Re: order by - Mailing list pgsql-general

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.millas@mokadb.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