org.apache.calcite.linq4j.QueryProviderImpl Maven / Gradle / Ivy

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/*
 * 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}.
 *
 * Derived class needs to implement {@link #executeQuery}.
 */
public abstract class QueryProviderImpl implements QueryProvider {
  /**
   * Creates a QueryProviderImpl.
   */
  protected QueryProviderImpl() {
    super();
  }

  @Override public  Queryable createQuery(Expression expression, Class rowType) {
    return new QueryableImpl<>(this, rowType, expression);
  }

  @Override public  Queryable createQuery(Expression expression, Type rowType) {
    return new QueryableImpl<>(this, rowType, expression);
  }

  @Override public  T execute(Expression expression, Class type) {
    throw new UnsupportedOperationException();
  }

  @Override public  T execute(Expression expression, Type type) {
    throw new UnsupportedOperationException();
  }

  /**
   * Binds an expression to this query provider.
   *
   * @param  element type
   */
  public static class QueryableImpl extends BaseQueryable {
    public QueryableImpl(QueryProviderImpl provider, Type elementType,
        Expression expression) {
      super(provider, elementType, expression);
    }

    @Override public String toString() {
      return "Queryable(expr=" + expression + ")";
    }
  }
}