Scan Keys

I'm a bit confused about how scan keys work. Is there any simple way given a
list of Datums of the same type as the index tuple attributes to get all
matching index entries? This is for a non-system index.

It seems like the only place in the code where non-system index lookups are
done is nodeIndexscan.c where it has the strategy number, subtype, and
function to use from the work that's previously been done on the expression.

But I want to do something more like what btree does inside btinsert where it
knows that no cross-type functions could be necessary and the only function of
interest is equality.

I tried just using index_getprocinfo(...,BTORDER) with InvalidStrategy like
btree does but _bt_preprocess_keys runs into problems without a valid strategy
number. And in any case that would be btree specific which seems like it ought
not be necessary.

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greg