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.materialize;
  
  import org.apache.calcite.plan.RelOptTable;
  import org.apache.calcite.util.mapping.IntPair;
  
  import com.google.common.collect.ImmutableList;
  
  import org.checkerframework.checker.initialization.qual.Initialized;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  
  import static com.google.common.base.Preconditions.checkArgument;
  
  import static java.util.Objects.requireNonNull;
  
  /** Source relation of a lattice.
   *
   * <p>Relations form a tree; all relations except the root relation
   * (the fact table) have precisely one parent and an equi-join
   * condition on one or more pairs of columns linking to it. */
  public abstract class LatticeNode {
    public final LatticeTable table;
    final int startCol;
    final int endCol;
    public final @Nullable String alias;
    private final ImmutableList<LatticeChildNode> children;
    public final String digest;
  
    /** Creates a LatticeNode.
     *
     * <p>The {@code parent} and {@code mutableNode} arguments are used only
     * during construction. */
    LatticeNode(LatticeSpace space, @Nullable LatticeNode parent, MutableNode mutableNode) {
      this.table = requireNonNull(mutableNode.table);
      this.startCol = mutableNode.startCol;
      this.endCol = mutableNode.endCol;
      this.alias = mutableNode.alias;
      checkArgument(startCol >= 0);
      checkArgument(endCol > startCol);
  
      final StringBuilder sb = new StringBuilder()
          .append(space.simpleName(table));
      if (parent != null) {
        sb.append(':');
        int i = 0;
        for (IntPair p : requireNonNull(mutableNode.step, "mutableNode.step").keys) {
          if (i++ > 0) {
            sb.append(",");
          }
          sb.append(space.fieldName(parent.table, p.source));
        }
      }
      if (mutableNode.children.isEmpty()) {
        this.children = ImmutableList.of();
      } else {
        sb.append(" (");
        final ImmutableList.Builder<LatticeChildNode> b = ImmutableList.builder();
        int i = 0;
        for (MutableNode mutableChild : mutableNode.children) {
          if (i++ > 0) {
            sb.append(' ');
          }
          @SuppressWarnings({"argument.type.incompatible", "assignment.type.incompatible"})
          final @Initialized LatticeChildNode node =
              new LatticeChildNode(space, this, mutableChild);
          sb.append(node.digest);
          b.add(node);
        }
        this.children = b.build();
        sb.append(")");
      }
      this.digest = sb.toString();
  
    }
  
    @Override public String toString() {
      return digest;
    }
  
    public RelOptTable relOptTable() {
      return table.t;
    }
  
    abstract void use(List<LatticeNode> usedNodes);
  
    void flattenTo(ImmutableList.Builder<LatticeNode> builder) {
      builder.add(this);
      for (LatticeChildNode child : children) {
        child.flattenTo(builder);
      }
    }
  
    void createPathsRecurse(LatticeSpace space, List<Step> steps,
        List<Path> paths) {
      paths.add(space.addPath(steps));
      for (LatticeChildNode child : children) {
        steps.add(space.addEdge(table, child.table, child.link));
        child.createPathsRecurse(space, steps, paths);
        steps.remove(steps.size() - 1);
      }
    }
  
  }
  