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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/acl.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/acl.c')
| -rw-r--r-- | src/backend/utils/adt/acl.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/src/backend/utils/adt/acl.c b/src/backend/utils/adt/acl.c index 2efb6c94e11..0c26e44d820 100644 --- a/src/backend/utils/adt/acl.c +++ b/src/backend/utils/adt/acl.c @@ -16,6 +16,7 @@ #include <ctype.h> +#include "access/hash.h" #include "access/htup_details.h" #include "catalog/catalog.h" #include "catalog/namespace.h" @@ -717,6 +718,20 @@ hash_aclitem(PG_FUNCTION_ARGS) PG_RETURN_UINT32((uint32) (a->ai_privs + a->ai_grantee + a->ai_grantor)); } +/* + * 64-bit hash function for aclitem. + * + * Similar to hash_aclitem, but accepts a seed and returns a uint64 value. + */ +Datum +hash_aclitem_extended(PG_FUNCTION_ARGS) +{ + AclItem *a = PG_GETARG_ACLITEM_P(0); + uint64 seed = PG_GETARG_INT64(1); + uint32 sum = (uint32) (a->ai_privs + a->ai_grantee + a->ai_grantor); + + return (seed == 0) ? UInt64GetDatum(sum) : hash_uint32_extended(sum, seed); +} /* * acldefault() --- create an ACL describing default access permissions |