Re: Regarding query optimisation (select for update)

On Tue, 2025-07-15 at 18:26 +0530, Durgamahesh Manne wrote:
> On Tue, Jul 15, 2025 at 6:14 PM Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> wrote:
> > On Tue, 2025-07-15 at 15:40 +0530, Durgamahesh Manne wrote:
> > > We are facing issues with slow running query 
> > >    SELECT betid, versionid, betdata, processed, messagetime, createdat, updatedat
> > >     FROM praermabetdata where processed = 'false'
> > >     ORDER BY betid, versionid LIMIT 200 OFFSET 0 FOR UPDATE;  
> > >
> > >                                                          QUERY PLAN
> > > --------------------------------------------------------------------------------------------------------------------------------
> > >  Limit  (cost=0.28..1.89 rows=1 width=78)
> > >    ->  LockRows  (cost=0.28..1.89 rows=1 width=78)
> > >          ->  Index Scan using idx_praermabetdata_processed_betid_versionid on praermabetdata  (cost=0.28..1.88 rows=1 width=78)
> > >                Index Cond: (processed = false)
> > >
> > > image.png
> > >
> > > Do we have any alternative way to improve the performance?
> > > Sometimes processed column use true as well as false 
> >
> > Please provide EXPLAIN (ANALYZE, BUFFERS) output and use "log_lock_waits"
> > to see if you are hanging behind locks for a longer time.
>
> image.png

Text is easier to read than images...

Anyway, this statement was done in under a millisecond.
I wouldn't call that slow...

Yours,
Laurenz Albe