On Fri, Jan 07, 2022 at 03:25:28PM +0100, Peter Eisentraut wrote:
>
> I tested this a bit. I used the following setup:
>
> create table t1 (a text);
> insert into t1 select md5(generate_series(1, 10000000)::text);
> select count(*) from t1 where a > '';
>
> And then I changed in varstr_cmp():
>
> if (collid != DEFAULT_COLLATION_OID)
> mylocale = pg_newlocale_from_collation(collid);
>
> to just
>
> mylocale = pg_newlocale_from_collation(collid);
>
> I find that the \timing results are indistinguishable. (I used locale
> "en_US.UTF-8" and made sure that that code path is actually hit.)
>
> Does anyone have other insights?
Looking at the git history, you added this comment in 414c5a2ea65.
After a bit a digging in the lists, I found that you introduced it to fix a
reported 13% slowdown in varstr_cmp():
https://www.postgresql.org/message-id/20110129075253.GA18784%40tornado.leadboat.com
https://www.postgresql.org/message-id/1296748408.6442.1.camel%40vanquo.pezone.net