pgbench: Add a real expression syntax to \set

Previously, you could do \set variable operand1 operator operand2, but
nothing more complicated.  Now, you can \set variable expression, which
makes it much simpler to do multi-step calculations here.  This also
adds support for the modulo operator (%), with the same semantics as in
C.

Robert Haas and Fabien Coelho, reviewed by Álvaro Herrera and
Stephen Frost

contrib/pgbench/.gitignore

@@ -1 +1,3 @@
+/exprparse.c
+/exprscan.c
 /pgbench

contrib/pgbench/Makefile

@@ -4,7 +4,9 @@ PGFILEDESC = "pgbench - a simple program for running benchmark tests"
 PGAPPICON = win32
 
 PROGRAM = pgbench
-OBJS	= pgbench.o $(WIN32RES)
+OBJS	= pgbench.o exprparse.o $(WIN32RES)
+
+EXTRA_CLEAN	= exprparse.c exprscan.c
 
 PG_CPPFLAGS = -I$(libpq_srcdir)
 PG_LIBS = $(libpq_pgport) $(PTHREAD_LIBS)
@@ -18,8 +20,21 @@ subdir = contrib/pgbench
 top_builddir = ../..
 include $(top_builddir)/src/Makefile.global
 include $(top_srcdir)/contrib/contrib-global.mk
+
+distprep: exprparse.c exprscan.c
 endif
 
 ifneq ($(PORTNAME), win32)
 override CFLAGS += $(PTHREAD_CFLAGS)
 endif
+
+# There is no correct way to write a rule that generates two files.
+# Rules with two targets don't have that meaning, they are merely
+# shorthand for two otherwise separate rules.  To be safe for parallel
+# make, we must chain the dependencies like this.  The semicolon is
+# important; otherwise, make will choose the built-in rule.
+
+exprparse.h: exprparse.c ;
+
+# exprscan is compiled as part of exprparse
+exprparse.o: exprscan.c

contrib/pgbench/exprparse.y

@@ -0,0 +1,96 @@
+%{
+/*-------------------------------------------------------------------------
+ *
+ * exprparse.y
+ *	  bison grammar for a simple expression syntax
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres_fe.h"
+
+#include "pgbench.h"
+
+PgBenchExpr *expr_parse_result;
+
+static PgBenchExpr *make_integer_constant(int64 ival);
+static PgBenchExpr *make_variable(char *varname);
+static PgBenchExpr *make_op(char operator, PgBenchExpr *lexpr,
+		PgBenchExpr *rexpr);
+
+%}
+
+%expect 0
+%name-prefix="expr_yy"
+
+%union
+{
+	int64		ival;
+	char	   *str;
+	PgBenchExpr *expr;
+}
+
+%type <expr> expr
+%type <ival> INTEGER
+%type <str> VARIABLE
+%token INTEGER VARIABLE
+%token CHAR_ERROR /* never used, will raise a syntax error */
+
+%left	'+' '-'
+%left	'*' '/' '%'
+%right	UMINUS
+
+%%
+
+result: expr				{ expr_parse_result = $1; }
+
+expr: '(' expr ')'			{ $$ = $2; }
+	| '+' expr %prec UMINUS	{ $$ = $2; }
+	| '-' expr %prec UMINUS	{ $$ = make_op('-', make_integer_constant(0), $2); }
+	| expr '+' expr			{ $$ = make_op('+', $1, $3); }
+	| expr '-' expr			{ $$ = make_op('-', $1, $3); }
+	| expr '*' expr			{ $$ = make_op('*', $1, $3); }
+	| expr '/' expr			{ $$ = make_op('/', $1, $3); }
+	| expr '%' expr			{ $$ = make_op('%', $1, $3); }
+	| INTEGER				{ $$ = make_integer_constant($1); }
+	| VARIABLE 				{ $$ = make_variable($1); }
+	;
+
+%%
+
+static PgBenchExpr *
+make_integer_constant(int64 ival)
+{
+	PgBenchExpr *expr = pg_malloc(sizeof(PgBenchExpr));
+
+	expr->etype = ENODE_INTEGER_CONSTANT;
+	expr->u.integer_constant.ival = ival;
+	return expr;
+}
+
+static PgBenchExpr *
+make_variable(char *varname)
+{
+	PgBenchExpr *expr = pg_malloc(sizeof(PgBenchExpr));
+
+	expr->etype = ENODE_VARIABLE;
+	expr->u.variable.varname = varname;
+	return expr;
+}
+
+static PgBenchExpr *
+make_op(char operator, PgBenchExpr *lexpr, PgBenchExpr *rexpr)
+{
+	PgBenchExpr *expr = pg_malloc(sizeof(PgBenchExpr));
+
+	expr->etype = ENODE_OPERATOR;
+	expr->u.operator.operator = operator;
+	expr->u.operator.lexpr = lexpr;
+	expr->u.operator.rexpr = rexpr;
+	return expr;
+}
+
+#include "exprscan.c"

