[GitHub] [calcite] chunweilei commented on a change in pull request #1619: [CALCITE-3537] Add ProjectAggregateTransposeRule to normalize materialized view in SubstitutionVisitor

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chunweilei commented on a change in pull request #1619: [CALCITE-3537] Add ProjectAggregateTransposeRule to normalize materialized view in SubstitutionVisitor
URL: https://github.com/apache/calcite/pull/1619#discussion_r353048207
 
 

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 File path: core/src/main/java/org/apache/calcite/rel/rules/ProjectAggregateTransposeRule.java
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+/*
+ * 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.plan.RelOptRule;
+import org.apache.calcite.plan.RelOptRuleCall;
+import org.apache.calcite.rel.RelNode;
+import org.apache.calcite.rel.core.Aggregate;
+import org.apache.calcite.rel.core.Project;
+import org.apache.calcite.rel.core.RelFactories;
+import org.apache.calcite.rel.logical.LogicalAggregate;
+import org.apache.calcite.rel.logical.LogicalProject;
+import org.apache.calcite.rel.type.RelDataTypeField;
+import org.apache.calcite.rex.RexInputRef;
+import org.apache.calcite.rex.RexNode;
+import org.apache.calcite.tools.RelBuilder;
+import org.apache.calcite.tools.RelBuilderFactory;
+import org.apache.calcite.util.Pair;
+import org.apache.calcite.util.mapping.Mappings;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * Planner rule that pushes a {@link org.apache.calcite.rel.core.Project}
+ * past a {@link org.apache.calcite.rel.core.Aggregate}.
+ */
+public class ProjectAggregateTransposeRule extends RelOptRule {
+
+  public static final ProjectAggregateTransposeRule INSTANCE =
+      new ProjectAggregateTransposeRule(Project.class,
+          Aggregate.class, RelFactories.LOGICAL_BUILDER);
+
+  /**
+   * Creates a ProjectAggregateTransposeRule.
+   */
+  private ProjectAggregateTransposeRule(Class<? extends Project> project,
+      Class<? extends Aggregate> aggregate, RelBuilderFactory relBuilderFactory) {
+    super(operand(project, operand(aggregate, any())),
+        relBuilderFactory, "ProjectAggregateTransposeRule");
+  }
+
+  public void onMatch(RelOptRuleCall call) {
+    final LogicalProject proRel = call.rel(0);
+    final LogicalAggregate aggRel = call.rel(1);
+
+    final Mappings.TargetMapping mapping =
+        Project.getMapping(aggRel.getRowType().getFieldCount(), proRel.getProjects());
+    if (mapping == null || Mappings.keepsOrdering(mapping)) {
+      // do nothing
+      return;
+    }
+    // Project              Aggregate
+    //    Aggregate  --->      Project
+    final List<Pair<Integer, Integer>> pairs = new ArrayList<>();
+    final List<Integer> groupings = aggRel.getGroupSet().toList();
+    RelBuilder relBuilder = call.builder();
+    final List<Integer> posList = new ArrayList<>();
+
+    for (int i = 0; i < groupings.size(); i++) {
+      pairs.add(Pair.of(mapping.getTarget(groupings.get(i)), i));
+    }
+    Collections.sort(pairs);
+    pairs.forEach(pair -> posList.add(pair.right));
+
+    for (int i = posList.size(); i < aggRel.getInput().getRowType().getFieldCount(); i++) {
+      posList.add(i);
+    }
+    List<RexNode> newProj = posList.stream().map(
+        pos -> RexInputRef.of(pos, aggRel.getInput().getRowType()))
+        .collect(Collectors.toList());
+    final RelNode project = relBuilder.push(aggRel.getInput()).project(newProj).build();
+
+    RelNode newAgg = relBuilder.push(project).aggregate(relBuilder.groupKey(aggRel.getGroupSet()),
+        aggRel.getAggCallList()).build();
+
+    if (!rowTypesAreEquivalent(proRel, newAgg)) {
+      return;
+    }
+
+    call.transformTo(newAgg);
+  }
+
+  private boolean rowTypesAreEquivalent(
+      RelNode rel0, RelNode rel1) {
+    if (rel0.getRowType().getFieldCount() != rel1.getRowType().getFieldCount()) {
+      return false;
+    }
 
 Review comment:
   You can use `RelOptUtils#areRowTypesEqual` to compare whether two RelDataTypes equal.

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