The following commit has caused a devastating performance regression
in concurrent refresh of MV:
Author: Tom Lane <t...@sss.pgh.pa.us>
Date: Wed Nov 29 22:00:29 2017 -0500
Fix neqjoinsel's behavior for semi/anti join cases.
The below reproduction goes from taking about 1 second to refresh, to
taking an amount of time I don't have the patience to measure.
drop table foobar2 cascade;
create table foobar2 as select * from generate_series(1,200000);
create materialized view foobar3 as select * from foobar2;
create unique index on foobar3 (generate_series );
refresh materialized view CONCURRENTLY foobar3 ;
When I interrupt the refresh, I get a message including this line:
CONTEXT: SQL statement "SELECT newdata FROM pg_temp_3.pg_temp_16420
newdata WHERE newdata IS NOT NULL AND EXISTS (SELECT * FROM
pg_temp_3.pg_temp_16420 newdata2 WHERE newdata2 IS NOT NULL AND newdata2
OPERATOR(pg_catalog.*=) newdata AND newdata2.ctid OPERATOR(pg_catalog.<>)
newdata.ctid) LIMIT 1"
So I makes sense that the commit in question could have caused a change in
the execution plan. Because these are temp tables, I can't easily get my
hands on them to investigate further.