Simon Riggs <simon@2ndQuadrant.com> writes:
> On Tue, 2010-04-27 at 13:52 -0400, Tom Lane wrote:
>> WTF? Either the comment is wrong or this should not be an elog
>> condition.
> That section of code has been rewritten many times. I think it is now
> inaccurate and should be removed. I left it there because the
> unfortunate history of the project has been the removal of comments and
> then later rediscovery of the truth, sometimes more than once. I could
> no longer reproduce that error; someone else may know differently.
I haven't tested this, but it appears to me that the failure would occur
in overflow situations. If we have too many subxacts, we'll generate
XLOG_XACT_ASSIGNMENT, which will cause the subxids to be removed from
KnownAssignedXids[]. Then later when the top-level xact commits or
aborts we'll try to remove them again as a consequence of processing
the top-level's commit/abort record. No?
regards, tom lane
