Re: PostgreSQL 15-->18 slowdown? - Mailing list pgsql-general

From Adrian Klaver
Subject Re: PostgreSQL 15-->18 slowdown?
Date
Msg-id 2ce465f0-f7f3-4c6a-9f68-b53439416336@aklaver.com
Whole thread
In response to PostgreSQL 15-->18 slowdown?  (Israel Brewster <ijbrewster@alaska.edu>)
Responses Re: PostgreSQL 15-->18 slowdown?
Re: PostgreSQL 15-->18 slowdown?
List pgsql-general

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?
> 
> 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
> 




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