[CALCITE-6846] Support basic dphyp join reorder algorithm

core/src/main/java/org/apache/calcite/rel/rules/CoreRules.java

@@ -16,6 +16,7 @@
  */
 package org.apache.calcite.rel.rules;
 
+import org.apache.calcite.linq4j.function.Experimental;
 import org.apache.calcite.rel.RelNode;
 import org.apache.calcite.rel.core.Aggregate;
 import org.apache.calcite.rel.core.Calc;
@@ -816,4 +817,17 @@ private CoreRules() {}
       WINDOW_REDUCE_EXPRESSIONS =
       ReduceExpressionsRule.WindowReduceExpressionsRule.WindowReduceExpressionsRuleConfig
           .DEFAULT.toRule();
+
+  /** Rule that flattens a tree of {@link LogicalJoin}s
+   * into a single {@link HyperGraph} with N inputs. */
+  @Experimental
+  public static final JoinToHyperGraphRule JOIN_TO_HYPER_GRAPH =
+      JoinToHyperGraphRule.Config.DEFAULT.toRule();
+
+  /** Rule that re-orders a {@link Join} tree using dphyp algorithm.
+   *
+   * @see #JOIN_TO_HYPER_GRAPH */
+  @Experimental
+  public static final DphypJoinReorderRule HYPER_GRAPH_OPTIMIZE =
+      DphypJoinReorderRule.Config.DEFAULT.toRule();
 }

