On 2016/01/28 12:13, Robert Haas wrote:
On Thu, Jan 21, 2016 at 5:55 AM, Etsuro Fujita
<fujita.ets...@lab.ntt.co.jp> wrote:
On 2016/01/21 7:04, Alvaro Herrera wrote:
Etsuro Fujita wrote:
On second thought, I noticed that detecting whether we see a system
column
that way needs more cycles in cases where the reltargetlist and the
restriction clauses don't contain any system columns. ISTM that such
cases
are rather common, so I'm inclined to keep that code as-is.
Ah, I see now what you did there. I was thinking you'd have the
foreach(restrictinfo) loop, then once the loop is complete scan the
bitmapset; not scan the bitmap set scan inside the other loop.
Ah, I got to the point. I think that is a good idea. The additional cycles
for the worst case are bounded and negligible. Please find attached an
updated patch.
I don't think this is a good idea. Most of the time, no system
columns will be present, and we'll just be scanning the Bitmapset
twice rather than once. Sure, that doesn't take many extra cycles,
but if the point of all this is to micro-optimize this code, that
particular change is going in the wrong direction.
I thought that is a good idea, considering the additional overhead is
little, because that would be useful for some use-cases. But I think we
need more discussions about that, so if there are no objections from
Alvaro (or anyone), I'll leave that part as-is.
Best regards,
Etsuro Fujita
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