internally via DBO_TRX/startAtomic() */
  44         const TRANSACTION_INTERNAL = 'implicit';
  45
  46         /** @var string Transaction operation comes from service managing all DBs */
  47         const FLUSHING_ALL_PEERS = 'flush';
  48         /** @var string Transaction operation comes from the database class internally */
  49         const FLUSHING_INTERNAL = 'flush';
  50
  51         /** @var string Do not remember the prior flags */
  52         const REMEMBER_NOTHING = '';
  53         /** @var string Remember the prior flags */
  54         const REMEMBER_PRIOR = 'remember';
  55         /** @var string Restore to the prior flag state */
  56         const RESTORE_PRIOR = 'prior';
  57         /** @var string Restore to the initial flag state */
  58         const RESTORE_INITIAL = 'initial';
  59
  60         /** @var string Estimate total time (RTT, scanning, waiting on locks, applying) */
  61         const ESTIMATE_TOTAL = 'total';
  62         /** @var string Estimate time to apply (scanning, applying) */
  63         const ESTIMATE_DB_APPLY = 'apply';
  64
  65         /** @var int Combine list with comma delimeters */
  66         const LIST_COMMA = 0;
  67         /** @var int Combine list with AND clauses */
  68         const LIST_AND = 1;
  69         /** @var int Convert map into a SET clause */
  70         const LIST_SET = 2;
  71         /** @var int Treat as field name and do not apply value escaping */
  72         const LIST_NAMES = 3;
  73         /** @var int Combine list with OR clauses */
  74         const LIST_OR = 4;
  75
  76         /** @var int Enable debug logging */
  77         const DBO_DEBUG = 1;
  78         /** @var int Disable query buffering (only one result set can be iterated at a time) */
  79         const DBO_NOBUFFER = 2;
  80         /** @var int Ignore query errors (internal use only!) */
  81         const DBO_IGNORE = 4;
  82         /** @var int Autoatically start transaction on first query (work with ILoadBalancer rounds) */
  83         const DBO_TRX = 8;
  84         /** @var int Use DBO_TRX in non-CLI mode */
  85         const DBO_DEFAULT = 16;
  86         /** @var int Use DB persistent connections if possible */
  87         const DBO_PERSISTENT = 32;
  88         /** @var int DBA session mode; mostly for Oracle */
  89         const DBO_SYSDBA = 64;
  90         /** @var int Schema file mode; mostly for Oracle */
  91         const DBO_DDLMODE = 128;
  92         /** @var int Enable SSL/TLS in connection protocol */
  93         const DBO_SSL = 256;
  94         /** @var int Enable compression in connection protocol */
  95         const DBO_COMPRESS = 512;
  96
  97         /**
  98          * A string describing the current software version, and possibly
  99          * other details in a user-friendly way. Will be listed on Special:Version, etc.
 100          * Use getServerVersion() to get machine-friendly information.
 101          *
 102          * @return string Version information from the database server
 103          */
 104         public function getServerInfo();
 105
 106         /**
 107          * Turns buffering of SQL result sets on (true) or off (false). Default is "on".
 108          *
 109          * Unbuffered queries are very troublesome in MySQL:
 110          *
 111          *   - If another query is executed while the first query is being read
 112          *     out, the first query is killed. This means you can't call normal
 113          *     Database functions while you are reading an unbuffered query result
 114          *     from a normal Database connection.
 115          *
 116          *   - Unbuffered queries cause the MySQL server to use large amounts of
 117          *     memory and to hold broad locks which block other queries.
 118          *
 119          * If you want to limit client-side memory, it's almost always better to
 120          * split up queries into batches using a LIMIT clause than to switch off
 121          * buffering.
 122          *
 123          * @param null|bool $buffer
 124          * @return null|bool The previous value of the flag
 125          */
 126         public function bufferResults( $buffer = null );
 127
 128         /**
 129          * Gets the current transaction level.
 130          *
 131          * Historically, transactions were allowed to be "nested". This is no
 132          * longer supported, so this function really only returns a boolean.
 133          *
 134          * @return int The previous value
 135          */
 136         public function trxLevel();
 137
 138         /**
 139          * Get the UNIX timestamp of the time that the transaction was established
 140          *
 141          * This can be used to reason about the staleness of SELECT data
 142          * in REPEATABLE-READ transaction isolation level.
 143          *
 144          * @return float|null Returns null if there is not active transaction
 145          * @since 1.25
 146          */
 147         public function trxTimestamp();
 148
 149         /**
 150          * @return bool Whether an explicit transaction or atomic sections are still open
 151          * @since 1.28
 152          */
 153         public function explicitTrxActive();
 154
 155         /**
 156          * Get/set the table prefix.
 157          * @param string $prefix The table prefix to set, or omitted to leave it unchanged.
 158          * @return string The previous table prefix.
 159          */
 160         public function tablePrefix( $prefix = null );
 161
 162         /**
 163          * Get/set the db schema.
 164          * @param string $schema The database schema to set, or omitted to leave it unchanged.
 165          * @return string The previous db schema.
 166          */
 167         public function dbSchema( $schema = null );
 168
 169         /**
 170          * Get properties passed down from the server info array of the load
 171          * balancer.
 172          *
 173          * @param string $name The entry of the info array to get, or null to get the
 174          *   whole array
 175          *
 176          * @return array|mixed|null
 177          */
 178         public function getLBInfo( $name = null );
 179
 180         /**
 181          * Set the LB info array, or a member of it. If called with one parameter,
 182          * the LB info array is set to that parameter. If it is called with two
 183          * parameters, the member with the given name is set to the given value.
 184          *
 185          * @param string $name
 186          * @param array $value
 187          */
 188         public function setLBInfo( $name, $value = null );
 189
 190         /**
 191          * Set a lazy-connecting DB handle to the master DB (for replication status purposes)
 192          *
 193          * @param IDatabase $conn
 194          * @since 1.27
 195          */
 196         public function setLazyMasterHandle( IDatabase $conn );
 197
 198         /**
 199          * Returns true if this database does an implicit sort when doing GROUP BY
 200          *
 201          * @return bool
 202          */
 203         public function implicitGroupby();
 204
 205         /**
 206          * Returns true if this database does an implicit order by when the column has an index
 207          * For example: SELECT page_title FROM page LIMIT 1
 208          *
 209          * @return bool
 210          */
 211         public function implicitOrderby();
 212
 213         /**
 214          * Return the last query that went through IDatabase::query()
 215          * @return string
 216          */
 217         public function lastQuery();
 218
 219         /**
 220          * Returns true if the connection may have been used for write queries.
 221          * Should return true if unsure.
 222          *
 223          * @return bool
 224          */
 225         public function doneWrites();
 226
 227         /**
 228          * Returns the last time the connection may have been used for write queries.
 229          * Should return a timestamp if unsure.
 230          *
 231          * @return int|float UNIX timestamp or false
 232          * @since 1.24
 233          */
 234         public function lastDoneWrites();
 235
 236         /**
 237          * @return bool Whether there is a transaction open with possible write queries
 238          * @since 1.27
 239          */
 240         public function writesPending();
 241
 242         /**
 243          * Returns true if there is a transaction open with possible write
 244          * queries or transaction pre-commit/idle callbacks waiting on it to finish.
 245          * This does *not* count recurring callbacks, e.g. from setTransactionListener().
 246          *
 247          * @return bool
 248          */
 249         public function writesOrCallbacksPending();
 250
 251         /**
 252          * Get the time spend running write queries for this transaction
 253          *
 254          * High times could be due to scanning, updates, locking, and such
 255          *
 256          * @param string $type IDatabase::ESTIMATE_* constant [default: ESTIMATE_ALL]
 257          * @return float|bool Returns false if not transaction is active
 258          * @since 1.26
 259          */
 260         public function pendingWriteQueryDuration( $type = self::ESTIMATE_TOTAL );
 261
 262         /**
 263          * Get the list of method names that did write queries for this transaction
 264          *
 265          * @return array
 266          * @since 1.27
 267          */
 268         public function pendingWriteCallers();
 269
 270         /**
 271          * Is a connection to the database open?
