Thread: Accidental setting of XLogReaderState.private_data ?

StartupDecodingContext() initializes ctx->reader->private_data with ctx, and
it even does so twice. I couldn't find a place in the code where the
(LogicalDecodingContext *) pointer is retrieved from the reader, and a simple
test of logical replication works if the patch below is applied. Thus I assume
that assignment is a thinko, isn't it?

-- 
Antonin Houska
Web: https://www.cybertec-postgresql.com

Antonin Houska <ah@cybertec.at> writes:
> StartupDecodingContext() initializes ctx->reader->private_data with ctx, and
> it even does so twice. I couldn't find a place in the code where the
> (LogicalDecodingContext *) pointer is retrieved from the reader, and a simple
> test of logical replication works if the patch below is applied. Thus I assume
> that assignment is a thinko, isn't it?

Hmm.  The second, duplicate assignment is surely pointless, but I think
that setting the ctx as the private_data is a good idea.  It hardly seems
out of the question that it might be needed in future.

            regards, tom lane

On Mon, Apr 15, 2019 at 11:06:18AM -0400, Tom Lane wrote:
> Hmm.  The second, duplicate assignment is surely pointless, but I think
> that setting the ctx as the private_data is a good idea.  It hardly seems
> out of the question that it might be needed in future.

Agreed that we should keep the assignment done with
XLogReaderAllocate().  I have committed the patch which removes the
useless assignment though.
--
Michael