>>>>> "Kyotaro" == Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp> writes:
Kyotaro> ammarkpos/amrestrpos are called in merge joins. By the stepsKyotaro> shown below, I had 1M times of markpos
andno restorepos forKyotaro> 1M result rows, and had 500k times of markpos and the sameKyotaro> number of times of
restoreposfor 2M rows result by a bitKyotaro> different configuration. I suppose we can say that they areKyotaro> the
worstcase considering maskpos/restrpos. The call countsKyotaro> can be taken using the attached patch.
You might want to try running the same test, but after patching
ExecSupportsMarkRestore to return false for index scans. This will cause
the planner to insert a Materialize node to handle the mark/restore.
This way, you can get an idea of how much gain (if any) the direct
support of mark/restore in the scan is actually providing.
--
Andrew (irc:RhodiumToad)