Re: Performance optimization of btree binary search

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> Hmm. And yet, there's this:

> * When a type narrower than Datum is stored in a Datum, we place it in the
> * low-order bits and are careful that the DatumGetXXX macro for it discards
> * the unused high-order bits (as opposed to, say, assuming they are zero).
> * This is needed to support old-style user-defined functions, since depending
> * on architecture and compiler, the return value of a function returning char
> * or short may contain garbage when called as if it returned Datum.

> And record_image_eq does a rather elaborate dance around here, calling
> the appropriate GET_x_BYTES macro depending on the type-width. If we
> can really count on the high-order bits to be zero, that's all
> completely unnecessary tomfoolery.

Yeah, that's another thing we could simplify if we fixed this problem
at the source. I think these decisions date from a time when we still
cared about the speed of fmgr_oldstyle.

regards, tom lane