From: Peter Headland <pheadland@actuate.com>
To: pgsql-sql@postgresql.org
Subject: Updating a specific number of rows in pl/pgsql
Date: Mon, 10 Aug 2009 17:52:36 -0700
Message-ID: <71F491F5DA99604A80DE49424BF3D02B0C7290CA@exchange8.actuate.com> (raw)
I'm working on a queuing application. As part of this I'm trying to
write a pl/pgsql function that updates a specific number of rows in the
most efficient way possible. Multiple queues are contained within a
single table.
I can get the rows I want to update like this:
SELECT *
FROM queue
WHERE id = p_queue_id
ORDER BY rank
LIMIT p_number_of_items;
Of course, there may not be p_number_of_items available in the queue.
I want to update all the rows in the cursor in the same way:
UPDATE queue SET assigned = TRUE;
The "obvious" solution is to get a cursor on the query and attempt to
MOVE through that cursor in a loop, using the row count from the SELECT
to tell me when I am done. I can then use UPDATE ... WHERE CURRENT OF
... to do the updates. This seems cumbersome and inefficient to me. Is
there a better way?
Ideally, I'd like to do something like:
UPDATE (SELECT ... ) ...
--
Peter Headland
Architect
Actuate Corporation
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To: pgsql-sql@postgresql.org
Cc: pheadland@actuate.com
Subject: Re: Updating a specific number of rows in pl/pgsql
In-Reply-To: <71F491F5DA99604A80DE49424BF3D02B0C7290CA@exchange8.actuate.com>
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