[Summary view]

   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  }