Tom Lane wrote:
Heikki Linnakangas <[EMAIL PROTECTED]> writes:
I fixed a little off-by-one in "backward scan, not inited" branch, but I was unable to test it. It seems that code is actually never used because that case is optimized to a rewind in the executor. I marked those seemingly unreachable places in the code with a comment.

Actually it's not equivalent to a rewind, it's more like the startup
condition for an Index Scan Backward: start at the far end of the
relation and go backwards.  I suspect that the whole thing may be
unreachable code because the planner knows that seqscans are unordered
and backward-scan is only of interest for an ordered scan.

Right. I was looking at the case where you open a cursor and start immediately scanning backwards. That's optimized to a rewind.

  Heikki Linnakangas

---------------------------(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

Reply via email to