Add transformUp method to expressions (#27)

Author: ajnavarro

sql/expression.go

@@ -5,4 +5,5 @@ type Expression interface {
 	Type() Type
 	Name() string
 	Eval(Row) interface{}
+	TransformUp(func(Expression) Expression) Expression
 }

sql/expression/boolean.go

@@ -21,3 +21,10 @@ func (e Not) Eval(row sql.Row) interface{} {
 func (e Not) Name() string {
 	return "Not(" + e.Child.Name() + ")"
 }
+
+func (e *Not) TransformUp(f func(sql.Expression) sql.Expression) sql.Expression {
+	c := e.UnaryExpression.Child.TransformUp(f)
+	n := &Not{UnaryExpression{c}}
+
+	return f(n)
+}

sql/expression/comparison.go

@@ -35,6 +35,13 @@ func (e Equals) Eval(row sql.Row) interface{} {
 	return e.ChildType.Compare(a, b) == 0
 }
 
+func (c *Equals) TransformUp(f func(sql.Expression) sql.Expression) sql.Expression {
+	lc := c.BinaryExpression.Left.TransformUp(f)
+	rc := c.BinaryExpression.Right.TransformUp(f)
+
+	return f(NewEquals(lc, rc))
+}
+
 type GreaterThan struct {
 	Comparison
 }
@@ -51,6 +58,13 @@ func (e GreaterThan) Eval(row sql.Row) interface{} {
 	return e.ChildType.Compare(a, b) == 1
 }
 
+func (c *GreaterThan) TransformUp(f func(sql.Expression) sql.Expression) sql.Expression {
+	lc := c.BinaryExpression.Left.TransformUp(f)
+	rc := c.BinaryExpression.Right.TransformUp(f)
+
+	return f(NewGreaterThan(lc, rc))
+}
+
 type LessThan struct {
 	Comparison
 }
@@ -67,6 +81,13 @@ func (e LessThan) Eval(row sql.Row) interface{} {
 	return e.ChildType.Compare(a, b) == -1
 }
 
+func (c *LessThan) TransformUp(f func(sql.Expression) sql.Expression) sql.Expression {
+	lc := c.BinaryExpression.Left.TransformUp(f)
+	rc := c.BinaryExpression.Right.TransformUp(f)
+
+	return f(NewLessThan(lc, rc))
+}
+
 type GreaterThanOrEqual struct {
 	Comparison
 }
@@ -83,6 +104,13 @@ func (e GreaterThanOrEqual) Eval(row sql.Row) interface{} {
 	return e.ChildType.Compare(a, b) > -1
 }
 
+func (c *GreaterThanOrEqual) TransformUp(f func(sql.Expression) sql.Expression) sql.Expression {
+	lc := c.BinaryExpression.Left.TransformUp(f)
+	rc := c.BinaryExpression.Right.TransformUp(f)
+
+	return f(NewGreaterThanOrEqual(lc, rc))
+}
+
 type LessThanOrEqual struct {
 	Comparison
 }
@@ -99,6 +127,13 @@ func (e LessThanOrEqual) Eval(row sql.Row) interface{} {
 	return e.ChildType.Compare(a, b) < 1
 }
 
+func (c *LessThanOrEqual) TransformUp(f func(sql.Expression) sql.Expression) sql.Expression {
+	lc := c.BinaryExpression.Left.TransformUp(f)
+	rc := c.BinaryExpression.Right.TransformUp(f)
+
+	return f(NewLessThanOrEqual(lc, rc))
+}
+
 func checkEqualTypes(a sql.Expression, b sql.Expression) {
 	if a.Resolved() && b.Resolved() && a.Type() != b.Type() {
 		panic(fmt.Errorf("both types should be equal: %v and %v\n", a, b))

sql/expression/get_field.go

@@ -31,3 +31,8 @@ func (p GetField) Eval(row sql.Row) interface{} {
 func (p GetField) Name() string {
 	return p.fieldName
 }
+
+func (p *GetField) TransformUp(f func(sql.Expression) sql.Expression) sql.Expression {
+	n := *p
+	return f(&n)
+}

sql/expression/literal.go

@@ -31,3 +31,8 @@ func (p Literal) Eval(row sql.Row) interface{} {
 func (p Literal) Name() string {
 	return p.name
 }
+
+func (p *Literal) TransformUp(f func(sql.Expression) sql.Expression) sql.Expression {
+	n := *p
+	return f(&n)
+}

sql/expression/unresolved.go

@@ -25,3 +25,8 @@ func (c UnresolvedColumn) Name() string {
 func (UnresolvedColumn) Eval(r sql.Row) interface{} {
 	return "FAIL" //FIXME
 }
+
+func (p *UnresolvedColumn) TransformUp(f func(sql.Expression) sql.Expression) sql.Expression {
+	n := *p
+	return f(&n)
+}