After DB backup and restore: Call to undefined function user_access() in ...includes/menu.inc

Question

This question pertains to a Drupal 7 multi-site install. As a test for some future backup/migrate bash scripting that I am doing for work, I made a backup/dump of my test site postgres DB. I then dropped the DB and recreated it with the same (old) name. I then restored the DB from my backup. I did not touch any files. I thought everything had worked out well, except I have an error that I cannot figure out:

Call to undefined function user_access() in .../includes/menu.inc on line 634.

Things I've tried:

• As a sanity check, I made sure that User module was in my core files and that user_access was defined in user.module
• Checked out the restored database in pgAdmin, made sure that user 0 (anonymous user) was still there

• Truncated any table starting with '_cache':

  Truncate table prefix_cache;
  Truncate table prefix_cache_block;
  Truncate table prefix_cache_bootstrap;
  Truncate table prefix_sessions;  
  Truncate table prefix_cache_field;
  Truncate table prefix_cache_filter;
  Truncate table prefix_cache_form;
  Truncate table prefix_cache_image;
  Truncate table prefix_cache_menu;
  Truncate table prefix_cache_page;
  Truncate table prefix_cache_path;
  

• Checked the system table and disabled, checked and re-enabled various modules including user module via the 'status integer' value/col. (I'm not sure if this is the way to enable and re-enable modules in the DB).

• Tried to install Drush on my server but file permissions are very restrictive. It seems that Drush has limited abilities. Drush can only clear its own cache even after I setup an alias for the site in question.
• Created a 'modules' directory inside of the site's multi-site directory and copied the user module out of core and put it there.
• Tried the export using utf8 as the encoding of the DB and re-importing (no change in error)

Answer 1

Here are few tips:

• make sure your Drupal core has all the files in the right place (especially user module),
• upgrade your Drupal core to the latest version (drush fr && drush up drupal)
• clear all your caches (drush -y cc all), including your memcached (killall memcached),
• rebuild your registry by using Registry Rebuild,
• if you're using modules which are implementing drupal_bootstrap() (such as Secure Site), disable them,
• try disabling your PHP cache engines (such as XCache, Zend optimizer) to see if that's the problem,
• use XDebug and generate a trace file to analyse the code execution,
• or use IDE debugger, breakpoint on the failing line and check why the function doesn't exist,
• test it on different environment/machine,
• eventually restore your database from the point where it was working before.