From 36af5457dc795a2d869dfacf4a03cbad5df5e1eb Mon Sep 17 00:00:00 2001
From: Paul Holden <paulh@moodle.com>
Date: Tue, 25 Jul 2023 00:20:18 +0100
Subject: [PATCH] MDL-78787 dml: native casting to char in SQL Server driver.

Ensure the same is used during concatentation to prevent truncation
of data, which was previously set at 255 characters per field.
---
 lib/dml/sqlsrv_native_moodle_database.php | 12 +++-
 lib/dml/tests/dml_test.php                | 73 +++++++++++++++++------
 2 files changed, 67 insertions(+), 18 deletions(-)

diff --git a/lib/dml/sqlsrv_native_moodle_database.php b/lib/dml/sqlsrv_native_moodle_database.php
index 8b8ebf8c7ef..9afc56b9e8c 100644
--- a/lib/dml/sqlsrv_native_moodle_database.php
+++ b/lib/dml/sqlsrv_native_moodle_database.php
@@ -1318,6 +1318,16 @@ class sqlsrv_native_moodle_database extends moodle_database {
         return true;
     }
 
+    /**
+     * Return SQL for casting to char of given field/expression
+     *
+     * @param string $field Table field or SQL expression to be cast
+     * @return string
+     */
+    public function sql_cast_to_char(string $field): string {
+        return "CAST({$field} AS NVARCHAR(MAX))";
+    }
+
 
     public function sql_cast_char2int($fieldname, $text = false) {
         if (!$text) {
@@ -1441,7 +1451,7 @@ class sqlsrv_native_moodle_database extends moodle_database {
         $arr = func_get_args();
 
         foreach ($arr as $key => $ele) {
-            $arr[$key] = ' CAST('.$ele.' AS NVARCHAR(255)) ';
+            $arr[$key] = $this->sql_cast_to_char($ele);
         }
         $s = implode(' + ', $arr);
 
diff --git a/lib/dml/tests/dml_test.php b/lib/dml/tests/dml_test.php
index 0667f73b517..38a1b906f06 100644
--- a/lib/dml/tests/dml_test.php
+++ b/lib/dml/tests/dml_test.php
@@ -4366,29 +4366,68 @@ EOD;
         $tablename = $table->getName();
 
         $table->add_field('id', XMLDB_TYPE_INTEGER, '10', null, XMLDB_NOTNULL, XMLDB_SEQUENCE, null);
-        $table->add_field('description', XMLDB_TYPE_TEXT, 'big', null, null, null, null);
+        $table->add_field('charshort', XMLDB_TYPE_CHAR, '255');
+        $table->add_field('charlong', XMLDB_TYPE_CHAR, '1333');
+        $table->add_field('description', XMLDB_TYPE_TEXT, 'big');
         $table->add_key('primary', XMLDB_KEY_PRIMARY, array('id'));
         $dbman->create_table($table);
 
-        $DB->insert_record($tablename, array('description'=>'áéíóú'));
-        $DB->insert_record($tablename, array('description'=>'dxxx'));
-        $DB->insert_record($tablename, array('description'=>'bcde'));
+        // Regarding 1300 length - all drivers except Oracle support larger values (2K+), but this hits a limit on Oracle.
+        $DB->insert_record($tablename, [
+            'charshort' => 'áéíóú',
+            'charlong' => str_repeat('A', 512),
+            'description' => str_repeat('X', 1300),
+        ]);
+        $DB->insert_record($tablename, [
+            'charshort' => 'dxxx',
+            'charlong' => str_repeat('B', 512),
+            'description' => str_repeat('Y', 1300),
+        ]);
+        $DB->insert_record($tablename, [
+            'charshort' => 'bcde',
+            'charlong' => str_repeat('C', 512),
+            'description' => str_repeat('Z', 1300),
+        ]);
+
+        // Char (short) fieldnames and values.
+        $fieldsql = $DB->sql_concat('charshort', "'harcoded'", '?', '?');
+        $this->assertEqualsCanonicalizing([
+            'áéíóúharcoded123.45test',
+            'dxxxharcoded123.45test',
+            'bcdeharcoded123.45test',
+        ], $DB->get_fieldset_select($tablename, $fieldsql, '', [123.45, 'test']));
+
+        // Char (long) fieldnames and values.
+        $fieldsql = $DB->sql_concat('charlong', "'harcoded'", '?', '?');
+        $this->assertEqualsCanonicalizing([
+            str_repeat('A', 512) . 'harcoded123.45test',
+            str_repeat('B', 512) . 'harcoded123.45test',
+            str_repeat('C', 512) . 'harcoded123.45test',
+        ], $DB->get_fieldset_select($tablename, $fieldsql, '', [123.45, 'test']));
+
+        // Text fieldnames and values.
+        $fieldsql = $DB->sql_concat('description', "'harcoded'", '?', '?');
+        $this->assertEqualsCanonicalizing([
+            str_repeat('X', 1300) . 'harcoded123.45test',
+            str_repeat('Y', 1300) . 'harcoded123.45test',
+            str_repeat('Z', 1300) . 'harcoded123.45test',
+        ], $DB->get_fieldset_select($tablename, $fieldsql, '', [123.45, 'test']));
 
-        // Fieldnames and values mixed.
-        $sql = 'SELECT id, ' . $DB->sql_concat('description', "'harcoded'", '?', '?') . ' AS result FROM {' . $tablename . '}';
-        $records = $DB->get_records_sql($sql, array(123.45, 'test'));
-        $this->assertCount(3, $records);
-        $this->assertSame('áéíóúharcoded123.45test', $records[1]->result);
         // Integer fieldnames and values.
-        $sql = 'SELECT id, ' . $DB->sql_concat('id', "'harcoded'", '?', '?') . ' AS result FROM {' . $tablename . '}';
-        $records = $DB->get_records_sql($sql, array(123.45, 'test'));
-        $this->assertCount(3, $records);
-        $this->assertSame('1harcoded123.45test', $records[1]->result);
+        $fieldsql = $DB->sql_concat('id', "'harcoded'", '?', '?');
+        $this->assertEqualsCanonicalizing([
+            '1harcoded123.45test',
+            '2harcoded123.45test',
+            '3harcoded123.45test',
+        ], $DB->get_fieldset_select($tablename, $fieldsql, '', [123.45, 'test']));
+
         // All integer fieldnames.
-        $sql = 'SELECT id, ' . $DB->sql_concat('id', 'id', 'id') . ' AS result FROM {' . $tablename . '}';
-        $records = $DB->get_records_sql($sql, array());
-        $this->assertCount(3, $records);
-        $this->assertSame('111', $records[1]->result);
+        $fieldsql = $DB->sql_concat('id', 'id', 'id');
+        $this->assertEqualsCanonicalizing([
+            '111',
+            '222',
+            '333',
+        ], $DB->get_fieldset_select($tablename, $fieldsql, ''));
 
     }