#76819 by smsimms and sammys. Move part of the sql rewriting down into the database abstraction layer and add extra rewriting needed only for Postgres.

1 files changed, 17 insertions, 0 deletions

diff --git a/includes/database.mysql.inc b/includes/database.mysql.inc
index b0ffd2692..18eeee019 100644
--- a/includes/database.mysql.inc
+++ b/includes/database.mysql.inc
@@ -418,6 +418,23 @@ function db_table_exists($table) {
 }
 
 /**
+ * Wraps the given table.field entry with a DISTINCT(). The wrapper is added to
+ * the SELECT list entry of the given query and the resulting query is returned.
+ * This function only applies the wrapper if a DISTINCT doesn't already exist in
+ * the query.
+ *
+ * @param $table Table containing the field to set as DISTINCT
+ * @param $field Field to set as DISTINCT
+ * @param $query Query to apply the wrapper to
+ * @return SQL query with the DISTINCT wrapper surrounding the given table.field.
+ */
+function db_distinct_field($table, $field, $query) {
+  $field_to_select = 'DISTINCT('. $table .'.'. $field .')';
+  // (?<!text) is a negative look-behind (no need to rewrite queries that already use DISTINCT).
+  return preg_replace('/(SELECT.*)('. $table .'\.)?(?<!DISTINCT\()(?<!DISTINCT\('. $table .'\.)'. $field .'(.*FROM )/AUsi', '\1'. $field_to_select .'\3', $query);
+}
+
+/**
  * @} End of "ingroup database".
  */