Fixed problems with StrExpr, which was being used for other purposes by Doltgres query execution

Author: zachmu

sql/plan/str_expr.go

@@ -13,7 +13,7 @@ func AliasSubqueryString(e sql.Expression) string {
 	e, _, err := transform.Expr(e, func(e sql.Expression) (sql.Expression, transform.TreeIdentity, error) {
 		switch e := e.(type) {
 		case *Subquery:
-			return NewSubquery(NewStrExpr(e.QueryString), e.QueryString), transform.NewTree, nil
+			return NewSubquery(NewStrExpr(e.QueryString, e), e.QueryString), transform.NewTree, nil
 		default:
 			return e, transform.SameTree, nil
 		}
@@ -33,57 +33,49 @@ func AliasSubqueryString(e sql.Expression) string {
 }
 
 // StrExpr is used exclusively for overriding the .String()
-// method of a node.
+// method of a subquery expression for efficiency and display purposes.
 type StrExpr struct {
-	s string
+	s        string
+	original *Subquery
 }
 
 var _ sql.Node = (*StrExpr)(nil)
 
+func NewStrExpr(s string, orig *Subquery) *StrExpr {
+	return &StrExpr{
+		s:        s,
+		original: orig,
+	}
+}
+
 func (s *StrExpr) Schema() sql.Schema {
-	//TODO implement me
-	panic("implement me")
+	return s.original.Query.Schema()
 }
 
 func (s *StrExpr) Children() []sql.Node {
-	//TODO implement me
-	panic("implement me")
+	panic("StrExpr.Children should never be called")
 }
 
 func (s *StrExpr) WithChildren(children ...sql.Node) (sql.Node, error) {
-	//TODO implement me
-	panic("implement me")
+	panic("StrExpr.WithChildren should never be called")
 }
 
 func (s *StrExpr) IsReadOnly() bool {
-	//TODO implement me
-	panic("implement me")
-}
-
-func NewStrExpr(s string) *StrExpr {
-	return &StrExpr{s: s}
+	panic("StrExpr.IsReadOnly should never be called")
 }
 
 func (s *StrExpr) Resolved() bool {
-	//TODO implement me
-	panic("implement me")
+	return s.original.Resolved()
 }
 
 func (s *StrExpr) String() string {
 	return s.s
 }
 
-func (s *StrExpr) Type() sql.Type {
-	//TODO implement me
-	panic("implement me")
-}
-
 func (s *StrExpr) IsNullable() bool {
-	//TODO implement me
-	panic("implement me")
+	panic("StrExpr.IsNullable should never be called")
 }
 
 func (s *StrExpr) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
-	//TODO implement me
-	panic("implement me")
+	panic("StrExpr.Eval should never be called")
 }