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/varchar.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'src/backend/utils/adt/varchar.c') diff --git a/src/backend/utils/adt/varchar.c b/src/backend/utils/adt/varchar.c index cbc62b00be2..2df6f2ccb00 100644 --- a/src/backend/utils/adt/varchar.c +++ b/src/backend/utils/adt/varchar.c @@ -947,6 +947,24 @@ hashbpchar(PG_FUNCTION_ARGS) return result; } +Datum +hashbpcharextended(PG_FUNCTION_ARGS) +{ + BpChar *key = PG_GETARG_BPCHAR_PP(0); + char *keydata; + int keylen; + Datum result; + + keydata = VARDATA_ANY(key); + keylen = bcTruelen(key); + + result = hash_any_extended((unsigned char *) keydata, keylen, + PG_GETARG_INT64(1)); + + PG_FREE_IF_COPY(key, 0); + + return result; +} /* * The following operators support character-by-character comparison -- cgit v1.2.3