xiedeyantu commented on code in PR #4598: URL: https://github.com/apache/calcite/pull/4598#discussion_r2463148386
########## core/src/main/java/org/apache/calcite/rel/rules/AggregateExtractLiteralAggRule.java: ########## @@ -0,0 +1,134 @@ +/* + * 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.RelOptRuleCall; +import org.apache.calcite.plan.RelRule; +import org.apache.calcite.rel.RelNode; +import org.apache.calcite.rel.core.Aggregate; +import org.apache.calcite.rel.core.AggregateCall; +import org.apache.calcite.rex.RexBuilder; +import org.apache.calcite.rex.RexNode; +import org.apache.calcite.sql.SqlKind; +import org.apache.calcite.tools.RelBuilder; + +import org.immutables.value.Value; + +import java.util.ArrayList; +import java.util.HashMap; +import java.util.List; +import java.util.Map; + +/** + * Rule transforms an {@link org.apache.calcite.rel.core.Aggregate} containing + * {@code LITERAL_AGG} aggregate function into an {@code Aggregate} that still + * performs "group by" on the relevant groups, while placing a {@code Project} + * RelNode on top that returns the literal value. + */ [email protected] +public class AggregateExtractLiteralAggRule + extends RelRule<AggregateExtractLiteralAggRule.Config> + implements TransformationRule { + + protected AggregateExtractLiteralAggRule(Config config) { + super(config); + } + + @Override public void onMatch(RelOptRuleCall call) { + final RelBuilder relBuilder = call.builder(); + final Aggregate aggregate = call.rel(0); + final List<AggregateCall> aggCalls = aggregate.getAggCallList(); + if (aggCalls.isEmpty()) { + return; + } + + // Collect indices of LITERAL_AGG calls. + final List<Integer> literalAggIndices = new ArrayList<>(); + for (int i = 0; i < aggCalls.size(); i++) { + final AggregateCall ac = aggCalls.get(i); + if (ac.getAggregation().getKind() == SqlKind.LITERAL_AGG) { + literalAggIndices.add(i); + } + } + + if (literalAggIndices.isEmpty()) { + // nothing to do + return; + } + + // Build new AggregateCall list without LITERAL_AGG entries. + final List<AggregateCall> newAggCalls = new ArrayList<>(); + final Map<Integer, Integer> oldAggIndexToNewAggIndex = new HashMap<>(); + int newAggPos = 0; + for (int i = 0; i < aggCalls.size(); i++) { + if (!literalAggIndices.contains(i)) { + newAggCalls.add(aggCalls.get(i)); + oldAggIndexToNewAggIndex.put(i, newAggPos++); + } + } + + relBuilder.push(aggregate.getInput()); + final RelBuilder.GroupKey groupKey = + relBuilder.groupKey(aggregate.getGroupSet(), aggregate.getGroupSets()); + final RelNode newAggregate = relBuilder.aggregate(groupKey, newAggCalls).build(); + + final RexBuilder rexBuilder = aggregate.getCluster().getRexBuilder(); + + // Number of group columns in output (group keys appear first). + final int groupCount = aggregate.getGroupSet().cardinality(); + final int origAggCount = aggCalls.size(); + final int origOutputCount = groupCount + origAggCount; + + // Build projection expressions to restore original output layout. + final List<RexNode> projects = new ArrayList<>(origOutputCount); + for (int outPos = 0; outPos < origOutputCount; outPos++) { + if (outPos < groupCount) { + // Group key columns remain in the same positions. + projects.add(rexBuilder.makeInputRef(newAggregate, outPos)); + } else { + // Aggregate output: determine original aggregate index. + final int origAggIndex = outPos - groupCount; + if (literalAggIndices.contains(origAggIndex)) { + // Replacement for LITERAL_AGG: try to extract literal from the original AggregateCall. + projects.add(aggCalls.get(origAggIndex).rexList.get(0)); + } else { + // Non-literal aggregate: compute its new output index in newAggregate. + final Integer newAggIndex = oldAggIndexToNewAggIndex.get(origAggIndex); + if (newAggIndex != null) { + projects.add(rexBuilder.makeInputRef(newAggregate, groupCount + newAggIndex)); + } + } + } + } + + relBuilder.push(newAggregate); Review Comment: if `final RelNode newAggregate = relBuilder.aggregate(groupKey, newAggCalls).build();` change to `final RelNode newAggregate = relBuilder.aggregate(groupKey, newAggCalls);`, This push should be omitted. This is a minor, non-essential suggestion. ########## core/src/main/java/org/apache/calcite/rel/rules/CoreRules.java: ########## @@ -945,4 +945,8 @@ private CoreRules() {} * into equivalent {@link Union} ALL of GROUP BY operations. */ public static final AggregateGroupingSetsToUnionRule AGGREGATE_GROUPING_SETS_TO_UNION = AggregateGroupingSetsToUnionRule.Config.DEFAULT.toRule(); + + /** Rule that gets rid of the LITERAL_AGG into most databases can handle. */ Review Comment: I think a brief description of how the plan is transformed from one form to