 272          * @return bool
 273          */
 274         public function isOpen();
 275
 276         /**
 277          * Set a flag for this connection
 278          *
 279          * @param int $flag DBO_* constants from Defines.php:
 280          *   - DBO_DEBUG: output some debug info (same as debug())
 281          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 282          *   - DBO_TRX: automatically start transactions
 283          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 284          *       and removes it in command line mode
 285          *   - DBO_PERSISTENT: use persistant database connection
 286          * @param string $remember IDatabase::REMEMBER_* constant [default: REMEMBER_NOTHING]
 287          */
 288         public function setFlag( $flag, $remember = self::REMEMBER_NOTHING );
 289
 290         /**
 291          * Clear a flag for this connection
 292          *
 293          * @param int $flag DBO_* constants from Defines.php:
 294          *   - DBO_DEBUG: output some debug info (same as debug())
 295          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 296          *   - DBO_TRX: automatically start transactions
 297          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 298          *       and removes it in command line mode
 299          *   - DBO_PERSISTENT: use persistant database connection
 300          * @param string $remember IDatabase::REMEMBER_* constant [default: REMEMBER_NOTHING]
 301          */
 302         public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING );
 303
 304         /**
 305          * Restore the flags to their prior state before the last setFlag/clearFlag call
 306          *
 307          * @param string $state IDatabase::RESTORE_* constant. [default: RESTORE_PRIOR]
 308          * @since 1.28
 309          */
 310         public function restoreFlags( $state = self::RESTORE_PRIOR );
 311
 312         /**
 313          * Returns a boolean whether the flag $flag is set for this connection
 314          *
 315          * @param int $flag DBO_* constants from Defines.php:
 316          *   - DBO_DEBUG: output some debug info (same as debug())
 317          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 318          *   - DBO_TRX: automatically start transactions
 319          *   - DBO_PERSISTENT: use persistant database connection
 320          * @return bool
 321          */
 322         public function getFlag( $flag );
 323
 324         /**
 325          * General read-only accessor
 326          *
 327          * @param string $name
 328          * @return string
 329          */
 330         public function getProperty( $name );
 331
 332         /**
 333          * @return string
 334          */
 335         public function getDomainID();
 336
 337         /**
 338          * Alias for getDomainID()
 339          *
 340          * @return string
 341          */
 342         public function getWikiID();
 343
 344         /**
 345          * Get the type of the DBMS, as it appears in $wgDBtype.
 346          *
 347          * @return string
 348          */
 349         public function getType();
 350
 351         /**
 352          * Open a connection to the database. Usually aborts on failure
 353          *
 354          * @param string $server Database server host
 355          * @param string $user Database user name
 356          * @param string $password Database user password
 357          * @param string $dbName Database name
 358          * @return bool
 359          * @throws DBConnectionError
 360          */
 361         public function open( $server, $user, $password, $dbName );
 362
 363         /**
 364          * Fetch the next row from the given result object, in object form.
 365          * Fields can be retrieved with $row->fieldname, with fields acting like
 366          * member variables.
 367          * If no more rows are available, false is returned.
 368          *
 369          * @param ResultWrapper|stdClass $res Object as returned from IDatabase::query(), etc.
 370          * @return stdClass|bool
 371          * @throws DBUnexpectedError Thrown if the database returns an error
 372          */
 373         public function fetchObject( $res );
 374
 375         /**
 376          * Fetch the next row from the given result object, in associative array
 377          * form. Fields are retrieved with $row['fieldname'].
 378          * If no more rows are available, false is returned.
 379          *
 380          * @param ResultWrapper $res Result object as returned from IDatabase::query(), etc.
 381          * @return array|bool
 382          * @throws DBUnexpectedError Thrown if the database returns an error
 383          */
 384         public function fetchRow( $res );
 385
 386         /**
 387          * Get the number of rows in a result object
 388          *
 389          * @param mixed $res A SQL result
 390          * @return int
 391          */
 392         public function numRows( $res );
 393
 394         /**
 395          * Get the number of fields in a result object
 396          * @see http://www.php.net/mysql_num_fields
 397          *
 398          * @param mixed $res A SQL result
 399          * @return int
 400          */
 401         public function numFields( $res );
 402
 403         /**
 404          * Get a field name in a result object
 405          * @see http://www.php.net/mysql_field_name
 406          *
 407          * @param mixed $res A SQL result
 408          * @param int $n
 409          * @return string
 410          */
 411         public function fieldName( $res, $n );
 412
 413         /**
 414          * Get the inserted value of an auto-increment row
 415          *
 416          * The value inserted should be fetched from nextSequenceValue()
 417          *
 418          * Example:
 419          * $id = $dbw->nextSequenceValue( 'page_page_id_seq' );
 420          * $dbw->insert( 'page', [ 'page_id' => $id ] );
 421          * $id = $dbw->insertId();
 422          *
 423          * @return int
 424          */
 425         public function insertId();
 426
 427         /**
 428          * Change the position of the cursor in a result object
 429          * @see http://www.php.net/mysql_data_seek
 430          *
 431          * @param mixed $res A SQL result
 432          * @param int $row
 433          */
 434         public function dataSeek( $res, $row );
 435
 436         /**
 437          * Get the last error number
 438          * @see http://www.php.net/mysql_errno
 439          *
 440          * @return int
 441          */
 442         public function lastErrno();
 443
 444         /**
 445          * Get a description of the last error
 446          * @see http://www.php.net/mysql_error
 447          *
 448          * @return string
 449          */
 450         public function lastError();
 451
 452         /**
 453          * mysql_fetch_field() wrapper
 454          * Returns false if the field doesn't exist
 455          *
 456          * @param string $table Table name
 457          * @param string $field Field name
 458          *
 459          * @return Field
 460          */
 461         public function fieldInfo( $table, $field );
 462
 463         /**
 464          * Get the number of rows affected by the last write query
 465          * @see http://www.php.net/mysql_affected_rows
 466          *
 467          * @return int
 468          */
 469         public function affectedRows();
 470
 471         /**
 472          * Returns a wikitext link to the DB's website, e.g.,
 473          *   return "[http://www.mysql.com/ MySQL]";
 474          * Should at least contain plain text, if for some reason
 475          * your database has no website.
 476          *
 477          * @return string Wikitext of a link to the server software's web site
 478          */
 479         public function getSoftwareLink();
 480
 481         /**
 482          * A string describing the current software version, like from
 483          * mysql_get_server_info().
 484          *
 485          * @return string Version information from the database server.
 486          */
 487         public function getServerVersion();
 488
 489         /**
 490          * Closes a database connection.
 491          * if it is open : commits any open transactions
 492          *
 493          * @throws DBError
 494          * @return bool Operation success. true if already closed.
 495          */
 496         public function close();
 497
 498         /**
 499          * @param string $error Fallback error message, used if none is given by DB
 500          * @throws DBConnectionError
 501          */
 502         public function reportConnectionError( $error = 'Unknown error' );
 503
 504         /**
 505          * Run an SQL query and return the result. Normally throws a DBQueryError
 506          * on failure. If errors are ignored, returns false instead.
 507          *
 508          * In new code, the query wrappers select(), insert(), update(), delete(),
 509          * etc. should be used where possible, since they give much better DBMS
 510          * independence and automatically quote or validate user input in a variety
 511          * of contexts. This function is generally only useful for queries which are
 512          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 513          * as CREATE TABLE.
