add support for the LEAST function (pingcap#2360)

edric-shen · Dec 31, 2016 · f0fbe16 · f0fbe16
1 parent b5c9650
commit f0fbe16
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Showing 9 changed files with 79 additions and 12 deletions.
diff --git a/ast/functions.go b/ast/functions.go
@@ -74,6 +74,7 @@ const (
 	// common functions
 	Coalesce = "coalesce"
 	Greatest = "greatest"
+	Least    = "least"
 
 	// math functions
 	Abs     = "abs"

diff --git a/bootstrap.go b/bootstrap.go
@@ -324,7 +324,7 @@ func doDMLWorks(s Session) {
 		mysql.SystemDB, mysql.TiDBTable, bootstrappedVar, bootstrappedVarTrue, bootstrappedVarTrue)
 	mustExecute(s, sql)
 
-	sql = fmt.Sprintf(`INSERT INTO %s.%s VALUES("%s", "%d", "Bootstrap version. Do not delete")`,
+	sql = fmt.Sprintf(`INSERT INTO %s.%s VALUES("%s", "%d", "Bootstrap version. Do not delete.")`,
 		mysql.SystemDB, mysql.TiDBTable, tidbServerVersionVar, currentBootstrapVersion)
 	mustExecute(s, sql)
 

diff --git a/expression/builtin.go b/expression/builtin.go
@@ -125,6 +125,7 @@ var Funcs = map[string]Func{
 	ast.Coalesce: {builtinCoalesce, 1, -1},
 	ast.IsNull:   {builtinIsNull, 1, 1},
 	ast.Greatest: {builtinGreatest, 2, -1},
+	ast.Least:    {builtinLeast, 2, -1},
 
 	// math functions
 	ast.Abs:     {builtinAbs, 1, 1},
@@ -307,11 +308,13 @@ func builtinIsNull(args []types.Datum, _ context.Context) (d types.Datum, err er
 
 // See http://dev.mysql.com/doc/refman/5.7/en/comparison-operators.html#function_greatest
 func builtinGreatest(args []types.Datum, ctx context.Context) (d types.Datum, err error) {
+	if args[0].IsNull() {
+		return
+	}
 	max := 0
 	sc := ctx.GetSessionVars().StmtCtx
-	for i := 0; i < len(args); i++ {
+	for i := 1; i < len(args); i++ {
 		if args[i].IsNull() {
-			d.SetNull()
 			return
 		}
 
@@ -327,3 +330,28 @@ func builtinGreatest(args []types.Datum, ctx context.Context) (d types.Datum, er
 	d = args[max]
 	return
 }
+
+// See http://dev.mysql.com/doc/refman/5.7/en/comparison-operators.html#function_least
+func builtinLeast(args []types.Datum, ctx context.Context) (d types.Datum, err error) {
+	if args[0].IsNull() {
+		return
+	}
+	min := 0
+	sc := ctx.GetSessionVars().StmtCtx
+	for i := 1; i < len(args); i++ {
+		if args[i].IsNull() {
+			return
+		}
+
+		var cmp int
+		if cmp, err = args[i].CompareDatum(sc, args[min]); err != nil {
+			return
+		}
+
+		if cmp < 0 {
+			min = i
+		}
+	}
+	d = args[min]
+	return
+}
diff --git a/expression/builtin_test.go b/expression/builtin_test.go
@@ -70,23 +70,49 @@ func (s *testEvaluatorSuite) TestCoalesce(c *C) {
 	c.Assert(v, testutil.DatumEquals, types.NewDatum(nil))
 }
 
-func (s *testEvaluatorSuite) TestGreatestFunc(c *C) {
+func (s *testEvaluatorSuite) TestGreatestLeastFuncs(c *C) {
 	defer testleak.AfterTest(c)()
 
-	v, err := builtinGreatest(types.MakeDatums(2, 0), s.ctx)
+	var datums []types.Datum
+
+	datums = types.MakeDatums(2, 0)
+	v, err := builtinGreatest(datums, s.ctx)
 	c.Assert(err, IsNil)
 	c.Assert(v.GetInt64(), Equals, int64(2))
+	v, err = builtinLeast(datums, s.ctx)
+	c.Assert(err, IsNil)
+	c.Assert(v.GetInt64(), Equals, int64(0))
 
