Use unique log_conn_id in logging

The process of recording logging entries involves recording a row in the log table with the user_id, log_conn_id, log_date and log_action being undertaken.

When viewing the reports I have found they are flakey because there is some wierd argy-bargey around ensuring that you are getting records relevant to a particular log_conn_id within a 10 seconds. Of course if the process is slow or long 10 seconds may not be enough. The query can also have speed implications - in particular in the default scenario where the field is not indexed.

After some playing around & looking at old tickets I came across the reason for this 10 second rule. The log_conn_id field is actually only unique within the connections at the time. However, a later connection might have the same ID.

My proposal is to replace the complexity of getting data out with better data in. Instead of setting log_conn_id to connection_id() set it to uniquid() + connection_id() - uniquid is generated in php and is unique to within a microsecond. Since that is not guaranteed completely unique I propose to add the connection_id - which IS unique within a microsecond.

CRM_Core_DAO::executeQuery('SET @uniqueID = CONCAT("' . uniqid() . '", CONNECTION_ID())');

This involves changing the log tables from int(11) to varchar(24) - which might make it a slower upgrade.

Since we won't have truly unique ids from before the conversion I think we need to records in the settings the date of the conversion and consider this date when presenting logging data - ie. we still need the 10 sec argy bargey before this date.