another is needed here, rather than describing where the rule will be used. ########## core/src/test/java/org/apache/calcite/test/RelOptRulesTest.java: ########## @@ -11413,4 +11413,88 @@ private void checkLoptOptimizeJoinRule(LoptOptimizeJoinRule rule) { }) .check(); } + + /** Test case of + * <a href="https://issues.apache.org/jira/browse/CALCITE-7242";>[CALCITE-7242] + * Implement a rule to eliminate LITERAL_AGG so that other databases can handle it</a>. */ + @Test void testAggregateExtractLiteralAggRule1() { Review Comment: If a rule requires multiple test cases, it's best to avoid naming them with a simple incrementing number suffix.. This makes it difficult to quickly understand the purpose of each test. For example, this name could be changed to something like `testAggregateExtractLiteralAggRuleSomeLessThan`. ########## core/src/main/java/org/apache/calcite/rel/rules/AggregateExtractLiteralAggRule.java: ########## @@ -0,0 +1,134 @@ +/* + * 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.RelOptRuleCall; +import org.apache.calcite.plan.RelRule; +import org.apache.calcite.rel.RelNode; +import org.apache.calcite.rel.core.Aggregate; +import org.apache.calcite.rel.core.AggregateCall; +import org.apache.calcite.rex.RexBuilder; +import org.apache.calcite.rex.RexNode; +import org.apache.calcite.sql.SqlKind; +import org.apache.calcite.tools.RelBuilder; + +import org.immutables.value.Value; + +import java.util.ArrayList; +import java.util.HashMap; +import java.util.List; +import java.util.Map; + +/** + * Rule transforms an {@link org.apache.calcite.rel.core.Aggregate} containing + * {@code LITERAL_AGG} aggregate function into an {@code Aggregate} that still + * performs "group by" on the relevant groups, while placing a {@code Project} + * RelNode on top that returns the literal value. + */ [email protected] +public class AggregateExtractLiteralAggRule + extends RelRule<AggregateExtractLiteralAggRule.Config> + implements TransformationRule { + + protected AggregateExtractLiteralAggRule(Config config) { + super(config); + } + + @Override public void onMatch(RelOptRuleCall call) { + final RelBuilder relBuilder = call.builder(); + final Aggregate aggregate = call.rel(0); + final List<AggregateCall> aggCalls = aggregate.getAggCallList(); + if (aggCalls.isEmpty()) { + return; + } + + // Collect indices of LITERAL_AGG calls. + final List<Integer> literalAggIndices = new ArrayList<>(); + for (int i = 0; i < aggCalls.size(); i++) { + final AggregateCall ac = aggCalls.get(i); + if (ac.getAggregation().getKind() == SqlKind.LITERAL_AGG) { + literalAggIndices.add(i); + } + } + + if (literalAggIndices.isEmpty()) { + // nothing to do + return; + } + + // Build new AggregateCall list without LITERAL_AGG entries. + final List<AggregateCall> newAggCalls = new ArrayList<>(); + final Map<Integer, Integer> oldAggIndexToNewAggIndex = new HashMap<>(); + int newAggPos = 0; + for (int i = 0; i < aggCalls.size(); i++) { + if (!literalAggIndices.contains(i)) { + newAggCalls.add(aggCalls.get(i)); + oldAggIndexToNewAggIndex.put(i, newAggPos++); + } + } + + relBuilder.push(aggregate.getInput()); + final RelBuilder.GroupKey groupKey = + relBuilder.groupKey(aggregate.getGroupSet(), aggregate.getGroupSets()); + final RelNode newAggregate = relBuilder.aggregate(groupKey, newAggCalls).build(); + + final RexBuilder rexBuilder = aggregate.getCluster().getRexBuilder(); + + // Number of group columns in output (group keys appear first). + final int groupCount = aggregate.getGroupSet().cardinality(); + final int origAggCount = aggCalls.size(); + final int origOutputCount = groupCount + origAggCount; + + // Build projection expressions to restore original output layout. + final List<RexNode> projects = new ArrayList<>(origOutputCount); + for (int outPos = 0; outPos < origOutputCount; outPos++) { + if (outPos < groupCount) { + // Group key columns remain in the same positions. + projects.add(rexBuilder.makeInputRef(newAggregate, outPos)); + } else { + // Aggregate output: determine original aggregate index. + final int origAggIndex = outPos - groupCount; + if (literalAggIndices.contains(origAggIndex)) { + // Replacement for LITERAL_AGG: try to extract literal from the original AggregateCall. + projects.add(aggCalls.get(origAggIndex).rexList.get(0)); + } else { + // Non-literal aggregate: compute its new output index in newAggregate. + final Integer newAggIndex = oldAggIndexToNewAggIndex.get(origAggIndex); + if (newAggIndex != null) { Review Comment: `assert newAggIndex != null` ？Could the index here be null? -- This is an automated message from the Apache Git Service. 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