From aa0a602b106921bdc64effa33115a1a94c3248cc Mon Sep 17 00:00:00 2001
From: Matteo Scaramuccia <moodle@matteoscaramuccia.com>
Date: Sun, 19 May 2019 20:29:20 +0200
Subject: [PATCH] MDL-65811 database: Fix subsetting in MSSQL
---
lib/dml/sqlsrv_native_moodle_database.php | 28 ++++-
.../sqlsrv_native_moodle_database_test.php | 118 ++++++++++++++++++
2 files changed, 144 insertions(+), 2 deletions(-)
diff --git a/lib/dml/sqlsrv_native_moodle_database.php b/lib/dml/sqlsrv_native_moodle_database.php
index 9174f70c600..a91317dc71d 100644
--- a/lib/dml/sqlsrv_native_moodle_database.php
+++ b/lib/dml/sqlsrv_native_moodle_database.php
@@ -841,6 +841,30 @@ class sqlsrv_native_moodle_database extends moodle_database {
return true;
}
+ /**
+ * Whether the given SQL statement has the ORDER BY clause in the main query.
+ *
+ * @param string $sql the SQL statement
+ * @return bool true if the main query has the ORDER BY clause; otherwise, false.
+ */
+ protected static function has_query_order_by(string $sql) {
+ $sqltoupper = strtoupper($sql);
+ // Fail fast if there is no ORDER BY clause in the original query.
+ if (strpos($sqltoupper, 'ORDER BY') === false) {
+ return false;
+ }
+
+ // Search for an ORDER BY clause in the main query, not in any subquery (not always allowed in MSSQL)
+ // or in clauses like OVER with a window function e.g. ROW_NUMBER() OVER (ORDER BY ...) or RANK() OVER (ORDER BY ...):
+ // use PHP PCRE recursive patterns to remove everything found within round brackets.
+ $mainquery = preg_replace('/\(((?>[^()]+)|(?R))*\)/', '()', $sqltoupper);
+ if (strpos($mainquery, 'ORDER BY') !== false) {
+ return true;
+ }
+
+ return false;
+ }
+
/**
* Get a number of records as a moodle_recordset using a SQL statement.
*
@@ -876,9 +900,9 @@ class sqlsrv_native_moodle_database extends moodle_database {
} else {
$needscrollable = false; // Using supported fetch/offset, no need to scroll anymore.
$sql = (substr($sql, -1) === ';') ? substr($sql, 0, -1) : $sql;
- // We need order by to use FETCH/OFFSET.
+ // We need ORDER BY to use FETCH/OFFSET.
// Ordering by first column shouldn't break anything if there was no order in the first place.
- if (!strpos(strtoupper($sql), "ORDER BY")) {
+ if (!self::has_query_order_by($sql)) {
$sql .= " ORDER BY 1";
}
diff --git a/lib/dml/tests/sqlsrv_native_moodle_database_test.php b/lib/dml/tests/sqlsrv_native_moodle_database_test.php
index 65cd4706e7a..8736d795b8e 100644
--- a/lib/dml/tests/sqlsrv_native_moodle_database_test.php
+++ b/lib/dml/tests/sqlsrv_native_moodle_database_test.php
@@ -134,6 +134,124 @@ class sqlsrv_native_moodle_database_testcase extends advanced_testcase {
$temptablesproperty->setValue($sqlsrv, null);
$this->assertEquals($expected, $result);
}
+
+ /**
+ * Data provider for test_has_query_order_by
+ *
+ * @return array data for test_has_query_order_by
+ */
+ public function has_query_order_by_provider() {
+ // Fixtures taken from https://docs.moodle.org/en/ad-hoc_contributed_reports.
