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.sql.type;
  
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeFactory;
  import org.apache.calcite.rel.type.RelProtoDataType;
  import org.apache.calcite.sql.SqlOperatorBinding;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * A {@link SqlReturnTypeInference} which always returns the same SQL type.
   */
  public class ExplicitReturnTypeInference implements SqlReturnTypeInference {
    //~ Instance fields --------------------------------------------------------
  
    protected final RelProtoDataType protoType;
  
    //~ Constructors -----------------------------------------------------------
  
    /**
     * Creates an inference rule which always returns the same type object.
     *
     * <p>If the requesting type factory is different, returns a copy of the
     * type object made using {@link RelDataTypeFactory#copyType(RelDataType)}
     * within the requesting type factory.
     *
     * <p>A copy of the type is required because each statement is prepared using
     * a different type factory; each type factory maintains its own cache of
     * canonical instances of each type.
     *
     * @param protoType Type object
     */
    protected ExplicitReturnTypeInference(RelProtoDataType protoType) {
      this.protoType = requireNonNull(protoType, "protoType");
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public RelDataType inferReturnType(SqlOperatorBinding opBinding) {
      return protoType.apply(opBinding.getTypeFactory());
    }
  }
  