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<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
/**
* Generic temptables object store
*
* Provides support to databases lacking some "expected behaviour" related
* with some operations with temporary tables like:
*
* - databases not retrieving temp tables from information schema tables (mysql)
* - databases using a different name schema for temp tables (like mssql).
* - databases that don't collect planner stats for temp tables (like PgSQL).
*
* Basically it works as a simple store of created temporary tables, providing
* some simple getters/setters methods. Each database can extend it for its own
* purposes (for example, return correct name, see the mssql implementation)
*
* The unique instance of the object by database connection is shared by the database
* and the sql_generator, so both are able to use its facilities, with the final goal
* of doing temporary tables support 100% cross-db and transparent within the DB API.
*
* @package core_dml
* @copyright 2009 onwards Eloy Lafuente (stronk7) {@link http://stronk7.com}
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
defined('MOODLE_INTERNAL') || die();
class moodle_temptables {
/** @var circular reference, to be able to use DB facilities here if needed */
protected $mdb;
/** @var prefix to be used for all the DB objects */
protected $prefix;
/** @var simple array of moodle, not prefixed 'tablename' => DB, final (prefixed) 'tablename' */
protected $temptables;
/**
* Creates new moodle_temptables instance
* @param moodle_database $mdb An instance of moodle_database.
*/
public function __construct($mdb) {
$this->mdb = $mdb;
$this->prefix = $mdb->get_prefix();
$this->temptables = array();
}
/**
* Add one temptable to the store
*
* Given one moodle temptable name (without prefix), add it to the store, with the
* key being the original moodle name and the value being the real db temptable name
* already prefixed
*
* Override and use this *only* if the database requires modification in the table name.
*
* @param string $tablename name without prefix of the table created as temptable
*/
public function add_temptable($tablename) {
// TODO: throw exception if exists: if ($this->is_temptable...
$this->temptables[$tablename] = $tablename;
}
/**
* Delete one temptable from the store
*
* @param string $tablename name without prefix of the dropped temptable
*/
public function delete_temptable($tablename) {
// TODO: throw exception if not exists: if (!$this->is_temptable....
unset($this->temptables[$tablename]);
}
/**
* Returns all the tablenames (without prefix) existing in the store
*
* @return array containing all the tablenames in the store (tablename both key and value)
*/
public function get_temptables() {
return $this->temptables;
}
/**
* Returns if one table, based in the information present in the store, is a temp table
*
* @param string $tablename name without prefix of the table we are asking about
* @return bool true if the table is a temp table (based in the store info), false if not
*/
public function is_temptable($tablename) {
return !empty($this->temptables[$tablename]);
}
/**
* Given one tablename (no prefix), return the name of the corresponding temporary table,
* If the table isn't a "registered" temp table, returns null
*
* @param string $tablename name without prefix which corresponding temp tablename needs to know
* @return mixed DB name of the temp table or null if it isn't a temp table
*/
public function get_correct_name($tablename) {
if ($this->is_temptable($tablename)) {
return $this->temptables[$tablename];
}
return null;
}
/**
* Analyze the data in temporary tables to force statistics collection after bulk data loads.
* The database class detects all temporary tables and will automatically analyze all created tables
*
* @return void
*/
public function update_stats() {
// By default most databases do automatic on temporary tables, PgSQL does not.
// As a result, update_stats call immediately return for non-interesting database types.
}
/**
* Dispose the temptables stuff, checking for wrong situations, informing and recovering from them
*/
public function dispose() {
// We shouldn't have any temp table registered at the end of the script.
// So we error_log that and, at the same time, drop all the pending temptables
if ($temptables = $this->get_temptables()) {
error_log('Potential coding error - existing temptables found when disposing database. Must be dropped!');
foreach ($temptables as $temptable) {
$this->mdb->get_manager()->drop_table(new xmldb_table($temptable));
}
}
$this->mdb = null;
}
}