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Introduce 64-bit hash functions with a 64-bit seed.

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This will be useful for hash partitioning, which needs a way to seed
the hash functions to avoid problems such as a hash index on a hash
partitioned table clumping all values into a small portion of the
bucket space; it's also useful for anything that wants a 64-bit hash
value rather than a 32-bit hash value.

Just in case somebody wants a 64-bit hash value that is compatible
with the existing 32-bit hash values, make the low 32-bits of the
64-bit hash value match the 32-bit hash value when the seed is 0.

Robert Haas and Amul Sul

Discussion: http://postgr.es/m/CA+Tgmoafx2yoJuhCQQOL5CocEi-w_uG4S2xT0EtgiJnPGcHW3g@mail.gmail.com
This commit is contained in:
Robert Haas
2017-08-31 22:21:21 -04:00
parent 2d44c58c79
commit 81c5e46c49
33 changed files with 1555 additions and 42 deletions
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18
src/backend/utils/adt/varchar.c
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@@ -947,6 +947,24 @@ hashbpchar(PG_FUNCTION_ARGS)
return result;
}
Datum
hashbpcharextended(PG_FUNCTION_ARGS)
{
BpChar *key = PG_GETARG_BPCHAR_PP(0);
char *keydata;
int keylen;
Datum result;
keydata = VARDATA_ANY(key);
keylen = bcTruelen(key);
result = hash_any_extended((unsigned char *) keydata, keylen,
PG_GETARG_INT64(1));
PG_FREE_IF_COPY(key, 0);
return result;
}
/*
* The following operators support character-by-character comparison