contrib/pgbench/exprscan.l

@@ -0,0 +1,105 @@
+%{
+/*-------------------------------------------------------------------------
+ *
+ * exprscan.l
+ *	  a lexical scanner for a simple expression syntax
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/* line and column number for error reporting */
+static int	yyline = 0, yycol = 0;
+
+/* Handles to the buffer that the lexer uses internally */
+static YY_BUFFER_STATE scanbufhandle;
+static char *scanbuf;
+static int	scanbuflen;
+
+/* flex 2.5.4 doesn't bother with a decl for this */
+int expr_yylex(void);
+
+%}
+
+%option 8bit
+%option never-interactive
+%option nodefault
+%option noinput
+%option nounput
+%option noyywrap
+%option warn
+%option prefix="expr_yy"
+
+non_newline		[^\n\r]
+space			[ \t\r\f]
+
+%%
+
+"+"				{ yycol += yyleng; return '+'; }
+"-"				{ yycol += yyleng; return '-'; }
+"*"				{ yycol += yyleng; return '*'; }
+"/"				{ yycol += yyleng; return '/'; }
+"%"				{ yycol += yyleng; return '%'; }
+"("				{ yycol += yyleng; return '('; }
+")"				{ 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; }
+
+[\n]			{ yycol = 0; yyline++; }
+{space}			{ yycol += yyleng; /* ignore */ }
+
+.				{
+					yycol += yyleng;
+					fprintf(stderr, "unexpected character '%s'\n", yytext);
+					return CHAR_ERROR;
+				}
+%%
+
+void
+yyerror(const char *message)
+{
+	/* yyline is always 1 as pgbench calls the parser for each line...
+	 * so the interesting location information is the column number */
+	fprintf(stderr, "%s at column %d\n", message, yycol);
+	/* go on to raise the error from pgbench with more information */
+	/* exit(1); */
+}
+
+/*
+ * Called before any actual parsing is done
+ */
+void
+expr_scanner_init(const char *str)
+{
+	Size	slen = strlen(str);
+
+	/*
+	 * Might be left over after error
+	 */
+	if (YY_CURRENT_BUFFER)
+		yy_delete_buffer(YY_CURRENT_BUFFER);
+
+	/*
+	 * Make a scan buffer with special termination needed by flex.
+	 */
+	scanbuflen = slen;
+	scanbuf = pg_malloc(slen + 2);
+	memcpy(scanbuf, str, slen);
+	scanbuf[slen] = scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
+	scanbufhandle = yy_scan_buffer(scanbuf, slen + 2);
+
+	BEGIN(INITIAL);
+}
+
+
+/*
+ * Called after parsing is done to clean up after seg_scanner_init()
+ */
+void
+expr_scanner_finish(void)
+{
+	yy_delete_buffer(scanbufhandle);
+	pg_free(scanbuf);
+}

contrib/pgbench/pgbench.c

@@ -57,6 +57,8 @@
 #define M_PI 3.14159265358979323846
 #endif
 
+#include "pgbench.h"
+
 /*
  * Multi-platform pthread implementations
  */
@@ -289,6 +291,7 @@ typedef struct
 	int			type;			/* command type (SQL_COMMAND or META_COMMAND) */
 	int			argc;			/* number of command words */
 	char	   *argv[MAX_ARGS]; /* command word list */
+	PgBenchExpr *expr;			/* parsed expression */
 } Command;
 
 typedef struct
@@ -423,7 +426,7 @@ usage(void)
  * This function is a modified version of scanint8() from
  * src/backend/utils/adt/int8.c.
  */
-static int64
+int64
 strtoint64(const char *str)
 {
 	const char *ptr = str;
@@ -879,6 +882,91 @@ getQueryParams(CState *st, const Command *command, const char **params)
 		params[i] = getVariable(st, command->argv[i + 1]);
 }
 
