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