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Fix BRIN minmax-multi distance for inet type

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The distance calculation ignored the mask, unlike the inet comparator,
which resulted in negative distance in some cases. Fixed by applying the
mask in brin_minmax_multi_distance_inet. I've considered simply calling
inetmi() to calculate the delta, but that does not consider mask either.

Reviewed-by: Zhihong Yu
Discussion: https://postgr.es/m/1a0a7b9d-9bda-e3a2-7fa4-88f15042a051%40enterprisedb.com
This commit is contained in:
Tomas Vondra
2021-04-04 19:23:30 +02:00
parent 7262f2421a
commit e1fbe1181c
1 changed files with 51 additions and 8 deletions
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59
src/backend/access/brin/brin_minmax_multi.c
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@ -2297,6 +2297,9 @@ brin_minmax_multi_distance_inet(PG_FUNCTION_ARGS)
inet *ipa = PG_GETARG_INET_PP(0);
inet *ipb = PG_GETARG_INET_PP(1);
int lena,
lenb;
/*
* If the addresses are from different families, consider them to be in
* maximal possible distance (which is 1.0).
@ -2304,24 +2307,64 @@ brin_minmax_multi_distance_inet(PG_FUNCTION_ARGS)
if (ip_family(ipa) != ip_family(ipb))
PG_RETURN_FLOAT8(1.0);
/* ipv4 or ipv6 */
if (ip_family(ipa) == PGSQL_AF_INET)
len = 4;
else
len = 16; /* NS_IN6ADDRSZ */
addra = (unsigned char *) palloc(ip_addrsize(ipa));
memcpy(addra, ip_addr(ipa), ip_addrsize(ipa));
addra = ip_addr(ipa);
addrb = ip_addr(ipb);
addrb = (unsigned char *) palloc(ip_addrsize(ipb));
memcpy(addrb, ip_addr(ipb), ip_addrsize(ipb));
/*
* The length is calculated from the mask length, because we sort the
* addresses by first address in the range, so A.B.C.D/24 < A.B.C.1
* (the first range starts at A.B.C.0, which is before A.B.C.1). We
* don't want to produce negative delta in this case, so we just cut
* the extra bytes.
*
* XXX Maybe this should be a bit more careful and cut the bits, not
* just whole bytes.
*/
lena = ip_bits(ipa);
lenb = ip_bits(ipb);
len = ip_addrsize(ipa);
/* apply the network mask to both addresses */
for (i = 0; i < len; i++)
{
unsigned char mask;
int nbits;
nbits = lena - (i * 8);
if (nbits < 8)
{
mask = (0xFF << (8 - nbits));
addra[i] = (addra[i] & mask);
}
nbits = lenb - (i * 8);
if (nbits < 8)
{
mask = (0xFF << (8 - nbits));
addrb[i] = (addrb[i] & mask);
}
}
/* Calculate the difference between the addresses. */
delta = 0;
for (i = len - 1; i >= 0; i--)
{
delta += (float8) addrb[i] - (float8) addra[i];
unsigned char a = addra[i];
unsigned char b = addrb[i];
delta += (float8) b - (float8) a;
delta /= 256;
}
Assert((delta >= 0) && (delta <= 1));
pfree(addra);
pfree(addrb);
PG_RETURN_FLOAT8(delta);
}