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Posted to commits@hive.apache.org by jc...@apache.org on 2017/07/13 18:21:00 UTC

[09/10] hive git commit: HIVE-16888: Upgrade Calcite to 1.13 and Avatica to 1.10 (Remus Rusanu and Jesus Camacho Rodriguez, reviewed by Ashutosh Chauhan)

http://git-wip-us.apache.org/repos/asf/hive/blob/4a567f86/ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/views/SubstitutionVisitor.java
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diff --git a/ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/views/SubstitutionVisitor.java b/ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/views/SubstitutionVisitor.java
deleted file mode 100644
index 93dcc0e..0000000
--- a/ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/views/SubstitutionVisitor.java
+++ /dev/null
@@ -1,2458 +0,0 @@
-/**
- * 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.hadoop.hive.ql.optimizer.calcite.rules.views;
-
-import static org.apache.calcite.rex.RexUtil.andNot;
-import static org.apache.calcite.rex.RexUtil.removeAll;
-import static org.apache.calcite.rex.RexUtil.simplify;
-
-import java.util.AbstractList;
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.Objects;
-import java.util.Set;
-
-import org.apache.calcite.avatica.util.Spaces;
-import org.apache.calcite.linq4j.Ord;
-import org.apache.calcite.plan.RelOptCluster;
-import org.apache.calcite.plan.RelOptRule;
-import org.apache.calcite.plan.RelOptRuleCall;
-import org.apache.calcite.plan.RelOptUtil;
-import org.apache.calcite.plan.RexImplicationChecker;
-import org.apache.calcite.rel.RelCollation;
-import org.apache.calcite.rel.RelNode;
-import org.apache.calcite.rel.SingleRel;
-import org.apache.calcite.rel.core.Aggregate;
-import org.apache.calcite.rel.core.AggregateCall;
-import org.apache.calcite.rel.core.CorrelationId;
-import org.apache.calcite.rel.core.Filter;
-import org.apache.calcite.rel.core.Join;
-import org.apache.calcite.rel.core.JoinRelType;
-import org.apache.calcite.rel.core.Project;
-import org.apache.calcite.rel.core.RelFactories;
-import org.apache.calcite.rel.core.Sort;
-import org.apache.calcite.rel.core.TableScan;
-import org.apache.calcite.rel.core.Values;
-import org.apache.calcite.rel.logical.LogicalAggregate;
-import org.apache.calcite.rel.logical.LogicalJoin;
-import org.apache.calcite.rel.logical.LogicalSort;
-import org.apache.calcite.rel.logical.LogicalUnion;
-import org.apache.calcite.rel.type.RelDataType;
-import org.apache.calcite.rel.type.RelDataTypeField;
-import org.apache.calcite.rex.RexBuilder;
-import org.apache.calcite.rex.RexCall;
-import org.apache.calcite.rex.RexExecutorImpl;
-import org.apache.calcite.rex.RexInputRef;
-import org.apache.calcite.rex.RexLiteral;
-import org.apache.calcite.rex.RexNode;
-import org.apache.calcite.rex.RexShuttle;
-import org.apache.calcite.rex.RexUtil;
-import org.apache.calcite.sql.SqlAggFunction;
-import org.apache.calcite.sql.fun.SqlStdOperatorTable;
-import org.apache.calcite.sql.validate.SqlValidatorUtil;
-import org.apache.calcite.tools.RelBuilder;
-import org.apache.calcite.tools.RelBuilderFactory;
-import org.apache.calcite.util.Bug;
-import org.apache.calcite.util.ControlFlowException;
-import org.apache.calcite.util.ImmutableBitSet;
-import org.apache.calcite.util.Litmus;
-import org.apache.calcite.util.Pair;
-import org.apache.calcite.util.Util;
-import org.apache.calcite.util.mapping.Mapping;
-import org.apache.calcite.util.mapping.Mappings;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import com.google.common.annotations.VisibleForTesting;
-import com.google.common.base.Equivalence;
-import com.google.common.base.Function;
-import com.google.common.base.Preconditions;
-import com.google.common.base.Predicate;
-import com.google.common.collect.ImmutableList;
-import com.google.common.collect.ImmutableSet;
-import com.google.common.collect.LinkedHashMultimap;
-import com.google.common.collect.Lists;
-import com.google.common.collect.Maps;
-import com.google.common.collect.Multimap;
-import com.google.common.collect.Sets;
-
-/**
- * Substitutes part of a tree of relational expressions with another tree.
- *
- * <p>The call {@code new SubstitutionVisitor(target, query).go(replacement))}
- * will return {@code query} with every occurrence of {@code target} replaced
- * by {@code replacement}.</p>
- *
- * <p>The following example shows how {@code SubstitutionVisitor} can be used
- * for materialized view recognition.</p>
- *
- * <ul>
- * <li>query = SELECT a, c FROM t WHERE x = 5 AND b = 4</li>
- * <li>target = SELECT a, b, c FROM t WHERE x = 5</li>
- * <li>replacement = SELECT * FROM mv</li>
- * <li>result = SELECT a, c FROM mv WHERE b = 4</li>
- * </ul>
- *
- * <p>Note that {@code result} uses the materialized view table {@code mv} and a
- * simplified condition {@code b = 4}.</p>
- *
- * <p>Uses a bottom-up matching algorithm. Nodes do not need to be identical.
- * At each level, returns the residue.</p>
- *
- * <p>The inputs must only include the core relational operators:
- * {@link org.apache.calcite.rel.logical.LogicalTableScan},
- * {@link org.apache.calcite.rel.logical.LogicalFilter},
- * {@link org.apache.calcite.rel.logical.LogicalProject},
- * {@link org.apache.calcite.rel.logical.LogicalJoin},
- * {@link org.apache.calcite.rel.logical.LogicalUnion},
- * {@link org.apache.calcite.rel.logical.LogicalAggregate}.</p>
- *
- * TODO: Remove when we upgrade to Calcite version using builders.
- */
-public class SubstitutionVisitor {
-
-  private static final Logger LOGGER = LoggerFactory.getLogger(SubstitutionVisitor.class);
-
-  /** Equivalence that compares objects by their {@link Object#toString()}
-   * method. */
-  private static final Equivalence<Object> STRING_EQUIVALENCE =
-      new Equivalence<Object>() {
-        @Override protected boolean doEquivalent(Object o, Object o2) {
-          return o.toString().equals(o2.toString());
-        }
-
-        @Override protected int doHash(Object o) {
-          return o.toString().hashCode();
-        }
-      };
-
-  /** Equivalence that compares {@link Lists}s by the
-   * {@link Object#toString()} of their elements. */
-  @SuppressWarnings("unchecked")
-  private static final Equivalence<List<?>> PAIRWISE_STRING_EQUIVALENCE =
-      (Equivalence) STRING_EQUIVALENCE.pairwise();
-
-  protected static final ImmutableList<UnifyRule> DEFAULT_RULES =
-      ImmutableList.<UnifyRule>of(
-          TrivialRule.INSTANCE,
-          ScanToProjectUnifyRule.INSTANCE,
-          ProjectToProjectUnifyRule.INSTANCE,
-          FilterToProjectUnifyRule.INSTANCE,
-//          ProjectToFilterUnifyRule.INSTANCE,
-//          FilterToFilterUnifyRule.INSTANCE,
-          AggregateToAggregateUnifyRule.INSTANCE,
-          AggregateOnProjectToAggregateUnifyRule.INSTANCE);
-
-  /**
-   * Factory for a builder for relational expressions.
-   * <p>The actual builder is available via {@link RelOptRuleCall#builder()}.
-   */
-  protected final RelBuilder relBuilder;
-
-  private final ImmutableList<UnifyRule> rules;
-  private final Map<Pair<Class, Class>, List<UnifyRule>> ruleMap =
-      new HashMap<>();
-  private final RelOptCluster cluster;
-  private final Holder query;
-  private final MutableRel target;
-
-  /**
-   * Nodes in {@link #target} that have no children.
-   */
-  final List<MutableRel> targetLeaves;
-
-  /**
-   * Nodes in {@link #query} that have no children.
-   */
-  final List<MutableRel> queryLeaves;
-
-  final Map<MutableRel, MutableRel> replacementMap = new HashMap<>();
-
-  final Multimap<MutableRel, MutableRel> equivalents =
-      LinkedHashMultimap.create();
-
-  /** Workspace while rule is being matched.
-   * Careful, re-entrant!
-   * Assumes no rule needs more than 2 slots. */
-  protected final MutableRel[] slots = new MutableRel[2];
-
-  /** Creates a SubstitutionVisitor with the default rule set. */
-  public SubstitutionVisitor(RelNode target_, RelNode query_) {
-    this(target_, query_, DEFAULT_RULES);
-  }
-
-  public SubstitutionVisitor(RelNode target_, RelNode query_,
-          ImmutableList<UnifyRule> rules) {
-    this(target_, query_, rules, RelFactories.LOGICAL_BUILDER);
-  }
-
-  /** Creates a SubstitutionVisitor. */
-  public SubstitutionVisitor(RelNode target_, RelNode query_,
-      ImmutableList<UnifyRule> rules, RelBuilderFactory relBuilderFactory) {
-    this.cluster = target_.getCluster();
-    this.rules = rules;
-    this.query = Holder.of(toMutable(query_));
-    this.target = toMutable(target_);
-    this.relBuilder = relBuilderFactory.create(cluster, null);
-    final Set<MutableRel> parents = Sets.newIdentityHashSet();
-    final List<MutableRel> allNodes = new ArrayList<>();
-    final MutableRelVisitor visitor =
-        new MutableRelVisitor() {
-          public void visit(MutableRel node) {
-            parents.add(node.parent);
-            allNodes.add(node);
-            super.visit(node);
-          }
-        };
-    visitor.go(target);
-
-    // Populate the list of leaves in the tree under "target".
-    // Leaves are all nodes that are not parents.
-    // For determinism, it is important that the list is in scan order.
-    allNodes.removeAll(parents);
-    targetLeaves = ImmutableList.copyOf(allNodes);
-
-    allNodes.clear();
-    parents.clear();
-    visitor.go(query);
-    allNodes.removeAll(parents);
-    queryLeaves = ImmutableList.copyOf(allNodes);
-  }
-
-  private static MutableRel toMutable(RelNode rel) {
-    if (rel instanceof TableScan) {
-      return MutableScan.of((TableScan) rel);
-    }
-    if (rel instanceof Values) {
-      return MutableValues.of((Values) rel);
-    }
-    if (rel instanceof Project) {
-      final Project project = (Project) rel;
-      final MutableRel input = toMutable(project.getInput());
-      return MutableProject.of(input, project.getProjects(),
-          project.getRowType().getFieldNames());
-    }
-    if (rel instanceof Filter) {
-      final Filter filter = (Filter) rel;
-      final MutableRel input = toMutable(filter.getInput());
-      return MutableFilter.of(input, filter.getCondition());
-    }
-    if (rel instanceof Aggregate) {
-      final Aggregate aggregate = (Aggregate) rel;
-      final MutableRel input = toMutable(aggregate.getInput());
-      return MutableAggregate.of(input, aggregate.indicator,
-          aggregate.getGroupSet(), aggregate.getGroupSets(),
-          aggregate.getAggCallList());
-    }
-    if (rel instanceof Join) {
-      final Join join = (Join) rel;
-      final MutableRel left = toMutable(join.getLeft());
-      final MutableRel right = toMutable(join.getRight());
-      return MutableJoin.of(join.getCluster(), left, right,
-          join.getCondition(), join.getJoinType(), join.getVariablesSet());
-    }
-    if (rel instanceof Sort) {
-      final Sort sort = (Sort) rel;
-      final MutableRel input = toMutable(sort.getInput());
-      return MutableSort.of(input, sort.getCollation(), sort.offset, sort.fetch);
-    }
-    throw new RuntimeException("cannot translate " + rel + " to MutableRel");
-  }
-
-  void register(MutableRel result, MutableRel query) {
-  }
-
-  /**
-   * Maps a condition onto a target.
