Josh Berkus wrote: > Jaime, > > > why? seems that REPLACE only work if there are at least one row > > matching... > > Scenario: > > session1: REPLACE .... 1 > session2: REPLACE ..... 1 > session1: check to see that "1" exists .... no > session2: check to see that "1" exists .... no > session1: INSERT 1 > session2: INSERT 1 .... ERROR > > Get the picture? The only way to avoid a race condition is to be able to > do "predicate locking", that is to lock the table against any data write > matching that predicate.
Isn't the standard practice to do the INSERT, and if that fails, do the UPDATE? In fact, if someone is already doing a INSERT inside a transaction, it will wait for the transaction to complete so you can then do the UPDATE, or complete the INSERT if the transaction aborted. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
