Re: order by

Check the index creation has NULLS FIRST (or LAST) on both indexes that are
used. Use explain to see what indexes are used

See docs for create index:
https://www.postgresql.org/docs/current/sql-createindex.html

On Thu, May 11, 2023, 7:30 AM Marc Millas <marc(dot)millas(at)mokadb(dot)com> wrote:

> Hi,
>
> I keep on investigating on the "death postgres" subject
> but open a new thread as I don't know if it's related to my pb.
>
> I have 2 different clusters, on 2 different machines, one is prod, the
> second test.
> Same data volumes.
>
> On prod if I do
> select col_a, count(col_a) from table_a group by col_a order by col_a
> desc,
> I get the numbers of NULL on top.
> To get the number of NULL on top on the test db, I have to
> select col_a, count(col_a) from table_a group by col_a order by col_a asc.
>
> so, it looks like there is something different within the b-tree operator
> class of varchar (?!?)
> between those 2 clusters.
>
> What can I check to to explain this difference as, to my understanding,
> it's not a postgresql.conf parameter.
>
> thanks
>
> Marc MILLAS
> Senior Architect
> +33607850334
> www.mokadb.com
>
>