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