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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/cache/lsyscache.c vendored
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@ -490,8 +490,8 @@ get_compatible_hash_operators(Oid opno,
/*
* get_op_hash_functions
* Get the OID(s) of hash support function(s) compatible with the given
* operator, operating on its LHS and/or RHS datatype as required.
* Get the OID(s) of the standard hash support function(s) compatible with
* the given operator, operating on its LHS and/or RHS datatype as required.
*
* A function for the LHS type is sought and returned into *lhs_procno if
* lhs_procno isn't NULL. Similarly, a function for the RHS type is sought
@ -542,7 +542,7 @@ get_op_hash_functions(Oid opno,
*lhs_procno = get_opfamily_proc(aform->amopfamily,
aform->amoplefttype,
aform->amoplefttype,
HASHPROC);
HASHSTANDARD_PROC);
if (!OidIsValid(*lhs_procno))
continue;
/* Matching LHS found, done if caller doesn't want RHS */
@ -564,7 +564,7 @@ get_op_hash_functions(Oid opno,
*rhs_procno = get_opfamily_proc(aform->amopfamily,
aform->amoprighttype,
aform->amoprighttype,
HASHPROC);
HASHSTANDARD_PROC);
if (!OidIsValid(*rhs_procno))
{
/* Forget any LHS function from this opfamily */