-   *
-   * <p>If condition is stronger than target, returns the residue.
-   * If it is equal to target, returns the expression that evaluates to
-   * the constant {@code true}. If it is weaker than target, returns
-   * {@code null}.</p>
-   *
-   * <p>The terms satisfy the relation</p>
-   *
-   * <pre>
-   *     {@code condition = target AND residue}
-   * </pre>
-   *
-   * <p>and {@code residue} must be as weak as possible.</p>
-   *
-   * <p>Example #1: condition stronger than target</p>
-   * <ul>
-   * <li>condition: x = 1 AND y = 2</li>
-   * <li>target: x = 1</li>
-   * <li>residue: y = 2</li>
-   * </ul>
-   *
-   * <p>Note that residue {@code x &gt; 0 AND y = 2} would also satisfy the
-   * relation {@code condition = target AND residue} but is stronger than
-   * necessary, so we prefer {@code y = 2}.</p>
-   *
-   * <p>Example #2: target weaker than condition (valid, but not currently
-   * implemented)</p>
-   * <ul>
-   * <li>condition: x = 1</li>
-   * <li>target: x = 1 OR z = 3</li>
-   * <li>residue: NOT (z = 3)</li>
-   * </ul>
-   *
-   * <p>Example #3: condition and target are equivalent</p>
-   * <ul>
-   * <li>condition: x = 1 AND y = 2</li>
-   * <li>target: y = 2 AND x = 1</li>
-   * <li>residue: TRUE</li>
-   * </ul>
-   *
-   * <p>Example #4: condition weaker than target</p>
-   * <ul>
-   * <li>condition: x = 1</li>
-   * <li>target: x = 1 AND y = 2</li>
-   * <li>residue: null (i.e. no match)</li>
-   * </ul>
-   *
-   * <p>There are many other possible examples. It amounts to solving
-   * whether {@code condition AND NOT target} can ever evaluate to
-   * true, and therefore is a form of the NP-complete
-   * <a href="http://en.wikipedia.org/wiki/Satisfiability">Satisfiability</a>
-   * problem.</p>
-   */
-  @VisibleForTesting
-  public static RexNode splitFilter(
-      final RexBuilder rexBuilder, RexNode condition, RexNode target) {
-    // First, try splitting into ORs.
-    // Given target    c1 OR c2 OR c3 OR c4
-    // and condition   c2 OR c4
-    // residue is      NOT c1 AND NOT c3
-    // Also deals with case target [x] condition [x] yields residue [true].
-    RexNode z = splitOr(rexBuilder, condition, target);
-    if (z != null) {
-      return z;
-    }
-
-    RexNode x = andNot(rexBuilder, target, condition);
-    if (mayBeSatisfiable(x)) {
-      RexNode x2 = andNot(rexBuilder, condition, target);
-      return simplify(rexBuilder, x2);
-    }
-    return null;
-  }
-
-  private static RexNode splitOr(
-      final RexBuilder rexBuilder, RexNode condition, RexNode target) {
-    List<RexNode> targets = RelOptUtil.disjunctions(target);
-    for (RexNode e : RelOptUtil.disjunctions(condition)) {
-      boolean found = removeAll(targets, e);
-      if (!found) {
-        return null;
-      }
-    }
-    return RexUtil.composeConjunction(rexBuilder,
-        Lists.transform(targets, RexUtil.notFn(rexBuilder)), false);
-  }
-
-  /**
-   * Returns whether a boolean expression ever returns true.
-   *
-   * <p>This method may give false positives. For instance, it will say
-   * that {@code x = 5 AND x > 10} is satisfiable, because at present it
-   * cannot prove that it is not.</p>
-   */
-  public static boolean mayBeSatisfiable(RexNode e) {
-    // Example:
-    //  e: x = 1 AND y = 2 AND z = 3 AND NOT (x = 1 AND y = 2)
-    //  disjunctions: {x = 1, y = 2, z = 3}
-    //  notDisjunctions: {x = 1 AND y = 2}
-    final List<RexNode> disjunctions = new ArrayList<>();
-    final List<RexNode> notDisjunctions = new ArrayList<>();
-    RelOptUtil.decomposeConjunction(e, disjunctions, notDisjunctions);
-
-    // If there is a single FALSE or NOT TRUE, the whole expression is
-    // always false.
-    for (RexNode disjunction : disjunctions) {
-      switch (disjunction.getKind()) {
-      case LITERAL:
-        if (!RexLiteral.booleanValue(disjunction)) {
-          return false;
-        }
-      }
-    }
-    for (RexNode disjunction : notDisjunctions) {
-      switch (disjunction.getKind()) {
-      case LITERAL:
-        if (RexLiteral.booleanValue(disjunction)) {
-          return false;
-        }
-      }
-    }
-    // If one of the not-disjunctions is a disjunction that is wholly
-    // contained in the disjunctions list, the expression is not
-    // satisfiable.
-    //
-    // Example #1. x AND y AND z AND NOT (x AND y)  - not satisfiable
-    // Example #2. x AND y AND NOT (x AND y)        - not satisfiable
-    // Example #3. x AND y AND NOT (x AND y AND z)  - may be satisfiable
-    for (RexNode notDisjunction : notDisjunctions) {
-      final List<RexNode> disjunctions2 =
-          RelOptUtil.conjunctions(notDisjunction);
-      if (disjunctions.containsAll(disjunctions2)) {
-        return false;
-      }
-    }
-    return true;
-  }
-
-  public RelNode go0(RelNode replacement_) {
-    assert false; // not called
-    MutableRel replacement = toMutable(replacement_);
-    assert MutableRels.equalType(
-        "target", target, "replacement", replacement, Litmus.THROW);
-    replacementMap.put(target, replacement);
-    final UnifyResult unifyResult = matchRecurse(target);
-    if (unifyResult == null) {
-      return null;
-    }
-    final MutableRel node0 = unifyResult.result;
-    MutableRel node = node0; // replaceAncestors(node0);
-    if (LOGGER.isDebugEnabled()) {
-      LOGGER.debug("Convert: query:\n"
-          + query.deep()
-          + "\nunify.query:\n"
-          + unifyResult.call.query.deep()
-          + "\nunify.result:\n"
-          + unifyResult.result.deep()
-          + "\nunify.target:\n"
-          + unifyResult.call.target.deep()
-          + "\nnode0:\n"
-          + node0.deep()
-          + "\nnode:\n"
-          + node.deep());
-    }
-    return fromMutable(node);
-  }
-
-  /**
-   * Returns a list of all possible rels that result from substituting the
-   * matched RelNode with the replacement RelNode within the query.
-   *
-   * <p>For example, the substitution result of A join B, while A and B
-   * are both a qualified match for replacement R, is R join B, R join R,
-   * A join R.
-   */
-  public List<RelNode> go(RelNode replacement_) {
-    List<List<Replacement>> matches = go(toMutable(replacement_));
-    if (matches.isEmpty()) {
-      return ImmutableList.of();
-    }
-    List<RelNode> sub = Lists.newArrayList();
-    sub.add(fromMutable(query.input));
-    reverseSubstitute(query, matches, sub, 0, matches.size());
-    return sub;
-  }
-
-  /**
-   * Substitutes the query with replacement whenever possible but meanwhile
-   * keeps track of all the substitutions and their original rel before
-   * replacement, so that in later processing stage, the replacement can be
-   * recovered individually to produce a list of all possible rels with
-   * substitution in different places.
-   */
-  private List<List<Replacement>> go(MutableRel replacement) {
-    assert MutableRels.equalType(
-        "target", target, "replacement", replacement, Litmus.THROW);
-    final List<MutableRel> queryDescendants = MutableRels.descendants(query);
-    final List<MutableRel> targetDescendants = MutableRels.descendants(target);
-
-    // Populate "equivalents" with (q, t) for each query descendant q and
-    // target descendant t that are equal.
-    final Map<MutableRel, MutableRel> map = Maps.newHashMap();
-    for (MutableRel queryDescendant : queryDescendants) {
-      map.put(queryDescendant, queryDescendant);
-    }
-    for (MutableRel targetDescendant : targetDescendants) {
-      MutableRel queryDescendant = map.get(targetDescendant);
-      if (queryDescendant != null) {
-        assert queryDescendant.rowType.equals(targetDescendant.rowType);
-        equivalents.put(queryDescendant, targetDescendant);
-      }
-    }
-    map.clear();
-
-    final List<Replacement> attempted = Lists.newArrayList();
-    List<List<Replacement>> substitutions = Lists.newArrayList();
-
-    for (;;) {
-      int count = 0;
-      MutableRel queryDescendant = query;
-    outer:
-      while (queryDescendant != null) {
-        for (Replacement r : attempted) {
-          if (queryDescendant == r.after) {
-            // This node has been replaced by previous iterations in the
-            // hope to match its ancestors, so the node itself should not
-            // be matched again.
-            queryDescendant = MutableRels.preOrderTraverseNext(queryDescendant);
-            continue outer;
-          }
-        }
-        final MutableRel next = MutableRels.preOrderTraverseNext(queryDescendant);
-        final MutableRel childOrNext =
-            queryDescendant.getInputs().isEmpty()
-                ? next : queryDescendant.getInputs().get(0);
-        for (MutableRel targetDescendant : targetDescendants) {
-          for (UnifyRule rule
-              : applicableRules(queryDescendant, targetDescendant)) {
-            UnifyRuleCall call =
-                rule.match(this, queryDescendant, targetDescendant);
-            if (call != null) {
-              final UnifyResult result = rule.apply(call);
-              if (result != null) {
-                ++count;
-                attempted.add(new Replacement(result.call.query, result.result));
-                MutableRel parent = result.call.query.replaceInParent(result.result);
-
-                // Replace previous equivalents with new equivalents, higher up
-                // the tree.
-                for (int i = 0; i < rule.slotCount; i++) {
-                  Collection<MutableRel> equi = equivalents.get(slots[i]);
-                  if (!equi.isEmpty()) {
-                    equivalents.remove(slots[i], equi.iterator().next());
-                  }
-                }
-                assert result.result.rowType.equals(result.call.query.rowType)
-                    : Pair.of(result.result, result.call.query);
-                equivalents.put(result.result, result.call.query);
-                if (targetDescendant == target) {
-                  // A real substitution happens. We purge the attempted
-                  // replacement list and add them into substitution list.
