Zeugswetter Andreas DCP SD wrote: > > > > head of the chain yet. With an index scan, finding the head is > easy, > > > but for a sequential scan, it seems more difficult, and we don't > have > > > any free space in the tail of the chain to maintain a pointer to the > head. > > > > Thinking some more, there will need to be a bit to uniquely > > identify the head of a CITC. > > I don't think so. It would probably be sufficient to impose an order on > the CITC. > e.g. the oldest tuple version in the CITC is the head. > (An idea just in case we can't spare a bit :-)
Well, if we need to scan the page quickly, having the bit, or a bit combination that can only be the head, is helpful. What we usually do is to combine a SITC bit with another bit that would never be set for SITC, and that is the head, and you use macros to properly do tests. We do this already in a number of cases. -- Bruce Momjian [EMAIL PROTECTED] EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
