diff --git a/contrib/pgbench/exprparse.y b/contrib/pgbench/exprparse.y
index 243c6b9..fd396bd 100644
--- a/contrib/pgbench/exprparse.y
+++ b/contrib/pgbench/exprparse.y
@@ -20,6 +20,7 @@ static PgBenchExpr *make_integer_constant(int64 ival);
 static PgBenchExpr *make_variable(char *varname);
 static PgBenchExpr *make_op(char operator, PgBenchExpr *lexpr,
 		PgBenchExpr *rexpr);
+static PgBenchExpr *make_func(const char *fname, PgBenchExpr *arg1);

 %}

@@ -35,8 +36,8 @@ static PgBenchExpr *make_op(char operator, PgBenchExpr *lexpr,

 %type <expr> expr
 %type <ival> INTEGER
-%type <str> VARIABLE
-%token INTEGER VARIABLE
+%type <str> VARIABLE FUNCTION
+%token INTEGER VARIABLE FUNCTION
 %token CHAR_ERROR /* never used, will raise a syntax error */

 %left	'+' '-'
@@ -57,6 +58,7 @@ expr: '(' expr ')'			{ $$ = $2; }
 	| expr '%' expr			{ $$ = make_op('%', $1, $3); }
 	| INTEGER				{ $$ = make_integer_constant($1); }
 	| VARIABLE 				{ $$ = make_variable($1); }
+	| FUNCTION '(' expr ')' { $$ = make_func($1, $3); pg_free($1); }
 	;

 %%
@@ -93,4 +95,32 @@ make_op(char operator, PgBenchExpr *lexpr, PgBenchExpr *rexpr)
 	return expr;
 }

+static struct {
+	char * fname;
+	int nargs;
+	PgBenchFunction tag;
+} PGBENCH_FUNCTIONS[] = {
+	{ "abs", 1, PGBENCH_ABS }
+};
+
+static PgBenchExpr *
+make_func(const char * fname, PgBenchExpr *arg1)
+{
+	PgBenchExpr *expr = pg_malloc(sizeof(PgBenchExpr));
+	int nfunctions = sizeof(PGBENCH_FUNCTIONS) / sizeof(PGBENCH_FUNCTIONS[0]);
+	int i;
+
+	expr->etype = ENODE_FUNCTION;
+	expr->u.function.function = PGBENCH_NONE;
+
+	for (i = 0; i < nfunctions; i++)
+		if (pg_strcasecmp(fname, PGBENCH_FUNCTIONS[i].fname) == 0)
+			expr->u.function.function = PGBENCH_FUNCTIONS[i].tag;
+
+	Assert(expr->u.function.function != PGBENCH_NONE);
+
+	expr->u.function.arg1 = arg1;
+	return expr;
+}
+
 #include "exprscan.c"
diff --git a/contrib/pgbench/exprscan.l b/contrib/pgbench/exprscan.l
index 4c9229c..a276444 100644
--- a/contrib/pgbench/exprscan.l
+++ b/contrib/pgbench/exprscan.l
@@ -46,6 +46,7 @@ space			[ \t\r\f]
 ")"				{ yycol += yyleng; return ')'; }
 :[a-zA-Z0-9_]+	{ yycol += yyleng; yylval.str = pg_strdup(yytext + 1); return VARIABLE; }
 [0-9]+			{ yycol += yyleng; yylval.ival = strtoint64(yytext); return INTEGER; }
+[a-zA-Z]+       { yycol += yyleng; yylval.str = pg_strdup(yytext); return FUNCTION; }

 [\n]			{ yycol = 0; yyline++; }
 {space}			{ yycol += yyleng; /* ignore */ }
diff --git a/contrib/pgbench/pgbench.c b/contrib/pgbench/pgbench.c
index 706fdf5..1e9604d 100644
--- a/contrib/pgbench/pgbench.c
+++ b/contrib/pgbench/pgbench.c
@@ -959,6 +959,26 @@ evaluateExpr(CState *st, PgBenchExpr *expr, int64 *retval)
 				return false;
 			}

+		case ENODE_FUNCTION:
+			{
+				switch (expr->u.function.function)
+				{
+					case PGBENCH_ABS:
+					{
+						int64 arg1;
+						if (!evaluateExpr(st, expr->u.function.arg1, &arg1))
+							return false;
+
+						*retval = arg1 > 0? arg1: -arg1;
+						return true;
+					}
+					default:
+						fprintf(stderr, "bad function (%d)",
+								expr->u.function.function);
+						return false;
+				}
+			}
+
 		default:
 			break;
 	}
diff --git a/contrib/pgbench/pgbench.h b/contrib/pgbench/pgbench.h
index 128bf11..8697c7b 100644
--- a/contrib/pgbench/pgbench.h
+++ b/contrib/pgbench/pgbench.h
@@ -15,12 +15,19 @@ typedef enum PgBenchExprType
 {
 	ENODE_INTEGER_CONSTANT,
 	ENODE_VARIABLE,
-	ENODE_OPERATOR
+	ENODE_OPERATOR,
+	ENODE_FUNCTION
 } PgBenchExprType;

 struct PgBenchExpr;
 typedef struct PgBenchExpr PgBenchExpr;

+typedef enum PgBenchFunction
+{
+	PGBENCH_NONE,
+	PGBENCH_ABS
+} PgBenchFunction;
+
 struct PgBenchExpr
 {
 	PgBenchExprType	etype;
@@ -40,6 +47,11 @@ struct PgBenchExpr
 			PgBenchExpr	*lexpr;
 			PgBenchExpr *rexpr;
 		} operator;
+		struct
+		{
+			int function;
+			PgBenchExpr *arg1;
+		} function;
 	} u;
 };