From: Kevin Keith <kkeith@borderware.com>
To: pgsql-performance@postgresql.org
Subject: Partitioned tables in queries
Date: Fri, 21 Jul 2006 15:17:38 -0400
Message-ID: <44C12852.1040909@borderware.com> (raw)
I have a case where I am partitioning tables based on a date range in
version 8.1.4. For example:
table_with_millions_of_records
interaction_id char(16) primary key
start_date timestamp (without timezone) - indexed
.. other columns
child_1 start_date >= 2006-07-21 00:00:00
child_2 start_date >= 2006-07-20 00:00:00 and start_date < 2006-07-21
00:00:00
...
child_5 start_date >= 2006-07-17 00:00:00 and start_date < 2006-07-18
00:00:00
with rules on the parent and child tables that redirect the data to the
appropriate child table based on the start_date.
Because this table is going to grow very large (very quickly), and will
need to be purged daily, I created partitions, or child tables to hold
data for each day. I have done the same thing in Oracle in the past, and
the PostgreSQL solution works great. The archival process is very simple
- drop the expired child table. I am having one problem.
If I run a query on the full table (there are 5 child tables with data
for the last 5 days), and my where clause contains data for the current
day only:
where start_date > date_trunc('day', now())
all 5 child tables are scanned when I look at the output from explain
analyze.
My question is - can I force the planner to only scan the relevant child
table - when the key related to the partitioned data it part of the
where clause?
Thanks,
Kevin
...
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To: pgsql-performance@postgresql.org
Cc: kkeith@borderware.com
Subject: Re: Partitioned tables in queries
In-Reply-To: <44C12852.1040909@borderware.com>
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