Proyectos de Subversion Moodle

<?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;

    }

}