lib/dml/moodle_temptables.php

   1 <?php
   2 // This file is part of Moodle - http://moodle.org/
   3 //
   4 // Moodle is free software: you can redistribute it and/or modify
   5 // it under the terms of the GNU General Public License as published by
   6 // the Free Software Foundation, either version 3 of the License, or
   7 // (at your option) any later version.
   8 //
   9 // Moodle is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13 //
  14 // You should have received a copy of the GNU General Public License
  15 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 /**
  18  * Generic temptables object store
  19  *
  20  * Provides support to databases lacking some "expected behaviour" related
  21  * with some operations with temporary tables like:
  22  *
  23  *   - databases not retrieving temp tables from information schema tables (mysql)
  24  *   - databases using a different name schema for temp tables (like mssql).
  25  *   - databases that don't collect planner stats for temp tables (like PgSQL).
  26  *
  27  * Basically it works as a simple store of created temporary tables, providing
  28  * some simple getters/setters methods. Each database can extend it for its own
  29  * purposes (for example, return correct name, see the mssql implementation)
  30  *
  31  * The unique instance of the object by database connection is shared by the database
  32  * and the sql_generator, so both are able to use its facilities, with the final goal
  33  * of doing temporary tables support 100% cross-db and transparent within the DB API.
  34  *
  35  * @package    core_dml
  36  * @copyright  2009 onwards Eloy Lafuente (stronk7) {@link http://stronk7.com}
  37  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  38  */
  39
  40 defined('MOODLE_INTERNAL') || die();
  41
  42 class moodle_temptables {
  43
  44     /** @var circular reference, to be able to use DB facilities here if needed */
  45     protected $mdb;
  46     /** @var prefix to be used for all the DB objects */
  47     protected $prefix;
  48     /** @var simple array of moodle, not prefixed 'tablename' => DB, final (prefixed) 'tablename' */
  49     protected $temptables;
  50
  51     /**
  52      * Creates new moodle_temptables instance
  53      * @param moodle_database $mdb An instance of moodle_database.
  54      */
  55     public function __construct($mdb) {
  56         $this->mdb        = $mdb;
  57         $this->prefix     = $mdb->get_prefix();
  58         $this->temptables = array();
  59     }
  60
  61     /**
  62      * Add one temptable to the store
  63      *
  64      * Given one moodle temptable name (without prefix), add it to the store, with the
  65      * key being the original moodle name and the value being the real db temptable name
  66      * already prefixed
  67      *
  68      * Override and use this *only* if the database requires modification in the table name.
  69      *
  70      * @param string $tablename name without prefix of the table created as temptable
  71      */
  72     public function add_temptable($tablename) {
  73         // TODO: throw exception if exists: if ($this->is_temptable...
  74         $this->temptables[$tablename] = $tablename;
  75     }
  76
  77     /**
  78      * Delete one temptable from the store
  79      *
  80      * @param string $tablename name without prefix of the dropped temptable
  81      */
  82     public function delete_temptable($tablename) {
  83         // TODO: throw exception if not exists: if (!$this->is_temptable....
  84         unset($this->temptables[$tablename]);
  85     }
  86
  87     /**
  88      * Returns all the tablenames (without prefix) existing in the store
  89      *
  90      * @return array containing all the tablenames in the store (tablename both key and value)
  91      */
  92     public function get_temptables() {
  93         return $this->temptables;
  94     }
  95
  96     /**
  97      * Returns if one table, based in the information present in the store, is a temp table
  98      *
  99      * @param string $tablename name without prefix of the table we are asking about
 100      * @return bool true if the table is a temp table (based in the store info), false if not
 101      */
 102     public function is_temptable($tablename) {
 103         return !empty($this->temptables[$tablename]);
 104     }
 105
 106     /**
 107      * Given one tablename (no prefix), return the name of the corresponding temporary table,
 108      * If the table isn't a "registered" temp table, returns null
 109      *
 110      * @param string $tablename name without prefix which corresponding temp tablename needs to know
 111      * @return mixed DB name of the temp table or null if it isn't a temp table
 112      */
 113     public function get_correct_name($tablename) {
 114         if ($this->is_temptable($tablename)) {
 115             return $this->temptables[$tablename];
 116         }
 117         return null;
 118     }
 119
 120     /**
 121      * Analyze the data in temporary tables to force statistics collection after bulk data loads.
 122      * The database class detects all temporary tables and will automatically analyze all created tables
 123      *
 124      * @return void
 125      */
 126     public function update_stats() {
 127         // By default most databases do automatic on temporary tables, PgSQL does not.
 128         // As a result, update_stats call immediately return for non-interesting database types.
 129     }
 130
 131     /**
 132      * Dispose the temptables stuff, checking for wrong situations, informing and recovering from them
 133      */
 134     public function dispose() {
 135         // We shouldn't have any temp table registered at the end of the script.
 136         // So we error_log that and, at the same time, drop all the pending temptables
 137         if ($temptables = $this->get_temptables()) {
 138             error_log('Potential coding error - existing temptables found when disposing database. Must be dropped!');
 139             foreach ($temptables as $temptable) {
 140                  $this->mdb->get_manager()->drop_table(new xmldb_table($temptable));
 141             }
 142         }
 143         $this->mdb = null;
 144     }
 145 }