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Posted to reviews@iotdb.apache.org by "alpass163 (via GitHub)" <gi...@apache.org> on 2025/10/27 02:38:29 UTC
[PR] implement MergeUnion rule to flatten nested UnionNode [iotdb]
alpass163 opened a new pull request, #16657:
URL: https://github.com/apache/iotdb/pull/16657
Adds a new optimizer rule, SetOperationMerge, to flatten nested UnionNodes in the query plan.
For example, a plan tree like (A UNION ALL B) UNION ALL C will be rewritten into a single UnionNode with three children: A, B, and C.
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Re: [PR] implement MergeUnion rule to flatten nested UnionNode [iotdb]
Posted by "JackieTien97 (via GitHub)" <gi...@apache.org>.
JackieTien97 merged PR #16657:
URL: https://github.com/apache/iotdb/pull/16657
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Re: [PR] implement MergeUnion rule to flatten nested UnionNode [iotdb]
Posted by "Copilot (via GitHub)" <gi...@apache.org>.
Copilot commented on code in PR #16657:
URL: https://github.com/apache/iotdb/pull/16657#discussion_r2467726349
##########
iotdb-core/datanode/src/test/java/org/apache/iotdb/db/queryengine/plan/relational/analyzer/MergeUnionTest.java:
##########
@@ -0,0 +1,98 @@
+/*
+ * 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.iotdb.db.queryengine.plan.relational.analyzer;
+
+import org.apache.iotdb.db.queryengine.plan.planner.plan.LogicalQueryPlan;
+import org.apache.iotdb.db.queryengine.plan.relational.planner.SymbolAllocator;
+import org.apache.iotdb.db.queryengine.plan.relational.planner.TableLogicalPlanner;
+
+import org.junit.Test;
+
+import static org.apache.iotdb.db.queryengine.plan.relational.analyzer.AnalyzerTest.analyzeSQL;
+import static org.apache.iotdb.db.queryengine.plan.relational.analyzer.TestUtils.DEFAULT_WARNING;
+import static org.apache.iotdb.db.queryengine.plan.relational.analyzer.TestUtils.QUERY_CONTEXT;
+import static org.apache.iotdb.db.queryengine.plan.relational.analyzer.TestUtils.SESSION_INFO;
+import static org.apache.iotdb.db.queryengine.plan.relational.analyzer.TestUtils.TEST_MATADATA;
+import static org.apache.iotdb.db.queryengine.plan.relational.planner.assertions.PlanAssert.assertPlan;
+import static org.apache.iotdb.db.queryengine.plan.relational.planner.assertions.PlanMatchPattern.output;
+import static org.apache.iotdb.db.queryengine.plan.relational.planner.assertions.PlanMatchPattern.tableScan;
+import static org.apache.iotdb.db.queryengine.plan.relational.planner.assertions.PlanMatchPattern.union;
+
+public class MergeUnionTest {
+
+ @Test
+ public void simpleLeftDeepMerge() {
+
+ String sql =
+ "(select tag1 from t1 union all select tag1 from t2) union all select tag1 from t3 ";
+ Analysis analysis = analyzeSQL(sql, TEST_MATADATA, QUERY_CONTEXT);
+ SymbolAllocator symbolAllocator = new SymbolAllocator();
+ LogicalQueryPlan actualLogicalQueryPlan =
+ new TableLogicalPlanner(
+ QUERY_CONTEXT, TEST_MATADATA, SESSION_INFO, symbolAllocator, DEFAULT_WARNING)
+ .plan(analysis);
+
+ // just verify the Logical plan `Output - union - 3*tableScan`
+ assertPlan(
+ actualLogicalQueryPlan,
+ output((union(tableScan("testdb.t1"), tableScan("testdb.t2"), tableScan("testdb.t3")))));
+ }
+
+ @Test
+ public void simpleRightDeepMerge() {
+
+ String sql =
+ "select tag1 from t1 union all (select tag1 from t2 union all select tag1 from t3) ";
+ Analysis analysis = analyzeSQL(sql, TEST_MATADATA, QUERY_CONTEXT);
+ SymbolAllocator symbolAllocator = new SymbolAllocator();
+ LogicalQueryPlan actualLogicalQueryPlan =
+ new TableLogicalPlanner(
+ QUERY_CONTEXT, TEST_MATADATA, SESSION_INFO, symbolAllocator, DEFAULT_WARNING)
+ .plan(analysis);
+
+ // just verify the Logical plan `Output - union - 3*tableScan`
+ assertPlan(
+ actualLogicalQueryPlan,
+ output((union(tableScan("testdb.t1"), tableScan("testdb.t2"), tableScan("testdb.t3")))));
+ }
+
+ @Test
+ public void bushyTreeMerge() {
+
+ String sql =
+ "(select tag1 from t1 union all select tag1 from t2) union all (select tag1 from t3 union all select tag1 from t4) ";
+ Analysis analysis = analyzeSQL(sql, TEST_MATADATA, QUERY_CONTEXT);
+ SymbolAllocator symbolAllocator = new SymbolAllocator();
+ LogicalQueryPlan actualLogicalQueryPlan =
+ new TableLogicalPlanner(
+ QUERY_CONTEXT, TEST_MATADATA, SESSION_INFO, symbolAllocator, DEFAULT_WARNING)
+ .plan(analysis);
+
+ // just verify the Logical plan `Output - union - 3*tableScan`
Review Comment:
The comment indicates '3*tableScan' but the test actually verifies 4 table scans (t1, t2, t3, t4). Update the comment to '4*tableScan'.
