includes/libs/rdbms/database/IMaintainableDatabase.php

   1 <?php
   2
   3 /**
   4  * This file deals with database interface functions
   5  * and query specifics/optimisations.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License along
  18  * with this program; if not, write to the Free Software Foundation, Inc.,
  19  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  20  * http://www.gnu.org/copyleft/gpl.html
  21  *
  22  * @file
  23  * @ingroup Database
  24  */
  25 namespace Wikimedia\Rdbms;
  26
  27 use Exception;
  28 use RuntimeException;
  29 use DBUnexpectedError;
  30
  31 /**
  32  * Advanced database interface for IDatabase handles that include maintenance methods
  33  *
  34  * This is useful for type-hints used by installer, upgrader, and background scripts
  35  * that will make use of lower-level and longer-running queries, including schema changes.
  36  *
  37  * @ingroup Database
  38  * @since 1.28
  39  */
  40 interface IMaintainableDatabase extends IDatabase {
  41         /**
  42          * Format a table name ready for use in constructing an SQL query
  43          *
  44          * This does two important things: it quotes the table names to clean them up,
  45          * and it adds a table prefix if only given a table name with no quotes.
  46          *
  47          * All functions of this object which require a table name call this function
  48          * themselves. Pass the canonical name to such functions. This is only needed
  49          * when calling query() directly.
  50          *
  51          * @note This function does not sanitize user input. It is not safe to use
  52          *   this function to escape user input.
  53          * @param string $name Database table name
  54          * @param string $format One of:
  55          *   quoted - Automatically pass the table name through addIdentifierQuotes()
  56          *            so that it can be used in a query.
  57          *   raw - Do not add identifier quotes to the table name
  58          * @return string Full database name
  59          */
  60         public function tableName( $name, $format = 'quoted' );
  61
  62         /**
  63          * Fetch a number of table names into an array
  64          * This is handy when you need to construct SQL for joins
  65          *
  66          * Example:
  67          * extract( $dbr->tableNames( 'user', 'watchlist' ) );
  68          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
  69          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
  70          *
  71          * @return array
  72          */
  73         public function tableNames();
  74
  75         /**
  76          * Fetch a number of table names into an zero-indexed numerical array
  77          * This is handy when you need to construct SQL for joins
  78          *
  79          * Example:
  80          * list( $user, $watchlist ) = $dbr->tableNamesN( 'user', 'watchlist' );
  81          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
  82          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
  83          *
  84          * @return array
  85          */
  86         public function tableNamesN();
  87
  88         /**
  89          * Returns the size of a text field, or -1 for "unlimited"
  90          *
  91          * @param string $table
  92          * @param string $field
  93          * @return int
  94          */
  95         public function textFieldSize( $table, $field );
  96
  97         /**
  98          * Read and execute SQL commands from a file.
  99          *
 100          * Returns true on success, error string or exception on failure (depending
 101          * on object's error ignore settings).
 102          *
 103          * @param string $filename File name to open
 104          * @param callable|null $lineCallback Optional function called before reading each line
 105          * @param callable|null $resultCallback Optional function called for each MySQL result
 106          * @param bool|string $fname Calling function name or false if name should be
 107          *   generated dynamically using $filename
 108          * @param callable|null $inputCallback Optional function called for each
 109          *   complete line sent
 110          * @return bool|string
 111          * @throws Exception
 112          */
 113         public function sourceFile(
 114                 $filename,
 115                 callable $lineCallback = null,
 116                 callable $resultCallback = null,
 117                 $fname = false,
 118                 callable $inputCallback = null
 119         );
 120
 121         /**
 122          * Read and execute commands from an open file handle.
 123          *
 124          * Returns true on success, error string or exception on failure (depending
 125          * on object's error ignore settings).
 126          *
 127          * @param resource $fp File handle
 128          * @param callable|null $lineCallback Optional function called before reading each query
 129          * @param callable|null $resultCallback Optional function called for each MySQL result
 130          * @param string $fname Calling function name
 131          * @param callable|null $inputCallback Optional function called for each complete query sent
 132          * @return bool|string
 133          */
 134         public function sourceStream(
 135                 $fp,
 136                 callable $lineCallback = null,
 137                 callable $resultCallback = null,
 138                 $fname = __METHOD__,
 139                 callable $inputCallback = null
 140         );
 141
 142         /**
 143          * Called by sourceStream() to check if we've reached a statement end
 144          *
 145          * @param string &$sql SQL assembled so far
 146          * @param string &$newLine New line about to be added to $sql
 147          * @return bool Whether $newLine contains end of the statement
 148          */
 149         public function streamStatementEnd( &$sql, &$newLine );
 150
 151         /**
 152          * Delete a table
 153          * @param string $tableName
 154          * @param string $fName
 155          * @return bool|ResultWrapper
 156          */
 157         public function dropTable( $tableName, $fName = __METHOD__ );
 158
 159         /**
 160          * Perform a deadlock-prone transaction.
 161          *
 162          * This function invokes a callback function to perform a set of write
 163          * queries. If a deadlock occurs during the processing, the transaction
 164          * will be rolled back and the callback function will be called again.
