com.hazelcast.org.apache.calcite.rel.metadata.ChainedRelMetadataProvider 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 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.rel.RelNode;
import com.hazelcast.org.apache.calcite.util.Util;

import com.hazelcast.com.google.com.hazelcast.com.on.collect.ImmutableList;
import com.hazelcast.com.google.com.hazelcast.com.on.collect.ImmutableMultimap;
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.ArrayList;
import java.util.List;

/**
 * Implementation of the {@link RelMetadataProvider}
 * interface via the
 * {@link com.hazelcast.org.apache.calcite.util.Glossary#CHAIN_OF_RESPONSIBILITY_PATTERN}.
 *
 * When a consumer calls the {@link #apply} method to ask for a provider
 * for a particular type of {@link RelNode} and {@link Metadata}, scans the list
 * of underlying providers.
 */
public class ChainedRelMetadataProvider implements RelMetadataProvider {
  //~ Instance fields --------------------------------------------------------

  private final ImmutableList providers;

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

  /**
   * Creates a chain.
   */
  protected ChainedRelMetadataProvider(
      ImmutableList providers) {
    this.providers = providers;
    assert !providers.contains(this);
  }

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

  @Override public boolean equals(Object obj) {
    return obj == this
        || obj instanceof ChainedRelMetadataProvider
        && providers.equals(((ChainedRelMetadataProvider) obj).providers);
  }

  @Override public int hashCode() {
    return providers.hashCode();
  }

  public  UnboundMetadata apply(
      Class relClass,
      final Class metadataClass) {
    final List> functions = new ArrayList<>();
    for (RelMetadataProvider provider : providers) {
      final UnboundMetadata function =
          provider.apply(relClass, metadataClass);
      if (function == null) {
        continue;
      }
      functions.add(function);
    }
    switch (functions.size()) {
    case 0:
      return null;
    case 1:
      return functions.get(0);
    default:
      return (rel, mq) -> {
        final List metadataList = new ArrayList<>();
        for (UnboundMetadata function : functions) {
          final Metadata metadata = function.bind(rel, mq);
          if (metadata != null) {
            metadataList.add(metadata);
          }
        }
        return metadataClass.cast(
            Proxy.newProxyInstance(metadataClass.getClassLoader(),
                new Class[]{metadataClass},
                new ChainedInvocationHandler(metadataList)));
      };
    }
  }

  public  Multimap> handlers(
      MetadataDef def) {
    final ImmutableMultimap.Builder> builder =
        ImmutableMultimap.builder();
    for (RelMetadataProvider provider : providers.reverse()) {
      builder.putAll(provider.handlers(def));
    }
    return builder.build();
  }

  /** Creates a chain. */
  public static RelMetadataProvider of(List list) {
    return new ChainedRelMetadataProvider(ImmutableList.copyOf(list));
  }

  /** Invocation handler that calls a list of {@link Metadata} objects,
   * returning the first non-null value. */
  private static class ChainedInvocationHandler implements InvocationHandler {
    private final List metadataList;

    ChainedInvocationHandler(List metadataList) {
      this.metadataList = ImmutableList.copyOf(metadataList);
    }

    public Object invoke(Object proxy, Method method, Object[] args)
        throws Throwable {
      for (Metadata metadata : metadataList) {
        try {
          final Object o = method.invoke(metadata, args);
          if (o != null) {
            return o;
          }
        } catch (InvocationTargetException e) {
          if (e.getCause() instanceof CyclicMetadataException) {
            continue;
          }
          Util.throwIfUnchecked(e.getCause());
          throw new RuntimeException(e.getCause());
        }
      }
      return null;
    }
  }
}