+/*
+ * Recursive evaluation of an expression in a pgbench script
+ * using the current state of variables.
+ * Returns whether the evaluation was ok,
+ * the value itself is returned through the retval pointer.
+ */
+static bool
+evaluateExpr(CState *st, PgBenchExpr *expr, int64 *retval)
+{
+	switch (expr->etype)
+	{
+		case ENODE_INTEGER_CONSTANT:
+			{
+				*retval = expr->u.integer_constant.ival;
+				return true;
+			}
+
+		case ENODE_VARIABLE:
+			{
+				char	   *var;
+
+				if ((var = getVariable(st, expr->u.variable.varname)) == NULL)
+				{
+					fprintf(stderr, "undefined variable %s\n",
+						expr->u.variable.varname);
+					return false;
+				}
+				*retval = strtoint64(var);
+				return true;
+			}
+
+		case ENODE_OPERATOR:
+			{
+				int64	lval;
+				int64	rval;
+
+				if (!evaluateExpr(st, expr->u.operator.lexpr, &lval))
+					return false;
+				if (!evaluateExpr(st, expr->u.operator.rexpr, &rval))
+					return false;
+				switch (expr->u.operator.operator)
+				{
+					case '+':
+						*retval = lval + rval;
+						return true;
+
+					case '-':
+						*retval = lval - rval;
+						return true;
+
+					case '*':
+						*retval = lval * rval;
+						return true;
+
+					case '/':
+						if (rval == 0)
+						{
+							fprintf(stderr, "division by zero\n");
+							return false;
+						}
+						*retval = lval / rval;
+						return true;
+
+					case '%':
+						if (rval == 0)
+						{
+							fprintf(stderr, "division by zero\n");
+							return false;
+						}
+						*retval = lval % rval;
+						return true;
+				}
+
+				fprintf(stderr, "bad operator\n");
+				return false;
+			}
+
+		default:
+			break;
+	}
+
+	fprintf(stderr, "bad expression\n");
+	return false;
+}
+
 /*
  * Run a shell command. The result is assigned to the variable if not NULL.
  * Return true if succeeded, or false on error.
@@ -1515,64 +1603,16 @@ top:
 		}
 		else if (pg_strcasecmp(argv[0], "set") == 0)
 		{
-			char	   *var;
-			int64		ope1,
-						ope2;
 			char		res[64];
+			PgBenchExpr *expr = commands[st->state]->expr;
+			int64		result;
 
-			if (*argv[2] == ':')
+			if (!evaluateExpr(st, expr, &result))
 			{
-				if ((var = getVariable(st, argv[2] + 1)) == NULL)
-				{
-					fprintf(stderr, "%s: undefined variable %s\n", argv[0], argv[2]);
 				st->ecnt++;
 				return true;
 			}
-				ope1 = strtoint64(var);
-			}
-			else
-				ope1 = strtoint64(argv[2]);
-
-			if (argc < 5)
-				snprintf(res, sizeof(res), INT64_FORMAT, ope1);
-			else
-			{
-				if (*argv[4] == ':')
-				{
-					if ((var = getVariable(st, argv[4] + 1)) == NULL)
-					{
-						fprintf(stderr, "%s: undefined variable %s\n", argv[0], argv[4]);
-						st->ecnt++;
-						return true;
-					}
-					ope2 = strtoint64(var);
-				}
-				else
-					ope2 = strtoint64(argv[4]);
-
-				if (strcmp(argv[3], "+") == 0)
-					snprintf(res, sizeof(res), INT64_FORMAT, ope1 + ope2);
-				else if (strcmp(argv[3], "-") == 0)
-					snprintf(res, sizeof(res), INT64_FORMAT, ope1 - ope2);
-				else if (strcmp(argv[3], "*") == 0)
-					snprintf(res, sizeof(res), INT64_FORMAT, ope1 * ope2);
-				else if (strcmp(argv[3], "/") == 0)
-				{
-					if (ope2 == 0)
-					{
-						fprintf(stderr, "%s: division by zero\n", argv[0]);
-						st->ecnt++;
-						return true;
-					}
-					snprintf(res, sizeof(res), INT64_FORMAT, ope1 / ope2);
-				}
-				else
-				{
-					fprintf(stderr, "%s: unsupported operator %s\n", argv[0], argv[3]);
-					st->ecnt++;
-					return true;
-				}
-			}
+			sprintf(res, INT64_FORMAT, result);
 
 			if (!putVariable(st, argv[0], argv[1], res))
 			{
@@ -2151,7 +2191,7 @@ parseQuery(Command *cmd, const char *raw_sql)
 
