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