core/src/main/java/org/apache/calcite/rel/rules/DpHyp.java

@@ -0,0 +1,226 @@
+/*
+ * 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.rel.rules;
+
+import org.apache.calcite.linq4j.function.Experimental;
+import org.apache.calcite.plan.RelOptCost;
+import org.apache.calcite.rel.RelNode;
+import org.apache.calcite.rel.core.JoinRelType;
+import org.apache.calcite.rel.metadata.RelMetadataQuery;
+import org.apache.calcite.rex.RexNode;
+import org.apache.calcite.tools.RelBuilder;
+
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.HashMap;
+import java.util.List;
+
+/**
+ * The core process of dphyp enumeration algorithm.
+ */
+@Experimental
+public class DpHyp {
+
+  private final HyperGraph hyperGraph;
+
+  private final HashMap<Long, RelNode> dpTable;
+
+  private final RelBuilder builder;
+
+  private final RelMetadataQuery mq;
+
+  public DpHyp(HyperGraph hyperGraph, RelBuilder builder, RelMetadataQuery relMetadataQuery) {
+    this.hyperGraph =
+        hyperGraph.copy(
+            hyperGraph.getTraitSet(),
+            hyperGraph.getInputs());
+    this.dpTable = new HashMap<>();
+    this.builder = builder;
+    this.mq = relMetadataQuery;
+    // make all field name unique and convert the
+    // HyperEdge condition from RexInputRef to RexInputFieldName
+    this.hyperGraph.convertHyperEdgeCond(builder);
+  }
+
+  /**
+   * The entry function of the algorithm. We use a bitmap to represent a leaf node,
+   * which indicates the position of the corresponding leaf node in {@link HyperGraph}.
+   *
+   * <p>After the enumeration is completed, the best join order will be stored
+   * in the {@link DpHyp#dpTable}.
+   */
+  public void startEnumerateJoin() {
+    int size = hyperGraph.getInputs().size();
+    for (int i = 0; i < size; i++) {
+      long singleNode = LongBitmap.newBitmap(i);
+      dpTable.put(singleNode, hyperGraph.getInput(i));
+      hyperGraph.initEdgeBitMap(singleNode);
+    }
+
+    // start enumerating from the second to last
+    for (int i = size - 2; i >= 0; i--) {
+      long csg = LongBitmap.newBitmap(i);
+      long forbidden = csg - 1;
+      emitCsg(csg);
+      enumerateCsgRec(csg, forbidden);
+    }
+  }
+
+  /**
+   * Given a connected subgraph (csg), enumerate all possible complements subgraph (cmp)
+   * that do not include anything from the exclusion subset.
+   *
+   * <p>Corresponding to EmitCsg in origin paper.
+   */
+  private void emitCsg(long csg) {
+    long forbidden = csg | LongBitmap.getBvBitmap(csg);
+    long neighbors = hyperGraph.getNeighborBitmap(csg, forbidden);
+
+    LongBitmap.ReverseIterator reverseIterator = new LongBitmap.ReverseIterator(neighbors);
+    for (long cmp : reverseIterator) {
+      List<HyperEdge> edges = hyperGraph.connectCsgCmp(csg, cmp);
+      if (!edges.isEmpty()) {
+        emitCsgCmp(csg, cmp, edges);
+      }
+      // forbidden the nodes that smaller than current cmp when extend cmp, e.g.
+      // neighbors = {t1, t2}, t1 and t2 are connected.
+      // when extented t2, we will get (t1, t2)
+      // when extented t1, we will get (t1, t2) repeated
+      long newForbidden =
+              (cmp | LongBitmap.getBvBitmap(cmp)) & neighbors;
+      newForbidden = newForbidden | forbidden;
+      enumerateCmpRec(csg, cmp, newForbidden);
+    }
+  }
+
+  /**
+   * Given a connected subgraph (csg), expands it recursively by its neighbors.
+   * If the expanded csg is connected, try to enumerate its cmp (note that for complex hyperedge,
+   * we only select a single representative node to add to the neighbors, so csg and subNeighbor
+   * are not necessarily connected. However, it still needs to be expanded to prevent missing
+   * complex hyperedge). This method is called after the enumeration of csg is completed,
+   * that is, after {@link DpHyp#emitCsg(long csg)}.
+   *
+   * <p>Corresponding to EnumerateCsgRec in origin paper.
+   */
+  private void enumerateCsgRec(long csg, long forbidden) {
+    long neighbors = hyperGraph.getNeighborBitmap(csg, forbidden);
+    LongBitmap.SubsetIterator subsetIterator = new LongBitmap.SubsetIterator(neighbors);
+    for (long subNeighbor : subsetIterator) {
+      hyperGraph.updateEdgesForUnion(csg, subNeighbor);
+      long newCsg = csg | subNeighbor;
+      if (dpTable.containsKey(newCsg)) {
+        emitCsg(newCsg);
+      }
+    }
+    long newForbidden = forbidden | neighbors;
+    subsetIterator.reset();
+    for (long subNeighbor : subsetIterator) {
+      long newCsg = csg | subNeighbor;
+      enumerateCsgRec(newCsg, newForbidden);
+    }
+  }
+
+  /**
+   * Given a connected subgraph (csg) and its complement subgraph (cmp), expands the cmp
+   * recursively by neighbors of cmp (cmp and subNeighbor are not necessarily connected,
+   * which is the same logic as in {@link DpHyp#enumerateCsgRec}).
+   *
+   * <p>Corresponding to EnumerateCmpRec in origin paper.
+   */
+  private void enumerateCmpRec(long csg, long cmp, long forbidden) {
+    long neighbors = hyperGraph.getNeighborBitmap(cmp, forbidden);
+    LongBitmap.SubsetIterator subsetIterator = new LongBitmap.SubsetIterator(neighbors);
+    for (long subNeighbor : subsetIterator) {
+      long newCmp = cmp | subNeighbor;
+      hyperGraph.updateEdgesForUnion(cmp, subNeighbor);
+      if (dpTable.containsKey(newCmp)) {
+        List<HyperEdge> edges = hyperGraph.connectCsgCmp(csg, newCmp);
+        if (!edges.isEmpty()) {
+          emitCsgCmp(csg, newCmp, edges);
+        }
+      }
+    }
+    long newForbidden = forbidden | neighbors;
+    subsetIterator.reset();
+    for (long subNeighbor : subsetIterator) {
+      long newCmp = cmp | subNeighbor;
+      enumerateCmpRec(csg, newCmp, newForbidden);
+    }
+  }
+
+  /**
+   * Given a connected csg-cmp pair and the hyperedges that connect them, build the
+   * corresponding Join plan. If the new Join plan is better than the existing plan,
+   * update the {@link DpHyp#dpTable}.
+   *
+   * <p>Corresponding to EmitCsgCmp in origin paper.
+   */
+  private void emitCsgCmp(long csg, long cmp, List<HyperEdge> edges) {
+    RelNode child1 = dpTable.get(csg);
+    RelNode child2 = dpTable.get(cmp);
+    if (child1 == null || child2 == null) {
+      throw new IllegalArgumentException(
+          "csg and cmp were not enumerated in the previous dp process");
+    }
+
+    JoinRelType joinType = hyperGraph.extractJoinType(edges);
+    if (joinType == null) {
+      return;
+    }
+    RexNode joinCond1 = hyperGraph.extractJoinCond(child1, child2, edges);
+    RelNode newPlan1 = builder
+        .push(child1)
+        .push(child2)
+        .join(joinType, joinCond1)
+        .build();
+
+    // swap left and right
+    RexNode joinCond2 = hyperGraph.extractJoinCond(child2, child1, edges);
+    RelNode newPlan2 = builder
+        .push(child2)
+        .push(child1)
+        .join(joinType, joinCond2)
+        .build();
+    RelNode winPlan = chooseBetterPlan(newPlan1, newPlan2);
+
+    RelNode oriPlan = dpTable.get(csg | cmp);
+    if (oriPlan != null) {
+      winPlan = chooseBetterPlan(winPlan, oriPlan);
+    }
+    dpTable.put(csg | cmp, winPlan);
+  }
+
+  public @Nullable RelNode getBestPlan() {
+    int size = hyperGraph.getInputs().size();
+    long wholeGraph = LongBitmap.newBitmapBetween(0, size);
+    return dpTable.get(wholeGraph);
+  }
+
+  private RelNode chooseBetterPlan(RelNode plan1, RelNode plan2) {
+    RelOptCost cost1 = mq.getCumulativeCost(plan1);
+    RelOptCost cost2 = mq.getCumulativeCost(plan2);
+    if (cost1 != null && cost2 != null) {
+      return cost1.isLt(cost2) ? plan1 : plan2;
+    } else if (cost1 != null) {
+      return plan1;
+    } else {
+      return plan2;
+    }
+  }
+
+}

