Re: gist index build produces corrupt result on

At 10:28 PM 3/3/2004, Tom Lane wrote:
>Eric Davies <eric(at)barrodale(dot)com> writes:
> > We've looked at the contrib/cube code, but it's also a variable length
> > parameter, and it uses a very different parameter passing mechanism.
>
>Different how? I have a hard-to-pin-down intuition that your problem is

the parameter passing mechanism used by Postgis (and our 5D box) is to
pass a FunctionCallInfoData structure, via a PG_FUNCTION_ARGS macro.
The Postgis penalty function starts with:
/*
** The GiST Penalty method for boxes
** As in the R-tree paper, we use change in area as our penalty metric
*/
PG_FUNCTION_INFO_V1(gbox_penalty);
Datum gbox_penalty(PG_FUNCTION_ARGS)
{
GISTENTRY *origentry = (GISTENTRY *) PG_GETARG_POINTER(0);

the cube code appears to pass each argument separately, as one would
normally do with a
C program. Ie, the g_cube_penalty function starts with:
/*
** The GiST Penalty method for boxes
** As in the R-tree paper, we use change in area as our penalty metric
*/
float *
g_cube_penalty(GISTENTRY *origentry, GISTENTRY *newentry, float *result)
{
NDBOX *ud;
double tmp1,

Again, the postgis code seems to work fine with GiST indexes, so I would
rule out the argument passing mechanism as being of influence.

>closely associated with this issue, but without details it's impossible
>to say more. IIRC there were once assumptions in rtree and/or gist
>about the indexable datatype being pass-by-ref and/or varlena, and I'm
>not sure how much of that has been fixed.
>
>This seems a bit far afield for pgsql-general, however. I would
>suggest offering more details on -hackers. If you could post your code
>for people to play with, you'd likely get answers pretty quickly.

I figured likewise, but the etiquete for the postgresql.org group required
I try the more general group first. :-).
I'll give that a shot now.

> regards, tom lane

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Eric Davies, M.Sc.
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