Re: Top -N Query performance issue and high CPU usage

On Mon, Feb 2, 2026 at 3:17 AM Peter J. Holzer <hjp-pgsql(at)hjp(dot)at> wrote:

>
> If you do have that many simultaneous accesses to the landing page, and
> you can't speed up the query significantly (I take it you've seen the
> suggestion to check whether there's an index on
> APP_schema.txn_tbl.tran_date), then maybe you don't need to perform it
> for every user? I don't know what the query is supposed to do, but
> unless the "ent_id" is really a user id, it doesn't seem to be specific
> to the user. So maybe you can cache the result for a minute or an hour
> and show the same result to everybody who logs in during that time.
>
>
>

There was no index on column tran_date , I created one and it's making
the query finish in ~200ms, a lot faster than in the past. Below is the
portion of the query and its plan which actually consumes most of the
resource and time post the new index creation.

https://gist.github.com/databasetech0073/344df46c328e02b98961fab0cd221492

1) Now the part which takes time is the "nested loop" join on the
"ent_id" column. Can we do anything to make it much better/faster?

2) Also another question I had was, with this new index the table scan of
txn_tbl is now fully eliminated by the "Index Scan Backward" even i have
other columns from that table projected in the query, so how its getting
all those column values without visiting table but just that index scan
backward operation?