-	v, err = builtinGreatest(types.MakeDatums(34.0, 3.0, 5.0, 767.0), s.ctx)
+	datums = types.MakeDatums(34.0, 3.0, 5.0, 767.0)
+	v, err = builtinGreatest(datums, s.ctx)
 	c.Assert(err, IsNil)
 	c.Assert(v.GetFloat64(), Equals, float64(767.0))
+	v, err = builtinLeast(datums, s.ctx)
+	c.Assert(err, IsNil)
+	c.Assert(v.GetFloat64(), Equals, float64(3.0))
 
-	v, err = builtinGreatest(types.MakeDatums("B", "A", "C"), s.ctx)
+	datums = types.MakeDatums("B", "A", "C")
+	v, err = builtinGreatest(datums, s.ctx)
 	c.Assert(err, IsNil)
 	c.Assert(v.GetString(), Equals, "C")
+	v, err = builtinLeast(datums, s.ctx)
+	c.Assert(err, IsNil)
+	c.Assert(v.GetString(), Equals, "A")
+
+	// GREATEST() and LEAST() return NULL if any argument is NULL.
+	datums = types.MakeDatums(nil, 1, 2)
+	v, err = builtinGreatest(datums, s.ctx)
+	c.Assert(err, IsNil)
+	c.Assert(v.IsNull(), IsTrue)
+	v, err = builtinLeast(datums, s.ctx)
+	c.Assert(err, IsNil)
+	c.Assert(v.IsNull(), IsTrue)
 
-	// GREATEST() returns NULL if any argument is NULL.
-	v, err = builtinGreatest(types.MakeDatums(1, nil, 2), s.ctx)
+	datums = types.MakeDatums(1, nil, 2)
+	v, err = builtinGreatest(datums, s.ctx)
+	c.Assert(err, IsNil)
+	c.Assert(v.IsNull(), IsTrue)
+	v, err = builtinLeast(datums, s.ctx)
 	c.Assert(err, IsNil)
 	c.Assert(v.IsNull(), IsTrue)
 }

diff --git a/parser/misc.go b/parser/misc.go
@@ -283,6 +283,7 @@ var tokenMap = map[string]int{
 	"KEYS":                keys,
 	"LAST_INSERT_ID":      lastInsertID,
 	"LEADING":             leading,
+	"LEAST":               least,
 	"LEFT":                left,
 	"LENGTH":              length,
 	"LESS":                less,

diff --git a/parser/parser.y b/parser/parser.y
@@ -245,6 +245,7 @@ import (
 	lastInsertID	"LAST_INSERT_ID"
 	lcase 		"LCASE"
 	length		"LENGTH"
+	least		"LEAST"
 	ln		"LN"
 	locate		"LOCATE"
 	log		"LOG"
@@ -2093,7 +2094,7 @@ ReservedKeyword:
 NotKeywordToken:
 	"ABS" | "ADDDATE" | "ADMIN" | "COALESCE" | "CONCAT" | "CONCAT_WS" | "CONNECTION_ID" | "CUR_TIME"| "COUNT" | "DAY"
 |	"DATE_ADD" | "DATE_FORMAT" | "DATE_SUB" | "DAYNAME" | "DAYOFMONTH" | "DAYOFWEEK" | "DAYOFYEAR" | "FOUND_ROWS"
-|	"GROUP_CONCAT"| "GREATEST" | "HOUR" | "HEX" | "UNHEX" | "IFNULL" | "ISNULL" | "LAST_INSERT_ID" | "LCASE" | "LENGTH" | "LOCATE" | "LOWER" | "LTRIM"
+|	"GROUP_CONCAT"| "GREATEST" | "LEAST" | "HOUR" | "HEX" | "UNHEX" | "IFNULL" | "ISNULL" | "LAST_INSERT_ID" | "LCASE" | "LENGTH" | "LOCATE" | "LOWER" | "LTRIM"
 |	"MAX" | "MICROSECOND" | "MIN" |	"MINUTE" | "NULLIF" | "MONTH" | "MONTHNAME" | "NOW" | "POW" | "POWER" | "RAND"
 |	"SECOND" | "SLEEP" | "SQL_CALC_FOUND_ROWS" | "STR_TO_DATE" | "SUBDATE" | "SUBSTRING" %prec lowerThanLeftParen |
 "SUBSTRING_INDEX" | "SUM" | "TRIM" | "RTRIM" | "UCASE" | "UPPER" | "VERSION" | "WEEKDAY" | "WEEKOFYEAR" | "YEARWEEK" | "ROUND"
@@ -2698,6 +2699,10 @@ FunctionCallNonKeyword:
 	{
 		$$ = &ast.FuncCallExpr{FnName: model.NewCIStr($1), Args: $3.([]ast.ExprNode)}
 	}
+|	"LEAST" '(' ExpressionList ')'
+	{
+		$$ = &ast.FuncCallExpr{FnName: model.NewCIStr($1), Args: $3.([]ast.ExprNode)}
+	}
 |	"HOUR" '(' Expression ')'
 	{
 		$$ = &ast.FuncCallExpr{FnName: model.NewCIStr($1), Args: []ast.ExprNode{$3.(ast.ExprNode)}}

