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.statistic;
  
  import org.apache.calcite.materialize.SqlStatisticProvider;
  import org.apache.calcite.plan.RelOptTable;
  import org.apache.calcite.util.ImmutableIntList;
  import org.apache.calcite.util.Util;
  
  import com.google.common.cache.Cache;
  import com.google.common.collect.ImmutableList;
  import com.google.common.util.concurrent.UncheckedExecutionException;
  
  import java.util.List;
  import java.util.concurrent.ExecutionException;
  
  /**
   * Implementation of {@link SqlStatisticProvider} that reads and writes a
   * cache.
   */
  public class CachingSqlStatisticProvider implements SqlStatisticProvider {
    private final SqlStatisticProvider provider;
    private final Cache<List, Object> cache;
  
    public CachingSqlStatisticProvider(SqlStatisticProvider provider,
        Cache<List, Object> cache) {
      super();
      this.provider = provider;
      this.cache = cache;
    }
  
    @Override public double tableCardinality(RelOptTable table) {
      try {
        final ImmutableList<Object> key =
            ImmutableList.of("tableCardinality",
                table.getQualifiedName());
        return (Double) cache.get(key,
            () -> provider.tableCardinality(table));
      } catch (UncheckedExecutionException | ExecutionException e) {
        throw Util.throwAsRuntime(Util.causeOrSelf(e));
      }
    }
  
    @Override public boolean isForeignKey(RelOptTable fromTable, List<Integer> fromColumns,
        RelOptTable toTable, List<Integer> toColumns) {
      try {
        final ImmutableList<Object> key =
            ImmutableList.of("isForeignKey",
                fromTable.getQualifiedName(),
                ImmutableIntList.copyOf(fromColumns),
                toTable.getQualifiedName(),
                ImmutableIntList.copyOf(toColumns));
        return (Boolean) cache.get(key,
            () -> provider.isForeignKey(fromTable, fromColumns, toTable,
                toColumns));
      } catch (UncheckedExecutionException | ExecutionException e) {
        throw Util.throwAsRuntime(Util.causeOrSelf(e));
      }
    }
  
    @Override public boolean isKey(RelOptTable table, List<Integer> columns) {
      try {
        final ImmutableList<Object> key =
            ImmutableList.of("isKey", table.getQualifiedName(),
                ImmutableIntList.copyOf(columns));
        return (Boolean) cache.get(key, () -> provider.isKey(table, columns));
      } catch (UncheckedExecutionException | ExecutionException e) {
        throw Util.throwAsRuntime(Util.causeOrSelf(e));
      }
    }
  }
  