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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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8
src/backend/utils/adt/uuid.c
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@ -408,3 +408,11 @@ uuid_hash(PG_FUNCTION_ARGS)
return hash_any(key->data, UUID_LEN);
}
Datum
uuid_hash_extended(PG_FUNCTION_ARGS)
{
pg_uuid_t *key = PG_GETARG_UUID_P(0);
return hash_any_extended(key->data, UUID_LEN, PG_GETARG_INT64(1));
}