On Tue, Aug 13, 2019 at 1:58 PM Michael Paquier <michael@paquier.xyz> wrote:
> On Sun, Aug 11, 2019 at 03:59:06PM -0400, Tom Lane wrote:
> > I hacked temp.sql to print a couple different plans (doing it that way,
> > rather than manually, just to ensure that I was getting plans matching
> > what would actually happen right there). And what I see, as attached,
> > is that IOS and plain index and bitmap scans all have pretty much the
> > same total cost. The planner then ought to prefer IOS or plain on the
> > secondary grounds of cheaper startup cost. However, it's not so hard
> > to believe that it might switch to bitmap if something caused the cost
> > estimates to change by a few percent. So probably we should write this
> > off as "something affected the plan choice" and just add the ORDER BY
> > as you suggest.
>
> That matches what I was seeing, except that I have done those tests
> manually. Still my plans matched with yours.
Here's another one that seems to fit that pattern.
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=skink&dt=2019-08-11%2007%3A33%3A39
+++ /home/andres/build/buildfarm/HEAD/pgsql.build/src/bin/pg_upgrade/tmp_check/regress/results/collate.icu.utf8.out
2019-08-11 08:29:11.792695714 +0000
@@ -1622,15 +1622,15 @@
SELECT typname FROM pg_type WHERE typname LIKE 'int_' AND typname <>
'INT2'::text COLLATE case_insensitive;
typname
---------
- int4
int8
+ int4
(2 rows)
--
Thomas Munro
https://enterprisedb.com