pgbench_pow_v10_ipow_overflow.patch

From 6cb8fb1a3eaffe680b85913b0acf0068dcb0d2a7 Mon Sep 17 00:00:00 2001
From: Raul Marin <rmrodriguez@cartodb.com>
Date: Thu, 21 Dec 2017 20:28:02 +0100
Subject: [PATCH] Add pow() support to pgbench

---
 doc/src/sgml/ref/pgbench.sgml                |   7 ++
 src/bin/pgbench/exprparse.y                  |   6 ++
 src/bin/pgbench/pgbench.c                    | 100 +++++++++++++++++++++++++++
 src/bin/pgbench/pgbench.h                    |   3 +-
 src/bin/pgbench/t/001_pgbench_with_server.pl |  22 +++++-
 5 files changed, 136 insertions(+), 2 deletions(-)

diff --git a/doc/src/sgml/ref/pgbench.sgml b/doc/src/sgml/ref/pgbench.sgml
index 4431fc3eb7..1519fe78ef 100644
--- a/doc/src/sgml/ref/pgbench.sgml
+++ b/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>
diff --git a/src/bin/pgbench/exprparse.y b/src/bin/pgbench/exprparse.y
index 25d5ad48e5..74ffe5e7a7 100644
--- a/src/bin/pgbench/exprparse.y
+++ b/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
diff --git a/src/bin/pgbench/pgbench.c b/src/bin/pgbench/pgbench.c
index 7ce6f607f5..07436af5a7 100644
--- a/src/bin/pgbench/pgbench.c
+++ b/src/bin/pgbench/pgbench.c
@@ -911,6 +911,64 @@ getZipfianRand(TState *thread, int64 min, int64 max, double s)
 					  : computeHarmonicZipfian(thread, n, s));
 }
 
+/* Position of the most significant bit */
+static int64
+ffs_i64(int64 i)
+{
+	int64 bits = 0;
+
+	if (i < 0)
+		i = -i;
+	while (i)
+	{
+		i>>=1;
+		bits++;
+	}
+
+	return bits;
+}
+
+/* Heuristic to check for ipow overflow */
+static bool
+ipow_check_overflow(int64 base, int64 exp)
+{
+	int64 msb_base,
+			msb_base_sqr;
+
+	Assert(exp >= 0);
+	if (base == 0 || base == 1 || base == -1 || exp <= 1)
+		return false;
+
+	msb_base = ffs_i64(base);
+	if (msb_base >= 32)
+		return true;
+
+	msb_base_sqr = ffs_i64(base * base);
+	if (msb_base_sqr <= msb_base)
+		return true;
+
+	return (msb_base + (msb_base_sqr - msb_base) * (exp -1)) > 63;
+}
+
+/* Faster power function for integer values with exp >= 0 */
+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
  */
@@ -1850,6 +1908,48 @@ 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, exp >= 0 and the output
+				 * fits in an int64 use the faster ipow(), 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 &&
+						!ipow_check_overflow(li,ri))
+						setDoubleValue(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 83fee1ae74..0e92882a4c 100644
--- a/src/bin/pgbench/pgbench.h
+++ b/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;
diff --git a/src/bin/pgbench/t/001_pgbench_with_server.pl b/src/bin/pgbench/t/001_pgbench_with_server.pl
index e3cdf28628..9cbeb2fc11 100644
--- a/src/bin/pgbench/t/001_pgbench_with_server.pl
+++ b/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))
 } });
 
 # backslash commands
-- 
2.15.1