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| author | Robert Haas <rhaas@postgresql.org> | 2017-08-31 22:21:21 -0400 |
|---|---|---|
| committer | Robert Haas <rhaas@postgresql.org> | 2017-08-31 22:21:21 -0400 |
| commit | 81c5e46c490e2426db243eada186995da5bb0ba7 (patch) | |
| tree | a6cb745131c45a06fa43746a17a69e1dc9daa44a /src/backend/utils/adt/jsonb_util.c | |
| parent | 2d44c58c79aeef2d376be0141057afbb9ec6b5bc (diff) | |
| download | postgresql-81c5e46c490e2426db243eada186995da5bb0ba7.tar.gz postgresql-81c5e46c490e2426db243eada186995da5bb0ba7.zip | |
Introduce 64-bit hash functions with a 64-bit seed.
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
Diffstat (limited to 'src/backend/utils/adt/jsonb_util.c')
| -rw-r--r-- | src/backend/utils/adt/jsonb_util.c | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/src/backend/utils/adt/jsonb_util.c b/src/backend/utils/adt/jsonb_util.c index 4850569bb5e..d425f324038 100644 --- a/src/backend/utils/adt/jsonb_util.c +++ b/src/backend/utils/adt/jsonb_util.c @@ -1250,6 +1250,49 @@ JsonbHashScalarValue(const JsonbValue *scalarVal, uint32 *hash) } /* + * Hash a value to a 64-bit value, with a seed. Otherwise, similar to + * JsonbHashScalarValue. + */ +void +JsonbHashScalarValueExtended(const JsonbValue *scalarVal, uint64 *hash, + uint64 seed) +{ + uint64 tmp; + + switch (scalarVal->type) + { + case jbvNull: + tmp = seed + 0x01; + break; + case jbvString: + tmp = DatumGetUInt64(hash_any_extended((const unsigned char *) scalarVal->val.string.val, + scalarVal->val.string.len, + seed)); + break; + case jbvNumeric: + tmp = DatumGetUInt64(DirectFunctionCall2(hash_numeric_extended, + NumericGetDatum(scalarVal->val.numeric), + UInt64GetDatum(seed))); + break; + case jbvBool: + if (seed) + tmp = DatumGetUInt64(DirectFunctionCall2(hashcharextended, + BoolGetDatum(scalarVal->val.boolean), + UInt64GetDatum(seed))); + else + tmp = scalarVal->val.boolean ? 0x02 : 0x04; + + break; + default: + elog(ERROR, "invalid jsonb scalar type"); + break; + } + + *hash = ROTATE_HIGH_AND_LOW_32BITS(*hash); + *hash ^= tmp; +} + +/* * Are two scalar JsonbValues of the same type a and b equal? */ static bool |