Revert back some escape_identifiers() to proect_identifiers() as the first one can't handle arrays
diff --git a/system/database/drivers/postgre/postgre_forge.php b/system/database/drivers/postgre/postgre_forge.php
index 98b484b..fc11245 100644
--- a/system/database/drivers/postgre/postgre_forge.php
+++ b/system/database/drivers/postgre/postgre_forge.php
@@ -174,7 +174,7 @@
 			foreach ($keys as $key)
 			{
 				$key = is_array($key)
-					? $this->db->escape_identifiers($key)
+					? $this->db->protect_identifiers($key)
 					: array($this->db->escape_identifiers($key));
 
 				foreach ($key as $field)