bugsummary_rollup_journal is slow

[Stuart Bishop]

The bugsummary_inc and _dec stored procedures are slow, making the rollup process slow.

Rework the UPDATEs to not use IS DISTINCT FROM and see if we can make use of the indexes instead of full table scans.

[Stuart Bishop (stub)]

We think this may be exacerbating timeouts due to row locks.

[Launchpad QA Bot (lpqabot)]

Fixed in db-stable r10832 <http://bazaar.launchpad.net/~launchpad-pqm/launchpad/db-stable/revision/10832>.

[Robert Collins (lifeless)]

cold, on qastaging with 600 summary changes:
lpmain_staging=# select count(*) from bugsummaryjournal;
 count
-------
   603
(1 row)

lpmain_staging=# explain analyze select bugsummary_rollup_journal();
                                        QUERY PLAN
------------------------------------------------------------------------------------------
 Result (cost=0.00..0.26 rows=1 width=0) (actual time=8543.085..8543.086 rows=1 loops=1)
 Total runtime: 8543.112 ms
(2 rows)

lpmain_staging=# select count(*) from bugsummaryjournal;
 count
-------
     0

so its at least working, though whether it fixes the performance issue I'm not sure.