core/src/main/java/org/apache/calcite/rel/rules/DphypJoinReorderRule.java

@@ -0,0 +1,85 @@
+/*
+ * 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.rel.rules;
+
+import org.apache.calcite.linq4j.function.Experimental;
+import org.apache.calcite.plan.RelOptRuleCall;
+import org.apache.calcite.plan.RelRule;
+import org.apache.calcite.rel.RelNode;
+import org.apache.calcite.rel.core.Join;
+import org.apache.calcite.rex.RexBuilder;
+import org.apache.calcite.rex.RexNode;
+import org.apache.calcite.tools.RelBuilder;
+
+import org.immutables.value.Value;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/** Rule that re-orders a {@link Join} tree using dphyp algorithm.
+ *
+ * @see CoreRules#HYPER_GRAPH_OPTIMIZE */
+@Value.Enclosing
+@Experimental
+public class DphypJoinReorderRule
+    extends RelRule<DphypJoinReorderRule.Config>
+    implements TransformationRule {
+
+  protected DphypJoinReorderRule(Config config) {
+    super(config);
+  }
+
+  @Override public void onMatch(RelOptRuleCall call) {
+    HyperGraph hyperGraph = call.rel(0);
+    RelBuilder relBuilder = call.builder();
+
+    // enumerate by Dphyp
+    DpHyp dpHyp = new DpHyp(hyperGraph, relBuilder, call.getMetadataQuery());
+    dpHyp.startEnumerateJoin();
+    RelNode orderedJoin = dpHyp.getBestPlan();
+    if (orderedJoin == null) {
+      return;
+    }
+
+    // permute field to origin order
+    List<String> oriNames = hyperGraph.getRowType().getFieldNames();
+    List<String> newNames = orderedJoin.getRowType().getFieldNames();
+    List<RexNode> projects = new ArrayList<>();
+    RexBuilder rexBuilder = hyperGraph.getCluster().getRexBuilder();
+    for (String oriName : oriNames) {
+      projects.add(rexBuilder.makeInputRef(orderedJoin, newNames.indexOf(oriName)));
+    }
+
+    RelNode result = call.builder()
+        .push(orderedJoin)
+        .project(projects)
+        .build();
+    call.transformTo(result);
+  }
+
+  /** Rule configuration. */
+  @Value.Immutable
+  public interface Config extends RelRule.Config {
+    Config DEFAULT = ImmutableDphypJoinReorderRule.Config.of()
+        .withOperandSupplier(b1 ->
+            b1.operand(HyperGraph.class).anyInputs());
+
+    @Override default DphypJoinReorderRule toRule() {
+      return new DphypJoinReorderRule(this);
+    }
+  }
+}