Hot standby, xlog_xact_assignment and unreported subxids.

In the hot standby patch, we have this comment in procarray.c:

> It is
>  * important that the XLOG_XACT_ASSIGNMENT record contain *all* subxids 
>  * not just those so far unreported because the sole purpose is to ensure
>  * we can remove the xids from KnownAssignedXids. 

As the patch stands, that's not what we do. We only include new subxids
in the XLOG_XACT_ASSIGNMENT record that we haven't included in any
previous ones. I think that comment is just obsolete and should be
removed, but am I missing something?

--  Heikki Linnakangas EnterpriseDB   http://www.enterprisedb.com