Re: Add “FOR UPDATE NOWAIT” lock details to the log.

On 2025/02/19 1:08, Fujii Masao wrote:
> Just an idea, but how about updating ConditionalXactLockTableWait() to 
> do the followings?
> - Use LockAcquireExtended() instead of LockAcquire() to retrieve the 
> LOCALLOCK value.
> - Generate a log message about the lock holders, from the retrieved 
> the LOCALLOCK value.
> - Return the generated log message to the caller (heap_lock_tuple()), 
> allowing it to log the message.
Thank you for your suggestion. I have two issues to discuss:


### 1. Issue with LockAcquireExtended()

It appears that in the dontWait case, LockAcquireExtended() is removing 
the local lock (locallock).

```
if (locallock->nLocks == 0)
     RemoveLocalLock(locallock);
```

Instead, the removal of locallock should be handled by 
ConditionalXactLockTableWait().


### 2. Issue with the LOCK TABLE Case

For the LOCK TABLE scenario, RangeVarGetRelidExtended() calls 
ConditionalLockRelationOid(), which seems to require a similar modification.


```
# tx1
BEGIN; LOCK TABLE pgbench_accounts;

# tx2
BEGIN; LOCK TABLE pgbench_accounts NOWAIT;
-- breakpoint -> LockAcquireExtended

# parts of CALLSTACK
LockAcquireExtended()
ConditionalLockRelationOid()
RangeVarGetRelidExtended()
LockTableCommand()
standard_ProcessUtility()
ProcessUtility()
```

I don't see a problem with it, though,
Do you think these are problems?

Regards,