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