 /* Parse a command; return a Command struct, or NULL if it's a comment */
 static Command *
-process_commands(char *buf)
+process_commands(char *buf, const char *source, const int lineno)
 {
 	const char	delim[] = " \f\n\r\t\v";
 
@@ -2182,15 +2222,22 @@ process_commands(char *buf)
 
 	if (*p == '\\')
 	{
+		int		max_args = -1;
 		my_commands->type = META_COMMAND;
 
 		j = 0;
 		tok = strtok(++p, delim);
 
+		if (tok != NULL && pg_strcasecmp(tok, "set") == 0)
+			max_args = 2;
+
 		while (tok != NULL)
 		{
 			my_commands->argv[j++] = pg_strdup(tok);
 			my_commands->argc++;
+			if (max_args >= 0 && my_commands->argc >= max_args)
+				tok = strtok(NULL, "");
+			else
 				tok = strtok(NULL, delim);
 		}
 
@@ -2250,9 +2297,17 @@ process_commands(char *buf)
 				exit(1);
 			}
 
-			for (j = my_commands->argc < 5 ? 3 : 5; j < my_commands->argc; j++)
-				fprintf(stderr, "%s: extra argument \"%s\" ignored\n",
-						my_commands->argv[0], my_commands->argv[j]);
+			expr_scanner_init(my_commands->argv[2]);
+
+			if (expr_yyparse() != 0)
+			{
+				fprintf(stderr, "%s: parse error\n", my_commands->argv[0]);
+				exit(1);
+			}
+
+			my_commands->expr = expr_parse_result;
+
+			expr_scanner_finish();
 		}
 		else if (pg_strcasecmp(my_commands->argv[0], "sleep") == 0)
 		{
@@ -2393,7 +2448,7 @@ process_file(char *filename)
 
 	Command   **my_commands;
 	FILE	   *fd;
-	int			lineno;
+	int			lineno, index;
 	char	   *buf;
 	int			alloc_num;
 
@@ -2416,22 +2471,24 @@ process_file(char *filename)
 	}
 
 	lineno = 0;
+	index = 0;
 
 	while ((buf = read_line_from_file(fd)) != NULL)
 	{
 		Command    *command;
+		lineno += 1;
 
-		command = process_commands(buf);
+		command = process_commands(buf, filename, lineno);
 
 		free(buf);
 
 		if (command == NULL)
 			continue;
 
-		my_commands[lineno] = command;
-		lineno++;
+		my_commands[index] = command;
+		index++;
 
-		if (lineno >= alloc_num)
+		if (index >= alloc_num)
 		{
 			alloc_num += COMMANDS_ALLOC_NUM;
 			my_commands = pg_realloc(my_commands, sizeof(Command *) * alloc_num);
@@ -2439,7 +2496,7 @@ process_file(char *filename)
 	}
 	fclose(fd);
 
-	my_commands[lineno] = NULL;
+	my_commands[index] = NULL;
 
 	sql_files[num_files++] = my_commands;
 
@@ -2447,12 +2504,12 @@ process_file(char *filename)
 }
 
 static Command **
-process_builtin(char *tb)
+process_builtin(char *tb, const char *source)
 {
 #define COMMANDS_ALLOC_NUM 128
 
 	Command   **my_commands;
-	int			lineno;
+	int			lineno, index;
 	char		buf[BUFSIZ];
 	int			alloc_num;
 
@@ -2460,6 +2517,7 @@ process_builtin(char *tb)
 	my_commands = (Command **) pg_malloc(sizeof(Command *) * alloc_num);
 
 	lineno = 0;
+	index = 0;
 
 	for (;;)
 	{
@@ -2478,21 +2536,23 @@ process_builtin(char *tb)
 
 		*p = '\0';
 
-		command = process_commands(buf);
+		lineno += 1;
+
+		command = process_commands(buf, source, lineno);
 		if (command == NULL)
 			continue;
 
-		my_commands[lineno] = command;
-		lineno++;
+		my_commands[index] = command;
+		index++;
 
-		if (lineno >= alloc_num)
+		if (index >= alloc_num)
 		{
 			alloc_num += COMMANDS_ALLOC_NUM;
 			my_commands = pg_realloc(my_commands, sizeof(Command *) * alloc_num);
 		}
 	}
 
