/*
 * Copyright © 2021 DataSQRL (contact@datasqrl.com)
 *
 * 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 com.datasqrl.function;

/**
 * A function that preserves one of its inputs, meaning it does not substantially change the value.
 *
 * <p>This is used in primary key and timestamp determination to identify when the value has been
 * preserved.
 */
public interface InputPreservingFunction extends FunctionMetadata {

  int preservedOperandIndex();
}
