Add support for IS NULL expressions with records

sql/expression/isnull.go

@@ -54,6 +54,17 @@ func (e *IsNull) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
 		return nil, err
 	}
 
+	// Slices of typed values (e.g. Record and Composite types in Postgres) evaluate
+	// to NULL if all of their entries are NULL.
+	if tupleValue, ok := v.([]types.TupleValue); ok {
+		for _, typedValue := range tupleValue {
+			if typedValue.Value != nil {
+				return false, nil
+			}
+		}
+		return true, nil
+	}
+
 	return v == nil, nil
 }
 

sql/types/tuple_value.go

@@ -0,0 +1,24 @@
+// Copyright 2025 Dolthub, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package types
+
+import "github.com/dolthub/go-mysql-server/sql"
+
+// TupleValue represents a value and its associated type information. TupleValue is used by collections of
+// values where the type information is not consistent across all values (e.g. Records in Postgres).
+type TupleValue struct {
+	Value any
+	Type  sql.Type
+}