Re: Hot Standby and prepared transactions

On Wed, 2009-12-16 at 19:35 +0900, Hiroyuki Yamada wrote:

>  * There is a window beween gathering lock information in GetRunningTransactionLocks()
>    and writing WAL in LogAccessExclusiveLocks().
>  * In current lock redo algorithm, locks are released when the transaction holding the lock
>    are commited or aborted.
> 
> ... then what happens if any transaction holding ACCESS EXCLUSIVE lock commits in the 
>    window ?

Yes, was a problem in that code. Fixed in git.

We were doing it for prepared transactions but not for normal xacts.
I will look again at that code.

Thanks very much for reading the code. Any more?!?

> Similary,
> 
>  * There is a window beween writing COMMIT WAL in RecordTransactionCommit() and
>     releasing locks in ResourceOwnerRelease()
> 
> ... then what happens when GetRunningTransactionLocks() gathers ACCESS EXCLUSIVE 
>    locks whose holder has already written the COMMIT WAL ?

Same issue, so fixed as well. Thanks to Heikki for making that the same
code path, so we have nothing to do for that.

> Are there any chances of releasing locks which have no COMMIT WAL for releasing them ?

No

-- Simon Riggs           www.2ndQuadrant.com