-                  // Meanwhile we stop matching the descendants and jump
-                  // to the next subtree in pre-order traversal.
-                  if (!target.equals(replacement)) {
-                    Replacement r = MutableRels.replace(
-                        query.input, target, copyMutable(replacement));
-                    assert r != null
-                        : rule + "should have returned a result containing the target.";
-                    attempted.add(r);
-                  }
-                  substitutions.add(ImmutableList.copyOf(attempted));
-                  attempted.clear();
-                  queryDescendant = next;
-                  continue outer;
-                }
-                // We will try walking the query tree all over again to see
-                // if there can be any substitutions after the replacement
-                // attempt.
-                break outer;
-              }
-            }
-          }
-        }
-        queryDescendant = childOrNext;
-      }
-      // Quit the entire loop if:
-      // 1) we have walked the entire query tree with one or more successful
-      //    substitutions, thus count != 0 && attempted.isEmpty();
-      // 2) we have walked the entire query tree but have made no replacement
-      //    attempt, thus count == 0 && attempted.isEmpty();
-      // 3) we had done some replacement attempt in a previous walk, but in
-      //    this one we have not found any potential matches or substitutions,
-      //    thus count == 0 && !attempted.isEmpty().
-      if (count == 0 || attempted.isEmpty()) {
-        break;
-      }
-    }
-    if (!attempted.isEmpty()) {
-      // We had done some replacement attempt in the previous walk, but that
-      // did not lead to any substitutions in this walk, so we need to recover
-      // the replacement.
-      undoReplacement(attempted);
-    }
-    return substitutions;
-  }
-
-  /**
-   * Represents a replacement action: before &rarr; after.
-   */
-  private static class Replacement {
-    final MutableRel before;
-    final MutableRel after;
-
-    Replacement(MutableRel before, MutableRel after) {
-      this.before = before;
-      this.after = after;
-    }
-  }
-
-  private static void undoReplacement(List<Replacement> replacement) {
-    for (int i = replacement.size() - 1; i >= 0; i--) {
-      Replacement r = replacement.get(i);
-      r.after.replaceInParent(r.before);
-    }
-  }
-
-  private static void redoReplacement(List<Replacement> replacement) {
-    for (Replacement r : replacement) {
-      r.before.replaceInParent(r.after);
-    }
-  }
-
-  private void reverseSubstitute(Holder query,
-      List<List<Replacement>> matches, List<RelNode> sub,
-      int replaceCount, int maxCount) {
-    if (matches.isEmpty()) {
-      return;
-    }
-    final List<List<Replacement>> rem = matches.subList(1, matches.size());
-    reverseSubstitute(query, rem, sub, replaceCount, maxCount);
-    undoReplacement(matches.get(0));
-    if (++replaceCount < maxCount) {
-      sub.add(fromMutable(query.input));
-    }
-    reverseSubstitute(query, rem, sub, replaceCount, maxCount);
-    redoReplacement(matches.get(0));
-  }
-
-  private List<RelNode> fromMutables(List<MutableRel> nodes) {
-    return Lists.transform(nodes,
-        new Function<MutableRel, RelNode>() {
-          public RelNode apply(MutableRel mutableRel) {
-            return fromMutable(mutableRel);
-          }
-        });
-  }
-
-  private RelNode fromMutable(MutableRel node) {
-    switch (node.type) {
-    case SCAN:
-    case VALUES:
-      return ((MutableLeafRel) node).rel;
-    case PROJECT:
-      final MutableProject project = (MutableProject) node;
-      relBuilder.push(fromMutable(project.input));
-      relBuilder.project(project.projects);
-      return relBuilder.build();
-    case FILTER:
-      final MutableFilter filter = (MutableFilter) node;
-      relBuilder.push(fromMutable(filter.input));
-      relBuilder.filter(filter.condition);
-      return relBuilder.build();
-    case AGGREGATE:
-      final MutableAggregate aggregate = (MutableAggregate) node;
-      return LogicalAggregate.create(fromMutable(aggregate.input),
-          aggregate.indicator, aggregate.groupSet, aggregate.groupSets,
-          aggregate.aggCalls);
-    case SORT:
-      final MutableSort sort = (MutableSort) node;
-      return LogicalSort.create(fromMutable(sort.input), sort.collation,
-          sort.offset, sort.fetch);
-    case UNION:
-      final MutableUnion union = (MutableUnion) node;
-      return LogicalUnion.create(fromMutables(union.inputs), union.all);
-    case JOIN:
-      final MutableJoin join = (MutableJoin) node;
-      return LogicalJoin.create(fromMutable(join.getLeft()), fromMutable(join.getRight()),
-          join.getCondition(), join.getVariablesSet(), join.getJoinType());
-    default:
-      throw new AssertionError(node.deep());
-    }
-  }
-
-  private static List<MutableRel> copyMutables(List<MutableRel> nodes) {
-    return Lists.transform(nodes,
-        new Function<MutableRel, MutableRel>() {
-          public MutableRel apply(MutableRel mutableRel) {
-            return copyMutable(mutableRel);
-          }
-        });
-  }
-
-  private static MutableRel copyMutable(MutableRel node) {
-    switch (node.type) {
-    case SCAN:
-      return MutableScan.of((TableScan) ((MutableScan) node).rel);
-    case VALUES:
-      return MutableValues.of((Values) ((MutableValues) node).rel);
-    case PROJECT:
-      final MutableProject project = (MutableProject) node;
-      return MutableProject.of(project.rowType,
-          copyMutable(project.input), project.projects);
-    case FILTER:
-      final MutableFilter filter = (MutableFilter) node;
-      return MutableFilter.of(copyMutable(filter.input), filter.condition);
-    case AGGREGATE:
-      final MutableAggregate aggregate = (MutableAggregate) node;
-      return MutableAggregate.of(copyMutable(aggregate.input),
-          aggregate.indicator, aggregate.groupSet, aggregate.groupSets,
-          aggregate.aggCalls);
-    case SORT:
-      final MutableSort sort = (MutableSort) node;
-      return MutableSort.of(copyMutable(sort.input), sort.collation,
-          sort.offset, sort.fetch);
-    case UNION:
-      final MutableUnion union = (MutableUnion) node;
-      return MutableUnion.of(copyMutables(union.inputs), union.all);
-    case JOIN:
-      final MutableJoin join = (MutableJoin) node;
-      return MutableJoin.of(join.cluster, copyMutable(join.getLeft()),
-          copyMutable(join.getRight()), join.getCondition(), join.getJoinType(),
-          join.getVariablesSet());
-    default:
-      throw new AssertionError(node.deep());
-    }
-  }
-
-  private UnifyResult matchRecurse(MutableRel target) {
-    assert false; // not called
-    final List<MutableRel> targetInputs = target.getInputs();
-    MutableRel queryParent = null;
-
-    for (MutableRel targetInput : targetInputs) {
-      UnifyResult unifyResult = matchRecurse(targetInput);
-      if (unifyResult == null) {
-        return null;
-      }
-      queryParent = unifyResult.call.query.replaceInParent(unifyResult.result);
-    }
-
-    if (targetInputs.isEmpty()) {
-      for (MutableRel queryLeaf : queryLeaves) {
-        for (UnifyRule rule : applicableRules(queryLeaf, target)) {
-          final UnifyResult x = apply(rule, queryLeaf, target);
-          if (x != null) {
-            if (LOGGER.isDebugEnabled()) {
-              LOGGER.debug("Rule: " + rule
-                  + "\nQuery:\n"
-                  + queryParent
-                  + (x.call.query != queryParent
-                     ? "\nQuery (original):\n"
-                     + queryParent
-                     : "")
-                  + "\nTarget:\n"
-                  + target.deep()
-                  + "\nResult:\n"
-                  + x.result.deep()
-                  + "\n");
-            }
-            return x;
-          }
-        }
-      }
-    } else {
-      assert queryParent != null;
-      for (UnifyRule rule : applicableRules(queryParent, target)) {
-        final UnifyResult x = apply(rule, queryParent, target);
-        if (x != null) {
-          if (LOGGER.isDebugEnabled()) {
-            LOGGER.debug(
-                "Rule: " + rule
-                + "\nQuery:\n"
-                + queryParent.deep()
-                + (x.call.query != queryParent
-                   ? "\nQuery (original):\n"
-                   + queryParent.toString()
-                   : "")
-                + "\nTarget:\n"
-                + target.deep()
-                + "\nResult:\n"
-                + x.result.deep()
-                + "\n");
-          }
-          return x;
-        }
-      }
-    }
-    if (LOGGER.isDebugEnabled()) {
-      LOGGER.debug(
-          "Unify failed:"
-          + "\nQuery:\n"
-          + queryParent.toString()
-          + "\nTarget:\n"
-          + target.toString()
-          + "\n");
-    }
-    return null;
-  }
-
-  private UnifyResult apply(UnifyRule rule, MutableRel query,
-      MutableRel target) {
-    final UnifyRuleCall call = new UnifyRuleCall(rule, query, target, null);
-    return rule.apply(call);
-  }
-
-  private List<UnifyRule> applicableRules(MutableRel query,
-      MutableRel target) {
-    final Class queryClass = query.getClass();
-    final Class targetClass = target.getClass();
-    final Pair<Class, Class> key = Pair.of(queryClass, targetClass);
-    List<UnifyRule> list = ruleMap.get(key);
-    if (list == null) {
-      final ImmutableList.Builder<UnifyRule> builder =
-          ImmutableList.builder();
-      for (UnifyRule rule : rules) {
-        //noinspection unchecked
-        if (mightMatch(rule, queryClass, targetClass)) {
-          builder.add(rule);
-        }
-      }
-      list = builder.build();
-      ruleMap.put(key, list);
-    }
-    return list;
-  }
-
-  private static boolean mightMatch(UnifyRule rule,
-      Class queryClass, Class targetClass) {
-    return rule.queryOperand.clazz.isAssignableFrom(queryClass)
-        && rule.targetOperand.clazz.isAssignableFrom(targetClass);
-  }
-
-  /** Exception thrown to exit a matcher. Not really an error. */
-  protected static class MatchFailed extends ControlFlowException {
-    @SuppressWarnings("ThrowableInstanceNeverThrown")
-    public static final MatchFailed INSTANCE = new MatchFailed();
-  }
-
-  /** Rule that attempts to match a query relational expression
-   * against a target relational expression.
-   *
-   * <p>The rule declares the query and target types; this allows the
-   * engine to fire only a few rules in a given context.</p>
-   */
-  protected abstract static class UnifyRule {
-    protected final int slotCount;
-    protected final Operand queryOperand;
-    protected final Operand targetOperand;
-
-    protected UnifyRule(int slotCount, Operand queryOperand,
-        Operand targetOperand) {
-      this.slotCount = slotCount;
-      this.queryOperand = queryOperand;
-      this.targetOperand = targetOperand;
-    }
-
-    /**
-     * <p>Applies this rule to a particular node in a query. The goal is
-     * to convert {@code query} into {@code target}. Before the rule is
-     * invoked, Calcite has made sure that query's children are equivalent
-     * to target's children.
