Estimate freezes

[joelcomit]

I'm able to get an estimate of how many recipients when I select a smaller list, 110 recipients. When I add larger lists (approx 2,000) I get "estimating", but it never arrives at an estimate.

[totten]

This sounds like https://issues.civicrm.org/jira/browse/CRM-16277 which should be patched in the upcoming v4.6.3. In a nutshell, the estimate generated a list of recipients - which included names+email addresses. The technique for determining names+emails was incredibly slow, which led to DB contention and apparent lockups. CRM-16277 uses a more efficient estimate and limits the names+email addresses to modest sample.

[scrubba]

I think I can add to this issue
In that we have a very similar problem - but not quite the same
This set up is running civi 4.6.2 and latest wordpress4.2.
Its a a good size db with 11,000 + contacts

So this morning the complaint was the civimail was hanging, in that a draft email couldn't be saved or sent.
Once a recipient group (of a few thousand contacts) was selected from the drop box, the estimate counter froze and eventually a fault was produced in pop up :
"Error: Failed to run Permission check: Unrecognized entity table (civicrm_participant)" 
See - attached graphic

This happened when admin tried to do this - so permission check was odd, and the table exists as normal.

So i tried a few experiments, I changed the recipient to a test group with 5 people in it. This time the estimate worked after about 2 seconds. Then it saved (indicated by top right corner) I then tried to click into the Recipient drop down a second time to (if I could) add another group. The system saved, then paused, then after about 15 seconds the fault message as above appeared, twice.

I then tried the same process a third time with only 2 people in the group, and this time everything worked and the fault had gone completely. But weirdly I tried to add a third person back in the group, and tried a fourth time, the fault message came back.
So I am having some odd times with this - it is not clear when / why things will work, or not. 

Seems related to this:https://issues.civicrm.org/jira/browse/CRM-16277
Let me know it you fixie folk cleverer than us need any more info