Hi,
Indeed, this is quite strange...
I don't want to go too deep into it, but you get stuff like this:
Select pow(2.0, -3)::text = pow(2, -3)::text;
?column?
----------
f
(1 row)
- you can simplify the ipow function by removing handling of y<0 case,
> maybe add an assert to be sure to avoid it.
I agree, done.
- you should add more symmetry and simplify the evaluation:
Done too.
Add a test case to show what happens on NULL arguments, hopefully the
> result is NULL.
Done and it does.
Thanks again for the review.
On Mon, Nov 6, 2017 at 4:14 PM, Fabien COELHO <coe...@cri.ensmp.fr> wrote:
>
> Hello,
>
> Sorry for the confusion, I wasn't aware that SQL pow changed types
>> depending on the input value.
>>
>
> Indeed, this is quite strange...
>
> fabien=# SELECT i, POW(2, i) FROM generate_series(-2, 2) AS i;
> -2 | 0.25
> -1 | 0.5
> 0 | 1
> 1 | 2
> 2 | 4
>
> I've modified the function to match more closely the behaviour of SQL,
>> except that 0^(negative) returns 'double inf'. Do you think there is any
>> value in raising an error instead?
>>
>
> fabien=# SELECT POW(0,-1);
> ERROR: zero raised to a negative power is undefined
>
> Hmmmm... I'm fine with double inf, because exception in pgbench means the
> end of the script, which is not desirable for benchmarking purposes.
>
> I think that:
>
> - you can simplify the ipow function by removing handling of y<0 case,
> maybe add an assert to be sure to avoid it.
>
> - you should add more symmetry and simplify the evaluation:
>
> if (int & int)
> {
> i1, i2 = ...;
> if (i2 >= 0)
> setIntValue(retval, ipow(i1, i2));
> else
> // conversion is done by C, no need to coerce again
> setDoubleValue(retval, pow(i1, i2));
> }
> else
> {
> d1, d2 = ...;
> setDoubleValue(retval, pow(d1, d2));
> }
>
> Add a test case to show what happens on NULL arguments, hopefully the
> result is NULL.
>
> --
> Fabien.
>
--
*Raúl Marín Rodríguez *carto.com
From 47f6ec396d3bc11c39066dbd4b31e75b76102094 Mon Sep 17 00:00:00 2001
From: Raul Marin <rmrodrig...@cartodb.com>
Date: Fri, 13 Oct 2017 17:42:23 +0200
Subject: [PATCH] Add pow() support to pgbench
---
doc/src/sgml/ref/pgbench.sgml | 7 ++++
src/bin/pgbench/exprparse.y | 3 ++
src/bin/pgbench/pgbench.c | 62 ++++++++++++++++++++++++++++
src/bin/pgbench/pgbench.h | 3 +-
src/bin/pgbench/t/001_pgbench_with_server.pl | 15 +++++++
5 files changed, 89 insertions(+), 1 deletion(-)
diff --git a/doc/src/sgml/ref/pgbench.sgml b/doc/src/sgml/ref/pgbench.sgml
index 1f55967e40a..32c94ba0dc1 100644
--- a/doc/src/sgml/ref/pgbench.sgml
+++ b/doc/src/sgml/ref/pgbench.sgml
@@ -1233,6 +1233,13 @@ pgbench <optional> <replaceable>options</replaceable> </optional> <replaceable>d
<entry><literal>sqrt(2.0)</literal></entry>
<entry><literal>1.414213562</literal></entry>
</row>
+ <row>
+ <entry><literal><function>pow(<replaceable>x</replaceable>, <replaceable>y</replaceable>)</function></literal></entry>
+ <entry>integer if <replaceable>x</replaceable> and <replaceable>y</replaceable> are integers and <literal><replaceable>y</replaceable> >= 0</literal>, else double</entry>
+ <entry>Numeric exponentiation</entry>
+ <entry><literal>pow(2.0, 10)</literal></entry>
+ <entry><literal>1024.0</literal></entry>
