From: | James David Smith <james(dot)david(dot)smith(at)gmail(dot)com> |
---|---|
To: | pgsql-novice(at)postgresql(dot)org |
Subject: | Make UPDATE query quicker? |
Date: | 2012-10-12 10:16:00 |
Message-ID: | CAMu32ACu5miM4Fc8wx_0ZDs5_PT=j6+PyJ8vQdAjoUbhmtH5og@mail.gmail.com |
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Lists: | pgsql-novice |
Hi all,
Wondered if someone had any tips about how to do this UPDATE query
quicker. I've got two tables:
CREATE TABLE import_table
( date_time TIMESTAMP
person_id, INTEGER
data REAL)
CREATE TABLE master_table
(date_time TIMESTAMP
person_id INTEGER
data REAL)
Each table has 172800 rows in it.
I want to move the 'data' from the import_table to the master_table by
matching on both the date_time and the person_id. I do this with this
query:
UPDATE master_table a
SET data =
(SELECT b.date
FROM import_table b
WHERE a.date_time = b.date_time AND a.person_id = b.person_id AND
b.data IS NOT NULL)
However I need to do this about 20 times, and the first time is still
running at the moment (about 15 minutes).
Am I doing something wrong? Should I put some indexes on the columns
somehow to improve performance?
Thanks
James
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