 514          *
 515          * However, the query wrappers themselves should call this function.
 516          *
 517          * @param string $sql SQL query
 518          * @param string $fname Name of the calling function, for profiling/SHOW PROCESSLIST
 519          *     comment (you can use __METHOD__ or add some extra info)
 520          * @param bool $tempIgnore Whether to avoid throwing an exception on errors...
 521          *     maybe best to catch the exception instead?
 522          * @throws DBError
 523          * @return bool|ResultWrapper True for a successful write query, ResultWrapper object
 524          *     for a successful read query, or false on failure if $tempIgnore set
 525          */
 526         public function query( $sql, $fname = __METHOD__, $tempIgnore = false );
 527
 528         /**
 529          * Report a query error. Log the error, and if neither the object ignore
 530          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
 531          *
 532          * @param string $error
 533          * @param int $errno
 534          * @param string $sql
 535          * @param string $fname
 536          * @param bool $tempIgnore
 537          * @throws DBQueryError
 538          */
 539         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false );
 540
 541         /**
 542          * Free a result object returned by query() or select(). It's usually not
 543          * necessary to call this, just use unset() or let the variable holding
 544          * the result object go out of scope.
 545          *
 546          * @param mixed $res A SQL result
 547          */
 548         public function freeResult( $res );
 549
 550         /**
 551          * A SELECT wrapper which returns a single field from a single result row.
 552          *
 553          * Usually throws a DBQueryError on failure. If errors are explicitly
 554          * ignored, returns false on failure.
 555          *
 556          * If no result rows are returned from the query, false is returned.
 557          *
 558          * @param string|array $table Table name. See IDatabase::select() for details.
 559          * @param string $var The field name to select. This must be a valid SQL
 560          *   fragment: do not use unvalidated user input.
 561          * @param string|array $cond The condition array. See IDatabase::select() for details.
 562          * @param string $fname The function name of the caller.
 563          * @param string|array $options The query options. See IDatabase::select() for details.
 564          *
 565          * @return bool|mixed The value from the field, or false on failure.
 566          */
 567         public function selectField(
 568                 $table, $var, $cond = '', $fname = __METHOD__, $options = []
 569         );
 570
 571         /**
 572          * A SELECT wrapper which returns a list of single field values from result rows.
 573          *
 574          * Usually throws a DBQueryError on failure. If errors are explicitly
 575          * ignored, returns false on failure.
 576          *
 577          * If no result rows are returned from the query, false is returned.
 578          *
 579          * @param string|array $table Table name. See IDatabase::select() for details.
 580          * @param string $var The field name to select. This must be a valid SQL
 581          *   fragment: do not use unvalidated user input.
 582          * @param string|array $cond The condition array. See IDatabase::select() for details.
 583          * @param string $fname The function name of the caller.
 584          * @param string|array $options The query options. See IDatabase::select() for details.
 585          *
 586          * @return bool|array The values from the field, or false on failure
 587          * @since 1.25
 588          */
 589         public function selectFieldValues(
 590                 $table, $var, $cond = '', $fname = __METHOD__, $options = []
 591         );
 592
 593         /**
 594          * Execute a SELECT query constructed using the various parameters provided.
 595          * See below for full details of the parameters.
 596          *
 597          * @param string|array $table Table name
 598          * @param string|array $vars Field names
 599          * @param string|array $conds Conditions
 600          * @param string $fname Caller function name
 601          * @param array $options Query options
 602          * @param array $join_conds Join conditions
 603          *
 604          *
 605          * @param string|array $table
 606          *
 607          * May be either an array of table names, or a single string holding a table
 608          * name. If an array is given, table aliases can be specified, for example:
 609          *
 610          *    [ 'a' => 'user' ]
 611          *
 612          * This includes the user table in the query, with the alias "a" available
 613          * for use in field names (e.g. a.user_name).
 614          *
 615          * All of the table names given here are automatically run through
 616          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
 617          * added, and various other table name mappings to be performed.
 618          *
 619          * Do not use untrusted user input as a table name. Alias names should
 620          * not have characters outside of the Basic multilingual plane.
 621          *
 622          * @param string|array $vars
 623          *
 624          * May be either a field name or an array of field names. The field names
 625          * can be complete fragments of SQL, for direct inclusion into the SELECT
 626          * query. If an array is given, field aliases can be specified, for example:
 627          *
 628          *   [ 'maxrev' => 'MAX(rev_id)' ]
 629          *
 630          * This includes an expression with the alias "maxrev" in the query.
 631          *
 632          * If an expression is given, care must be taken to ensure that it is
 633          * DBMS-independent.
 634          *
 635          * Untrusted user input must not be passed to this parameter.
 636          *
 637          * @param string|array $conds
 638          *
 639          * May be either a string containing a single condition, or an array of
 640          * conditions. If an array is given, the conditions constructed from each
 641          * element are combined with AND.
 642          *
 643          * Array elements may take one of two forms:
 644          *
 645          *   - Elements with a numeric key are interpreted as raw SQL fragments.
 646          *   - Elements with a string key are interpreted as equality conditions,
 647          *     where the key is the field name.
 648          *     - If the value of such an array element is a scalar (such as a
 649          *       string), it will be treated as data and thus quoted appropriately.
 650          *       If it is null, an IS NULL clause will be added.
 651          *     - If the value is an array, an IN (...) clause will be constructed
 652          *       from its non-null elements, and an IS NULL clause will be added
 653          *       if null is present, such that the field may match any of the
 654          *       elements in the array. The non-null elements will be quoted.
 655          *
 656          * Note that expressions are often DBMS-dependent in their syntax.
 657          * DBMS-independent wrappers are provided for constructing several types of
 658          * expression commonly used in condition queries. See:
 659          *    - IDatabase::buildLike()
 660          *    - IDatabase::conditional()
 661          *
 662          * Untrusted user input is safe in the values of string keys, however untrusted
 663          * input must not be used in the array key names or in the values of numeric keys.
 664          * Escaping of untrusted input used in values of numeric keys should be done via
 665          * IDatabase::addQuotes()
 666          *
 667          * @param string|array $options
 668          *
 669          * Optional: Array of query options. Boolean options are specified by
 670          * including them in the array as a string value with a numeric key, for
 671          * example:
 672          *
 673          *    [ 'FOR UPDATE' ]
 674          *
 675          * The supported options are:
 676          *
 677          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
 678          *     with LIMIT can theoretically be used for paging through a result set,
 679          *     but this is discouraged for performance reasons.
 680          *
 681          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
 682          *     and then the first rows are taken until the limit is reached. LIMIT
 683          *     is applied to a result set after OFFSET.
 684          *
 685          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
 686          *     changed until the next COMMIT.
 687          *
 688          *   - DISTINCT: Boolean: return only unique result rows.
 689          *
 690          *   - GROUP BY: May be either an SQL fragment string naming a field or
 691          *     expression to group by, or an array of such SQL fragments.
 692          *
 693          *   - HAVING: May be either an string containing a HAVING clause or an array of
 694          *     conditions building the HAVING clause. If an array is given, the conditions
 695          *     constructed from each element are combined with AND.
 696          *
 697          *   - ORDER BY: May be either an SQL fragment giving a field name or
 698          *     expression to order by, or an array of such SQL fragments.
 699          *
 700          *   - USE INDEX: This may be either a string giving the index name to use
 701          *     for the query, or an array. If it is an associative array, each key
 702          *     gives the table name (or alias), each value gives the index name to
 703          *     use for that table. All strings are SQL fragments and so should be
 704          *     validated by the caller.
 705          *
 706          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
 707          *     instead of SELECT.