-     *
-     * <p>There are 3 possible outcomes:</p>
-     *
-     * <ul>
-     *
-     * <li>{@code query} already exactly matches {@code target}; returns
-     * {@code target}</li>
-     *
-     * <li>{@code query} is sufficiently close to a match for
-     * {@code target}; returns {@code target}</li>
-     *
-     * <li>{@code query} cannot be made to match {@code target}; returns
-     * null</li>
-     *
-     * </ul>
-     *
-     * <p>REVIEW: Is possible that we match query PLUS one or more of its
-     * ancestors?</p>
-     *
-     * @param call Input parameters
-     */
-    protected abstract UnifyResult apply(UnifyRuleCall call);
-
-    protected UnifyRuleCall match(SubstitutionVisitor visitor, MutableRel query,
-        MutableRel target) {
-      if (queryOperand.matches(visitor, query)) {
-        if (targetOperand.matches(visitor, target)) {
-          return visitor.new UnifyRuleCall(this, query, target,
-              copy(visitor.slots, slotCount));
-        }
-      }
-      return null;
-    }
-
-    protected <E> ImmutableList<E> copy(E[] slots, int slotCount) {
-      // Optimize if there are 0 or 1 slots.
-      switch (slotCount) {
-      case 0:
-        return ImmutableList.of();
-      case 1:
-        return ImmutableList.of(slots[0]);
-      default:
-        return ImmutableList.copyOf(slots).subList(0, slotCount);
-      }
-    }
-  }
-
-  /**
-   * Arguments to an application of a {@link UnifyRule}.
-   */
-  protected class UnifyRuleCall {
-    protected final UnifyRule rule;
-    public final MutableRel query;
-    public final MutableRel target;
-    protected final ImmutableList<MutableRel> slots;
-
-    public UnifyRuleCall(UnifyRule rule, MutableRel query, MutableRel target,
-        ImmutableList<MutableRel> slots) {
-      this.rule = Preconditions.checkNotNull(rule);
-      this.query = Preconditions.checkNotNull(query);
-      this.target = Preconditions.checkNotNull(target);
-      this.slots = Preconditions.checkNotNull(slots);
-    }
-
-    public UnifyResult result(MutableRel result) {
-      assert MutableRels.contains(result, target);
-      assert MutableRels.equalType("result", result, "query", query,
-          Litmus.THROW);
-      MutableRel replace = replacementMap.get(target);
-      if (replace != null) {
-        assert false; // replacementMap is always empty
-        // result =
-        MutableRels.replace(result, target, replace);
-      }
-      register(result, query);
-      return new UnifyResult(this, result);
-    }
-
-    /**
-     * Creates a {@link UnifyRuleCall} based on the parent of {@code query}.
-     */
-    public UnifyRuleCall create(MutableRel query) {
-      return new UnifyRuleCall(rule, query, target, slots);
-    }
-
-    public RelOptCluster getCluster() {
-      return cluster;
-    }
-  }
-
-  /**
-   * Result of an application of a {@link UnifyRule} indicating that the
-   * rule successfully matched {@code query} against {@code target} and
-   * generated a {@code result} that is equivalent to {@code query} and
-   * contains {@code target}.
-   */
-  protected static class UnifyResult {
-    private final UnifyRuleCall call;
-    // equivalent to "query", contains "result"
-    private final MutableRel result;
-
-    UnifyResult(UnifyRuleCall call, MutableRel result) {
-      this.call = call;
-      assert MutableRels.equalType("query", call.query, "result", result,
-          Litmus.THROW);
-      this.result = result;
-    }
-  }
-
-  /** Abstract base class for implementing {@link UnifyRule}. */
-  protected abstract static class AbstractUnifyRule extends UnifyRule {
-    public AbstractUnifyRule(Operand queryOperand, Operand targetOperand,
-        int slotCount) {
-      super(slotCount, queryOperand, targetOperand);
-      //noinspection AssertWithSideEffects
-      assert isValid();
-    }
-
-    protected boolean isValid() {
-      final SlotCounter slotCounter = new SlotCounter();
-      slotCounter.visit(queryOperand);
-      assert slotCounter.queryCount == slotCount;
-      assert slotCounter.targetCount == 0;
-      slotCounter.queryCount = 0;
-      slotCounter.visit(targetOperand);
-      assert slotCounter.queryCount == 0;
-      assert slotCounter.targetCount == slotCount;
-      return true;
-    }
-
-    /** Creates an operand with given inputs. */
-    protected static Operand operand(Class<? extends MutableRel> clazz,
-        Operand... inputOperands) {
-      return new InternalOperand(clazz, ImmutableList.copyOf(inputOperands));
-    }
-
-    /** Creates an operand that doesn't check inputs. */
-    protected static Operand any(Class<? extends MutableRel> clazz) {
-      return new AnyOperand(clazz);
-    }
-
-    /** Creates an operand that matches a relational expression in the query. */
-    protected static Operand query(int ordinal) {
-      return new QueryOperand(ordinal);
-    }
-
-    /** Creates an operand that matches a relational expression in the
-     * target. */
-    protected static Operand target(int ordinal) {
-      return new TargetOperand(ordinal);
-    }
-  }
-
-  /** Implementation of {@link UnifyRule} that matches if the query is already
-   * equal to the target.
-   *
-   * <p>Matches scans to the same table, because these will be
-   * {@link MutableScan}s with the same
-   * {@link org.apache.calcite.rel.logical.LogicalTableScan} instance.</p>
-   */
-  private static class TrivialRule extends AbstractUnifyRule {
-    private static final TrivialRule INSTANCE = new TrivialRule();
-
-    private TrivialRule() {
-      super(any(MutableRel.class), any(MutableRel.class), 0);
-    }
-
-    public UnifyResult apply(UnifyRuleCall call) {
-      if (call.query.equals(call.target)) {
-        return call.result(call.query);
-      }
-      return null;
-    }
-  }
-
-  /** Implementation of {@link UnifyRule} that matches
-   * {@link org.apache.calcite.rel.logical.LogicalTableScan}. */
-  private static class ScanToProjectUnifyRule extends AbstractUnifyRule {
-    public static final ScanToProjectUnifyRule INSTANCE =
-        new ScanToProjectUnifyRule();
-
-    private ScanToProjectUnifyRule() {
-      super(any(MutableScan.class),
-          any(MutableProject.class), 0);
-    }
-
-    public UnifyResult apply(UnifyRuleCall call) {
-      final MutableProject target = (MutableProject) call.target;
-      final MutableScan query = (MutableScan) call.query;
-      // We do not need to check query's parent type to avoid duplication
-      // of ProjectToProjectUnifyRule or FilterToProjectUnifyRule, since
-      // SubstitutionVisitor performs a top-down match.
-      if (!query.equals(target.getInput())) {
-        return null;
-      }
-      final RexShuttle shuttle = getRexShuttle(target);
-      final RexBuilder rexBuilder = target.cluster.getRexBuilder();
-      final List<RexNode> newProjects;
-      try {
-        newProjects = (List<RexNode>)
-            shuttle.apply(rexBuilder.identityProjects(query.getRowType()));
-      } catch (MatchFailed e) {
-        return null;
-      }
-      final MutableProject newProject =
-          MutableProject.of(
-              query.getRowType(), target, newProjects);
-      final MutableRel newProject2 = MutableRels.strip(newProject);
-      return call.result(newProject2);
-    }
-  }
-
-  /** Implementation of {@link UnifyRule} that matches
-   * {@link org.apache.calcite.rel.logical.LogicalProject}. */
-  private static class ProjectToProjectUnifyRule extends AbstractUnifyRule {
-    public static final ProjectToProjectUnifyRule INSTANCE =
-        new ProjectToProjectUnifyRule();
-
-    private ProjectToProjectUnifyRule() {
-      super(operand(MutableProject.class, query(0)),
-          operand(MutableProject.class, target(0)), 1);
-    }
-
-    public UnifyResult apply(UnifyRuleCall call) {
-      final MutableProject target = (MutableProject) call.target;
-      final MutableProject query = (MutableProject) call.query;
-      final RexShuttle shuttle = getRexShuttle(target);
-      final List<RexNode> newProjects;
-      try {
-        newProjects = shuttle.apply(query.getProjects());
-      } catch (MatchFailed e) {
-        return null;
-      }
-      final MutableProject newProject =
-          MutableProject.of(
-              query.getRowType(), target, newProjects);
-      final MutableRel newProject2 = MutableRels.strip(newProject);
-      return call.result(newProject2);
-    }
-  }
-
-
-  /** Implementation of {@link UnifyRule} that matches a {@link MutableFilter}
-   * to a {@link MutableProject}. */
-  private static class FilterToProjectUnifyRule extends AbstractUnifyRule {
-    public static final FilterToProjectUnifyRule INSTANCE =
-        new FilterToProjectUnifyRule();
-
-    private FilterToProjectUnifyRule() {
-      super(operand(MutableFilter.class, query(0)),
-          operand(MutableProject.class, target(0)), 1);
-    }
-
-    public UnifyResult apply(UnifyRuleCall call) {
-      // Child of projectTarget is equivalent to child of filterQuery.