+ </row>
</tbody>
</tgroup>
</table>
diff --git a/src/bin/pgbench/exprparse.y b/src/bin/pgbench/exprparse.y
index 770be981f06..290bca99d12 100644
--- a/src/bin/pgbench/exprparse.y
+++ b/src/bin/pgbench/exprparse.y
@@ -334,6 +334,9 @@ static const struct
{
"!case_end", -2, PGBENCH_CASE
},
+ {
+ "pow", 2, PGBENCH_POW
+ },
/* keep as last array element */
{
NULL, 0, 0
diff --git a/src/bin/pgbench/pgbench.c b/src/bin/pgbench/pgbench.c
index add653bf90c..3781e75721d 100644
--- a/src/bin/pgbench/pgbench.c
+++ b/src/bin/pgbench/pgbench.c
@@ -739,6 +739,27 @@ getPoissonRand(TState *thread, int64 center)
}
/*
+ * pow() for integer values with exp >= 0. Matches SQL pow() behaviour
+ */
+static int64
+ipow(int64 base, int64 exp)
+{
+ int64 result = 1;
+
+ Assert(exp >= 0);
+
+ while (exp)
+ {
+ if (exp & 1)
+ result *= base;
+ exp >>= 1;
+ base *= base;
+ }
+
+ return result;
+}
+
+/*
* Initialize the given SimpleStats struct to all zeroes
*/
static void
@@ -1918,6 +1939,47 @@ evalFunc(TState *thread, CState *st,
return true;
}
+ case PGBENCH_POW:
+ {
+ PgBenchValue *lval = &vargs[0];
+ PgBenchValue *rval = &vargs[1];
+
+ Assert(nargs == 2);
+
+ /*
+ * If both operands are int and exp >= 0 use
+ * the ipow() function, else use pow()
+ */
+ if (lval->type == PGBT_INT &&
+ rval->type == PGBT_INT)
+ {
+
+ int64 li,
+ ri;
+
+ if (!coerceToInt(lval, &li) ||
+ !coerceToInt(rval, &ri))
+ return false;
+
+ if (ri >= 0)
+ setIntValue(retval, ipow(li, ri));
+ else
+ setDoubleValue(retval, pow(li, ri));
+ }
+ else
+ {
+ double ld,
+ rd;
+
+ if (!coerceToDouble(lval, &ld) ||
+ !coerceToDouble(rval, &rd))
+ return false;
+
+ setDoubleValue(retval, pow(ld, rd));
+ }
+ return true;
+ }
+
default:
/* cannot get here */
Assert(0);
diff --git a/src/bin/pgbench/pgbench.h b/src/bin/pgbench/pgbench.h
index e1277a1dde6..9f26af92bf6 100644
--- a/src/bin/pgbench/pgbench.h
+++ b/src/bin/pgbench/pgbench.h
@@ -94,7 +94,8 @@ typedef enum PgBenchFunction
PGBENCH_LE,
PGBENCH_LT,
PGBENCH_IS,
- PGBENCH_CASE
+ PGBENCH_CASE,
+ PGBENCH_POW
} PgBenchFunction;
typedef struct PgBenchExpr PgBenchExpr;
diff --git a/src/bin/pgbench/t/001_pgbench_with_server.pl b/src/bin/pgbench/t/001_pgbench_with_server.pl
index 8e19bbd3f45..644add6ea63 100644
--- a/src/bin/pgbench/t/001_pgbench_with_server.pl
+++ b/src/bin/pgbench/t/001_pgbench_with_server.pl
@@ -237,6 +237,13 @@ sub pgbench
qr{command=36.: int 36\b},
qr{command=37.: boolean true\b},
qr{command=38.: boolean true\b},
+ qr{command=44.: int -27\b},
+ qr{command=45.: double 1024\b},
+ qr{command=46.: int 1\b},
+ qr{command=47.: double 1\b},
+ qr{command=48.: double -0.125\b},
+ qr{command=49.: double -0.125\b},
+ qr{command=50.: null\b},
],
'pgbench expressions',
{ '001_pgbench_expressions' => q{-- integer functions
@@ -299,6 +306,14 @@ sub pgbench
\set v2 5432
\set v3 -54.21E-2
SELECT :v0, :v1, :v2, :v3;
+--- pow() operator
+\set poweri debug(pow(-3,3))
+\set powerd debug(pow(2.0,10))
+\set poweriz debug(pow(0,0))
+\set powerdz debug(pow(0.0,0.0))
+\set powernegi debug(pow(-2,-3))
+\set powernegd debug(pow(-2.0,-3.0))
+\set powernull debug(pow(NULL, NULL))
} });
=head
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