Peter Geoghegan <pg@bowt.ie> writes:
> My point is only that it's worth considering that this factor affects
> how representative your sympathetic case is. It's not clear how many
> PageIndexMultiDelete() calls are from opportunistic calls to
> _bt_vacuum_one_page(), how important that subset of calls is, and so
> on. Maybe it doesn't matter at all.
According to the perf measurements I took earlier, essentially all the
compactify_tuple calls in this test case are from PageRepairFragmentation
(from heap_page_prune), not PageIndexMultiDelete.
I'd be the first to agree that I doubt that test case is really
representative. I'd been whacking around Yura's original case to
try to get PageRepairFragmentation's runtime up to some measurable
fraction of the total, and while I eventually succeeded, I'm not
sure that too many real workloads will look like that. However,
if we can make it smaller as well as faster, that seems like a win
even if it's not a measurable fraction of most workloads.
regards, tom lane
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