Re: UUID datatype GiST index support

Thanks Alexander,

'Scalar datatype' - given me a hint...

Looking further in btree_gist source, for inet datatype, which seems a bit
complexier then uuid... (char, char, char[16]) structure for inet, compared
to jut char[16] for uuid.

GiST pattern works with double datatype... and there is method
convert_network_to_scalar(Datum, Oid), whick converts an inet value - to
scalar value... and then all index compare functions are based on the
doubles.... which leads me to conclusion (maybe is wrong) if I can convert
UUID value to double it would make a "job" a lot easier... and pretty
straight forward...

Any suggestion, how to convert UUID (char[16]) to scalar?

looking into convert inet to scalar, what confuses me, even there is
char[16] for an ip address... code is:

if (ip_family <http://doxygen.postgresql.org/network_8c.html#a7dc77a7bc93b675d36eca352d589b314>(ip)
== PGSQL_AF_INET
<http://doxygen.postgresql.org/utils_2inet_8h.html#a8ba3e5fe500d587d3eb8699968450b18>)
len = 4;
else
len = 5;

res = ip_family
<http://doxygen.postgresql.org/network_8c.html#a7dc77a7bc93b675d36eca352d589b314>(ip);
for (i = 0; i < len; i++)
{
res *= 256;
res += ip_addr
<http://doxygen.postgresql.org/network_8c.html#a54558e944989cddebdb93f2f6cd965a4>(ip)[i];
}
return res;

takes just first 4, or 5 values from ipaddres even there is 16 - (decalred
as char[16])

Many thanks,

Misa

2011/8/22 Alexander Korotkov <aekorotkov(at)gmail(dot)com>

> Hi!
>
> On Mon, Aug 22, 2011 at 2:54 PM, Misa Simic <misa(dot)simic(at)gmail(dot)com> wrote:
>
>> static int
>> m4_uuidkey_cmp(const void *a, const void *b)
>> {
>> uuidKEY *ia = (uuidKEY *) (((Usrt *) a)->t);
>> uuidKEY *ib = (uuidKEY *) (((Usrt *) b)->t);
>> int res;
>>
>> res = DatumGetInt32(DirectFunctionCall2(uuid_cmp,
>> UUIDPGetDatum(ia->upper), UUIDPGetDatum(ia->upper)));
>> if (res == 0)
>> return DatumGetInt32(DirectFunctionCall2(uuid_cmp,
>> UUIDPGetDatum(ia->upper), UUIDPGetDatum(ib->upper)));
>>
>> return res;
>> }
>>
>>
>> Getting error: aggregate error used where an integer was expected!
>>
> Seems that you need the address-of operator before ia->upper and ia->lower
> (likely one of operands should be "ia->lower"). UUIDPGetDatum except pointer
> as an argument, i.e. UUIDPGetDatum(&ia->upper).
>
>
>> It would be a lot appreciated if anyone could help me and suggest the best
>> way to make Gist support for UUID datatype...
>>
> I think you're on the right way. btree_gist is an extension which provides
> GiST indexing of scalar datatype. UUID is one of them. So, the module you
> are writing should be quite similar.
>
> ------
> With best regards,
> Alexander Korotkov.