core/src/main/java/org/apache/calcite/materialize/ProfilerLatticeStatisticProvider.java

/*
 * 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.materialize;

import org.apache.calcite.linq4j.Enumerable;
import org.apache.calcite.profile.Profiler;
import org.apache.calcite.profile.ProfilerImpl;
import org.apache.calcite.rel.metadata.NullSentinel;
import org.apache.calcite.schema.ScannableTable;
import org.apache.calcite.schema.Table;
import org.apache.calcite.util.ImmutableBitSet;

import com.google.common.base.Suppliers;
import com.google.common.collect.ImmutableList;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import java.util.function.Supplier;

/**
 * Implementation of {@link LatticeStatisticProvider} that uses a
 * {@link org.apache.calcite.profile.Profiler}.
 */
class ProfilerLatticeStatisticProvider implements LatticeStatisticProvider {
  static final Factory FACTORY = ProfilerLatticeStatisticProvider::new;

  private final Supplier<Profiler.Profile> profile;

  /** Creates a ProfilerLatticeStatisticProvider. */
  private ProfilerLatticeStatisticProvider(Lattice lattice) {
    Objects.requireNonNull(lattice);
    this.profile = Suppliers.memoize(() -> {
      final ProfilerImpl profiler =
          ProfilerImpl.builder()
              .withPassSize(200)
              .withMinimumSurprise(0.3D)
              .build();
      final List<Profiler.Column> columns = new ArrayList<>();
      for (Lattice.Column column : lattice.columns) {
        columns.add(new Profiler.Column(column.ordinal, column.alias));
      }
      final String sql =
          lattice.sql(ImmutableBitSet.range(lattice.columns.size()),
              false, ImmutableList.of());
      final Table table =
          new MaterializationService.DefaultTableFactory()
              .createTable(lattice.rootSchema, sql, ImmutableList.of());
      final ImmutableList<ImmutableBitSet> initialGroups =
          ImmutableList.of();
      final Enumerable<List<Comparable>> rows =
          ((ScannableTable) table).scan(null)
              .select(values -> {
                for (int i = 0; i < values.length; i++) {
                  if (values[i] == null) {
                    values[i] = NullSentinel.INSTANCE;
                  }
                }
                //noinspection unchecked
                return (List<Comparable>) (List) Arrays.asList(values);
              });
      return profiler.profile(rows, columns, initialGroups);
    })::get;
  }

  public double cardinality(List<Lattice.Column> columns) {
    final ImmutableBitSet build = Lattice.Column.toBitSet(columns);
    final double cardinality = profile.get().cardinality(build);
//    System.out.println(columns + ": " + cardinality);
    return cardinality;
  }
}

// End ProfilerLatticeStatisticProvider.java