Thanks, Rod, Josh and Bill, That' fantastic. have a nice day, rong :-)
> 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 > > ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org
