diff --git a/lib/ddl/postgres_sql_generator.php b/lib/ddl/postgres_sql_generator.php
index 2b44baaf2f7..1bcf44ac272 100644
--- a/lib/ddl/postgres_sql_generator.php
+++ b/lib/ddl/postgres_sql_generator.php
@@ -133,11 +133,11 @@ class postgres_sql_generator extends sql_generator {
         $hints = $xmldb_index->getHints();
         $fields = $xmldb_index->getFields();
         if (in_array('varchar_pattern_ops', $hints) and count($fields) == 1) {
-            // Add the pattern index and keep the normal one.
+            // Add the pattern index and keep the normal one, keep unique only the standard index to improve perf.
             foreach ($sqls as $sql) {
                 $field = reset($fields);
                 $count = 0;
-                $newindex = preg_replace("/^CREATE INDEX ([a-z0-9_]+) ON ([a-z0-9_]+) \($field\)$/", "CREATE INDEX \\1_pattern ON \\2 USING btree ($field varchar_pattern_ops)", $sql, -1, $count);
+                $newindex = preg_replace("/^CREATE( UNIQUE)? INDEX ([a-z0-9_]+) ON ([a-z0-9_]+) \($field\)$/", "CREATE INDEX \\2_pattern ON \\3 USING btree ($field varchar_pattern_ops)", $sql, -1, $count);
                 if ($count != 1) {
                     debugging('Unexpected getCreateIndexSQL() structure.');
                     continue;
diff --git a/lib/ddl/tests/ddl_test.php b/lib/ddl/tests/ddl_test.php
index 4ad5e359dc9..dfe7f457aab 100644
--- a/lib/ddl/tests/ddl_test.php
+++ b/lib/ddl/tests/ddl_test.php
@@ -1676,6 +1676,21 @@ class ddl_testcase extends database_driver_testcase {
         $table = new xmldb_table('testtable');
         $index = new xmldb_index('path', XMLDB_INDEX_NOTUNIQUE, array('path'), array('varchar_pattern_ops'));
         $this->assertTrue($dbman->index_exists($table, $index));
+
+        // Try unique indexes too.
+        $dbman->drop_table($this->tables[$tablename]);
+
+        $table = new xmldb_table('testtable');
+        $table->add_field('id', XMLDB_TYPE_INTEGER, '10', XMLDB_UNSIGNED, XMLDB_NOTNULL, XMLDB_SEQUENCE, null);
+        $table->add_field('path', XMLDB_TYPE_CHAR, 255, null, XMLDB_NOTNULL, null);
+        $table->add_key('primary', XMLDB_KEY_PRIMARY, array('id'));
+        $table->add_index('path', XMLDB_INDEX_UNIQUE, array('path'), array('varchar_pattern_ops'));
+        $dbman->create_table($table);
+        $this->tables[$tablename] = $table;
+
+        $table = new xmldb_table('testtable');
+        $index = new xmldb_index('path', XMLDB_INDEX_UNIQUE, array('path'), array('varchar_pattern_ops'));
+        $this->assertTrue($dbman->index_exists($table, $index));
     }
 
     public function test_index_max_bytes() {