Re: Numeric patch to add special-case representations for < 8 bytes

Gregory Stark schrieb am 27.02.2007 01:39:
> I've uploaded a quick hack to store numerics in < 8 bytes when possible.
>
>  http://community.enterprisedb.com/numeric-hack-1.patch
>
> This is a bit of a kludge since it doesn't actually provide any interface for
> external clients of the numeric module to parse the resulting data. Ie, the
> macros in numeric.h will return garbage.
>
> But I'm not entirely convinced that matters. It's not like those macros were
> really useful to any other modules anyways since there was no way to extract
> the actual digits.
>
> The patch is also slightly unsatisfactory because as I discovered numbers like
> 1.1 are stored as two digits currently. But it does work and it does save a
> substantial amount of space for integers.
>
> postgres=# select n,pg_column_size(n) from n;
>     n     | pg_column_size
> ----------+----------------
>         1 |              2
>        11 |              2
>       101 |              2
>      1001 |              3
>     10001 |              9
>    100001 |              9
>       1.1 |              9
>      10.1 |              9
>     100.1 |              9
>    1000.1 |              9
>   10000.1 |             11
>  100000.1 |             11
>
> I had hoped to get the second batch to be 3-4 bytes. But even now note how
> much space is saved for integers <10000.
>
>
Very nice :-) I'm looking forward to something like that. We store huge
quantities of numerics in our DB's (I strongly discourage using ANSI754
floats anywhere).
Maybe you want to have a look here:
http://www2.hursley.ibm.com/decimal/DPDecimal.html

just my 0.02$... ;-)

Patric