> > 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 :-) Andreas ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match