*: basic support for builtin function STR_TO_DATE

ast/functions.go

@@ -103,6 +103,7 @@ const (
 	MonthName        = "monthname"
 	Now              = "now"
 	Second           = "second"
+	StrToDate        = "str_to_date"
 	Sysdate          = "sysdate"
 	Time             = "time"
 	UTCDate          = "utc_date"

evaluator/builtin.go

@@ -77,6 +77,7 @@ var Funcs = map[string]Func{
 	ast.MonthName:        {builtinMonthName, 1, 1},
 	ast.Now:              {builtinNow, 0, 1},
 	ast.Second:           {builtinSecond, 1, 1},
+	ast.StrToDate:        {builtinStrToDate, 2, 2},
 	ast.Sysdate:          {builtinSysDate, 0, 1},
 	ast.Time:             {builtinTime, 1, 1},
 	ast.UTCDate:          {builtinUTCDate, 0, 0},