Re: Thoughts about bug #3883

Tom Lane wrote:

> What I propose we do about this is put the same check into TRUNCATE,
> CLUSTER, and REINDEX that is already in ALTER TABLE, namely that we
> reject the command if the current transaction is already holding
> the table open.

+1.

> The issue Steven directly complained of is a potential for undetected
> deadlock via LockBufferForCleanup. Ordinarily, buffer-level locks don't
> pose a deadlock risk because we don't hold one while trying to acquire
> another (except in UPDATE, which uses an ordering rule to avoid the
> risk). The problem with LockBufferForCleanup is that it can be blocked
> by a mere pin, which another backend could well hold while trying to
> acquire a lock that will be blocked by VACUUM.

Seems like a hard problem.

I wonder if we can invoke the deadlock checker in LockBufferForCleanup.

--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.