Re: Abbreviated keys for Numeric

>>>>> "Robert" == Robert Haas <robertmhaas(at)gmail(dot)com> writes:

>> It already does; it changes how int64 values are expected to be
>> stored in Datum variables. _Everything_ that currently stores an
>> int64 value in a Datum is affected.

Robert> But this isn't a value of the SQL type "int64". It's just a
Robert> bit pattern that has to fit inside however big a Datum happens
Robert> to be.

It's a bit pattern which is a signed 32-bit or 64-bit integer, computed
in an int32 or int64. Using something other than Int32GetDatum /
Int64GetDatum for it seems unnecessarily surprising.

>> The fact that making this one low-benefit change has introduced no
>> less than three separate bugs - the compile error with that #ifdef,
>> the use of Int64GetDatum for NANs, and the use of Int64GetDatum for
>> the return value of the abbreviation function should possibly be
>> taken as a hint to how bad an idea is.

Robert> But all of those are trivial, and the first would have been
Robert> caught by my compiler if I weren't using such a crappy old
Robert> compiler. If anything that might require as much as 10 lines
Robert> of code churn to fix is not worth doing, very little is worth
Robert> doing.

Trivial maybe, but subtle enough that you missed them (which suggests
that others might too), and a --disable-float8-byval build of the buggy
version only fails regression by a fluke.

(This does rather suggest to me that some better regression tests for
sorting would be a good idea, possibly even including on-disk sorts.)

>> If you're determined to go this route - over my protest - then you
>> need to do something like define a NumericAbbrevGetDatum(x) macro
>> and use it in place of the Int64GetDatum / Int32GetDatum ones for
>> both NAN and the return from numeric_abbrev_convert_var.

Robert> Patch for that attached.

That looks reasonable, though I think it could do with a comment
explaining _why_ it's defining its own macros rather than using
Int32*/Int64*. (And I wrote that before seeing Tom's message, even.)

--
Andrew (irc:RhodiumToad)