diff --git a/parser/parser_test.go b/parser/parser_test.go
@@ -87,7 +87,7 @@ func (s *testParserSuite) TestSimple(c *C) {
 		"delay_key_write", "isolation", "partitions", "repeatable", "committed", "uncommitted", "only", "serializable", "level",
 		"curtime", "variables", "dayname", "version", "btree", "hash", "row_format", "dynamic", "fixed", "compressed",
 		"compact", "redundant", "sql_no_cache sql_no_cache", "sql_cache sql_cache", "action", "round",
-		"enable", "disable", "reverse", "space", "privileges", "get_lock", "release_lock", "sleep", "no", "greatest",
+		"enable", "disable", "reverse", "space", "privileges", "get_lock", "release_lock", "sleep", "no", "greatest", "least",
 		"binlog", "hex", "unhex", "function", "indexes", "from_unixtime", "processlist", "events", "less", "than", "timediff",
 		"ln", "log", "log2", "log10",
 	}
@@ -526,6 +526,8 @@ func (s *testParserSuite) TestBuiltin(c *C) {
 
 		{"SELECT CONVERT('111', SIGNED);", true},
 
+		{"SELECT LEAST(1, 2, 3);", true},
+
 		// Information Functions
 		{"SELECT DATABASE();", true},
 		{"SELECT SCHEMA();", true},

diff --git a/plan/typeinferer.go b/plan/typeinferer.go
@@ -262,7 +262,7 @@ func (v *typeInferrer) handleFuncCallExpr(x *ast.FuncCallExpr) {
 		if x.FnName.L == "abs" && tp.Tp == mysql.TypeDatetime {
 			tp = types.NewFieldType(mysql.TypeDouble)
 		}
-	case "greatest":
+	case "greatest", "least":
 		for _, arg := range x.Args {
 			InferType(v.sc, arg)
 		}

diff --git a/plan/typeinferer_test.go b/plan/typeinferer_test.go
@@ -148,6 +148,10 @@ func (ts *testTypeInferrerSuite) TestInferType(c *C) {
 		{"greatest('TiDB', 'D', 'd')", mysql.TypeVarString, "utf8"},
 		{"greatest(1.1, 2.2)", mysql.TypeNewDecimal, charset.CharsetBin},
 		{"greatest('TiDB', 3)", mysql.TypeVarString, "utf8"},
+		{"least(1, 2, 3)", mysql.TypeLonglong, charset.CharsetBin},
+		{"least('TiDB', 'D', 'd')", mysql.TypeVarString, "utf8"},
+		{"least(1.1, 2.2)", mysql.TypeNewDecimal, charset.CharsetBin},
+		{"least('TiDB', 3)", mysql.TypeVarString, "utf8"},
 		{"hex('TiDB')", mysql.TypeVarString, "utf8"},
 		{"hex(12)", mysql.TypeVarString, "utf8"},
 		{"unhex('TiDB')", mysql.TypeVarString, "utf8"},