help understanding analyze - Mailing list pgsql-general

From Luca Ferrari
Subject help understanding analyze
Date
Msg-id 200612081253.12092.fluca1978@infinito.it
Whole thread Raw
Responses Re: help understanding analyze  (Bill Moran <wmoran@collaborativefusion.com>)
Re: help understanding analyze  (Tom Lane <tgl@sss.pgh.pa.us>)
Re: help understanding analyze  ("Shoaib Mir" <shoaibmir@gmail.com>)
List pgsql-general
Hi all,
excuse me for this trivial question, but here's my doubt:
create table person(varchar id, varchar surname, varchar name)
with id primary key. Now, the query:
select * from person order by surname,name
provide me an explaination that is sequential scan + sort, as I expected.
After that I build an index on surname,name (clustered) and run vacuum to
update statistics. Then I ran again the query and got the same results (scan
+ sort) with the same time.
Now my trivial question is: why another sort? The index is clustered so the
database should not need to sort the output, or am I using wrong the tools?
Someone can explain me that?

Thanks,
Luca

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