Rod Taylor wrote:
On Thu, 2003-10-02 at 14:30, Rong Wu wrote:
Hi,
I have a select like this:
SELECT MAX(transactionid) FROM cbntransaction WHERE transactiontypeid=0;
For various reasons (primarily MVCC and the ability to make custom
aggregates making it difficult) MAX() is not optimized in this fashion.
Try:
SELECT transactionid
FROM ...
WHERE ...
ORDER BY transactionid DESC
LIMIT 1;
Despite this good suggestion, if you're using this technique to generate
the next transaction ID, you're going to have errors as concurrency rises.
Use a SERIAL, which guarantees that you won't have two processes generate
the same number.
--
Bill Moran
Potential Technologies
http://www.potentialtech.com
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