 708          *
 709          * And also the following boolean MySQL extensions, see the MySQL manual
 710          * for documentation:
 711          *
 712          *    - LOCK IN SHARE MODE
 713          *    - STRAIGHT_JOIN
 714          *    - HIGH_PRIORITY
 715          *    - SQL_BIG_RESULT
 716          *    - SQL_BUFFER_RESULT
 717          *    - SQL_SMALL_RESULT
 718          *    - SQL_CALC_FOUND_ROWS
 719          *    - SQL_CACHE
 720          *    - SQL_NO_CACHE
 721          *
 722          *
 723          * @param string|array $join_conds
 724          *
 725          * Optional associative array of table-specific join conditions. In the
 726          * most common case, this is unnecessary, since the join condition can be
 727          * in $conds. However, it is useful for doing a LEFT JOIN.
 728          *
 729          * The key of the array contains the table name or alias. The value is an
 730          * array with two elements, numbered 0 and 1. The first gives the type of
 731          * join, the second is the same as the $conds parameter. Thus it can be
 732          * an SQL fragment, or an array where the string keys are equality and the
 733          * numeric keys are SQL fragments all AND'd together. For example:
 734          *
 735          *    [ 'page' => [ 'LEFT JOIN', 'page_latest=rev_id' ] ]
 736          *
 737          * @return ResultWrapper|bool If the query returned no rows, a ResultWrapper
 738          *   with no rows in it will be returned. If there was a query error, a
 739          *   DBQueryError exception will be thrown, except if the "ignore errors"
 740          *   option was set, in which case false will be returned.
 741          */
 742         public function select(
 743                 $table, $vars, $conds = '', $fname = __METHOD__,
 744                 $options = [], $join_conds = []
 745         );
 746
 747         /**
 748          * The equivalent of IDatabase::select() except that the constructed SQL
 749          * is returned, instead of being immediately executed. This can be useful for
 750          * doing UNION queries, where the SQL text of each query is needed. In general,
 751          * however, callers outside of Database classes should just use select().
 752          *
 753          * @param string|array $table Table name
 754          * @param string|array $vars Field names
 755          * @param string|array $conds Conditions
 756          * @param string $fname Caller function name
 757          * @param string|array $options Query options
 758          * @param string|array $join_conds Join conditions
 759          *
 760          * @return string SQL query string.
 761          * @see IDatabase::select()
 762          */
 763         public function selectSQLText(
 764                 $table, $vars, $conds = '', $fname = __METHOD__,
 765                 $options = [], $join_conds = []
 766         );
 767
 768         /**
 769          * Single row SELECT wrapper. Equivalent to IDatabase::select(), except
 770          * that a single row object is returned. If the query returns no rows,
 771          * false is returned.
 772          *
 773          * @param string|array $table Table name
 774          * @param string|array $vars Field names
 775          * @param array $conds Conditions
 776          * @param string $fname Caller function name
 777          * @param string|array $options Query options
 778          * @param array|string $join_conds Join conditions
 779          *
 780          * @return stdClass|bool
 781          */
 782         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
 783                 $options = [], $join_conds = []
 784         );
 785
 786         /**
 787          * Estimate the number of rows in dataset
 788          *
 789          * MySQL allows you to estimate the number of rows that would be returned
 790          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
 791          * index cardinality statistics, and is notoriously inaccurate, especially
 792          * when large numbers of rows have recently been added or deleted.
 793          *
 794          * For DBMSs that don't support fast result size estimation, this function
 795          * will actually perform the SELECT COUNT(*).
 796          *
 797          * Takes the same arguments as IDatabase::select().
 798          *
 799          * @param string $table Table name
 800          * @param string $vars Unused
 801          * @param array|string $conds Filters on the table
 802          * @param string $fname Function name for profiling
 803          * @param array $options Options for select
 804          * @return int Row count
 805          */
 806         public function estimateRowCount(
 807                 $table, $vars = '*', $conds = '', $fname = __METHOD__, $options = []
 808         );
 809
 810         /**
 811          * Get the number of rows in dataset
 812          *
 813          * This is useful when trying to do COUNT(*) but with a LIMIT for performance.
 814          *
 815          * Takes the same arguments as IDatabase::select().
 816          *
 817          * @since 1.27 Added $join_conds parameter
 818          *
 819          * @param array|string $tables Table names
 820          * @param string $vars Unused
 821          * @param array|string $conds Filters on the table
 822          * @param string $fname Function name for profiling
 823          * @param array $options Options for select
 824          * @param array $join_conds Join conditions (since 1.27)
 825          * @return int Row count
 826          */
 827         public function selectRowCount(
 828                 $tables, $vars = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
 829         );
 830
 831         /**
 832          * Determines whether a field exists in a table
 833          *
 834          * @param string $table Table name
 835          * @param string $field Filed to check on that table
 836          * @param string $fname Calling function name (optional)
 837          * @return bool Whether $table has filed $field
 838          */
 839         public function fieldExists( $table, $field, $fname = __METHOD__ );
 840
 841         /**
 842          * Determines whether an index exists
 843          * Usually throws a DBQueryError on failure
 844          * If errors are explicitly ignored, returns NULL on failure
 845          *
 846          * @param string $table
 847          * @param string $index
 848          * @param string $fname
 849          * @return bool|null
 850          */
 851         public function indexExists( $table, $index, $fname = __METHOD__ );
 852
 853         /**
 854          * Query whether a given table exists
 855          *
 856          * @param string $table
 857          * @param string $fname
 858          * @return bool
 859          */
 860         public function tableExists( $table, $fname = __METHOD__ );
 861
 862         /**
 863          * Determines if a given index is unique
 864          *
 865          * @param string $table
 866          * @param string $index
 867          *
 868          * @return bool
 869          */
 870         public function indexUnique( $table, $index );
 871
 872         /**
 873          * INSERT wrapper, inserts an array into a table.
 874          *
 875          * $a may be either:
 876          *
 877          *   - A single associative array. The array keys are the field names, and
 878          *     the values are the values to insert. The values are treated as data
 879          *     and will be quoted appropriately. If NULL is inserted, this will be
 880          *     converted to a database NULL.
 881          *   - An array with numeric keys, holding a list of associative arrays.
 882          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
 883          *     each subarray must be identical to each other, and in the same order.
 884          *
 885          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
 886          * returns success.
 887          *
 888          * $options is an array of options, with boolean options encoded as values
 889          * with numeric keys, in the same style as $options in
 890          * IDatabase::select(). Supported options are:
 891          *
 892          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
 893          *     any rows which cause duplicate key errors are not inserted. It's
 894          *     possible to determine how many rows were successfully inserted using
 895          *     IDatabase::affectedRows().
 896          *
 897          * @param string $table Table name. This will be passed through
 898          *   DatabaseBase::tableName().
 899          * @param array $a Array of rows to insert
 900          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
 901          * @param array $options Array of options
 902          *
 903          * @return bool
 904          */
 905         public function insert( $table, $a, $fname = __METHOD__, $options = [] );
 906
 907         /**
 908          * UPDATE wrapper. Takes a condition array and a SET array.
 909          *
 910          * @param string $table Name of the table to UPDATE. This will be passed through
 911          *   DatabaseBase::tableName().
 912          * @param array $values An array of values to SET. For each array element,
 913          *   the key gives the field name, and the value gives the data to set
 914          *   that field to. The data will be quoted by IDatabase::addQuotes().
 915          * @param array $conds An array of conditions (WHERE). See
 916          *   IDatabase::select() for the details of the format of condition
 917          *   arrays. Use '*' to update all rows.
 918          * @param string $fname The function name of the caller (from __METHOD__),
 919          *   for logging and profiling.
