Re: Hot standby, slot ids and stuff

On Sat, 2009-01-10 at 09:40 +0000, Simon Riggs wrote:

> This leads to an error when we SubTransSetParent(child_xid, top_xid);
> since this assumes that the top_xid is the parent, which it is not.
> Mostly you wouldn't notice unless you were looking up the subtrans
> status for an xid that had committed but was the child of an aborted
> subtransaction, with the top level xid having > 64 subtransactions.
> It's possible the confusion leads to other bugs in UnobservedXid
> processing, but I didn't look too hard at that.
> 
> AFAICS we need both parent and top xids.

I wonder if its possible to derive the parent by looking at the
highest/most newly assigned xid? Abort records would remove aborted
subtransactions and AFAIK we currently assign a new subtransaction only
ever from the latest current subtransaction. (This wouldn't be
necessarily true if supported true branch-anywhere subtransactions, but
we don't). Sounds correct, but not really sure.

-- Simon Riggs           www.2ndQuadrant.comPostgreSQL Training, Services and Support