 165          *
 166          * Avoid using this method outside of Job or Maintenance classes.
 167          *
 168          * Usage:
 169          *   $dbw->deadlockLoop( callback, ... );
 170          *
 171          * Extra arguments are passed through to the specified callback function.
 172          * This method requires that no transactions are already active to avoid
 173          * causing premature commits or exceptions.
 174          *
 175          * Returns whatever the callback function returned on its successful,
 176          * iteration, or false on error, for example if the retry limit was
 177          * reached.
 178          *
 179          * @return mixed
 180          * @throws DBUnexpectedError
 181          * @throws Exception
 182          */
 183         public function deadlockLoop();
 184
 185         /**
 186          * Lists all the VIEWs in the database
 187          *
 188          * @param string $prefix Only show VIEWs with this prefix, eg. unit_test_
 189          * @param string $fname Name of calling function
 190          * @throws RuntimeException
 191          * @return array
 192          */
 193         public function listViews( $prefix = null, $fname = __METHOD__ );
 194
 195         /**
 196          * Creates a new table with structure copied from existing table
 197          *
 198          * Note that unlike most database abstraction functions, this function does not
 199          * automatically append database prefix, because it works at a lower abstraction level.
 200          * The table names passed to this function shall not be quoted (this function calls
 201          * addIdentifierQuotes() when needed).
 202          *
 203          * @param string $oldName Name of table whose structure should be copied
 204          * @param string $newName Name of table to be created
 205          * @param bool $temporary Whether the new table should be temporary
 206          * @param string $fname Calling function name
 207          * @return bool True if operation was successful
 208          * @throws RuntimeException
 209          */
 210         public function duplicateTableStructure(
 211                 $oldName, $newName, $temporary = false, $fname = __METHOD__
 212         );
 213
 214         /**
 215          * Checks if table locks acquired by lockTables() are transaction-bound in their scope
 216          *
 217          * Transaction-bound table locks will be released when the current transaction terminates.
 218          * Table locks that are not bound to a transaction are not effected by BEGIN/COMMIT/ROLLBACK
 219          * and will last until either lockTables()/unlockTables() is called or the TCP connection to
 220          * the database is closed.
 221          *
 222          * @return bool
 223          * @since 1.29
 224          */
 225         public function tableLocksHaveTransactionScope();
 226
 227         /**
 228          * Lock specific tables
 229          *
 230          * Any pending transaction should be resolved before calling this method, since:
 231          *   a) Doing so resets any REPEATABLE-READ snapshot of the data to a fresh one.
 232          *   b) Previous row and table locks from the transaction or session may be released
 233          *      by LOCK TABLES, which may be unsafe for the changes in such a transaction.
 234          *   c) The main use case of lockTables() is to avoid deadlocks and timeouts by locking
 235          *      entire tables in order to do long-running, batched, and lag-aware, updates. Batching
 236          *      and replication lag checks do not work when all the updates happen in a transaction.
 237          *
 238          * Always get all relevant table locks up-front in one call, since LOCK TABLES might release
 239          * any prior table locks on some RDBMes (e.g MySQL).
 240          *
 241          * For compatibility, callers should check tableLocksHaveTransactionScope() before using
 242          * this method. If locks are scoped specifically to transactions then caller must either:
 243          *   - a) Start a new transaction and acquire table locks for the scope of that transaction,
 244          *        doing all row updates within that transaction. It will not be possible to update
 245          *        rows in batches; this might result in high replication lag.
 246          *   - b) Forgo table locks entirely and avoid calling this method. Careful use of hints like
 247          *        LOCK IN SHARE MODE and FOR UPDATE and the use of query batching may be preferrable
 248          *        to using table locks with a potentially large transaction. Use of MySQL and Postges
 249          *        style REPEATABLE-READ (Snapshot Isolation with or without First-Committer-Rule) can
 250          *        also be considered for certain tasks that require a consistent view of entire tables.
 251          *
 252          * If session scoped locks are not supported, then calling lockTables() will trigger
 253          * startAtomic(), with unlockTables() triggering endAtomic(). This will automatically
 254          * start a transaction if one is not already present and cause the locks to be released
 255          * when the transaction finishes (normally during the unlockTables() call).
 256          *
 257          * In any case, avoid using begin()/commit() in code that runs while such table locks are
 258          * acquired, as that breaks in case when a transaction is needed. The startAtomic() and
 259          * endAtomic() methods are safe, however, since they will join any existing transaction.
 260          *
 261          * @param array $read Array of tables to lock for read access
 262          * @param array $write Array of tables to lock for write access
 263          * @param string $method Name of caller
 264          * @return bool
 265          * @since 1.29
 266          */
 267         public function lockTables( array $read, array $write, $method );
 268
 269         /**
 270          * Unlock all tables locked via lockTables()
 271          *
 272          * If table locks are scoped to transactions, then locks might not be released until the
 273          * transaction ends, which could happen after this method is called.
 274          *
 275          * @param string $method The caller
 276          * @return bool
 277          * @since 1.29
 278          */
 279         public function unlockTables( $method );
 280 }
 281
 282 class_alias( IMaintainableDatabase::class, 'IMaintainableDatabase' );