 920          * @param array $options An array of UPDATE options, can be:
 921          *   - IGNORE: Ignore unique key conflicts
 922          *   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
 923          * @return bool
 924          */
 925         public function update( $table, $values, $conds, $fname = __METHOD__, $options = [] );
 926
 927         /**
 928          * Makes an encoded list of strings from an array
 929          *
 930          * These can be used to make conjunctions or disjunctions on SQL condition strings
 931          * derived from an array (see IDatabase::select() $conds documentation).
 932          *
 933          * Example usage:
 934          * @code
 935          *     $sql = $db->makeList( [
 936          *         'rev_user' => $id,
 937          *         $db->makeList( [ 'rev_minor' => 1, 'rev_len' < 500 ], $db::LIST_OR ] )
 938          *     ], $db::LIST_AND );
 939          * @endcode
 940          * This would set $sql to "rev_user = '$id' AND (rev_minor = '1' OR rev_len < '500')"
 941          *
 942          * @param array $a Containing the data
 943          * @param int $mode IDatabase class constant:
 944          *    - IDatabase::LIST_COMMA: Comma separated, no field names
 945          *    - IDatabase::LIST_AND:   ANDed WHERE clause (without the WHERE).
 946          *    - IDatabase::LIST_OR:    ORed WHERE clause (without the WHERE)
 947          *    - IDatabase::LIST_SET:   Comma separated with field names, like a SET clause
 948          *    - IDatabase::LIST_NAMES: Comma separated field names
 949          * @throws DBError
 950          * @return string
 951          */
 952         public function makeList( $a, $mode = self::LIST_COMMA );
 953
 954         /**
 955          * Build a partial where clause from a 2-d array such as used for LinkBatch.
 956          * The keys on each level may be either integers or strings.
 957          *
 958          * @param array $data Organized as 2-d
 959          *    [ baseKeyVal => [ subKeyVal => [ignored], ... ], ... ]
 960          * @param string $baseKey Field name to match the base-level keys to (eg 'pl_namespace')
 961          * @param string $subKey Field name to match the sub-level keys to (eg 'pl_title')
 962          * @return string|bool SQL fragment, or false if no items in array
 963          */
 964         public function makeWhereFrom2d( $data, $baseKey, $subKey );
 965
 966         /**
 967          * Return aggregated value alias
 968          *
 969          * @param array $valuedata
 970          * @param string $valuename
 971          *
 972          * @return string
 973          */
 974         public function aggregateValue( $valuedata, $valuename = 'value' );
 975
 976         /**
 977          * @param string $field
 978          * @return string
 979          */
 980         public function bitNot( $field );
 981
 982         /**
 983          * @param string $fieldLeft
 984          * @param string $fieldRight
 985          * @return string
 986          */
 987         public function bitAnd( $fieldLeft, $fieldRight );
 988
 989         /**
 990          * @param string $fieldLeft
 991          * @param string $fieldRight
 992          * @return string
 993          */
 994         public function bitOr( $fieldLeft, $fieldRight );
 995
 996         /**
 997          * Build a concatenation list to feed into a SQL query
 998          * @param array $stringList List of raw SQL expressions; caller is
 999          *   responsible for any quoting
1000          * @return string
1001          */
1002         public function buildConcat( $stringList );
1003
1004         /**
1005          * Build a GROUP_CONCAT or equivalent statement for a query.
1006          *
1007          * This is useful for combining a field for several rows into a single string.
1008          * NULL values will not appear in the output, duplicated values will appear,
1009          * and the resulting delimiter-separated values have no defined sort order.
1010          * Code using the results may need to use the PHP unique() or sort() methods.
1011          *
1012          * @param string $delim Glue to bind the results together
1013          * @param string|array $table Table name
1014          * @param string $field Field name
1015          * @param string|array $conds Conditions
1016          * @param string|array $join_conds Join conditions
1017          * @return string SQL text
1018          * @since 1.23
1019          */
1020         public function buildGroupConcatField(
1021                 $delim, $table, $field, $conds = '', $join_conds = []
1022         );
1023
1024         /**
1025          * @param string $field Field or column to cast
1026          * @return string
1027          * @since 1.28
1028          */
1029         public function buildStringCast( $field );
1030
1031         /**
1032          * Change the current database
1033          *
1034          * @param string $db
1035          * @return bool Success or failure
1036          */
1037         public function selectDB( $db );
1038
1039         /**
1040          * Get the current DB name
1041          * @return string
1042          */
1043         public function getDBname();
1044
1045         /**
1046          * Get the server hostname or IP address
1047          * @return string
1048          */
1049         public function getServer();
1050
1051         /**
1052          * Adds quotes and backslashes.
1053          *
1054          * @param string|int|null|bool|Blob $s
1055          * @return string|int
1056          */
1057         public function addQuotes( $s );
1058
1059         /**
1060          * LIKE statement wrapper, receives a variable-length argument list with
1061          * parts of pattern to match containing either string literals that will be
1062          * escaped or tokens returned by anyChar() or anyString(). Alternatively,
1063          * the function could be provided with an array of aforementioned
1064          * parameters.
1065          *
1066          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns
1067          * a LIKE clause that searches for subpages of 'My page title'.
1068          * Alternatively:
1069          *   $pattern = [ 'My_page_title/', $dbr->anyString() ];
1070          *   $query .= $dbr->buildLike( $pattern );
1071          *
1072          * @since 1.16
1073          * @return string Fully built LIKE statement
1074          */
1075         public function buildLike();
1076
1077         /**
1078          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
1079          *
1080          * @return LikeMatch
1081          */
1082         public function anyChar();
1083
1084         /**
1085          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
1086          *
1087          * @return LikeMatch
1088          */
1089         public function anyString();
1090
1091         /**
1092          * Returns an appropriately quoted sequence value for inserting a new row.
1093          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
1094          * subclass will return an integer, and save the value for insertId()
1095          *
1096          * Any implementation of this function should *not* involve reusing
1097          * sequence numbers created for rolled-back transactions.
1098          * See http://bugs.mysql.com/bug.php?id=30767 for details.
1099          * @param string $seqName
1100          * @return null|int
1101          */
1102         public function nextSequenceValue( $seqName );
1103
1104         /**
1105          * REPLACE query wrapper.
1106          *
1107          * REPLACE is a very handy MySQL extension, which functions like an INSERT
1108          * except that when there is a duplicate key error, the old row is deleted
1109          * and the new row is inserted in its place.
1110          *
1111          * We simulate this with standard SQL with a DELETE followed by INSERT. To
1112          * perform the delete, we need to know what the unique indexes are so that
1113          * we know how to find the conflicting rows.
1114          *
1115          * It may be more efficient to leave off unique indexes which are unlikely
1116          * to collide. However if you do this, you run the risk of encountering
1117          * errors which wouldn't have occurred in MySQL.
1118          *
1119          * @param string $table The table to replace the row(s) in.
1120          * @param array $uniqueIndexes Is an array of indexes. Each element may be either
1121          *    a field name or an array of field names
1122          * @param array $rows Can be either a single row to insert, or multiple rows,
1123          *    in the same format as for IDatabase::insert()
1124          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1125          */
1126         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ );
1127
1128         /**
1129          * INSERT ON DUPLICATE KEY UPDATE wrapper, upserts an array into a table.
1130          *
1131          * This updates any conflicting rows (according to the unique indexes) using
1132          * the provided SET clause and inserts any remaining (non-conflicted) rows.
1133          *
1134          * $rows may be either:
1135          *   - A single associative array. The array keys are the field names, and
1136          *     the values are the values to insert. The values are treated as data
1137          *     and will be quoted appropriately. If NULL is inserted, this will be
1138          *     converted to a database NULL.
1139          *   - An array with numeric keys, holding a list of associative arrays.
1140          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1141          *     each subarray must be identical to each other, and in the same order.
1142          *
1143          * It may be more efficient to leave off unique indexes which are unlikely
1144          * to collide. However if you do this, you run the risk of encountering
1145          * errors which wouldn't have occurred in MySQL.
