From: | Sergey Zaharchenko <doublef(dot)mobile(at)gmail(dot)com> |
---|---|
To: | pgsql-general(at)postgresql(dot)org |
Subject: | Query plan optimization: sorting vs. partitioning |
Date: | 2011-02-02 11:49:04 |
Message-ID: | AANLkTi=Yg_Vk_YE5tsWBBz+g7rT2zhjf+7ummVMTgV6M@mail.gmail.com |
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Lists: | pgsql-general |
Hello list,
I have a large time-indexed table (states) partitioned into several
tables based on the date. The smaller tables are clustered by their
time indices.The main table is empty.
I need to select some data in the time order. When I query a separate
smaller table, the index is used an no sorting is needed. However,
when I query the main table, it occurs:
...
-> Sort ...
Sort Key: ...
Sort Method: ...
-> Result ...
-> Append ...
-> Seq Scan on states
Filter: ...
-> Seq Scan on states_20101206
Filter: ...
...
I see the database doesn't understand that there are no entries in the
main table, so it has to assume the Append data is not ordered. Is
there a way to avoid sorting?
Please CC me as I'm not on the list. Thanks in advance,
--
DoubleF
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