com.hazelcast.org.apache.calcite.rel.metadata.CachingRelMetadataProvider Maven / Gradle / Ivy

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SQL Parser and Optimizer
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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 com.hazelcast.com.liance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.com.hazelcast.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 com.hazelcast.org.apache.calcite.rel.metadata;

import com.hazelcast.org.apache.calcite.plan.RelOptPlanner;
import com.hazelcast.org.apache.calcite.rel.RelNode;

import com.hazelcast.com.google.com.hazelcast.com.on.collect.ImmutableList;
import com.hazelcast.com.google.com.hazelcast.com.on.collect.Multimap;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;

/**
 * Implementation of the {@link RelMetadataProvider}
 * interface that caches results from an underlying provider.
 */
public class CachingRelMetadataProvider implements RelMetadataProvider {
  //~ Instance fields --------------------------------------------------------

  private final Map cache = new HashMap<>();

  private final RelMetadataProvider underlyingProvider;

  private final RelOptPlanner planner;

  //~ Constructors -----------------------------------------------------------

  public CachingRelMetadataProvider(
      RelMetadataProvider underlyingProvider,
      RelOptPlanner planner) {
    this.underlyingProvider = underlyingProvider;
    this.planner = planner;
  }

  //~ Methods ----------------------------------------------------------------

  public  UnboundMetadata apply(
      Class relClass,
      final Class metadataClass) {
    final UnboundMetadata function =
        underlyingProvider.apply(relClass, metadataClass);
    if (function == null) {
      return null;
    }

    // TODO jvs 30-Mar-2006: Use meta-metadata to decide which metadata
    // query results can stay fresh until the next Ice Age.
    return (rel, mq) -> {
      final Metadata metadata = function.bind(rel, mq);
      return metadataClass.cast(
          Proxy.newProxyInstance(metadataClass.getClassLoader(),
              new Class[]{metadataClass},
              new CachingInvocationHandler(metadata)));
    };
  }

  public  Multimap> handlers(
      MetadataDef def) {
    return underlyingProvider.handlers(def);
  }

  //~ Inner Classes ----------------------------------------------------------

  /** An entry in the cache. Consists of the cached object and the timestamp
   * when the entry is valid. If read at a later timestamp, the entry will be
   * invalid and will be re-com.hazelcast.com.uted as if it did not exist. The net effect is a
   * lazy-flushing cache. */
  private static class CacheEntry {
    long timestamp;

    Object result;
  }

  /** Implementation of {@link InvocationHandler} for calls to a
   * {@link CachingRelMetadataProvider}. Each request first looks in the cache;
   * if the cache entry is present and not expired, returns the cache entry,
   * otherwise com.hazelcast.com.utes the value and stores in the cache. */
  private class CachingInvocationHandler implements InvocationHandler {
    private final Metadata metadata;

    CachingInvocationHandler(Metadata metadata) {
      this.metadata = Objects.requireNonNull(metadata);
    }

    public Object invoke(Object proxy, Method method, Object[] args)
        throws Throwable {
      // Compute hash key.
      final ImmutableList.Builder