1146          *
1147          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1148          * returns success.
1149          *
1150          * @since 1.22
1151          *
1152          * @param string $table Table name. This will be passed through DatabaseBase::tableName().
1153          * @param array $rows A single row or list of rows to insert
1154          * @param array $uniqueIndexes List of single field names or field name tuples
1155          * @param array $set An array of values to SET. For each array element, the
1156          *   key gives the field name, and the value gives the data to set that
1157          *   field to. The data will be quoted by IDatabase::addQuotes().
1158          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1159          * @throws Exception
1160          * @return bool
1161          */
1162         public function upsert(
1163                 $table, array $rows, array $uniqueIndexes, array $set, $fname = __METHOD__
1164         );
1165
1166         /**
1167          * DELETE where the condition is a join.
1168          *
1169          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
1170          * we use sub-selects
1171          *
1172          * For safety, an empty $conds will not delete everything. If you want to
1173          * delete all rows where the join condition matches, set $conds='*'.
1174          *
1175          * DO NOT put the join condition in $conds.
1176          *
1177          * @param string $delTable The table to delete from.
1178          * @param string $joinTable The other table.
1179          * @param string $delVar The variable to join on, in the first table.
1180          * @param string $joinVar The variable to join on, in the second table.
1181          * @param array $conds Condition array of field names mapped to variables,
1182          *   ANDed together in the WHERE clause
1183          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
1184          * @throws DBUnexpectedError
1185          */
1186         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
1187                 $fname = __METHOD__
1188         );
1189
1190         /**
1191          * DELETE query wrapper.
1192          *
1193          * @param array $table Table name
1194          * @param string|array $conds Array of conditions. See $conds in IDatabase::select()
1195          *   for the format. Use $conds == "*" to delete all rows
1196          * @param string $fname Name of the calling function
1197          * @throws DBUnexpectedError
1198          * @return bool|ResultWrapper
1199          */
1200         public function delete( $table, $conds, $fname = __METHOD__ );
1201
1202         /**
1203          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
1204          * into another table.
1205          *
1206          * @param string $destTable The table name to insert into
1207          * @param string|array $srcTable May be either a table name, or an array of table names
1208          *    to include in a join.
1209          *
1210          * @param array $varMap Must be an associative array of the form
1211          *    [ 'dest1' => 'source1', ... ]. Source items may be literals
1212          *    rather than field names, but strings should be quoted with
1213          *    IDatabase::addQuotes()
1214          *
1215          * @param array $conds Condition array. See $conds in IDatabase::select() for
1216          *    the details of the format of condition arrays. May be "*" to copy the
1217          *    whole table.
1218          *
1219          * @param string $fname The function name of the caller, from __METHOD__
1220          *
1221          * @param array $insertOptions Options for the INSERT part of the query, see
1222          *    IDatabase::insert() for details.
1223          * @param array $selectOptions Options for the SELECT part of the query, see
1224          *    IDatabase::select() for details.
1225          *
1226          * @return ResultWrapper
1227          */
1228         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
1229                 $fname = __METHOD__,
1230                 $insertOptions = [], $selectOptions = []
1231         );
1232
1233         /**
1234          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
1235          * within the UNION construct.
1236          * @return bool
1237          */
1238         public function unionSupportsOrderAndLimit();
1239
1240         /**
1241          * Construct a UNION query
1242          * This is used for providing overload point for other DB abstractions
1243          * not compatible with the MySQL syntax.
1244          * @param array $sqls SQL statements to combine
1245          * @param bool $all Use UNION ALL
1246          * @return string SQL fragment
1247          */
1248         public function unionQueries( $sqls, $all );
1249
1250         /**
1251          * Returns an SQL expression for a simple conditional. This doesn't need
1252          * to be overridden unless CASE isn't supported in your DBMS.
1253          *
1254          * @param string|array $cond SQL expression which will result in a boolean value
1255          * @param string $trueVal SQL expression to return if true
1256          * @param string $falseVal SQL expression to return if false
1257          * @return string SQL fragment
1258          */
1259         public function conditional( $cond, $trueVal, $falseVal );
1260
1261         /**
1262          * Returns a comand for str_replace function in SQL query.
1263          * Uses REPLACE() in MySQL
1264          *
1265          * @param string $orig Column to modify
1266          * @param string $old Column to seek
1267          * @param string $new Column to replace with
1268          *
1269          * @return string
1270          */
1271         public function strreplace( $orig, $old, $new );
1272
1273         /**
1274          * Determines how long the server has been up
1275          *
1276          * @return int
1277          */
1278         public function getServerUptime();
1279
1280         /**
1281          * Determines if the last failure was due to a deadlock
1282          *
1283          * @return bool
1284          */
1285         public function wasDeadlock();
1286
1287         /**
1288          * Determines if the last failure was due to a lock timeout
1289          *
1290          * @return bool
1291          */
1292         public function wasLockTimeout();
1293
1294         /**
1295          * Determines if the last query error was due to a dropped connection and should
1296          * be dealt with by pinging the connection and reissuing the query.
1297          *
1298          * @return bool
1299          */
1300         public function wasErrorReissuable();
1301
1302         /**
1303          * Determines if the last failure was due to the database being read-only.
1304          *
1305          * @return bool
1306          */
1307         public function wasReadOnlyError();
1308
1309         /**
1310          * Wait for the replica DB to catch up to a given master position
1311          *
1312          * @param DBMasterPos $pos
1313          * @param int $timeout The maximum number of seconds to wait for synchronisation
1314          * @return int|null Zero if the replica DB was past that position already,
1315          *   greater than zero if we waited for some period of time, less than
1316          *   zero if it timed out, and null on error
1317          */
1318         public function masterPosWait( DBMasterPos $pos, $timeout );
1319
1320         /**
1321          * Get the replication position of this replica DB
1322          *
1323          * @return DBMasterPos|bool False if this is not a replica DB.
1324          */
1325         public function getSlavePos();
1326
1327         /**
1328          * Get the position of this master
1329          *
1330          * @return DBMasterPos|bool False if this is not a master
1331          */
1332         public function getMasterPos();
1333
1334         /**
1335          * @return bool Whether the DB is marked as read-only server-side
1336          * @since 1.28
1337          */
1338         public function serverIsReadOnly();
1339
1340         /**
1341          * Run a callback as soon as the current transaction commits or rolls back.
1342          * An error is thrown if no transaction is pending. Queries in the function will run in
1343          * AUTO-COMMIT mode unless there are begin() calls. Callbacks must commit any transactions
1344          * that they begin.
1345          *
1346          * This is useful for combining cooperative locks and DB transactions.
1347          *
1348          * The callback takes one argument:
1349          *   - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK)
1350          *
1351          * @param callable $callback
1352          * @param string $fname Caller name
1353          * @return mixed
1354          * @since 1.28
1355          */
1356         public function onTransactionResolution( callable $callback, $fname = __METHOD__ );
1357
1358         /**
1359          * Run a callback as soon as there is no transaction pending.
1360          * If there is a transaction and it is rolled back, then the callback is cancelled.
1361          * Queries in the function will run in AUTO-COMMIT mode unless there are begin() calls.
1362          * Callbacks must commit any transactions that they begin.
1363          *
1364          * This is useful for updates to different systems or when separate transactions are needed.
1365          * For example, one might want to enqueue jobs into a system outside the database, but only
1366          * after the database is updated so that the jobs will see the data when they actually run.
1367          * It can also be used for updates that easily cause deadlocks if locks are held too long.
1368          *
1369          * Updates will execute in the order they were enqueued.
