On Wed, Jun 28, 2023 at 6:48 PM Laurenz Albe <laurenz.albe@xxxxxxxxxxx> wrote:
On Wed, 2023-06-28 at 17:29 +0200, Marc Millas wrote:
> https://explain.depesz.com/s/Opk0
>
> The big table (10 billions raws) is split in around 130 partitions, one by month.
> the ladate column is the partition key, and it does have 1 value for each partition.
> there is an index on the numfic column. the distribution of values for that column may differ before and after 2019 january.
>
> The request is executed in a loop for all ten years of data, year 1,2,3, then year2,3,4 etc
> that request is also executed for columns other than cod, one column at a time (there are 107 columns...)
>
> I dont understand why the planner use a filter on the date, as its already within the partition structure.
If the grouping column is the partitioning key, try to set enable_partitionwise_join = on.
Otherwise, your best bet is to create an index that covers both WHERE conditions,
or a covering index, which will get you the best result:
CREATE INDEX ON table1 (numfic, ladate) INCLUDE (cod, nb_obs);
Hi Laurenz, as said, in each partition there is only one value for ladate.
I don't understand the point of creating an index for the tens of millions rows of each partition, index wich will contain the very same unique value within all of the index.
I did set enable_partitionwise_join = 'on' and retry,
but it doesn't seem to change the plan.
Yours,
Laurenz Albe
