[CALCITE-5994] When a sort's input max row cnt is 1,remove the redund…

…ant sort
apache · Sep 11, 2023 · 68ccac1 · 68ccac1
1 parent d4046d0
commit 68ccac1
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Showing 3 changed files with 95 additions and 17 deletions.
diff --git a/core/src/main/java/org/apache/calcite/rel/rules/SortRemoveRule.java b/core/src/main/java/org/apache/calcite/rel/rules/SortRemoveRule.java
@@ -52,25 +52,35 @@ public SortRemoveRule(RelBuilderFactory relBuilderFactory) {
   }
 
   @Override public void onMatch(RelOptRuleCall call) {
-    if (!call.getPlanner().getRelTraitDefs()
-        .contains(RelCollationTraitDef.INSTANCE)) {
-      // Collation is not an active trait.
-      return;
-    }
     final Sort sort = call.rel(0);
-    if (sort.offset != null || sort.fetch != null) {
-      // Don't remove sort if would also remove OFFSET or LIMIT.
-      return;
+    // Get the max row count for sort's input RelNode.
+    final Double maxRowCount = call.getMetadataQuery().getMaxRowCount(sort.getInput());
+    // If the max row count is not null and less than or equal to 1,
+    // then we could remove the sort.
+    if (maxRowCount != null && maxRowCount <= 1D) {
+      call.transformTo(sort.getInput());
+    } else {
+      if (!call.getPlanner().getRelTraitDefs()
+          .contains(RelCollationTraitDef.INSTANCE)) {
+        // Collation is not an active trait.
+        return;
+      }
+
+      if (sort.offset != null || sort.fetch != null) {
+        // Don't remove sort if would also remove OFFSET or LIMIT.
+        return;
+      }
+
+      // Express the "sortedness" requirement in terms of a collation trait and
+      // we can get rid of the sort. This allows us to use rels that just happen
+      // to be sorted but get the same effect.
+      final RelCollation collation = sort.getCollation();
+      assert collation == sort.getTraitSet()
+          .getTrait(RelCollationTraitDef.INSTANCE);
+      final RelTraitSet traits = sort.getInput().getTraitSet()
+          .replace(collation).replaceIf(ConventionTraitDef.INSTANCE, sort::getConvention);
+      call.transformTo(convert(call.getPlanner(), sort.getInput(), traits));
     }
-    // Express the "sortedness" requirement in terms of a collation trait and
-    // we can get rid of the sort. This allows us to use rels that just happen
-    // to be sorted but get the same effect.
-    final RelCollation collation = sort.getCollation();
-    assert collation == sort.getTraitSet()
-        .getTrait(RelCollationTraitDef.INSTANCE);
-    final RelTraitSet traits = sort.getInput().getTraitSet()
-        .replace(collation).replaceIf(ConventionTraitDef.INSTANCE, sort::getConvention);
-    call.transformTo(convert(call.getPlanner(), sort.getInput(), traits));
   }
 
   /** Rule configuration. */

diff --git a/core/src/test/java/org/apache/calcite/test/RelOptRulesTest.java b/core/src/test/java/org/apache/calcite/test/RelOptRulesTest.java
@@ -1214,6 +1214,31 @@ private void checkSemiOrAntiJoinProjectTranspose(JoinRelType type) {
         .check();
   }
 
+  /** Test case for
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-5994">[CALCITE-5994]
+   * When a sort's input max row cnt is 1,remove the redundant sort</a>. */
+  @Test void testSortRemoveWhenAggregateMaxRowCntIsOne() {
+    final String sql = "select count(*) as c\n"
+        + "from sales.emp order by c";
+    sql(sql)
+        .withRule(CoreRules.SORT_REMOVE)
+        .check();
+  }
+
+  /** Test case for
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-5994">[CALCITE-5994]
+   * When a sort's input max row cnt is 1,remove the redundant sort</a>. */
+  @Test void testSortRemoveWhenLimitMaxRowCntIsOne() {
+    final String sql = "select *\n"
+        + "from (select * from sales.emp limit 1)\n"
+        + "order by deptno";
+    sql(sql)
+        .withRule(CoreRules.SORT_REMOVE,
+            CoreRules.SORT_PROJECT_TRANSPOSE,
+            CoreRules.PROJECT_REMOVE)
+        .check();
+  }
+
   /** Tests that an {@link EnumerableLimit} and {@link EnumerableSort} are
    * replaced by an {@link EnumerableLimitSort}, per
    * <a href="https://issues.apache.org/jira/browse/CALCITE-3920">[CALCITE-3920]

diff --git a/core/src/test/resources/org/apache/calcite/test/RelOptRulesTest.xml b/core/src/test/resources/org/apache/calcite/test/RelOptRulesTest.xml
@@ -13781,6 +13781,49 @@ LogicalProject(C=[$0])
         LogicalProject(DEPTNO=[$7], SAL=[$5])
           LogicalFilter(condition=[=($7, 10)])
             LogicalTableScan(table=[[CATALOG, SALES, EMP]])
+]]>
+    </Resource>
+  </TestCase>
+  <TestCase name="testSortRemoveWhenAggregateMaxRowCntIsOne">
+    <Resource name="sql">
+      <![CDATA[select count(*) as c
+from sales.emp order by c]]>
+    </Resource>
+    <Resource name="planBefore">
+      <![CDATA[
+LogicalSort(sort0=[$0], dir0=[ASC])
+  LogicalAggregate(group=[{}], C=[COUNT()])
+    LogicalProject($f0=[0])
+      LogicalTableScan(table=[[CATALOG, SALES, EMP]])
+]]>
+    </Resource>
+    <Resource name="planAfter">
+      <![CDATA[
+LogicalAggregate(group=[{}], C=[COUNT()])
+  LogicalProject($f0=[0])
+    LogicalTableScan(table=[[CATALOG, SALES, EMP]])
+]]>
+    </Resource>
+  </TestCase>
+  <TestCase name="testSortRemoveWhenLimitMaxRowCntIsOne">
+    <Resource name="sql">
+      <![CDATA[select *
+from (select * from sales.emp limit 1)
+order by deptno]]>
+    </Resource>
+    <Resource name="planBefore">
+      <![CDATA[
+LogicalSort(sort0=[$7], dir0=[ASC])
+  LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4], SAL=[$5], COMM=[$6], DEPTNO=[$7], SLACKER=[$8])
+    LogicalSort(fetch=[1])
+      LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4], SAL=[$5], COMM=[$6], DEPTNO=[$7], SLACKER=[$8])
+        LogicalTableScan(table=[[CATALOG, SALES, EMP]])
+]]>
+    </Resource>
+    <Resource name="planAfter">
+      <![CDATA[
+LogicalSort(fetch=[1])
+  LogicalTableScan(table=[[CATALOG, SALES, EMP]])
 ]]>
     </Resource>
   </TestCase>