Can't restore profile-installed site after D7.12 core upgrade I have just attempted to do another minor core upgrade from 7.9 to 7.12. While the former went rather smooth, the latter is giving me a headache. I constantly get fatal errors like these below:

Notice: Undefined index: schema_fields_sql in /includes/entity.inc on line 265

Catchable fatal error: Argument 2 passed to SelectQuery::fields() must be an array, null given, called in /includes/entity.inc on line 284 and defined in /includes/database/select.inc on line 1300


I am now in the middle of yet another attempt to restore the site

The difference in that website, compared to that which successfully passed the core upgrade, is that this was originally installed using commerce kickstart profile. And my questions are:


Has anyone successfully performed core upgrade within a
profile-originated site?
What are safety rules to observe when doing
such upgrades (apart from obvious backing up the files and
database?)?
What approach you prefer for upgrading live sites? Do you usually create a new directory, which you test, and when ready, you redirect root catalog to that directory?


I hope your insights will bring back my confidence as per having chosen Drupal for commercial sites.
Did you remember to run update.php?

Also, Drupal 7.11 and 7.12 are both security updates. 7.12 includes bug fixes, while 7.11 only addresses the security problems. You might try 7.11 and see how it goes.

Also 2: Here's an issue thread about it.