Add pow(), aka power(), function to pgbench.

Raúl Marín Rodríguez, reviewed by Fabien Coelho and Michael Paquier,
with a minor fix by me.

Discussion: http://postgr.es/m/CAM6_UM4XiA14y9HnDqu9kAAOtwMhHZxW--q_ZACZW9Hsrsf-tg@mail.gmail.com

doc/src/sgml/ref/pgbench.sgml

@@ -1069,6 +1069,13 @@ pgbench <optional> <replaceable>options</replaceable> </optional> <replaceable>d
        <entry><literal>pi()</literal></entry>
        <entry><literal>3.14159265358979323846</literal></entry>
       </row>
+      <row>
+       <entry><literal><function>pow(<replaceable>x</replaceable>, <replaceable>y</replaceable>)</function>, <function>power(<replaceable>x</replaceable>, <replaceable>y</replaceable>)</function></literal></entry>
+       <entry>double</entry>
+       <entry>exponentiation</entry>
+       <entry><literal>pow(2.0, 10)</literal>, <literal>power(2.0, 10)</literal></entry>
+       <entry><literal>1024.0</literal></entry>
+      </row>
       <row>
        <entry><literal><function>random(<replaceable>lb</replaceable>, <replaceable>ub</replaceable>)</function></literal></entry>
        <entry>integer</entry>

src/bin/pgbench/exprparse.y

@@ -194,6 +194,12 @@ static const struct
 	{
 		"random_zipfian", 3, PGBENCH_RANDOM_ZIPFIAN
 	},
+	{
+		"pow", 2, PGBENCH_POW
+	},
+	{
+		"power", 2, PGBENCH_POW
+	},
 	/* keep as last array element */
 	{
 		NULL, 0, 0

src/bin/pgbench/pgbench.c

@@ -1850,6 +1850,24 @@ evalFunc(TState *thread, CState *st,
 				return true;
 			}
 
+		case PGBENCH_POW:
+			{
+				PgBenchValue *lval = &vargs[0];
+				PgBenchValue *rval = &vargs[1];
+				double		ld,
+							rd;
+
+				Assert(nargs == 2);
+
+				if (!coerceToDouble(lval, &ld) ||
+					!coerceToDouble(rval, &rd))
+					return false;
+
+				setDoubleValue(retval, pow(ld, rd));
+
+				return true;
+			}
+
 		default:
 			/* cannot get here */
 			Assert(0);

src/bin/pgbench/pgbench.h

@@ -76,7 +76,8 @@ typedef enum PgBenchFunction
 	PGBENCH_RANDOM,
 	PGBENCH_RANDOM_GAUSSIAN,
 	PGBENCH_RANDOM_EXPONENTIAL,
-	PGBENCH_RANDOM_ZIPFIAN
+	PGBENCH_RANDOM_ZIPFIAN,
+	PGBENCH_POW
 } PgBenchFunction;
 
 typedef struct PgBenchExpr PgBenchExpr;

src/bin/pgbench/t/001_pgbench_with_server.pl

@@ -232,7 +232,17 @@ pgbench(
 		qr{command=19.: double 19\b},
 		qr{command=20.: double 20\b},
 		qr{command=21.: int 9223372036854775807\b},
-		qr{command=23.: int [1-9]\b}, ],
+		qr{command=23.: int [1-9]\b},
+		qr{command=24.: double -27\b},
+		qr{command=25.: double 1024\b},
+		qr{command=26.: double 1\b},
+		qr{command=27.: double 1\b},
+		qr{command=28.: double -0.125\b},
+		qr{command=29.: double -0.125\b},
+		qr{command=30.: double -0.00032\b},
+		qr{command=31.: double 8.50705917302346e\+37\b},
+		qr{command=32.: double 1e\+30\b},
+	],
 	'pgbench expressions',
 	{   '001_pgbench_expressions' => q{-- integer functions
 \set i1 debug(random(1, 100))
@@ -264,6 +274,16 @@ pgbench(
 \set i1 0
 -- yet another integer function
 \set id debug(random_zipfian(1, 9, 1.3))
+--- pow and power
+\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 powernegd2 debug(power(-5.0,-5.0))
+\set powerov debug(pow(9223372036854775807, 2))
+\set powerov2 debug(pow(10,30))
 } });
 
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