+
+ return [
+ 'User with language => FALSE' => [
+ 'sql' => <<<EOT
+SELECT username, lang
+ FROM prefix_user
+EOT
+ ,
+ 'expectedmainquery' => <<<EOT
+SELECT username, lang
+ FROM prefix_user
+EOT
+ ,
+ 'expectedresult' => false
+ ],
+ 'List Users with extra info (email) in current course => FALSE' => [
+ 'sql' => <<<EOT
+SELECT u.firstname, u.lastname, u.email
+ FROM prefix_role_assignments AS ra
+ JOIN prefix_context AS context ON context.id = ra.contextid AND context.contextlevel = 50
+ JOIN prefix_course AS c ON c.id = context.instanceid AND c.id = %%COURSEID%%
+ JOIN prefix_user AS u ON u.id = ra.userid
+EOT
+ ,
+ 'expectedmainquery' => <<<EOT
+SELECT u.firstname, u.lastname, u.email
+ FROM prefix_role_assignments AS ra
+ JOIN prefix_context AS context ON context.id = ra.contextid AND context.contextlevel = 50
+ JOIN prefix_course AS c ON c.id = context.instanceid AND c.id = %%COURSEID%%
+ JOIN prefix_user AS u ON u.id = ra.userid
+EOT
+ ,
+ 'expectedresult' => false
+ ],
+ 'ROW_NUMBER() OVER (ORDER BY ...) => FALSE (https://github.com/jleyva/moodle-block_configurablereports/issues/120)' => [
+ 'sql' => <<<EOT
+SELECT COUNT(*) AS 'Users who have logged in today'
+ FROM (
+ SELECT ROW_NUMBER() OVER(ORDER BY lastaccess DESC) AS Row
+ FROM mdl_user
+ WHERE lastaccess > DATEDIFF(s, '1970-01-01 02:00:00', (SELECT Convert(DateTime, DATEDIFF(DAY, 0, GETDATE()))))
+ ) AS Logins
+EOT
+ ,
+ 'expectedmainquery' => <<<EOT
+SELECT COUNT() AS 'Users who have logged in today'
+ FROM () AS Logins
+EOT
+ ,
+ 'expectedresult' => false
+ ],
+ 'CONTRIB-7725 workaround) => TRUE' => [
+ 'sql' => <<<EOT
+SELECT COUNT(*) AS 'Users who have logged in today'
+ FROM (
+ SELECT ROW_NUMBER() OVER(ORDER BY lastaccess DESC) AS Row
+ FROM mdl_user
+ WHERE lastaccess > DATEDIFF(s, '1970-01-01 02:00:00', (SELECT Convert(DateTime, DATEDIFF(DAY, 0, GETDATE()))))
+ ) AS Logins ORDER BY 1
+EOT
+ ,
+ 'expectedmainquery' => <<<EOT
+SELECT COUNT() AS 'Users who have logged in today'
+ FROM () AS Logins ORDER BY 1
+EOT
+ ,
+ 'expectedresult' => true
+ ],
+ 'Enrolment count in each Course => TRUE' => [
+ 'sql' => <<<EOT
+ SELECT c.fullname, COUNT(ue.id) AS Enroled
+ FROM prefix_course AS c
+ JOIN prefix_enrol AS en ON en.courseid = c.id
+ JOIN prefix_user_enrolments AS ue ON ue.enrolid = en.id
+GROUP BY c.id
+ORDER BY c.fullname
+EOT
+ ,
+ 'expectedmainquery' => <<<EOT
+ SELECT c.fullname, COUNT() AS Enroled
+ FROM prefix_course AS c
+ JOIN prefix_enrol AS en ON en.courseid = c.id
+ JOIN prefix_user_enrolments AS ue ON ue.enrolid = en.id
+GROUP BY c.id
+ORDER BY c.fullname
+EOT
+ ,
+ 'expectedresult' => true
+ ],
+ ];
+ }
+
+ /**
+ * Test has_query_order_by
+ *
+ * @dataProvider has_query_order_by_provider
+ * @param string $sql the query
+ * @param string $expectedmainquery the expected main query
+ * @param bool $expectedresult the expected result
+ */
+ public function test_has_query_order_by(string $sql, string $expectedmainquery, bool $expectedresult) {
+ $mainquery = preg_replace('/\(((?>[^()]+)|(?R))*\)/', '()', $sql);
+ $this->assertSame($expectedmainquery, $mainquery);
+
+ // The has_query_order_by static method is protected. Use Reflection to call the method.
+ $method = new ReflectionMethod('sqlsrv_native_moodle_database', 'has_query_order_by');
+ $method->setAccessible(true);
+ $result = $method->invoke(null, $sql);
+ $this->assertSame($expectedresult, $result);
+ }
}
/**