Re: [GENERAL] Tuning queries on large database

> so it takes about 28 Gb instead of 68 Gb !

Huzzah!

> For my different queries, it's better but less performant than oracle :

Not surprising. Oracle has a number of optimizations that we don't have
implemented at this point, particularly where aggregates are involved.

One that PG could use, particularly for Q4, is the ability to execute a
selective sequential scan based on a read of the index -- right now it
pulls in actual data from the table structure while following the index
-- creates unnecessary disk-head movement.

The only solution to that, at the moment, is to cluster the table by
pk_data.

I am curious though, could you run the below query on both systems and
report back times?

select 'Q4', * from data where num_poste between 600 and 625;

I'm wondering if Oracle is using a shortcut since the count(*) doesn't
actually require the data -- just knowledge of whether a matching row
exists or not.