content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to you 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 org.apache.calcite.schema;
  
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeFactory;
  
  /**
   * Parameter to a {@link Function}.
   *
   * <p>NOTE: We'd have called it {@code Parameter} but the overlap with
   * {@link java.lang.reflect.Parameter} was too confusing.
   */
  public interface FunctionParameter {
    /**
     * Zero-based ordinal of this parameter within the member's parameter
     * list.
     *
     * @return Parameter ordinal
     */
    int getOrdinal();
  
    /**
     * Name of the parameter.
     *
     * @return Parameter name
     */
    String getName();
  
    /**
     * Returns the type of this parameter.
     *
     * @param typeFactory Type factory to be used to create the type
     *
     * @return Parameter type.
     */
    RelDataType getType(RelDataTypeFactory typeFactory);
  
    /**
     * Returns whether this parameter is optional.
     *
     * <p>If true, the value of the parameter can be supplied using the DEFAULT
     * SQL keyword, or it can be omitted from a function called using argument
     * assignment, or the function can be called with fewer parameters (if all
     * parameters after it are optional too).
     *
     * <p>If a parameter is optional its default value is NULL. We may in future
     * allow functions to specify other default values.
     */
    boolean isOptional();
  }
  