Document non-reserved keyword behaviour

Author: crtschin

src/Database/PostgreSQL/PQTypes/Model/Index.hs

@@ -65,6 +65,16 @@ instance Ord IndexColumn where
 instance IsString IndexColumn where
   fromString s = IndexColumn (fromString s) Nothing
 
+-- | Build an 'IndexColumn' from a column name.
+--
+-- If the column name is a non-reserved keyword in PostgreSQL it must be given
+-- double-quoted, e.g.
+--
+--   @timestamp@ -> @\"\\\"timestamp\\\"\"@
+--
+-- PostgreSQL stores the index definition with the keyword quoted, so the column
+-- name passed here has to match that exactly or the database consistency check
+-- will report a mismatch.
 indexColumn :: RawSQL () -> IndexColumn
 indexColumn col = IndexColumn col Nothing