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.linq4j;
  
  import org.apache.calcite.linq4j.tree.Expression;
  
  import java.lang.reflect.Type;
  
  /**
   * Partial implementation of {@link QueryProvider}.
   *
   * <p>Derived class needs to implement {@link #executeQuery}.
   */
  public abstract class QueryProviderImpl implements QueryProvider {
    /**
     * Creates a QueryProviderImpl.
     */
    protected QueryProviderImpl() {
      super();
    }
  
    @Override public <T> Queryable<T> createQuery(Expression expression, Class<T> rowType) {
      return new QueryableImpl<>(this, rowType, expression);
    }
  
    @Override public <T> Queryable<T> createQuery(Expression expression, Type rowType) {
      return new QueryableImpl<>(this, rowType, expression);
    }
  
    @Override public <T> T execute(Expression expression, Class<T> type) {
      throw new UnsupportedOperationException();
    }
  
    @Override public <T> T execute(Expression expression, Type type) {
      throw new UnsupportedOperationException();
    }
  
    /**
     * Binds an expression to this query provider.
     *
     * @param <T> element type
     */
    public static class QueryableImpl<T> extends BaseQueryable<T> {
      public QueryableImpl(QueryProviderImpl provider, Type elementType,
          Expression expression) {
        super(provider, elementType, expression);
      }
  
      @Override public String toString() {
        return "Queryable(expr=" + expression + ")";
      }
    }
  }
  