From 81c5e46c490e2426db243eada186995da5bb0ba7 Mon Sep 17 00:00:00 2001 From: Robert Haas Date: Thu, 31 Aug 2017 22:21:21 -0400 Subject: 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 --- src/backend/utils/adt/jsonb_op.c | 43 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) (limited to 'src/backend/utils/adt/jsonb_op.c') diff --git a/src/backend/utils/adt/jsonb_op.c b/src/backend/utils/adt/jsonb_op.c index d4c490e948a..c4a7dc3f13a 100644 --- a/src/backend/utils/adt/jsonb_op.c +++ b/src/backend/utils/adt/jsonb_op.c @@ -291,3 +291,46 @@ jsonb_hash(PG_FUNCTION_ARGS) PG_FREE_IF_COPY(jb, 0); PG_RETURN_INT32(hash); } + +Datum +jsonb_hash_extended(PG_FUNCTION_ARGS) +{ + Jsonb *jb = PG_GETARG_JSONB(0); + uint64 seed = PG_GETARG_INT64(1); + JsonbIterator *it; + JsonbValue v; + JsonbIteratorToken r; + uint64 hash = 0; + + if (JB_ROOT_COUNT(jb) == 0) + PG_RETURN_UINT64(seed); + + it = JsonbIteratorInit(&jb->root); + + while ((r = JsonbIteratorNext(&it, &v, false)) != WJB_DONE) + { + switch (r) + { + /* Rotation is left to JsonbHashScalarValueExtended() */ + case WJB_BEGIN_ARRAY: + hash ^= ((UINT64CONST(JB_FARRAY) << 32) | UINT64CONST(JB_FARRAY)); + break; + case WJB_BEGIN_OBJECT: + hash ^= ((UINT64CONST(JB_FOBJECT) << 32) | UINT64CONST(JB_FOBJECT)); + break; + case WJB_KEY: + case WJB_VALUE: + case WJB_ELEM: + JsonbHashScalarValueExtended(&v, &hash, seed); + break; + case WJB_END_ARRAY: + case WJB_END_OBJECT: + break; + default: + elog(ERROR, "invalid JsonbIteratorNext rc: %d", (int) r); + } + } + + PG_FREE_IF_COPY(jb, 0); + PG_RETURN_UINT64(hash); +} -- cgit v1.2.3