-      try {
-        // TODO: make sure that constants are ok
-        final MutableProject target = (MutableProject) call.target;
-        final RexShuttle shuttle = getRexShuttle(target);
-        final RexNode newCondition;
-        final MutableFilter query = (MutableFilter) call.query;
-        try {
-          newCondition = query.getCondition().accept(shuttle);
-        } catch (MatchFailed e) {
-          return null;
-        }
-        final MutableFilter newFilter = MutableFilter.of(target, newCondition);
-        if (query.parent instanceof MutableProject) {
-          final MutableRel inverse =
-              invert(((MutableProject) query.parent).getNamedProjects(),
-                  newFilter, shuttle);
-          return call.create(query.parent).result(inverse);
-        } else {
-          final MutableRel inverse = invert(query, newFilter, target);
-          return call.result(inverse);
-        }
-      } catch (MatchFailed e) {
-        return null;
-      }
-    }
-
-    protected MutableRel invert(List<Pair<RexNode, String>> namedProjects,
-        MutableRel input,
-        RexShuttle shuttle) {
-      LOGGER.trace("SubstitutionVisitor: invert:\nprojects: {}\ninput: {}\nproject: {}\n",
-          namedProjects, input, shuttle);
-      final List<RexNode> exprList = new ArrayList<>();
-      final RexBuilder rexBuilder = input.cluster.getRexBuilder();
-      final List<RexNode> projects = Pair.left(namedProjects);
-      for (RexNode expr : projects) {
-        exprList.add(rexBuilder.makeZeroLiteral(expr.getType()));
-      }
-      for (Ord<RexNode> expr : Ord.zip(projects)) {
-        final RexNode node = expr.e.accept(shuttle);
-        if (node == null) {
-          throw MatchFailed.INSTANCE;
-        }
-        exprList.set(expr.i, node);
-      }
-      return MutableProject.of(input, exprList, Pair.right(namedProjects));
-    }
-
-    protected MutableRel invert(MutableRel model, MutableRel input,
-        MutableProject project) {
-      LOGGER.trace("SubstitutionVisitor: invert:\nmodel: {}\ninput: {}\nproject: {}\n",
-          model, input, project);
-      if (project.getProjects().size() < model.getRowType().getFieldCount()) {
-        throw MatchFailed.INSTANCE;
-      }
-      final List<RexNode> exprList = new ArrayList<>();
-      final RexBuilder rexBuilder = model.cluster.getRexBuilder();
-      for (RelDataTypeField field : model.getRowType().getFieldList()) {
-        exprList.add(rexBuilder.makeZeroLiteral(field.getType()));
-      }
-      for (Ord<RexNode> expr : Ord.zip(project.getProjects())) {
-        if (expr.e instanceof RexInputRef) {
-          final int target = ((RexInputRef) expr.e).getIndex();
-          exprList.set(target,
-              rexBuilder.ensureType(expr.e.getType(),
-                  RexInputRef.of(expr.i, input.rowType),
-                  false));
-        } else {
-          throw MatchFailed.INSTANCE;
-        }
-      }
-      return MutableProject.of(model.rowType, input, exprList);
-    }
-  }
-
-  /** Implementation of {@link UnifyRule} that matches a
-   * {@link MutableFilter}. */
-  private static class FilterToFilterUnifyRule extends AbstractUnifyRule {
-    public static final FilterToFilterUnifyRule INSTANCE =
-        new FilterToFilterUnifyRule();
-
-    private FilterToFilterUnifyRule() {
-      super(operand(MutableFilter.class, query(0)),
-          operand(MutableFilter.class, target(0)), 1);
-    }
-
-    public UnifyResult apply(UnifyRuleCall call) {
-      // in.query can be rewritten in terms of in.target if its condition
-      // is weaker. For example:
-      //   query: SELECT * FROM t WHERE x = 1 AND y = 2
-      //   target: SELECT * FROM t WHERE x = 1
-      // transforms to
-      //   result: SELECT * FROM (target) WHERE y = 2
-      final MutableFilter query = (MutableFilter) call.query;
-      final MutableFilter target = (MutableFilter) call.target;
-      final MutableFilter newFilter =
-          createFilter(query, target);
-      if (newFilter == null) {
-        return null;
-      }
-      return call.result(newFilter);
-    }
-
-    MutableFilter createFilter(MutableFilter query, MutableFilter target) {
-      final RexNode newCondition =
-          splitFilter(query.cluster.getRexBuilder(), query.getCondition(),
-              target.getCondition());
-      if (newCondition == null) {
-        // Could not map query onto target.
-        return null;
-      }
-      if (newCondition.isAlwaysTrue()) {
-        return target;
-      }
-      return MutableFilter.of(target, newCondition);
-    }
-  }
-
-  /** Implementation of {@link UnifyRule} that matches a {@link MutableProject}
-   * to a {@link MutableFilter}. */
-  private static class ProjectToFilterUnifyRule extends AbstractUnifyRule {
-    public static final ProjectToFilterUnifyRule INSTANCE =
-        new ProjectToFilterUnifyRule();
-
-    private ProjectToFilterUnifyRule() {
-      super(operand(MutableProject.class, query(0)),
-          operand(MutableFilter.class, target(0)), 1);
-    }
-
-    public UnifyResult apply(UnifyRuleCall call) {
-      if (call.query.parent instanceof MutableFilter) {
-        final UnifyRuleCall in2 = call.create(call.query.parent);
-        final MutableFilter query = (MutableFilter) in2.query;
-        final MutableFilter target = (MutableFilter) in2.target;
-        final MutableFilter newFilter =
-            FilterToFilterUnifyRule.INSTANCE.createFilter(
-                query, target);
-        if (newFilter == null) {
-          return null;
-        }
-        return in2.result(query.replaceInParent(newFilter));
-      }
-      return null;
-    }
-  }
-
-  /** Implementation of {@link UnifyRule} that matches a
-   * {@link org.apache.calcite.rel.logical.LogicalAggregate} to a
-   * {@link org.apache.calcite.rel.logical.LogicalAggregate}, provided
-   * that they have the same child. */
-  private static class AggregateToAggregateUnifyRule extends AbstractUnifyRule {
-    public static final AggregateToAggregateUnifyRule INSTANCE =
-        new AggregateToAggregateUnifyRule();
-
-    private AggregateToAggregateUnifyRule() {
-      super(operand(MutableAggregate.class, query(0)),
-          operand(MutableAggregate.class, target(0)), 1);
-    }
-
-    public UnifyResult apply(UnifyRuleCall call) {
-      final MutableAggregate query = (MutableAggregate) call.query;
-      final MutableAggregate target = (MutableAggregate) call.target;
-      assert query != target;
-      // in.query can be rewritten in terms of in.target if its groupSet is
-      // a subset, and its aggCalls are a superset. For example:
-      //   query: SELECT x, COUNT(b) FROM t GROUP BY x
-      //   target: SELECT x, y, SUM(a) AS s, COUNT(b) AS cb FROM t GROUP BY x, y
-      // transforms to
-      //   result: SELECT x, SUM(cb) FROM (target) GROUP BY x
-      if (!target.getGroupSet().contains(query.getGroupSet())) {
-        return null;
-      }
-      MutableRel result = unifyAggregates(query, target);
-      if (result == null) {
-        return null;
-      }
-      return call.result(result);
-    }
-  }
-
-  public static MutableAggregate permute(MutableAggregate aggregate,
-      MutableRel input, Mapping mapping) {
-    ImmutableBitSet groupSet = Mappings.apply(mapping, aggregate.getGroupSet());
-    ImmutableList<ImmutableBitSet> groupSets =
-        Mappings.apply2(mapping, aggregate.getGroupSets());
-    List<AggregateCall> aggregateCalls =
-        apply(mapping, aggregate.getAggCallList());
-    return MutableAggregate.of(input, aggregate.indicator, groupSet, groupSets,
-        aggregateCalls);
-  }
-
-  private static List<AggregateCall> apply(final Mapping mapping,
-      List<AggregateCall> aggCallList) {
-    return Lists.transform(aggCallList,
-        new Function<AggregateCall, AggregateCall>() {
-          public AggregateCall apply(AggregateCall call) {
-            return call.copy(Mappings.apply2(mapping, call.getArgList()),
-                Mappings.apply(mapping, call.filterArg));
-          }
-        });
-  }
-
-  public static MutableRel unifyAggregates(MutableAggregate query,
-      MutableAggregate target) {
-    if (query.getGroupType() != Aggregate.Group.SIMPLE
-        || target.getGroupType() != Aggregate.Group.SIMPLE) {
-      throw new AssertionError(Bug.CALCITE_461_FIXED);
-    }
-    MutableRel result;
-    if (query.getGroupSet().equals(target.getGroupSet())) {
-      // Same level of aggregation. Generate a project.
-      final List<Integer> projects = Lists.newArrayList();
-      final int groupCount = query.getGroupSet().cardinality();
-      for (int i = 0; i < groupCount; i++) {
-        projects.add(i);
-      }
-      for (AggregateCall aggregateCall : query.getAggCallList()) {
-        int i = target.getAggCallList().indexOf(aggregateCall);
-        if (i < 0) {
-          return null;
-        }
-        projects.add(groupCount + i);
-      }
-      result = MutableRels.createProject(target, projects);
-    } else {
-      // Target is coarser level of aggregation. Generate an aggregate.
-      final ImmutableBitSet.Builder groupSet = ImmutableBitSet.builder();
-      final List<Integer> targetGroupList = target.getGroupSet().asList();
-      for (int c : query.getGroupSet()) {
-        int c2 = targetGroupList.indexOf(c);
-        if (c2 < 0) {
-          return null;
-        }
-        groupSet.set(c2);
-      }
-      final List<AggregateCall> aggregateCalls = Lists.newArrayList();
-      for (AggregateCall aggregateCall : query.getAggCallList()) {
-        if (aggregateCall.isDistinct()) {
-          return null;
-        }
-        int i = target.getAggCallList().indexOf(aggregateCall);
-        if (i < 0) {
-          return null;
-        }
-        aggregateCalls.add(
-            AggregateCall.create(getRollup(aggregateCall.getAggregation()),
-                aggregateCall.isDistinct(),
-                ImmutableList.of(target.groupSet.cardinality() + i), -1,
-                aggregateCall.type, aggregateCall.name));
-      }
-      result = MutableAggregate.of(target, false, groupSet.build(), null,
-          aggregateCalls);
-    }
-    return MutableRels.createCastRel(result, query.getRowType(), true);
-  }
-
-  /** Implementation of {@link UnifyRule} that matches a
-   * {@link MutableAggregate} on
-   * a {@link MutableProject} query to an {@link MutableAggregate} target.
-   *
-   * <p>The rule is necessary when we unify query=Aggregate(x) with
-   * target=Aggregate(x, y). Query will tend to have an extra Project(x) on its
-   * input, which this rule knows is safe to ignore.</p> */
-  private static class AggregateOnProjectToAggregateUnifyRule
-      extends AbstractUnifyRule {
-    public static final AggregateOnProjectToAggregateUnifyRule INSTANCE =
-        new AggregateOnProjectToAggregateUnifyRule();
-
-    private AggregateOnProjectToAggregateUnifyRule() {
-      super(
-          operand(MutableAggregate.class,
-              operand(MutableProject.class, query(0))),
-          operand(MutableAggregate.class, target(0)), 1);
-    }
-
-    public UnifyResult apply(UnifyRuleCall call) {
-      final MutableAggregate query = (MutableAggregate) call.query;
-      final MutableAggregate target = (MutableAggregate) call.target;
-      if (!(query.getInput() instanceof MutableProject)) {
-        return null;
-      }
-      final MutableProject project = (MutableProject) query.getInput();
-      if (project.getInput() != target.getInput()) {
-        return null;
-      }
-      final Mappings.TargetMapping mapping = project.getMapping();
-      if (mapping == null) {
-        return null;
-      }
-      final MutableAggregate aggregate2 =
-          permute(query, project.getInput(), mapping.inverse());
-      final MutableRel result = unifyAggregates(aggregate2, target);
-      return result == null ? null : call.result(result);
-    }
-  }
-
-  public static SqlAggFunction getRollup(SqlAggFunction aggregation) {
-    if (aggregation == SqlStdOperatorTable.SUM
-        || aggregation == SqlStdOperatorTable.MIN
-        || aggregation == SqlStdOperatorTable.MAX
-        || aggregation == SqlStdOperatorTable.SUM0) {
-      return aggregation;
-    } else if (aggregation == SqlStdOperatorTable.COUNT) {
-      return SqlStdOperatorTable.SUM0;
-    } else {
-      return null;
-    }
-  }
-
-  /** Builds a shuttle that stores a list of expressions, and can map incoming
-   * expressions to references to them. */
-  protected static RexShuttle getRexShuttle(MutableProject target) {
-    final Map<String, Integer> map = new HashMap<>();
-    for (RexNode e : target.getProjects()) {
-      map.put(e.toString(), map.size());
-    }
-    return new RexShuttle() {
-      @Override public RexNode visitInputRef(RexInputRef ref) {
-        final Integer integer = map.get(ref.getName());
-        if (integer != null) {
-          return new RexInputRef(integer, ref.getType());
-        }
-        throw MatchFailed.INSTANCE;
-      }
-
-      @Override public RexNode visitCall(RexCall call) {
-        final Integer integer = map.get(call.toString());
-        if (integer != null) {
-          return new RexInputRef(integer, call.getType());
-        }
-        return super.visitCall(call);
-      }
-    };
-  }
-
-  /** Type of {@code MutableRel}. */
-  private enum MutableRelType {
-    SCAN,
-    PROJECT,
-    FILTER,
-    AGGREGATE,
-    SORT,
-    UNION,
-    JOIN,
-    HOLDER,
-    VALUES
-  }
-
-  /** Visitor over {@link MutableRel}. */
-  private static class MutableRelVisitor {
-    private MutableRel root;
-
-    public void visit(MutableRel node) {
-      node.childrenAccept(this);
-    }
-
-    public MutableRel go(MutableRel p) {
-      this.root = p;
-      visit(p);
-      return root;
-    }
-  }
-
-  /** Mutable equivalent of {@link RelNode}.
