On 6/26/26 11:14 AM, Adrian Klaver wrote:
On 6/26/26 10:58 AM, Israel Brewster wrote:
In postgreSQL 15, I had the below query that worked quickly. Now, I
make no claims that the query is the best possible, or even a good
query, but it DID work, and it did so quickly enough to be un-
noticable when running.
Then I upgrade to PostgreSQL 18 - and now the query never completes
(as in, I get a command timeout after at least half an hour before I
get a result). Looking at the EXPLAIN (https://explain.depesz.com/s/
llAQ <https://explain.depesz.com/s/llAQ>) makes it pretty obvious why:
we have a sequence scan on a large table inside a nested loop - and
that sequence scan is apparently not short circuiting.
The link provided shows no times or rows, did you pick the correct one?
Yes you did: "I get a command timeout after at least half an hour"
Was not thinking.
I tried the obvious: REINDEX database and VACUUM ANALYZE, but neither
helped. I have my default_statistics_target set to 500 at the moment.
Then I tried SET enable_seqscan = off; Lo and behold, the query ran in
only 123.888 ms (fun number :-D ) - https://explain.depesz.com/s/K2K9
<https://explain.depesz.com/s/K2K9>
This one does not show the actual query.
---
Israel Brewster
Software Engineer
Alaska Volcano Observatory
Geophysical Institute - UAF
2156 Koyukuk Drive
Fairbanks AK 99775-7320
Work: 907-474-5172
cell: 907-328-9145