-	my_commands[lineno] = NULL;
+	my_commands[index] = NULL;
 
 	return my_commands;
 }
@@ -3222,17 +3282,20 @@ main(int argc, char **argv)
 	switch (ttype)
 	{
 		case 0:
-			sql_files[0] = process_builtin(tpc_b);
+			sql_files[0] = process_builtin(tpc_b,
+										   "<builtin: TPC-B (sort of)>");
 			num_files = 1;
 			break;
 
 		case 1:
-			sql_files[0] = process_builtin(select_only);
+			sql_files[0] = process_builtin(select_only,
+										   "<builtin: select only>");
 			num_files = 1;
 			break;
 
 		case 2:
-			sql_files[0] = process_builtin(simple_update);
+			sql_files[0] = process_builtin(simple_update,
+										   "<builtin: simple update>");
 			num_files = 1;
 			break;
 

contrib/pgbench/pgbench.h

@@ -0,0 +1,56 @@
+/*-------------------------------------------------------------------------
+ *
+ * pgbench.h
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef PGBENCH_H
+#define PGBENCH_H
+
+typedef enum PgBenchExprType
+{
+	ENODE_INTEGER_CONSTANT,
+	ENODE_VARIABLE,
+	ENODE_OPERATOR
+} PgBenchExprType;
+
+struct PgBenchExpr;
+typedef struct PgBenchExpr PgBenchExpr;
+
+struct PgBenchExpr
+{
+	PgBenchExprType	etype;
+	union
+	{
+		struct
+		{
+			int64 ival;
+		} integer_constant;
+		struct
+		{
+			char *varname;
+		} variable;
+		struct
+		{
+			char operator;
+			PgBenchExpr	*lexpr;
+			PgBenchExpr *rexpr;
+		} operator;
+	} u;
+};
+
+extern PgBenchExpr *expr_parse_result;
+
+extern int      expr_yyparse(void);
+extern int      expr_yylex(void);
+extern void expr_yyerror(const char *str);
+extern void expr_scanner_init(const char *str);
+extern void expr_scanner_finish(void);
+
+extern int64 strtoint64(const char *str);
+
+#endif

doc/src/sgml/pgbench.sgml

@@ -751,22 +751,25 @@ pgbench <optional> <replaceable>options</> </optional> <replaceable>dbname</>
   <variablelist>
    <varlistentry>
     <term>
-     <literal>\set <replaceable>varname</> <replaceable>operand1</> [ <replaceable>operator</> <replaceable>operand2</> ]</literal>
+     <literal>\set <replaceable>varname</> <replaceable>expression</>
     </term>
 
     <listitem>
      <para>
-      Sets variable <replaceable>varname</> to a calculated integer value.
-      Each <replaceable>operand</> is either an integer constant or a
-      <literal>:</><replaceable>variablename</> reference to a variable
-      having an integer value.  The <replaceable>operator</> can be
-      <literal>+</>, <literal>-</>, <literal>*</>, or <literal>/</>.
+      Sets variable <replaceable>varname</> to an integer value calculated
+      from <replaceable>expression</>.
+      The expression may contain integer constants such as <literal>5432</>,
+      references to variables <literal>:</><replaceable>variablename</>,
+      and expressions composed of unary (<literal>-</>) or binary operators
+      (<literal>+</>, <literal>-</>, <literal>*</>, <literal>/</>, <literal>%</>)
+      with their usual associativity, and parentheses.
      </para>
 
      <para>
-      Example:
+      Examples:
 <programlisting>
 \set ntellers 10 * :scale
+\set aid (1021 * :aid) % (100000 * :scale) + 1
 </programlisting></para>
     </listitem>
    </varlistentry>

src/tools/msvc/Mkvcbuild.pm

@@ -49,6 +49,7 @@ my $contrib_extraincludes =
   { 'tsearch2' => ['contrib/tsearch2'], 'dblink' => ['src/backend'] };
 my $contrib_extrasource = {
 	'cube' => [ 'cubescan.l', 'cubeparse.y' ],
+	'pgbench' => [ 'exprscan.l', 'exprparse.y' ],
 	'seg'  => [ 'segscan.l',  'segparse.y' ], };
 my @contrib_excludes = ('pgcrypto', 'intagg', 'sepgsql');