-   *
-   * <p>Each node has mutable state, and keeps track of its parent and position
-   * within parent.
-   * It doesn't make sense to canonize {@code MutableRels},
-   * otherwise one node could end up with multiple parents.
-   * It follows that {@code #hashCode} and {@code #equals} are less efficient
-   * than their {@code RelNode} counterparts.
-   * But, you don't need to copy a {@code MutableRel} in order to change it.
-   * For this reason, you should use {@code MutableRel} for short-lived
-   * operations, and transcribe back to {@code RelNode} when you are done.</p>
-   */
-  protected abstract static class MutableRel {
-    MutableRel parent;
-    int ordinalInParent;
-    public final RelOptCluster cluster;
-    final RelDataType rowType;
-    final MutableRelType type;
-
-    private MutableRel(RelOptCluster cluster, RelDataType rowType,
-        MutableRelType type) {
-      this.cluster = cluster;
-      this.rowType = rowType;
-      this.type = type;
-    }
-
-    public RelDataType getRowType() {
-      return rowType;
-    }
-
-    public abstract void setInput(int ordinalInParent, MutableRel input);
-
-    public abstract List<MutableRel> getInputs();
-
-    public abstract void childrenAccept(MutableRelVisitor visitor);
-
-    /** Replaces this {@code MutableRel} in its parent with another node at the
-     * same position.
-     *
-     * <p>Before the method, {@code child} must be an orphan (have null parent)
-     * and after this method, this {@code MutableRel} is an orphan.
-     *
-     * @return The parent
-     */
-    public MutableRel replaceInParent(MutableRel child) {
-      final MutableRel parent = this.parent;
-      if (this != child) {
-/*
-        if (child.parent != null) {
-          child.parent.setInput(child.ordinalInParent, null);
-          child.parent = null;
-        }
-*/
-        if (parent != null) {
-          parent.setInput(ordinalInParent, child);
-          this.parent = null;
-          this.ordinalInParent = 0;
-        }
-      }
-      return parent;
-    }
-
-    public abstract StringBuilder digest(StringBuilder buf);
-
-    public final String deep() {
-      return new MutableRelDumper().apply(this);
-    }
-
-    @Override public final String toString() {
-      return deep();
-    }
-
-    public MutableRel getParent() { return parent; }
-  }
-
-  /** Implementation of {@link MutableRel} whose only purpose is to have a
-   * child. Used as the root of a tree. */
-  private static class Holder extends MutableSingleRel {
-    private Holder(MutableRelType type, RelDataType rowType, MutableRel input) {
-      super(type, rowType, input);
-    }
-
-    static Holder of(MutableRel input) {
-      return new Holder(MutableRelType.HOLDER, input.rowType, input);
-    }
-
-    @Override public StringBuilder digest(StringBuilder buf) {
-      return buf.append("Holder");
-    }
-  }
-
-   /** Abstract base class for implementations of {@link MutableRel} that have
-   * no inputs. */
-  protected abstract static class MutableLeafRel extends MutableRel {
-    protected final RelNode rel;
-
-    MutableLeafRel(MutableRelType type, RelNode rel) {
-      super(rel.getCluster(), rel.getRowType(), type);
-      this.rel = rel;
-    }
-
-    public void setInput(int ordinalInParent, MutableRel input) {
-      throw new IllegalArgumentException();
-    }
-
-    public List<MutableRel> getInputs() {
-      return ImmutableList.of();
-    }
-
-    public void childrenAccept(MutableRelVisitor visitor) {
-      // no children - nothing to do
-    }
-  }
-
-  /** Mutable equivalent of {@link SingleRel}. */
-  protected abstract static class MutableSingleRel extends MutableRel {
-    protected MutableRel input;
-
-    MutableSingleRel(MutableRelType type, RelDataType rowType,
-        MutableRel input) {
-      super(input.cluster, rowType, type);
-      this.input = input;
-      input.parent = this;
-      input.ordinalInParent = 0;
-    }
-
-    public void setInput(int ordinalInParent, MutableRel input) {
-      if (ordinalInParent >= 1) {
-        throw new IllegalArgumentException();
-      }
-      this.input = input;
-      if (input != null) {
-        input.parent = this;
-        input.ordinalInParent = 0;
-      }
-    }
-
-    public List<MutableRel> getInputs() {
-      return ImmutableList.of(input);
-    }
-
-    public void childrenAccept(MutableRelVisitor visitor) {
-      visitor.visit(input);
-    }
-
-    public MutableRel getInput() {
-      return input;
-    }
-  }
-
-  /** Mutable equivalent of
-   * {@link org.apache.calcite.rel.logical.LogicalTableScan}. */
-  protected static class MutableScan extends MutableLeafRel {
-    private MutableScan(TableScan rel) {
-      super(MutableRelType.SCAN, rel);
-    }
-
-    static MutableScan of(TableScan rel) {
-      return new MutableScan(rel);
-    }
-
-    @Override public boolean equals(Object obj) {
-      return obj == this
-          || obj instanceof MutableScan
-          && rel.getTable().equals(((MutableScan) obj).rel.getTable());
-    }
-
-    @Override public int hashCode() {
-      return rel.getTable().hashCode();
-    }
-
-    @Override public StringBuilder digest(StringBuilder buf) {
-      return buf.append("Scan(table: ")
-          .append(rel.getTable().getQualifiedName()).append(")");
-    }
-  }
-
-  /** Mutable equivalent of {@link org.apache.calcite.rel.core.Values}. */
-  protected static class MutableValues extends MutableLeafRel {
-    private MutableValues(Values rel) {
-      super(MutableRelType.VALUES, rel);
-    }
-
-    static MutableValues of(Values rel) {
-      return new MutableValues(rel);
-    }
-
-    @Override public boolean equals(Object obj) {
-      return obj == this
-          || obj instanceof MutableValues
-          && rel == ((MutableValues) obj).rel;
-    }
-
-    @Override public int hashCode() {
-      return rel.hashCode();
-    }
-
-    @Override public StringBuilder digest(StringBuilder buf) {
-      return buf.append("Values(tuples: ")
-          .append(((Values) rel).getTuples()).append(")");
-    }
-  }
-
-  /** Mutable equivalent of
-   * {@link org.apache.calcite.rel.logical.LogicalProject}. */
-  protected static class MutableProject extends MutableSingleRel {
-    private final List<RexNode> projects;
-
-    private MutableProject(RelDataType rowType, MutableRel input,
-        List<RexNode> projects) {
-      super(MutableRelType.PROJECT, rowType, input);
-      this.projects = projects;
-      assert RexUtil.compatibleTypes(projects, rowType, Litmus.THROW);
-    }
-
-    public static MutableProject of(RelDataType rowType, MutableRel input,
-        List<RexNode> projects) {
-      return new MutableProject(rowType, input, projects);
-    }
-
-    /** Equivalent to
-     * {@link RelOptUtil#createProject(org.apache.calcite.rel.RelNode, java.util.List, java.util.List)}
-     * for {@link MutableRel}. */
-    public static MutableRel of(MutableRel child, List<RexNode> exprList,
-        List<String> fieldNameList) {
-      final RelDataType rowType =
-          RexUtil.createStructType(child.cluster.getTypeFactory(), exprList,
-              fieldNameList, SqlValidatorUtil.F_SUGGESTER);
-      return of(rowType, child, exprList);
-    }
-
-    @Override public boolean equals(Object obj) {
-      return obj == this
-          || obj instanceof MutableProject
-          && PAIRWISE_STRING_EQUIVALENCE.equivalent(
-              projects, ((MutableProject) obj).projects)
-          && input.equals(((MutableProject) obj).input);
-    }
-
-    @Override public int hashCode() {
-      return Objects.hash(input,
-          PAIRWISE_STRING_EQUIVALENCE.hash(projects));
-    }
-
-    @Override public StringBuilder digest(StringBuilder buf) {
-      return buf.append("Project(projects: ").append(projects).append(")");
-    }
-
-    public List<RexNode> getProjects() {
-      return projects;
-    }
-
-    /** Returns a list of (expression, name) pairs. */
-    public final List<Pair<RexNode, String>> getNamedProjects() {
-      return Pair.zip(getProjects(), getRowType().getFieldNames());
-    }
-
-    public Mappings.TargetMapping getMapping() {
-      return Project.getMapping(
-          input.getRowType().getFieldCount(), projects);
-    }
-  }
-
-  /** Mutable equivalent of
-   * {@link org.apache.calcite.rel.logical.LogicalFilter}. */
-  protected static class MutableFilter extends MutableSingleRel {
-    private final RexNode condition;
-
-    private MutableFilter(MutableRel input, RexNode condition) {
-      super(MutableRelType.FILTER, input.rowType, input);
-      this.condition = condition;
-    }
-
-    public static MutableFilter of(MutableRel input, RexNode condition) {
-      return new MutableFilter(input, condition);
-    }
-
-    @Override public boolean equals(Object obj) {
-      return obj == this
-          || obj instanceof MutableFilter
-          && condition.toString().equals(
-              ((MutableFilter) obj).condition.toString())
-          && input.equals(((MutableFilter) obj).input);
-    }
-
-    @Override public int hashCode() {
-      return Objects.hash(input, condition.toString());
-    }
-
-    @Override public StringBuilder digest(StringBuilder buf) {
-      return buf.append("Filter(condition: ").append(condition).append(")");
-    }
-
-    public RexNode getCondition() {
-      return condition;
-    }
-  }
-
-  /** Mutable equivalent of
-   * {@link org.apache.calcite.rel.logical.LogicalAggregate}. */
-  protected static class MutableAggregate extends MutableSingleRel {
-    public final boolean indicator;
-    private final ImmutableBitSet groupSet;
-    private final ImmutableList<ImmutableBitSet> groupSets;
-    private final List<AggregateCall> aggCalls;
-
-    private MutableAggregate(MutableRel input, RelDataType rowType,
-        boolean indicator, ImmutableBitSet groupSet,
-        List<ImmutableBitSet> groupSets, List<AggregateCall> aggCalls) {
-      super(MutableRelType.AGGREGATE, rowType, input);
-      this.indicator = indicator;
-      this.groupSet = groupSet;
-      this.groupSets = groupSets == null
-          ? ImmutableList.of(groupSet)
-          : ImmutableList.copyOf(groupSets);
-      this.aggCalls = aggCalls;
-    }
-
-    static MutableAggregate of(MutableRel input, boolean indicator,
-        ImmutableBitSet groupSet, ImmutableList<ImmutableBitSet> groupSets,
-        List<AggregateCall> aggCalls) {
-      RelDataType rowType =
-          Aggregate.deriveRowType(input.cluster.getTypeFactory(),
-              input.getRowType(), indicator, groupSet, groupSets, aggCalls);
-      return new MutableAggregate(input, rowType, indicator, groupSet,
