From: | Ben <midfield(at)gmail(dot)com> |
---|---|
To: | Igor Neyman <ineyman(at)perceptron(dot)com> |
Cc: | <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: partitioning question 1 |
Date: | 2010-10-29 16:16:13 |
Message-ID: | 59555E0F-71C2-4062-AD23-F1B7B9993354@gmail.com |
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Thread: | |
Lists: | pgsql-performance |
On Oct 29, 2010, at 7:38 AM, Igor Neyman wrote:
>> is my intuition completely off on this?
>>
>> best regards, ben
>>
>
> If your SELECT retrieves substantial amount of records, table scan could
> be more efficient than index access.
>
> Now, if while retrieving large amount of records "WHERE clause" of this
> SELECT still satisfies constraints on some partition(s), then obviously
> one (or few) partition scans will be more efficient than full table scan
> of non-partitioned table.
>
> So, yes partitioning provides performance improvements, not only
> maintenance convenience.
my impression was that a *clustered* index would give a lot of the same I/O benefits, in a more flexible way. if you're clustered on the column in question, then an index scan for a range is much like a sequential scan over a partition (as far as i understand.)
b
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