```suggestion
// just verify the Logical plan `Output - union - 4*tableScan`
```
##########
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/planner/optimizations/LogicalOptimizeFactory.java:
##########
@@ -255,6 +257,17 @@ public LogicalOptimizeFactory(PlannerContext plannerContext) {
.build()),
simplifyOptimizer,
new UnaliasSymbolReferences(plannerContext.getMetadata()),
+ new IterativeOptimizer(
+ plannerContext,
+ ruleStats,
+ ImmutableSet.<Rule<?>>builder()
+ .addAll(
+ ImmutableSet.of(
+ new MergeUnion(),
+ // new MergeIntersect
+ // new MergeExcpet
Review Comment:
Corrected spelling of 'Excpet' to 'Except'.
```suggestion
// new MergeExcept
```
##########
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/planner/iterative/rule/SetOperationMerge.java:
##########
@@ -0,0 +1,144 @@
+/*
+ * 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.iotdb.db.queryengine.plan.relational.planner.iterative.rule;
+
+import org.apache.iotdb.db.queryengine.plan.planner.plan.node.PlanNode;
+import org.apache.iotdb.db.queryengine.plan.relational.planner.Symbol;
+import org.apache.iotdb.db.queryengine.plan.relational.planner.iterative.Lookup;
+import org.apache.iotdb.db.queryengine.plan.relational.planner.iterative.Rule;
+import org.apache.iotdb.db.queryengine.plan.relational.planner.node.SetOperationNode;
+import org.apache.iotdb.db.queryengine.plan.relational.planner.node.UnionNode;
+
+import com.google.common.collect.ImmutableListMultimap;
+import com.google.common.collect.Iterables;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+import static com.google.common.base.Preconditions.checkState;
+import static com.google.common.collect.ImmutableList.toImmutableList;
+
+public class SetOperationMerge {
+
+ private final Rule.Context context;
+ private final SetOperationNode node;
+ private final List<PlanNode> newSources;
+
+ public SetOperationMerge(SetOperationNode node, Rule.Context context) {
+ this.node = node;
+ this.context = context;
+ this.newSources = new ArrayList<>();
+ }
+
+ // Merge multiple union into one union
+ public Optional<SetOperationNode> merge() {
+
+ checkState(
+ node instanceof UnionNode, "unexpected node type: %s", node.getClass().getSimpleName());
+ Lookup lookup = context.getLookup();
+ // Pre-check
+ boolean anyMerge =
+ node.getChildren().stream()
+ .map(lookup::resolve)
+ .anyMatch(child -> node.getClass().equals(child.getClass()));
+ if (!anyMerge) {
+ return Optional.empty();
+ }
+
+ List<PlanNode> childrenOfUnion =
+ node.getChildren().stream().map(lookup::resolve).collect(toImmutableList());
+
+ ImmutableListMultimap.Builder<Symbol, Symbol> newMappingsBuilder =
+ ImmutableListMultimap.builder();
+
+ boolean rewritten = false;
+
+ for (int i = 0; i < childrenOfUnion.size(); i++) {
+ PlanNode child = childrenOfUnion.get(i);
+
+ // Determine if set operations can be merged and whether the resulting set operation is
+ // quantified DISTINCT or ALL
+ Optional<Boolean> mergedQuantifier = mergedQuantifierIsDistinct(node, child);
+ if (mergedQuantifier.isPresent()) {
+ addMergedMappings((SetOperationNode) child, i, newMappingsBuilder);
+ rewritten = true;
+ } else {
+ // Keep mapping as it is
+ addOriginalMappings(child, i, newMappingsBuilder);
+ }
+ }
+
+ if (!rewritten) {
+ return Optional.empty();
+ }
+
+ // the union has merged
+ return Optional.of(
+ new UnionNode(
+ node.getPlanNodeId(), newSources, newMappingsBuilder.build(), node.getOutputSymbols()));
+ }
+
+ private void addMergedMappings(
+ SetOperationNode child,
+ int childIndex,
+ ImmutableListMultimap.Builder<Symbol, Symbol> newMappingsBuilder) {
+
+ newSources.addAll(child.getChildren());
+ Map<Symbol, Collection<Symbol>> symbolMappings = node.getSymbolMapping().asMap();
+ for (Map.Entry<Symbol, Collection<Symbol>> mapping : symbolMappings.entrySet()) {
+ Symbol input = Iterables.get(mapping.getValue(), childIndex);
+ newMappingsBuilder.putAll(mapping.getKey(), child.getSymbolMapping().get(input));
+ }
+ }
+
+ private void addOriginalMappings(
+ PlanNode child,
+ int childIndex,
+ ImmutableListMultimap.Builder<Symbol, Symbol> newMappingsBuilder) {
+
+ newSources.add(child);
+ Map<Symbol, Collection<Symbol>> symbolMappings = node.getSymbolMapping().asMap();
+ for (Map.Entry<Symbol, Collection<Symbol>> mapping : symbolMappings.entrySet()) {
+ newMappingsBuilder.put(mapping.getKey(), Iterables.get(mapping.getValue(), childIndex));
+ }
+ }
+
+ /**
+ * Check if node and child are mergable based on their set operation type and quantifier.
Review Comment:
Corrected spelling of 'mergable' to 'mergeable'.
```suggestion
* Check if node and child are mergeable based on their set operation type and quantifier.
```
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