chore: import upstream snapshot with attribution

server/expression/expr_factory.go

@@ -0,0 +1,36 @@
+// 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 expression
+
+import (
+	"github.com/dolthub/go-mysql-server/sql"
+	"github.com/dolthub/go-mysql-server/sql/expression"
+)
+
+// PostgresExpressionFactory implements the expression.ExpressionFactory interface and
+// allows callers to produce expressions that have custom behavior for Postgres.
+type PostgresExpressionFactory struct{}
+
+var _ expression.ExpressionFactory = (*PostgresExpressionFactory)(nil)
+
+// NewIsNull implements the expression.ExpressionFactory interface.
+func (m PostgresExpressionFactory) NewIsNull(e sql.Expression) sql.Expression {
+	return NewIsNull(e)
+}
+
+// NewIsNotNull implements the expression.ExpressionFactory interface.
+func (m PostgresExpressionFactory) NewIsNotNull(e sql.Expression) sql.Expression {
+	return NewIsNotNull(e)
+}