Fix #4173
This reverts commit 7cc6cea2d421862726081a39e932dbceeefcc775
from PR #3968.
At the time this seemed logical, but turns out it breaks the
ability to create non-PRIMARY composite keys, so ...
diff --git a/system/database/DB_forge.php b/system/database/DB_forge.php
index dde2855..f9cf76a 100644
--- a/system/database/DB_forge.php
+++ b/system/database/DB_forge.php
@@ -239,7 +239,13 @@
*/
public function add_key($key, $primary = FALSE)
{
- if (is_array($key))
+ // DO NOT change this! This condition is only applicable
+ // for PRIMARY keys because you can only have one such,
+ // and therefore all fields you add to it will be included
+ // in the same, composite PRIMARY KEY.
+ //
+ // It's not the same for regular indexes.
+ if ($primary === TRUE && is_array($key))
{
foreach ($key as $one)
{