1370          *
1371          * The callback takes one argument:
1372          *   - How the transaction ended (IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_IDLE)
1373          *
1374          * @param callable $callback
1375          * @param string $fname Caller name
1376          * @since 1.20
1377          */
1378         public function onTransactionIdle( callable $callback, $fname = __METHOD__ );
1379
1380         /**
1381          * Run a callback before the current transaction commits or now if there is none.
1382          * If there is a transaction and it is rolled back, then the callback is cancelled.
1383          * Callbacks must not start nor commit any transactions. If no transaction is active,
1384          * then a transaction will wrap the callback.
1385          *
1386          * This is useful for updates that easily cause deadlocks if locks are held too long
1387          * but where atomicity is strongly desired for these updates and some related updates.
1388          *
1389          * Updates will execute in the order they were enqueued.
1390          *
1391          * @param callable $callback
1392          * @param string $fname Caller name
1393          * @since 1.22
1394          */
1395         public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ );
1396
1397         /**
1398          * Run a callback each time any transaction commits or rolls back
1399          *
1400          * The callback takes two arguments:
1401          *   - IDatabase::TRIGGER_COMMIT or IDatabase::TRIGGER_ROLLBACK
1402          *   - This IDatabase object
1403          * Callbacks must commit any transactions that they begin.
1404          *
1405          * Registering a callback here will not affect writesOrCallbacks() pending
1406          *
1407          * @param string $name Callback name
1408          * @param callable|null $callback Use null to unset a listener
1409          * @return mixed
1410          * @since 1.28
1411          */
1412         public function setTransactionListener( $name, callable $callback = null );
1413
1414         /**
1415          * Begin an atomic section of statements
1416          *
1417          * If a transaction has been started already, just keep track of the given
1418          * section name to make sure the transaction is not committed pre-maturely.
1419          * This function can be used in layers (with sub-sections), so use a stack
1420          * to keep track of the different atomic sections. If there is no transaction,
1421          * start one implicitly.
1422          *
1423          * The goal of this function is to create an atomic section of SQL queries
1424          * without having to start a new transaction if it already exists.
1425          *
1426          * All atomic levels *must* be explicitly closed using IDatabase::endAtomic(),
1427          * and any database transactions cannot be began or committed until all atomic
1428          * levels are closed. There is no such thing as implicitly opening or closing
1429          * an atomic section.
1430          *
1431          * @since 1.23
1432          * @param string $fname
1433          * @throws DBError
1434          */
1435         public function startAtomic( $fname = __METHOD__ );
1436
1437         /**
1438          * Ends an atomic section of SQL statements
1439          *
1440          * Ends the next section of atomic SQL statements and commits the transaction
1441          * if necessary.
1442          *
1443          * @since 1.23
1444          * @see IDatabase::startAtomic
1445          * @param string $fname
1446          * @throws DBError
1447          */
1448         public function endAtomic( $fname = __METHOD__ );
1449
1450         /**
1451          * Run a callback to do an atomic set of updates for this database
1452          *
1453          * The $callback takes the following arguments:
1454          *   - This database object
1455          *   - The value of $fname
1456          *
1457          * If any exception occurs in the callback, then rollback() will be called and the error will
1458          * be re-thrown. It may also be that the rollback itself fails with an exception before then.
1459          * In any case, such errors are expected to terminate the request, without any outside caller
1460          * attempting to catch errors and commit anyway. Note that any rollback undoes all prior
1461          * atomic section and uncommitted updates, which trashes the current request, requiring an
1462          * error to be displayed.
1463          *
1464          * This can be an alternative to explicit startAtomic()/endAtomic() calls.
1465          *
1466          * @see DatabaseBase::startAtomic
1467          * @see DatabaseBase::endAtomic
1468          *
1469          * @param string $fname Caller name (usually __METHOD__)
1470          * @param callable $callback Callback that issues DB updates
1471          * @return mixed $res Result of the callback (since 1.28)
1472          * @throws DBError
1473          * @throws RuntimeException
1474          * @throws UnexpectedValueException
1475          * @since 1.27
1476          */
1477         public function doAtomicSection( $fname, callable $callback );
1478
1479         /**
1480          * Begin a transaction. If a transaction is already in progress,
1481          * that transaction will be committed before the new transaction is started.
1482          *
1483          * Only call this from code with outer transcation scope.
1484          * See https://www.mediawiki.org/wiki/Database_transactions for details.
1485          * Nesting of transactions is not supported.
1486          *
1487          * Note that when the DBO_TRX flag is set (which is usually the case for web
1488          * requests, but not for maintenance scripts), any previous database query
1489          * will have started a transaction automatically.
1490          *
1491          * Nesting of transactions is not supported. Attempts to nest transactions
1492          * will cause a warning, unless the current transaction was started
1493          * automatically because of the DBO_TRX flag.
1494          *
1495          * @param string $fname Calling function name
1496          * @param string $mode A situationally valid IDatabase::TRANSACTION_* constant [optional]
1497          * @throws DBError
1498          */
1499         public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT );
1500
1501         /**
1502          * Commits a transaction previously started using begin().
1503          * If no transaction is in progress, a warning is issued.
1504          *
1505          * Only call this from code with outer transcation scope.
1506          * See https://www.mediawiki.org/wiki/Database_transactions for details.
1507          * Nesting of transactions is not supported.
1508          *
1509          * @param string $fname
1510          * @param string $flush Flush flag, set to situationally valid IDatabase::FLUSHING_*
1511          *   constant to disable warnings about explicitly committing implicit transactions,
1512          *   or calling commit when no transaction is in progress.
1513          *
1514          *   This will trigger an exception if there is an ongoing explicit transaction.
1515          *
1516          *   Only set the flush flag if you are sure that these warnings are not applicable,
1517          *   and no explicit transactions are open.
1518          *
1519          * @throws DBUnexpectedError
1520          */
1521         public function commit( $fname = __METHOD__, $flush = '' );
1522
1523         /**
1524          * Rollback a transaction previously started using begin().
1525          * If no transaction is in progress, a warning is issued.
1526          *
1527          * Only call this from code with outer transcation scope.
1528          * See https://www.mediawiki.org/wiki/Database_transactions for details.
1529          * Nesting of transactions is not supported. If a serious unexpected error occurs,
1530          * throwing an Exception is preferrable, using a pre-installed error handler to trigger
1531          * rollback (in any case, failure to issue COMMIT will cause rollback server-side).
1532          *
1533          * @param string $fname Calling function name
1534          * @param string $flush Flush flag, set to a situationally valid IDatabase::FLUSHING_*
1535          *   constant to disable warnings about calling rollback when no transaction is in
1536          *   progress. This will silently break any ongoing explicit transaction. Only set the
1537          *   flush flag if you are sure that it is safe to ignore these warnings in your context.
1538          * @throws DBUnexpectedError
1539          * @since 1.23 Added $flush parameter
1540          */
1541         public function rollback( $fname = __METHOD__, $flush = '' );
1542
1543         /**
1544          * Commit any transaction but error out if writes or callbacks are pending
1545          *
1546          * This is intended for clearing out REPEATABLE-READ snapshots so that callers can
1547          * see a new point-in-time of the database. This is useful when one of many transaction
1548          * rounds finished and significant time will pass in the script's lifetime. It is also
1549          * useful to call on a replica DB after waiting on replication to catch up to the master.
1550          *
1551          * @param string $fname Calling function name
1552          * @throws DBUnexpectedError
1553          * @since 1.28
1554          */
1555         public function flushSnapshot( $fname = __METHOD__ );
1556
1557         /**
1558          * List all tables on the database
1559          *
1560          * @param string $prefix Only show tables with this prefix, e.g. mw_
1561          * @param string $fname Calling function name
1562          * @throws DBError
1563          * @return array
1564          */
1565         public function listTables( $prefix = null, $fname = __METHOD__ );
1566
1567         /**
1568          * Convert a timestamp in one of the formats accepted by wfTimestamp()
1569          * to the format used for inserting into timestamp fields in this DBMS.
