Обсуждение: Table Truncate and Locks

What sort of lock does truncate require?  If it is not an access exclusive lock, what locks would block the truncate?

Thanks,

Chris

If I do :
Session 1:
decibel=# begin;
BEGIN
decibel=# select * from i where i=1 for update nowait;
i
---
1
(1 row)

decibel=# begin;
BEGIN
decibel=# select * from i where i=2 for update nowait;
i
---
2
(1 row)

Session 2 :

decibel=# select * from i where i=1 for update nowait;
ERROR:  could not obtain lock on row in relation "i"
decibel=# select * from i where i=3 for update nowait;
ERROR:  current transaction is aborted, commands ignored until end of
transaction block
decibel=#  ==> Why ? :'(

Why i can't do any "Select for update" (current transaction aborted) after
having receive a not obtain lock ???
Thank you for your answer !

_________________________________________________________________
Windows Live Messenger sur i-mode™ : dialoguez avec vos amis depuis votre
mobile comme sur PC ! http://mobile.live.fr/messenger/bouygues/

On Thu, Sep 28, 2006 at 03:26:36PM +0000, Mathias Laurent wrote:
> If I do :
> Session 1:
> decibel=# begin;

Does decibel have some meaning in some language other than english?

> BEGIN
> decibel=# select * from i where i=1 for update nowait;
> i
> ---
> 1
> (1 row)
>
> decibel=# begin;
> BEGIN
> decibel=# select * from i where i=2 for update nowait;
> i
> ---
> 2
> (1 row)
>
> Session 2 :
>
> decibel=# select * from i where i=1 for update nowait;
> ERROR:  could not obtain lock on row in relation "i"
> decibel=# select * from i where i=3 for update nowait;
> ERROR:  current transaction is aborted, commands ignored until end of
> transaction block
> decibel=#  ==> Why ? :'(
>
> Why i can't do any "Select for update" (current transaction aborted) after
> having receive a not obtain lock ???
> Thank you for your answer !

Because as soon as there is an error in a transaction, the entire
transaction is void. You have to rollback the transaction (or return to
a savepoint).
--
Jim Nasby                                            jim@nasby.net
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)