Merge pull request #23 from pingcap/shenli/builtin-convert

Add convert type function

expression/expressions/cast.go

@@ -29,6 +29,8 @@ type FunctionCast struct {
 	Expr expression.Expression
 	// Tp is the conversion type.
 	Tp *types.FieldType
+	// Cast and Convert share this struct.
+	IsConvert bool
 }
 
 // Clone implements the Expression Clone interface.
@@ -38,8 +40,9 @@ func (f *FunctionCast) Clone() (expression.Expression, error) {
 		return nil, err
 	}
 	nf := &FunctionCast{
-		Expr: expr,
-		Tp:   f.Tp,
+		Expr:      expr,
+		Tp:        f.Tp,
+		IsConvert: f.IsConvert,
 	}
 	return nf, nil
 }
@@ -61,6 +64,9 @@ func (f *FunctionCast) String() string {
 	} else {
 		tpStr = f.Tp.String()
 	}
+	if f.IsConvert {
+		return fmt.Sprintf("CONVERT(%s, %s)", f.Expr.String(), tpStr)
+	}
 	return fmt.Sprintf("CAST(%s AS %s)", f.Expr.String(), tpStr)
 }
 

expression/expressions/cast_test.go

@@ -74,4 +74,16 @@ func (s *testCastSuite) TestCast(c *C) {
 
 	_, err = expr.Eval(nil, nil)
 	c.Assert(err, NotNil)
+
+	// For String()
+	f = types.NewFieldType(mysql.TypeLonglong)
+	expr = &FunctionCast{
+		Expr: Value{1},
+		Tp:   f,
+	}
+	str := expr.String()
+	c.Assert(str, Equals, "CAST(1 AS SIGNED)")
+	expr.IsConvert = true
+	str = expr.String()
+	c.Assert(str, Equals, "CONVERT(1, SIGNED)")
 }

parser/parser.y

@@ -1808,6 +1808,15 @@ Function:
 			Charset: $5.(string),
 		}	
 	}
+|	"CONVERT" '(' Expression ',' CastType ')' 
+	{
+		// See: https://dev.mysql.com/doc/refman/5.7/en/cast-functions.html#function_convert
+		$$ = &expressions.FunctionCast{
+			Expr: $3.(expression.Expression), 
+			Tp: $5.(*types.FieldType),
+			IsConvert: true,
+		}	
+	}
 |	"SUBSTRING" '(' Expression ',' Expression ')'
 	{
 		$$ = &expressions.FunctionSubstring{

parser/parser_test.go

@@ -18,6 +18,8 @@ import (
 	"testing"
 
 	. "github.com/pingcap/check"
+	"github.com/pingcap/tidb/expression/expressions"
+	"github.com/pingcap/tidb/stmt/stmts"
 )
 
 func TestT(t *testing.T) {
@@ -257,6 +259,8 @@ func (s *testParserSuite) TestParser0(c *C) {
 		{"SELECT SUBSTRING('Quadratically' FROM 5);", true},
 		{"SELECT SUBSTRING('Quadratically' FROM 5 FOR 3);", true},
 
+		{"SELECT CONVERT('111', SIGNED);", true},
+
 		// For delete statement
 		{"DELETE t1, t2 FROM t1 INNER JOIN t2 INNER JOIN t3 WHERE t1.id=t2.id AND t2.id=t3.id;", true},
 		{"DELETE FROM t1, t2 USING t1 INNER JOIN t2 INNER JOIN t3 WHERE t1.id=t2.id AND t2.id=t3.id;", true},
@@ -284,8 +288,7 @@ func (s *testParserSuite) TestParser0(c *C) {
 	src := "SELECT id+?, id+? from t;"
 	l := NewLexer(src)
 	l.SetPrepare()
-	ok := yyParse(l) == 0
-	c.Assert(ok, Equals, true)
+	c.Assert(yyParse(l), Equals, 0)
 	c.Assert(len(l.ParamList), Equals, 2)
 	c.Assert(len(l.Stmts()), Equals, 1)
 
@@ -293,7 +296,17 @@ func (s *testParserSuite) TestParser0(c *C) {
 	src = "CREATE TABLE foo (a SMALLINT UNSIGNED, b INT UNSIGNED,); -- foo\nSelect --1 from foo;"
 	l = NewLexer(src)
 	l.SetPrepare()
-	ok = yyParse(l) == 0
-	c.Assert(ok, Equals, true)
+	c.Assert(yyParse(l), Equals, 0)
 	c.Assert(len(l.Stmts()), Equals, 2)
+
+	// Testcase for CONVERT(expr,type)
+	src = "SELECT CONVERT('111', SIGNED);"
+	l = NewLexer(src)
+	c.Assert(yyParse(l), Equals, 0)
+	st := l.Stmts()[0]
+	ss, ok := st.(*stmts.SelectStmt)
+	c.Assert(ok, IsTrue)
+	cv, ok := ss.Fields[0].Expr.(*expressions.FunctionCast)
+	c.Assert(ok, IsTrue)
+	c.Assert(cv.IsConvert, IsTrue)
 }