1570          *
1571          * The result is unquoted, and needs to be passed through addQuotes()
1572          * before it can be included in raw SQL.
1573          *
1574          * @param string|int $ts
1575          *
1576          * @return string
1577          */
1578         public function timestamp( $ts = 0 );
1579
1580         /**
1581          * Convert a timestamp in one of the formats accepted by wfTimestamp()
1582          * to the format used for inserting into timestamp fields in this DBMS. If
1583          * NULL is input, it is passed through, allowing NULL values to be inserted
1584          * into timestamp fields.
1585          *
1586          * The result is unquoted, and needs to be passed through addQuotes()
1587          * before it can be included in raw SQL.
1588          *
1589          * @param string|int $ts
1590          *
1591          * @return string
1592          */
1593         public function timestampOrNull( $ts = null );
1594
1595         /**
1596          * Ping the server and try to reconnect if it there is no connection
1597          *
1598          * @param float|null &$rtt Value to store the estimated RTT [optional]
1599          * @return bool Success or failure
1600          */
1601         public function ping( &$rtt = null );
1602
1603         /**
1604          * Get replica DB lag. Currently supported only by MySQL.
1605          *
1606          * Note that this function will generate a fatal error on many
1607          * installations. Most callers should use LoadBalancer::safeGetLag()
1608          * instead.
1609          *
1610          * @return int|bool Database replication lag in seconds or false on error
1611          */
1612         public function getLag();
1613
1614         /**
1615          * Get the replica DB lag when the current transaction started
1616          * or a general lag estimate if not transaction is active
1617          *
1618          * This is useful when transactions might use snapshot isolation
1619          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
1620          * is this lag plus transaction duration. If they don't, it is still
1621          * safe to be pessimistic. In AUTO-COMMIT mode, this still gives an
1622          * indication of the staleness of subsequent reads.
1623          *
1624          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
1625          * @since 1.27
1626          */
1627         public function getSessionLagStatus();
1628
1629         /**
1630          * Return the maximum number of items allowed in a list, or 0 for unlimited.
1631          *
1632          * @return int
1633          */
1634         public function maxListLen();
1635
1636         /**
1637          * Some DBMSs have a special format for inserting into blob fields, they
1638          * don't allow simple quoted strings to be inserted. To insert into such
1639          * a field, pass the data through this function before passing it to
1640          * IDatabase::insert().
1641          *
1642          * @param string $b
1643          * @return string
1644          */
1645         public function encodeBlob( $b );
1646
1647         /**
1648          * Some DBMSs return a special placeholder object representing blob fields
1649          * in result objects. Pass the object through this function to return the
1650          * original string.
1651          *
1652          * @param string|Blob $b
1653          * @return string
1654          */
1655         public function decodeBlob( $b );
1656
1657         /**
1658          * Override database's default behavior. $options include:
1659          *     'connTimeout' : Set the connection timeout value in seconds.
1660          *                     May be useful for very long batch queries such as
1661          *                     full-wiki dumps, where a single query reads out over
1662          *                     hours or days.
1663          *
1664          * @param array $options
1665          * @return void
1666          */
1667         public function setSessionOptions( array $options );
1668
1669         /**
1670          * Set variables to be used in sourceFile/sourceStream, in preference to the
1671          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
1672          * all. If it's set to false, $GLOBALS will be used.
1673          *
1674          * @param bool|array $vars Mapping variable name to value.
1675          */
1676         public function setSchemaVars( $vars );
1677
1678         /**
1679          * Check to see if a named lock is available (non-blocking)
1680          *
1681          * @param string $lockName Name of lock to poll
1682          * @param string $method Name of method calling us
1683          * @return bool
1684          * @since 1.20
1685          */
1686         public function lockIsFree( $lockName, $method );
1687
1688         /**
1689          * Acquire a named lock
1690          *
1691          * Named locks are not related to transactions
1692          *
1693          * @param string $lockName Name of lock to aquire
1694          * @param string $method Name of the calling method
1695          * @param int $timeout Acquisition timeout in seconds
1696          * @return bool
1697          */
1698         public function lock( $lockName, $method, $timeout = 5 );
1699
1700         /**
1701          * Release a lock
1702          *
1703          * Named locks are not related to transactions
1704          *
1705          * @param string $lockName Name of lock to release
1706          * @param string $method Name of the calling method
1707          *
1708          * @return int Returns 1 if the lock was released, 0 if the lock was not established
1709          * by this thread (in which case the lock is not released), and NULL if the named
1710          * lock did not exist
1711          */
1712         public function unlock( $lockName, $method );
1713
1714         /**
1715          * Acquire a named lock, flush any transaction, and return an RAII style unlocker object
1716          *
1717          * Only call this from outer transcation scope and when only one DB will be affected.
1718          * See https://www.mediawiki.org/wiki/Database_transactions for details.
1719          *
1720          * This is suitiable for transactions that need to be serialized using cooperative locks,
1721          * where each transaction can see each others' changes. Any transaction is flushed to clear
1722          * out stale REPEATABLE-READ snapshot data. Once the returned object falls out of PHP scope,
1723          * the lock will be released unless a transaction is active. If one is active, then the lock
1724          * will be released when it either commits or rolls back.
1725          *
1726          * If the lock acquisition failed, then no transaction flush happens, and null is returned.
1727          *
1728          * @param string $lockKey Name of lock to release
1729          * @param string $fname Name of the calling method
1730          * @param int $timeout Acquisition timeout in seconds
1731          * @return ScopedCallback|null
1732          * @throws DBUnexpectedError
1733          * @since 1.27
1734          */
1735         public function getScopedLockAndFlush( $lockKey, $fname, $timeout );
1736
1737         /**
1738          * Check to see if a named lock used by lock() use blocking queues
1739          *
1740          * @return bool
1741          * @since 1.26
1742          */
1743         public function namedLocksEnqueue();
1744
1745         /**
1746          * Find out when 'infinity' is. Most DBMSes support this. This is a special
1747          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
1748          * because "i" sorts after all numbers.
1749          *
1750          * @return string
1751          */
1752         public function getInfinity();
1753
1754         /**
1755          * Encode an expiry time into the DBMS dependent format
1756          *
1757          * @param string $expiry Timestamp for expiry, or the 'infinity' string
1758          * @return string
1759          */
1760         public function encodeExpiry( $expiry );
1761
1762         /**
1763          * Decode an expiry time into a DBMS independent format
1764          *
1765          * @param string $expiry DB timestamp field value for expiry
1766          * @param int $format TS_* constant, defaults to TS_MW
1767          * @return string
1768          */
1769         public function decodeExpiry( $expiry, $format = TS_MW );
1770
1771         /**
1772          * Allow or deny "big selects" for this session only. This is done by setting
1773          * the sql_big_selects session variable.
1774          *
1775          * This is a MySQL-specific feature.
1776          *
1777          * @param bool|string $value True for allow, false for deny, or "default" to
1778          *   restore the initial value
1779          */
1780         public function setBigSelects( $value = true );
1781
1782         /**
1783          * @return bool Whether this DB is read-only
1784          * @since 1.27
1785          */
1786         public function isReadOnly();
1787
1788         /**
1789          * Make certain table names use their own database, schema, and table prefix
1790          * when passed into SQL queries pre-escaped and without a qualified database name
1791          *
1792          * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
1793          * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
1794          *
1795          * Calling this twice will completely clear any old table aliases. Also, note that
1796          * callers are responsible for making sure the schemas and databases actually exist.
1797          *
1798          * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
1799          * @since 1.28
1800          */
1801         public function setTableAliases( array $aliases );
1802 }