-          groupSets, aggCalls);
-    }
-
-    @Override public boolean equals(Object obj) {
-      return obj == this
-          || obj instanceof MutableAggregate
-          && groupSet.equals(((MutableAggregate) obj).groupSet)
-          && aggCalls.equals(((MutableAggregate) obj).aggCalls)
-          && input.equals(((MutableAggregate) obj).input);
-    }
-
-    @Override public int hashCode() {
-      return Objects.hash(input, groupSet, aggCalls);
-    }
-
-    @Override public StringBuilder digest(StringBuilder buf) {
-      return buf.append("Aggregate(groupSet: ").append(groupSet)
-          .append(", groupSets: ").append(groupSets)
-          .append(", calls: ").append(aggCalls).append(")");
-    }
-
-    public ImmutableBitSet getGroupSet() {
-      return groupSet;
-    }
-
-    public ImmutableList<ImmutableBitSet> getGroupSets() {
-      return groupSets;
-    }
-
-    public List<AggregateCall> getAggCallList() {
-      return aggCalls;
-    }
-
-    public Aggregate.Group getGroupType() {
-      return Aggregate.Group.induce(groupSet, groupSets);
-    }
-  }
-
-  /** Mutable equivalent of {@link org.apache.calcite.rel.core.Sort}. */
-  protected static class MutableSort extends MutableSingleRel {
-    private final RelCollation collation;
-    private final RexNode offset;
-    private final RexNode fetch;
-
-    private MutableSort(MutableRel input, RelCollation collation,
-        RexNode offset, RexNode fetch) {
-      super(MutableRelType.SORT, input.rowType, input);
-      this.collation = collation;
-      this.offset = offset;
-      this.fetch = fetch;
-    }
-
-    static MutableSort of(MutableRel input, RelCollation collation,
-        RexNode offset, RexNode fetch) {
-      return new MutableSort(input, collation, offset, fetch);
-    }
-
-    @Override public boolean equals(Object obj) {
-      return obj == this
-          || obj instanceof MutableSort
-          && collation.equals(((MutableSort) obj).collation)
-          && Objects.equals(offset, ((MutableSort) obj).offset)
-          && Objects.equals(fetch, ((MutableSort) obj).fetch)
-          && input.equals(((MutableSort) obj).input);
-    }
-
-    @Override public int hashCode() {
-      return Objects.hash(input, collation, offset, fetch);
-    }
-
-    @Override public StringBuilder digest(StringBuilder buf) {
-      buf.append("Sort(collation: ").append(collation);
-      if (offset != null) {
-        buf.append(", offset: ").append(offset);
-      }
-      if (fetch != null) {
-        buf.append(", fetch: ").append(fetch);
-      }
-      return buf.append(")");
-    }
-  }
-
-  /** Base class for set-operations. */
-  protected abstract static class MutableSetOp extends MutableRel {
-    protected final List<MutableRel> inputs;
-
-    private MutableSetOp(RelOptCluster cluster, RelDataType rowType,
-        MutableRelType type, List<MutableRel> inputs) {
-      super(cluster, rowType, type);
-      this.inputs = inputs;
-    }
-
-    @Override public void setInput(int ordinalInParent, MutableRel input) {
-      inputs.set(ordinalInParent, input);
-      if (input != null) {
-        input.parent = this;
-        input.ordinalInParent = ordinalInParent;
-      }
-    }
-
-    @Override public List<MutableRel> getInputs() {
-      return inputs;
-    }
-
-    @Override public void childrenAccept(MutableRelVisitor visitor) {
-      for (MutableRel input : inputs) {
-        visitor.visit(input);
-      }
-    }
-  }
-
-  /** Mutable equivalent of
-   * {@link org.apache.calcite.rel.logical.LogicalUnion}. */
-  protected static class MutableUnion extends MutableSetOp {
-    public boolean all;
-
-    private MutableUnion(RelOptCluster cluster, RelDataType rowType,
-        List<MutableRel> inputs, boolean all) {
-      super(cluster, rowType, MutableRelType.UNION, inputs);
-      this.all = all;
-    }
-
-    static MutableUnion of(List<MutableRel> inputs, boolean all) {
-      assert inputs.size() >= 2;
-      final MutableRel input0 = inputs.get(0);
-      return new MutableUnion(input0.cluster, input0.rowType, inputs, all);
-    }
-
-    @Override public boolean equals(Object obj) {
-      return obj == this
-          || obj instanceof MutableUnion
-          && inputs.equals(((MutableUnion) obj).getInputs());
-    }
-
-    @Override public int hashCode() {
-      return Objects.hash(type, inputs);
-    }
-
-    @Override public StringBuilder digest(StringBuilder buf) {
-      return buf.append("Union");
-    }
-  }
-
-  /** Base Class for relations with two inputs */
-  private abstract static class MutableBiRel extends MutableRel {
-    protected MutableRel left;
-    protected MutableRel right;
-
-    MutableBiRel(MutableRelType type, RelOptCluster cluster, RelDataType rowType,
-                        MutableRel left, MutableRel right) {
-      super(cluster, rowType, type);
-      this.left = left;
-      left.parent = this;
-      left.ordinalInParent = 0;
-
-      this.right = right;
-      right.parent = this;
-      right.ordinalInParent = 1;
-    }
-
-    public void setInput(int ordinalInParent, MutableRel input) {
-      if (ordinalInParent > 1) {
-        throw new IllegalArgumentException();
-      }
-      if (ordinalInParent == 0) {
-        this.left = input;
-      } else {
-        this.right = input;
-      }
-      if (input != null) {
-        input.parent = this;
-        input.ordinalInParent = ordinalInParent;
-      }
-    }
-
-    public List<MutableRel> getInputs() {
-      return ImmutableList.of(left, right);
-    }
-
-    public MutableRel getLeft() {
-      return left;
-    }
-
-    public MutableRel getRight() {
-      return right;
-    }
-
-    public void childrenAccept(MutableRelVisitor visitor) {
-
-      visitor.visit(left);
-      visitor.visit(right);
-    }
-  }
-
-  /** Mutable equivalent of
-   * {@link org.apache.calcite.rel.logical.LogicalJoin}. */
-  private static class MutableJoin extends MutableBiRel {
-    //~ Instance fields --------------------------------------------------------
-
-    protected final RexNode condition;
-    protected final ImmutableSet<CorrelationId> variablesSet;
-
-    /**
-     * Values must be of enumeration {@link JoinRelType}, except that
-     * {@link JoinRelType#RIGHT} is disallowed.
-     */
-    protected JoinRelType joinType;
-
-    private MutableJoin(
-        RelDataType rowType,
-        MutableRel left,
-        MutableRel right,
-        RexNode condition,
-        JoinRelType joinType,
-        Set<CorrelationId> variablesSet) {
-      super(MutableRelType.JOIN, left.cluster, rowType, left, right);
-      this.condition = Preconditions.checkNotNull(condition);
-      this.variablesSet = ImmutableSet.copyOf(variablesSet);
-      this.joinType = Preconditions.checkNotNull(joinType);
-    }
-
-    public RexNode getCondition() {
-      return condition;
-    }
-
-    public JoinRelType getJoinType() {
-      return joinType;
-    }
-
-    public ImmutableSet<CorrelationId> getVariablesSet() {
-      return variablesSet;
-    }
-
-    static MutableJoin of(RelOptCluster cluster, MutableRel left,
-        MutableRel right, RexNode condition, JoinRelType joinType,
-        Set<CorrelationId> variablesStopped) {
-      List<RelDataTypeField> fieldList = Collections.emptyList();
-      RelDataType rowType =
-          SqlValidatorUtil.deriveJoinRowType(left.getRowType(),
-              right.getRowType(), joinType, cluster.getTypeFactory(), null,
-              fieldList);
-      return new MutableJoin(rowType, left, right, condition, joinType,
-          variablesStopped);
-    }
-
-    @Override public boolean equals(Object obj) {
-      return obj == this
-          || obj instanceof MutableJoin
-          && joinType == ((MutableJoin) obj).joinType
-          && condition.toString().equals(
-              ((MutableJoin) obj).condition.toString())
-          && left.equals(((MutableJoin) obj).left)
-          && right.equals(((MutableJoin) obj).right);
-    }
-
-    @Override public int hashCode() {
-      return Objects.hash(left, right, condition.toString(), joinType);
-    }
-
-    @Override public StringBuilder digest(StringBuilder buf) {
-      return buf.append("Join(left: ").append(left)
-          .append(", right:").append(right)
-          .append(")");
-    }
-  }
-
-  /** Utilities for dealing with {@link MutableRel}s. */
-  protected static class MutableRels {
-    public static boolean contains(MutableRel ancestor,
-        final MutableRel target) {
-      if (ancestor.equals(target)) {
-        // Short-cut common case.
-        return true;
-      }
-      try {
-        new MutableRelVisitor() {
-          @Override public void visit(MutableRel node) {
-            if (node.equals(target)) {
-              throw Util.FoundOne.NULL;
-            }
-            super.visit(node);
-          }
-          // CHECKSTYLE: IGNORE 1
-        }.go(ancestor);
-        return false;
-      } catch (Util.FoundOne e) {
-        return true;
-      }
-    }
-
-    public static MutableRel preOrderTraverseNext(MutableRel node) {
-      MutableRel parent = node.getParent();
-      int ordinal = node.ordinalInParent + 1;
-      while (parent != null) {
-        if (parent.getInputs().size() > ordinal) {
-          return parent.getInputs().get(ordinal);
-        }
-        node = parent;
-        parent = node.getParent();
-        ordinal = node.ordinalInParent + 1;
-      }
-      return null;
-    }
-
-    private static List<MutableRel> descendants(MutableRel query) {
-      final List<MutableRel> list = new ArrayList<>();
-      descendantsRecurse(list, query);
-      return list;
-    }
-
-    private static void descendantsRecurse(List<MutableRel> list,
-        MutableRel rel) {
-      list.add(rel);
-      for (MutableRel input : rel.getInputs()) {
-        descendantsRecurse(list, input);
-      }
-    }
-
-    /** Returns whether two relational expressions have the same row-type. */
-    public static boolean equalType(String desc0, MutableRel rel0, String desc1,
-        MutableRel rel1, Litmus litmus) {
-      return RelOptUtil.equal(desc0, rel0.getRowType(),
-          desc1, rel1.getRowType(), litmus);
-    }
-
-    /** Within a relational expression {@code query}, replaces occurrences of
-     * {@code find} with {@code replace}.
-     *
-     * <p>Assumes relational expressions (and their descendants) are not null.
-     * Does not handle cycles. */
-    public static Replacement replace(MutableRel query, MutableRel find,
-        MutableRel replace) {
-      if (find.equals(replace)) {
-        // Short-cut common case.
