Re: Query plan on identical tables differs . Why ?

Fabio Panizzutti wrote:
> storico=# explain select tag_id,valore_tag,data_tag from storico_misure
> where (data_tag>'2004-05-03' and data_tag <'2004-05-12') and
> tag_id=37423 ;

Can you please post explain analyze? That includes actual timings.

Looking at the schema, can you try "and tag_id=37423::integer" instead?

> enable_hashagg = false
> enable_hashjoin = false
> enable_indexscan = true
> enable_mergejoin = true
> enable_nestloop = false
> enable_seqscan = true
> enable_sort = false
> enable_tidscan = false

Why do you have these off? AFAIK, 7.4 improved hash aggregates a lot. So you
might miss on these in this case.

> # - Planner Cost Constants -
>
> #effective_cache_size = 1000    # typically 8KB each

You might set it to something realistic.

And what is your hardware setup? Disks/CPU/RAM?

Just to be sure, you went thr.
http://www.varlena.com/varlena/GeneralBits/Tidbits/annotated_conf_e.html and
http://www.varlena.com/varlena/GeneralBits/Tidbits/perf.html?

HTH

  Regards
    Shridhar