From: Aleksandr Vinokurov <aleksandr.vin@gmail.com>
To: Scott Marlowe <scott.marlowe@gmail.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Partial index and query plan
Date: Wed, 22 Aug 2007 19:02:03 +0400
Message-ID: <b048c51b0708220802u24d78e15i916bf7c52a303280@mail.gmail.com> (raw)
In-Reply-To: <dcc563d10708220743h37f85ae5scb183bb9e6e85073@mail.gmail.com>
References: <b048c51b0708220557g18cc9a6p7bf2ab195539c3bd@mail.gmail.com>
<dcc563d10708220743h37f85ae5scb183bb9e6e85073@mail.gmail.com>
Scott Marlowe wrote:
>
> I don't see the issue here. The index being used is the same partial
> index you created. Maybe it's just a question of semantics?
>
As I understand final filter is:
a) pointed at the index creation
b) is redundant as all the indexed records have action <> 0.
So checking of it is a time wasting.
And the plan should be this:
>> Limit (cost=0.00..3.05 rows=1 width=8) (actual time=4.798..4.798
>> rows=0 loops=1)
>> -> Index Scan using indx_date_action12_uid_user_his on
>> user_history (cost=0.00..6.10 rows=2 width=8) (actual
>> time=4.791..4.791 rows=0 loops=1)
>> Index Cond: ((date > '2007-08-18 14:33:40.60664'::timestamp
>> without time zone) AND (date <= '2007-08-18 16:30:00'::timestamp
>> without time zone) AND (uid = 138658))
I suggest that this 'Filter' check will not be noticed as it always
return TRUE, and so will be checked only once, -- because of the
"limit 1". :)
But thanks, Aleksandr.
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To: pgsql-sql@postgresql.org
Cc: aleksandr.vin@gmail.com, scott.marlowe@gmail.com
Subject: Re: Partial index and query plan
In-Reply-To: <b048c51b0708220802u24d78e15i916bf7c52a303280@mail.gmail.com>
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