-        return null;
-      }
-      assert equalType("find", find, "replace", replace, Litmus.THROW);
-      return replaceRecurse(query, find, replace);
-    }
-
-    /** Helper for {@link #replace}. */
-    private static Replacement replaceRecurse(MutableRel query,
-        MutableRel find, MutableRel replace) {
-      if (find.equals(query)) {
-        query.replaceInParent(replace);
-        return new Replacement(query, replace);
-      }
-      for (MutableRel input : query.getInputs()) {
-        Replacement r = replaceRecurse(input, find, replace);
-        if (r != null) {
-          return r;
-        }
-      }
-      return null;
-    }
-
-    /** Based on
-     * {@link org.apache.calcite.rel.rules.ProjectRemoveRule#strip}. */
-    public static MutableRel strip(MutableProject project) {
-      return isTrivial(project) ? project.getInput() : project;
-    }
-
-    /** Based on
-     * {@link org.apache.calcite.rel.rules.ProjectRemoveRule#isTrivial(org.apache.calcite.rel.core.Project)}. */
-    public static boolean isTrivial(MutableProject project) {
-      MutableRel child = project.getInput();
-      final RelDataType childRowType = child.getRowType();
-      return RexUtil.isIdentity(project.getProjects(), childRowType);
-    }
-
-    /** Equivalent to
-     * {@link RelOptUtil#createProject(org.apache.calcite.rel.RelNode, java.util.List)}
-     * for {@link MutableRel}. */
-    public static MutableRel createProject(final MutableRel child,
-        final List<Integer> posList) {
-      final RelDataType rowType = child.getRowType();
-      if (Mappings.isIdentity(posList, rowType.getFieldCount())) {
-        return child;
-      }
-      return MutableProject.of(
-          RelOptUtil.permute(child.cluster.getTypeFactory(), rowType,
-              Mappings.bijection(posList)),
-          child,
-          new AbstractList<RexNode>() {
-            public int size() {
-              return posList.size();
-            }
-
-            public RexNode get(int index) {
-              final int pos = posList.get(index);
-              return RexInputRef.of(pos, rowType);
-            }
-          });
-    }
-
-    /** Equivalence to {@link org.apache.calcite.plan.RelOptUtil#createCastRel}
-     * for {@link MutableRel}. */
-    public static MutableRel createCastRel(MutableRel rel,
-        RelDataType castRowType, boolean rename) {
-      RelDataType rowType = rel.getRowType();
-      if (RelOptUtil.areRowTypesEqual(rowType, castRowType, rename)) {
-        // nothing to do
-        return rel;
-      }
-      List<RexNode> castExps =
-          RexUtil.generateCastExpressions(rel.cluster.getRexBuilder(),
-              castRowType, rowType);
-      final List<String> fieldNames =
-          rename ? castRowType.getFieldNames() : rowType.getFieldNames();
-      return MutableProject.of(rel, castExps, fieldNames);
-    }
-  }
-
-  /** Visitor that prints an indented tree of {@link MutableRel}s. */
-  protected static class MutableRelDumper extends MutableRelVisitor {
-    private final StringBuilder buf = new StringBuilder();
-    private int level;
-
-    @Override public void visit(MutableRel node) {
-      Spaces.append(buf, level * 2);
-      if (node == null) {
-        buf.append("null");
-      } else {
-        node.digest(buf);
-        buf.append("\n");
-        ++level;
-        super.visit(node);
-        --level;
-      }
-    }
-
-    public String apply(MutableRel rel) {
-      go(rel);
-      return buf.toString();
-    }
-  }
-
-  /** Returns if one rel is weaker than another. */
-  protected boolean isWeaker(MutableRel rel0, MutableRel rel) {
-    if (rel0 == rel || equivalents.get(rel0).contains(rel)) {
-      return false;
-    }
-
-    if (!(rel0 instanceof MutableFilter)
-        || !(rel instanceof MutableFilter)) {
-      return false;
-    }
-
-    if (!rel.getRowType().equals(rel0.getRowType())) {
-      return false;
-    }
-
-    final MutableRel rel0input = ((MutableFilter) rel0).getInput();
-    final MutableRel relinput = ((MutableFilter) rel).getInput();
-    if (rel0input != relinput
-        && !equivalents.get(rel0input).contains(relinput)) {
-      return false;
-    }
-
-    RexExecutorImpl rexImpl =
-        (RexExecutorImpl) (rel.cluster.getPlanner().getExecutor());
-    RexImplicationChecker rexImplicationChecker = new RexImplicationChecker(
-        rel.cluster.getRexBuilder(),
-        rexImpl, rel.getRowType());
-
-    return rexImplicationChecker.implies(((MutableFilter) rel0).getCondition(),
-        ((MutableFilter) rel).getCondition());
-  }
-
-  /** Operand to a {@link UnifyRule}. */
-  protected abstract static class Operand {
-    protected final Class<? extends MutableRel> clazz;
-
-    protected Operand(Class<? extends MutableRel> clazz) {
-      this.clazz = clazz;
-    }
-
-    public abstract boolean matches(SubstitutionVisitor visitor, MutableRel rel);
-
-    public boolean isWeaker(SubstitutionVisitor visitor, MutableRel rel) {
-      return false;
-    }
-  }
-
-  /** Operand to a {@link UnifyRule} that matches a relational expression of a
-   * given type. It has zero or more child operands. */
-  private static class InternalOperand extends Operand {
-    private final List<Operand> inputs;
-
-    InternalOperand(Class<? extends MutableRel> clazz, List<Operand> inputs) {
-      super(clazz);
-      this.inputs = inputs;
-    }
-
-    @Override public boolean matches(SubstitutionVisitor visitor, MutableRel rel) {
-      return clazz.isInstance(rel)
-          && allMatch(visitor, inputs, rel.getInputs());
-    }
-
-    @Override public boolean isWeaker(SubstitutionVisitor visitor, MutableRel rel) {
-      return clazz.isInstance(rel)
-          && allWeaker(visitor, inputs, rel.getInputs());
-    }
-    private static boolean allMatch(SubstitutionVisitor visitor,
-        List<Operand> operands, List<MutableRel> rels) {
-      if (operands.size() != rels.size()) {
-        return false;
-      }
-      for (Pair<Operand, MutableRel> pair : Pair.zip(operands, rels)) {
-        if (!pair.left.matches(visitor, pair.right)) {
-          return false;
-        }
-      }
-      return true;
-    }
-
-    private static boolean allWeaker(
-        SubstitutionVisitor visitor,
-        List<Operand> operands, List<MutableRel> rels) {
-      if (operands.size() != rels.size()) {
-        return false;
-      }
-      for (Pair<Operand, MutableRel> pair : Pair.zip(operands, rels)) {
-        if (!pair.left.isWeaker(visitor, pair.right)) {
-          return false;
-        }
-      }
-      return true;
-    }
-  }
-
-  /** Operand to a {@link UnifyRule} that matches a relational expression of a
-   * given type. */
-  private static class AnyOperand extends Operand {
-    AnyOperand(Class<? extends MutableRel> clazz) {
-      super(clazz);
-    }
-
-    @Override public boolean matches(SubstitutionVisitor visitor, MutableRel rel) {
-      return clazz.isInstance(rel);
-    }
-  }
-
-  /** Operand that assigns a particular relational expression to a variable.
-   *
-   * <p>It is applied to a descendant of the query, writes the operand into the
-   * slots array, and always matches.
-   * There is a corresponding operand of type {@link TargetOperand} that checks
-   * whether its relational expression, a descendant of the target, is
-   * equivalent to this {@code QueryOperand}'s relational expression.
-   */
-  private static class QueryOperand extends Operand {
-    private final int ordinal;
-
-    protected QueryOperand(int ordinal) {
-      super(MutableRel.class);
-      this.ordinal = ordinal;
-    }
-
-    @Override public boolean matches(SubstitutionVisitor visitor, MutableRel rel) {
-      visitor.slots[ordinal] = rel;
-      return true;
-    }
-  }
-
-  /** Operand that checks that a relational expression matches the corresponding
-   * relational expression that was passed to a {@link QueryOperand}. */
-  private static class TargetOperand extends Operand {
-    private final int ordinal;
-
-    protected TargetOperand(int ordinal) {
-      super(MutableRel.class);
-      this.ordinal = ordinal;
-    }
-
-    @Override public boolean matches(SubstitutionVisitor visitor, MutableRel rel) {
-      final MutableRel rel0 = visitor.slots[ordinal];
-      assert rel0 != null : "QueryOperand should have been called first";
-      return rel0 == rel || visitor.equivalents.get(rel0).contains(rel);
-    }
-
-    @Override public boolean isWeaker(SubstitutionVisitor visitor, MutableRel rel) {
-      final MutableRel rel0 = visitor.slots[ordinal];
-      assert rel0 != null : "QueryOperand should have been called first";
-      return visitor.isWeaker(rel0, rel);
-    }
-  }
-
-  /** Visitor that counts how many {@link QueryOperand} and
-   * {@link TargetOperand} in an operand tree. */
-  private static class SlotCounter {
-    int queryCount;
-    int targetCount;
-
-    void visit(Operand operand) {
-      if (operand instanceof QueryOperand) {
-        ++queryCount;
-      } else if (operand instanceof TargetOperand) {
-        ++targetCount;
-      } else if (operand instanceof AnyOperand) {
-        // nothing
-      } else {
-        for (Operand input : ((InternalOperand) operand).inputs) {
-          visit(input);
-        }
-      }
-    }
-  }
-
-  /**
-   * Rule that converts a {@link org.apache.calcite.rel.logical.LogicalFilter}
-   * on top of a {@link org.apache.calcite.rel.logical.LogicalProject} into a
-   * trivial filter (on a boolean column).
-   */
-  public static class FilterOnProjectRule extends RelOptRule {
-    private static final Predicate<Filter> PREDICATE =
-        new Predicate<Filter>() {
-          public boolean apply(Filter input) {
-            return input.getCondition() instanceof RexInputRef;
-          }
-        };
-
-    public static final FilterOnProjectRule INSTANCE =
-        new FilterOnProjectRule();
-
-    private FilterOnProjectRule() {
-      super(
-          operand(Filter.class, null, PREDICATE,
-              some(operand(Project.class, any()))));
-    }
-
-    public void onMatch(RelOptRuleCall call) {
-      final Filter filter = call.rel(0);
-      final Project project = call.rel(1);
-
-      final List<RexNode> newProjects = new ArrayList<>(project.getProjects());
-      newProjects.add(filter.getCondition());
-
-      final RelOptCluster cluster = filter.getCluster();
-      RelDataType newRowType =
-          cluster.getTypeFactory().builder()
-              .addAll(project.getRowType().getFieldList())
-              .add("condition", Util.last(newProjects).getType())
-              .build();
-      final RelNode newProject =
-          project.copy(project.getTraitSet(),
-              project.getInput(),
-              newProjects,
-              newRowType);
-
-      final RexInputRef newCondition =
-          cluster.getRexBuilder().makeInputRef(newProject,
-              newProjects.size() - 1);
-
-      call.transformTo(filter.copy(filter.getTraitSet(), newProject, newCondition));
-    }
-  }
-}
-
-// End SubstitutionVisitor.java