Re: Transaction settings: nowait

2009/5/6 Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at>:
> durumdara wrote:
>> In FireBird the transactions have these settings:
>>
>>
>> SET TRANSACTION
>>    [NAME hostvar]
>>    [READ WRITE | READ ONLY]
>>    [ [ISOLATION LEVEL] { SNAPSHOT [TABLE STABILITY]
>>                          | READ COMMITTED [[NO] RECORD_VERSION] } ]
>>    [WAIT | NO WAIT]
>>    [LOCK TIMEOUT seconds]
>> And this is the important thing:
>>
>>
>> [WAIT | NO WAIT]
>>    [LOCK TIMEOUT seconds]
>> If set wait and timeout, the Firebird is waiting for the
>> locked resource (record) for X seconds before it show deadlock error.
>>
>> But when you set no wait, the deadlock error immediately
>> shown by the server.
>>
>> I wanna ask that if I want to avoid the full deadlocks.
>>
>> For. example: I forget to make commit, or rollback on
>> exception then all resources I used (updated) is locked.
>>
>> If I use nowait, the clients immediately get the error
>> message, and they are are not sitting deafly and blindly
>> before the screen, waiting for what will happen.
>>
>> So: have PGSQL same mechanism like nowait?

'select...for update' has a nowait clause, as does 'lock'. also
advisory locks, using pg_try_advisory_lock.

another tactic is to send queries asynchronously and fire a cancel
based on client driven logic.

merlin