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<?php
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// This file is part of Moodle - http://moodle.org/
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//
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// Moodle is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Moodle is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
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declare(strict_types=1);
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namespace core_reportbuilder\local\aggregation;
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use lang_string;
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use core_reportbuilder\local\helpers\database;
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/**
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* Column group concatenation distinct aggregation type
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*
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* @package core_reportbuilder
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* @copyright 2021 Paul Holden <paulh@moodle.com>
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* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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*/
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class groupconcatdistinct extends groupconcat {
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/**
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* Return aggregation name
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*
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* @return lang_string
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*/
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public static function get_name(): lang_string {
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return new lang_string('aggregationgroupconcatdistinct', 'core_reportbuilder');
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}
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/**
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* This aggregation can be performed on all non-timestamp columns in MySQL, Postgres and Oracle only
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*
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* @param int $columntype
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* @return bool
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*/
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public static function compatible(int $columntype): bool {
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global $DB;
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$dbsupportedtype = in_array($DB->get_dbfamily(), [
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'mysql',
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'postgres',
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'oracle',
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]);
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return $dbsupportedtype && parent::compatible($columntype);
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}
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/**
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* Return the aggregated field SQL
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*
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* @param string $field
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* @param int $columntype
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* @return string
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*/
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public static function get_field_sql(string $field, int $columntype): string {
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global $DB;
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$fieldsort = database::sql_group_concat_sort($field);
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// Postgres handles group concatenation differently in that it requires the expression to be cast to char, so we can't
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// simply pass "DISTINCT {$field}" to the {@see \moodle_database::sql_group_concat} method in all cases.
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if ($DB->get_dbfamily() === 'postgres') {
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$field = $DB->sql_cast_to_char($field);
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if ($fieldsort !== '') {
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$fieldsort = "ORDER BY {$fieldsort}";
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}
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return "STRING_AGG(DISTINCT {$field}, '" . self::FIELD_VALUE_DELIMETER . "' {$fieldsort})";
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} else {
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return $DB->sql_group_concat("DISTINCT {$field}", self::FIELD_VALUE_DELIMETER, $fieldsort);
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}
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}
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}
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