kgyrtkirk commented on code in PR #3396: URL: https://github.com/apache/calcite/pull/3396#discussion_r1310312042
########## core/src/main/java/org/apache/calcite/rel/rules/SortMergeRule.java: ########## @@ -0,0 +1,146 @@ +/* + * 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.core.Sort; +import org.apache.calcite.rex.RexLiteral; +import org.apache.calcite.rex.RexNode; +import org.apache.calcite.tools.RelBuilder; + +import com.google.common.collect.ImmutableList; + +import org.immutables.value.Value; + +/** + * This rule try to merge the double {@link Sort},one is Limit semantics, + * another sort is Limit or TOPN semantics. + * + * <p> It generally used with the {@link SortProjectTransposeRule} rule. + * + * <p> For example: + * <blockquote><pre>{@code + * select + * concat('-', N_REGIONKEY) from + * ( + * select + * * + * from nation limit 10000) limit 10} + * </pre></blockquote> + * + * <p> will convert to + * <blockquote><pre>{@code + * select + * concat('-', N_REGIONKEY) + * from + * nation limit 10 + * }</pre></blockquote> + * + * <p> The sql : + * <blockquote><pre>{@code + * select concat('-',N_REGIONKEY) from + * (SELECT * FROM nation order BY N_REGIONKEY DESC LIMIT 10000) limit 10 + * }</pre></blockquote> + * + * <p> will convert to + * <blockquote><pre>{@code + * SELECT concat('-',N_REGIONKEY) FROM nation order BY N_REGIONKEY DESC LIMIT 10 + * }</pre></blockquote> + * + * <p> In the future,we could also extend other sort merge logic in this rule. + */ +@Value.Enclosing +public class SortMergeRule + extends RelRule<SortMergeRule.Config> + implements TransformationRule { + + protected SortMergeRule(final SortMergeRule.Config config) { + super(config); + } + + @Override public void onMatch(final RelOptRuleCall call) { + config.matchHandler().accept(this, call); + } + + private static void limitMerge(SortMergeRule rule, + RelOptRuleCall call) { + final Sort sort = call.rel(0); + final Sort child = call.rel(1); + + if (child.offset != null || child.fetch == null) { + // we could do nothing here + return; + } + + final RelBuilder builder = call.builder(); + + final int limitCnt = sort.fetch instanceof RexLiteral + ? RexLiteral.intValue(sort.fetch) : -1; + + final int childLimitCnt = child.fetch instanceof RexLiteral + ? RexLiteral.intValue(child.fetch) : -1; + + if (limitCnt == -1 || childLimitCnt == -1) { + return; + } + + // Get the minimum limit value from parent and child sort RelNode + int minLimit = limitCnt < childLimitCnt Review Comment: nit: isn't `Math.min` is more readable? ########## core/src/main/java/org/apache/calcite/rel/rules/SortMergeRule.java: ########## @@ -0,0 +1,146 @@ +/* + * 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.core.Sort; +import org.apache.calcite.rex.RexLiteral; +import org.apache.calcite.rex.RexNode; +import org.apache.calcite.tools.RelBuilder; + +import com.google.common.collect.ImmutableList; + +import org.immutables.value.Value; + +/** + * This rule try to merge the double {@link Sort},one is Limit semantics, + * another sort is Limit or TOPN semantics. + * + * <p> It generally used with the {@link SortProjectTransposeRule} rule. + * + * <p> For example: + * <blockquote><pre>{@code + * select + * concat('-', N_REGIONKEY) from + * ( + * select + * * + * from nation limit 10000) limit 10} + * </pre></blockquote> + * + * <p> will convert to + * <blockquote><pre>{@code + * select + * concat('-', N_REGIONKEY) + * from + * nation limit 10 + * }</pre></blockquote> + * + * <p> The sql : + * <blockquote><pre>{@code + * select concat('-',N_REGIONKEY) from + * (SELECT * FROM nation order BY N_REGIONKEY DESC LIMIT 10000) limit 10 + * }</pre></blockquote> + * + * <p> will convert to + * <blockquote><pre>{@code + * SELECT concat('-',N_REGIONKEY) FROM nation order BY N_REGIONKEY DESC LIMIT 10 + * }</pre></blockquote> + * + * <p> In the future,we could also extend other sort merge logic in this rule. + */ +@Value.Enclosing +public class SortMergeRule + extends RelRule<SortMergeRule.Config> + implements TransformationRule { + + protected SortMergeRule(final SortMergeRule.Config config) { + super(config); + } + + @Override public void onMatch(final RelOptRuleCall call) { + config.matchHandler().accept(this, call); + } + + private static void limitMerge(SortMergeRule rule, + RelOptRuleCall call) { + final Sort sort = call.rel(0); + final Sort child = call.rel(1); Review Comment: nit: I find the naming of these 2 a bit confusing - they are both `Sort` nodes - and they are being evaluated as such - so `child` doesn't really match that.. could you rename them something like: `topSort` / `bottomSort` or similar ? ########## core/src/test/java/org/apache/calcite/test/RelOptRulesTest.java: ########## @@ -1254,6 +1254,30 @@ private void checkSemiOrAntiJoinProjectTranspose(JoinRelType type) { diffRepos.assertEquals("planAfter", "${planAfter}", planAfter); } + /** Test case for + * <a href="https://issues.apache.org/jira/browse/CALCITE-5940";>[CALCITE-5940] + * Add the Rules to optimize Limit</a>. */ + @Test void testLimitMerge() { + final String sql = "select deptno from " + + "(select deptno from emp where sal > 100 limit 10000) limit 10"; + sql(sql) + .withPreRule(CoreRules.SORT_PROJECT_TRANSPOSE) + .withRule(CoreRules.LIMIT_MREGE, CoreRules.PROJECT_REMOVE) + .check(); + } + + /** Test case for + * <a href="https://issues.apache.org/jira/browse/CALCITE-5940";>[CALCITE-5940] + * Add the Rules to optimize Limit</a>. */ + @Test void testLimitMerge1() { Review Comment: I know its not covered in this patch ; but if you could add some test(s) with offset so that its "tested" that those cases are not covered right now ########## core/src/main/java/org/apache/calcite/rel/rules/SortMergeRule.java: ########## @@ -0,0 +1,146 @@ +/* + * 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.core.Sort; +import org.apache.calcite.rex.RexLiteral; +import org.apache.calcite.rex.RexNode; +import org.apache.calcite.tools.RelBuilder; + +import com.google.common.collect.ImmutableList; + +import org.immutables.value.Value; + +/** + * This rule try to merge the double {@link Sort},one is Limit semantics, + * another sort is Limit or TOPN semantics. + * + * <p> It generally used with the {@link SortProjectTransposeRule} rule. + * + * <p> For example: + * <blockquote><pre>{@code + * select + * concat('-', N_REGIONKEY) from + * ( + * select + * * + * from nation limit 10000) limit 10} + * </pre></blockquote> + * + * <p> will convert to + * <blockquote><pre>{@code + * select + * concat('-', N_REGIONKEY) + * from + * nation limit 10 + * }</pre></blockquote> + * + * <p> The sql : + * <blockquote><pre>{@code + * select concat('-',N_REGIONKEY) from + * (SELECT * FROM nation order BY N_REGIONKEY DESC LIMIT 10000) limit 10 + * }</pre></blockquote> + * + * <p> will convert to + * <blockquote><pre>{@code + * SELECT concat('-',N_REGIONKEY) FROM nation order BY N_REGIONKEY DESC LIMIT 10 + * }</pre></blockquote> + * + * <p> In the future,we could also extend other sort merge logic in this rule. + */ +@Value.Enclosing +public class SortMergeRule + extends RelRule<SortMergeRule.Config> + implements TransformationRule { + + protected SortMergeRule(final SortMergeRule.Config config) { + super(config); + } + + @Override public void onMatch(final RelOptRuleCall call) { + config.matchHandler().accept(this, call); + } + + private static void limitMerge(SortMergeRule rule, + RelOptRuleCall call) { + final Sort sort = call.rel(0); + final Sort child = call.rel(1); + + if (child.offset != null || child.fetch == null) { + // we could do nothing here + return; + } + + final RelBuilder builder = call.builder(); + + final int limitCnt = sort.fetch instanceof RexLiteral Review Comment: I think it might be better to stick with the naming we already have - and use the term `fetch` in this case -- This is an automated message from the Apache Git Service. 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