lib/dml/moodle_temptables.php

   1 <?php
   2
   3 // This file is part of Moodle - http://moodle.org/
   4 //
   5 // Moodle is free software: you can redistribute it and/or modify
   6 // it under the terms of the GNU General Public License as published by
   7 // the Free Software Foundation, either version 3 of the License, or
   8 // (at your option) any later version.
   9 //
  10 // Moodle is distributed in the hope that it will be useful,
  11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 // GNU General Public License for more details.
  14 //
  15 // You should have received a copy of the GNU General Public License
  16 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  17
  18 /**
  19  * Generic temptables object store
  20  *
  21  * Provides support to databases lacking some "expected behaviour" related
  22  * with some operations with temporary tables like:
  23  *
  24  *   - databases not retrieving temp tables from information schema tables (mysql)
  25  *   - databases using a different name schema for temp tables (like mssql).
  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  * Only drivers needing it will use this store. Neither moodle_database (abstract) or
  36  * databases like postgres need this, because they don't lack any temp functionality.
  37  *
  38  * @package    core
  39  * @subpackage dml
  40  * @copyright  2009 onwards Eloy Lafuente (stronk7) {@link http://stronk7.com}
  41  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  42  */
  43
  44 defined('MOODLE_INTERNAL') || die();
  45
  46 class moodle_temptables {
  47
  48     protected $mdb;        // circular reference, to be able to use DB facilities here if needed
  49     protected $prefix;     // prefix to be used for all the DB objects
  50     protected $temptables; // simple array of moodle, not prefixed 'tablename' => DB, final (prefixed) 'tablename'
  51
  52     /**
  53      * Creates new moodle_temptables instance
  54      * @param object moodle_database instance
  55      */
  56     public function __construct($mdb) {
  57         $this->mdb        = $mdb;
  58         $this->prefix     = $mdb->get_prefix();
  59         $this->temptables = array();
  60     }
  61
  62     /**
  63      * Add one temptable to the store
  64      *
  65      * Given one moodle temptable name (without prefix), add it to the store, with the
  66      * key being the original moodle name and the value being the real db temptable name
  67      * already prefixed
  68      *
  69      * Override and use this *only* if the database requires modification in the table name.
  70      *
  71      * @param string $tablename name without prefix of the table created as temptable
  72      */
  73     public function add_temptable($tablename) {
  74         // TODO: throw exception if exists: if ($this->is_temptable...
  75         $this->temptables[$tablename] = $tablename;
  76     }
  77
  78     /**
  79      * Delete one temptable from the store
  80      *
  81      * @param string $tablename name without prefix of the dropped temptable
  82      */
  83     public function delete_temptable($tablename) {
  84         // TODO: throw exception if not exists: if (!$this->is_temptable....
  85         unset($this->temptables[$tablename]);
  86     }
  87
  88     /**
  89      * Returns all the tablenames (without prefix) existing in the store
  90      *
  91      * @return array containing all the tablenames in the store (tablename both key and value)
  92      */
  93     public function get_temptables() {
  94         return array_keys($this->temptables);
  95     }
  96
  97     /**
  98      * Returns if one table, based in the information present in the store, is a temp table
  99      *
 100      * @param string $tablename name without prefix of the table we are asking about
 101      * @return bool true if the table is a temp table (based in the store info), false if not
 102      */
 103     public function is_temptable($tablename) {
 104         return !empty($this->temptables[$tablename]);
 105     }
 106
 107     /**
 108      * Given one tablename (no prefix), return the name of the corresponding temporary table,
 109      * If the table isn't a "registered" temp table, returns null
 110      *
 111      * @param string $tablename name without prefix which corresponding temp tablename needs to know
 112      * @return mixed DB name of the temp table or null if it isn't a temp table
 113      */
 114     public function get_correct_name($tablename) {
 115         if ($this->is_temptable($tablename)) {
 116             return $this->temptables[$tablename];
 117         }
 118         return null;
 119     }
 120
 121     /**
 122      * Dispose the temptables stuff, checking for wrong situations, informing and recovering from them
 123      */
 124     public function dispose() {
 125         // We shouldn't have any temp table registered at the end of the script.
 126         // So we error_log that and, at the same time, drop all the pending temptables
 127         if ($temptables = $this->get_temptables()) {
 128             error_log('Potential coding error - existing temptables found when disposing database. Must be dropped!');
 129             foreach ($temptables as $temptable) {
 130                  $this->mdb->get_manager()->drop_temp_table(new xmldb_table($temptable));
 131             }
 132         }
 133         $this->mdb = null;
 134     }
 135 }