server, mysql: return correct column name and column label name (#7600)

Author: eurekaka

executor/adapter.go

@@ -65,14 +65,18 @@ func schema2ResultFields(schema *expression.Schema, defaultDB string) (rfs []*as
 		if dbName == "" && col.TblName.L != "" {
 			dbName = defaultDB
 		}
+		origColName := col.OrigColName
+		if origColName.L == "" {
+			origColName = col.ColName
+		}
 		rf := &ast.ResultField{
 			ColumnAsName: col.ColName,
 			TableAsName:  col.TblName,
 			DBName:       model.NewCIStr(dbName),
 			Table:        &model.TableInfo{Name: col.OrigTblName},
 			Column: &model.ColumnInfo{
 				FieldType: *col.RetType,
-				Name:      col.ColName,
+				Name:      origColName,
 			},
 		}
 		rfs = append(rfs, rf)

executor/executor_test.go

@@ -1768,26 +1768,31 @@ func (s *testSuite) TestColumnName(c *C) {
 	fields := rs.Fields()
 	c.Check(len(fields), Equals, 2)
 	c.Check(fields[0].Column.Name.L, Equals, "1 + c")
+	c.Check(fields[0].ColumnAsName.L, Equals, "1 + c")
 	c.Check(fields[1].Column.Name.L, Equals, "count(*)")
+	c.Check(fields[1].ColumnAsName.L, Equals, "count(*)")
 	rs, err = tk.Exec("select (c) > all (select c from t) from t")
 	c.Check(err, IsNil)
 	fields = rs.Fields()
 	c.Check(len(fields), Equals, 1)
 	c.Check(fields[0].Column.Name.L, Equals, "(c) > all (select c from t)")
+	c.Check(fields[0].ColumnAsName.L, Equals, "(c) > all (select c from t)")
 	tk.MustExec("begin")
 	tk.MustExec("insert t values(1,1)")
 	rs, err = tk.Exec("select c d, d c from t")
 	c.Check(err, IsNil)
 	fields = rs.Fields()
 	c.Check(len(fields), Equals, 2)
-	c.Check(fields[0].Column.Name.L, Equals, "d")
-	c.Check(fields[1].Column.Name.L, Equals, "c")
+	c.Check(fields[0].Column.Name.L, Equals, "c")
+	c.Check(fields[0].ColumnAsName.L, Equals, "d")
+	c.Check(fields[1].Column.Name.L, Equals, "d")
+	c.Check(fields[1].ColumnAsName.L, Equals, "c")
 	// Test case for query a column of a table.
 	// In this case, all attributes have values.
 	rs, err = tk.Exec("select c as a from t as t2")
 	c.Check(err, IsNil)
 	fields = rs.Fields()
-	c.Check(fields[0].Column.Name.L, Equals, "a")
+	c.Check(fields[0].Column.Name.L, Equals, "c")
 	c.Check(fields[0].ColumnAsName.L, Equals, "a")
 	c.Check(fields[0].Table.Name.L, Equals, "t")
 	c.Check(fields[0].TableAsName.L, Equals, "t2")

expression/column.go

@@ -142,6 +142,7 @@ func (col *CorrelatedColumn) resolveIndices(_ *Schema) {
 
 // Column represents a column.
 type Column struct {
+	OrigColName model.CIStr
 	ColName     model.CIStr
 	DBName      model.CIStr
 	OrigTblName model.CIStr

plan/logical_plan_builder.go

@@ -472,20 +472,22 @@ func (b *planBuilder) buildSelection(p LogicalPlan, where ast.ExprNode, AggMappe
 }
 
 // buildProjectionFieldNameFromColumns builds the field name, table name and database name when field expression is a column reference.
-func (b *planBuilder) buildProjectionFieldNameFromColumns(field *ast.SelectField, c *expression.Column) (colName, tblName, origTblName, dbName model.CIStr) {
+func (b *planBuilder) buildProjectionFieldNameFromColumns(field *ast.SelectField, c *expression.Column) (colName, origColName, tblName, origTblName, dbName model.CIStr) {
 	if astCol, ok := getInnerFromParentheses(field.Expr).(*ast.ColumnNameExpr); ok {
-		colName, tblName, dbName = astCol.Name.Name, astCol.Name.Table, astCol.Name.Schema
+		origColName, tblName, dbName = astCol.Name.Name, astCol.Name.Table, astCol.Name.Schema
 	}
 	if field.AsName.L != "" {
 		colName = field.AsName
+	} else {
+		colName = origColName
 	}
 	if tblName.L == "" {
 		tblName = c.TblName
 	}
 	if dbName.L == "" {
 		dbName = c.DBName
 	}
-	return colName, tblName, c.OrigTblName, c.DBName
+	return colName, origColName, tblName, c.OrigTblName, c.DBName
 }
 
 // buildProjectionFieldNameFromExpressions builds the field name when field expression is a normal expression.
@@ -531,10 +533,10 @@ func (b *planBuilder) buildProjectionFieldNameFromExpressions(field *ast.SelectF
 
 // buildProjectionField builds the field object according to SelectField in projection.
 func (b *planBuilder) buildProjectionField(id, position int, field *ast.SelectField, expr expression.Expression) *expression.Column {
-	var origTblName, tblName, colName, dbName model.CIStr
+	var origTblName, tblName, origColName, colName, dbName model.CIStr
 	if c, ok := expr.(*expression.Column); ok && !c.IsAggOrSubq {
 		// Field is a column reference.
-		colName, tblName, origTblName, dbName = b.buildProjectionFieldNameFromColumns(field, c)
+		colName, origColName, tblName, origTblName, dbName = b.buildProjectionFieldNameFromColumns(field, c)
 	} else if field.AsName.L != "" {
 		// Field has alias.
 		colName = field.AsName
@@ -547,6 +549,7 @@ func (b *planBuilder) buildProjectionField(id, position int, field *ast.SelectFi
 		TblName:     tblName,
 		OrigTblName: origTblName,
 		ColName:     colName,
+		OrigColName: origColName,
 		DBName:      dbName,
 		RetType:     expr.GetType(),
 	}