org.apache.calcite.linq4j.RawQueryable 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 org.checkerframework.checker.nullness.qual.Nullable;
import org.checkerframework.framework.qual.Covariant;

import java.lang.reflect.Type;

/**
 * Core methods that define a {@link Queryable}.
 *
 * The other methods in {@link Queryable}, defined in
 * {@link ExtendedQueryable}, can easily be implemented by calling the
 * corresponding static methods in {@link Extensions}.
 *
 * @param  Element type
 */
@Covariant(0)
public interface RawQueryable extends Enumerable {
  /**
   * Gets the type of the element(s) that are returned when the expression
   * tree associated with this Queryable is executed.
   */
  Type getElementType();

  /**
   * Gets the expression tree that is associated with this Queryable.
   * @return null if the expression is not available
   */
  @Nullable Expression getExpression();

  /**
   * Gets the query provider that is associated with this data source.
   */
  QueryProvider getProvider();
}