Fix migrations, Add perf logging, id search limit shortcut

[bitner]

[v0.7.7]

Fixed

• Fix migrations for 0.7.4->0.7.5 and 0.7.5->0.7.6 to use the partition_view rather than the materialized view to avoid issue with refreshing the materialized view when run in the same statement that is accessing the view. Fixes Migration fails from 0.7.4 #180.

Added

• Add a short cirucit for id searches that sets the limit to be no more than the number of ids in the filter.
• Add 'timing' configuration variable that adds a "timing" element to the return object with the amount of time that it took to return a search.
• Reduce locking when updating statistics in the search table. Use skip locked to skip updating last_used and count when there is a lock being held.

[mmcfarland]

Just following the logic here: the subtraction is so that when the search limit is bumped by 1 to check to see if it needs a "next token", it evens out and still doesn't keep scanning?

[bitner]

yep, otherwise it would keep scanning for a next item which we know it wouldn't find