Robert Haas <> writes:
> On Thu, Dec 1, 2011 at 10:48 PM, Tom Lane <> wrote:
>> I am thinking that the btree code, at least, would want to just
>> unconditionally do
>>        colsortinfo->comparator(datum1, datum2, colsortinfo)
>> so for an opclass that fails to supply the low-overhead comparator,
>> it would insert into the "comparator" pointer a shim function that
>> calls the opclass' old-style FCI-using comparator.  (Anybody who
>> complains about the added overhead would be told to get busy and
>> supply a low-overhead comparator for their datatype...)  But to do
>> that, we have to have enough infrastructure here to cover all cases,
>> so omitting collation or not having a place to stash an FmgrInfo
>> won't do.

> I'm slightly worried about whether that'll be adding too much overhead
> to the case where there is no non-FCI comparator.  But it may be no
> worse than what we're doing now.

It should be the same or better.  Right now, we are going through
FunctionCall2Coll to reach the FCI-style comparator.  The shim function
would be more or less equivalent to that, and since it's quite special
purpose I would hope we could shave a cycle or two.  For instance, we
could probably afford to set up a dedicated FunctionCallInfo struct
associated with the SortSupportInfo struct, and not have to reinitialize
one each time.

                        regards, tom lane

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