Hello Fabien,
25/12/2017 19:17, Fabien COELHO пишет:
>
>>> However, the key can be used if controlled so that different values do
>>> not have the same randomization in different part of the script, so as
>>> to avoid using the same patterns for different things if not desirable.
>>
>> Original murmur algorithm accepts seed as a parameter, which can be used
>> for this purpose. I used value itself as a seed in the patch, but I can
>> turn it into a function argument.
>
> Hmmm. Possibly. However it needs a default, something like
>
> x = hash(v[, key])
>
> with key some pseudo-random value?
>
Sorry for a long delay. I've added hash() function which is just an
alias for murmur2. I've also utilized variable arguments feature from
least()/greates() functions to make optional seed parameter, but I
consider this as a hack. Should we probably add some infrastructure for
optional arguments? Docs and tests are on their way.
Thanks!
--
Ildar Musin
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company
diff --git a/src/bin/pgbench/exprparse.y b/src/bin/pgbench/exprparse.y
index 26494fd..340c020 100644
--- a/src/bin/pgbench/exprparse.y
+++ b/src/bin/pgbench/exprparse.y
@@ -131,7 +131,8 @@ make_op(yyscan_t yyscanner, const char *operator,
* List of available functions:
* - fname: function name
* - nargs: number of arguments
- * -1 is a special value for least & greatest meaning
#args >= 1
+ * -1 is a special value for least, greatest & hash
functions
+ * meaning variable arguments number
* - tag: function identifier from PgBenchFunction enum
*/
static const struct
@@ -200,6 +201,15 @@ static const struct
{
"power", 2, PGBENCH_POW
},
+ {
+ "hash", -1, PGBENCH_HASH_MURMUR2
+ },
+ {
+ "hash_murmur2", -1, PGBENCH_HASH_MURMUR2
+ },
+ {
+ "hash_fnv1a", -1, PGBENCH_HASH_FNV1A
+ },
/* keep as last array element */
{
NULL, 0, 0
diff --git a/src/bin/pgbench/pgbench.c b/src/bin/pgbench/pgbench.c
index fc2c734..71e4814 100644
--- a/src/bin/pgbench/pgbench.c
+++ b/src/bin/pgbench/pgbench.c
@@ -61,6 +61,14 @@
#define ERRCODE_UNDEFINED_TABLE "42P01"
/*
+ * Hashing constants
+ */
+#define FNV_PRIME 0x100000001b3
+#define FNV_OFFSET_BASIS 0xcbf29ce484222325
+#define MM2_MUL 0xc6a4a7935bd1e995
+#define MM2_ROT 47
+
+/*
* Multi-platform pthread implementations
*/
@@ -912,6 +920,51 @@ getZipfianRand(TState *thread, int64 min, int64 max,
double s)
}
/*
+ * FNV-1a hash function
+ */
+static int64
+getHashFnv1a(int64 val, uint64 seed)
+{
+ int64 result;
+ int i;
+
+ result = FNV_OFFSET_BASIS ^ seed;
+ for (i = 0; i < 8; ++i)
+ {
+ int32 octet = val & 0xff;
+
+ val = val >> 8;
+ result = result ^ octet;
+ result = result * FNV_PRIME;
+ }
+
+ return result;
+}
+
+/*
+ * Murmur2 hash function
+ */
+static int64
+getHashMurmur2(int64 val, uint64 seed)
+{
+ uint64 result = seed ^ (sizeof(int64) * MM2_MUL);
+ uint64 k = (uint64) val;
+
+ k *= MM2_MUL;
+ k ^= k >> MM2_ROT;
+ k *= MM2_MUL;
+
+ result ^= k;
+ result *= MM2_MUL;
+
+ result ^= result >> MM2_ROT;
+ result *= MM2_MUL;
+ result ^= result >> MM2_ROT;
+
+ return (int64) result;
+}
+
+/*
* Initialize the given SimpleStats struct to all zeroes
*/
static void
@@ -1868,6 +1921,37 @@ evalFunc(TState *thread, CState *st,
return true;
}
+ /* hashing */
+ case PGBENCH_HASH_FNV1A:
+ case PGBENCH_HASH_MURMUR2:
+ {
+ int64 val;
+ int64 seed = 0;
+ int64 result;
+
+ Assert(nargs >= 1);
+
+ if (!coerceToInt(&vargs[0], &val))
+ return false;
+
+ if (nargs > 2)
+ {
+ fprintf(stderr,
+ "hash function accepts
maximum of two arguments\n");
+ return false;
+ }
+
+ /* read optional seed value */
+ if (nargs > 1)
+ if (!coerceToInt(&vargs[1], &seed))
+ return false;
+
+ result = (func == PGBENCH_HASH_FNV1A) ?
+ getHashFnv1a(val, seed) :
getHashMurmur2(val, seed);
+ setIntValue(retval, result);
+ return true;
+ }
+
default:
/* cannot get here */
Assert(0);
diff --git a/src/bin/pgbench/pgbench.h b/src/bin/pgbench/pgbench.h
index ce3c260..527e2a8 100644
--- a/src/bin/pgbench/pgbench.h
+++ b/src/bin/pgbench/pgbench.h
@@ -77,7 +77,9 @@ typedef enum PgBenchFunction
PGBENCH_RANDOM_GAUSSIAN,
PGBENCH_RANDOM_EXPONENTIAL,
PGBENCH_RANDOM_ZIPFIAN,
- PGBENCH_POW
+ PGBENCH_POW,
+ PGBENCH_HASH_FNV1A,
+ PGBENCH_HASH_MURMUR2
} PgBenchFunction;
typedef struct PgBenchExpr PgBenchExpr;
