[GitHub] [doris] Reminiscent commented on a diff in pull request #18784: [feature](Nereids): pushdown filter through window

["Reminiscent (via GitHub)" <gi...@apache.org>]

Reminiscent commented on code in PR #18784:
URL: https://github.com/apache/doris/pull/18784#discussion_r1173465854


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fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/logical/PushdownFilterThroughWindow.java:
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@@ -0,0 +1,174 @@
+// 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.doris.nereids.rules.rewrite.logical;
+
+import org.apache.doris.nereids.rules.Rule;
+import org.apache.doris.nereids.rules.RuleType;
+import org.apache.doris.nereids.rules.rewrite.OneRewriteRuleFactory;
+import org.apache.doris.nereids.trees.expressions.BinaryOperator;
+import org.apache.doris.nereids.trees.expressions.ExprId;
+import org.apache.doris.nereids.trees.expressions.Expression;
+import org.apache.doris.nereids.trees.expressions.LessThan;
+import org.apache.doris.nereids.trees.expressions.LessThanEqual;
+import org.apache.doris.nereids.trees.expressions.NamedExpression;
+import org.apache.doris.nereids.trees.expressions.SlotReference;
+import org.apache.doris.nereids.trees.expressions.WindowExpression;
+import org.apache.doris.nereids.trees.expressions.WindowFrame;
+import org.apache.doris.nereids.trees.expressions.functions.window.DenseRank;
+import org.apache.doris.nereids.trees.expressions.functions.window.Rank;
+import org.apache.doris.nereids.trees.expressions.functions.window.RowNumber;
+import org.apache.doris.nereids.trees.expressions.literal.IntegerLikeLiteral;
+import org.apache.doris.nereids.trees.plans.Plan;
+import org.apache.doris.nereids.trees.plans.logical.LogicalWindow;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.Set;
+
+/**
+ * Push down the 'filter' into the 'window'.
+ * It will convert the filter condition to the 'limit value' and embed it to the 'window'.
+ * But there are some restrictions, the details are explained below.
+ * For example:
+ * 'SELECT * FROM (
+ *     SELECT *, ROW_NUMBER() OVER (ORDER BY b) AS row_number
+ *     FROM t
+ * ) AS tt WHERE row_number <= 100;'
+ * The filter 'row_number <= 100' can be pushed down into the window operator.
+ * The following will demonstrate how the plan changes:
+ * Logical plan tree:
+ *                 any_node
+ *                   |
+ *                filter (row_number <= 100)
+ *                   |
+ *                window (PARTITION BY a ORDER BY b)
+ *                   |
+ *                 any_node
+ * transformed to:
+ *                 any_node
+ *                   |
+ *                filter (row_number <= 100)
+ *                   |
+ *                window (PARTITION BY a ORDER BY b) [Limit: 100]
+ *                   |
+ *                 any_node
+ */
+
+public class PushdownFilterThroughWindow extends OneRewriteRuleFactory {
+
+    @Override
+    public Rule build() {
+        return logicalFilter(logicalWindow()).then(filter -> {
+            LogicalWindow<Plan> window = filter.child();
+
+            // Check the filter conditions. Now, we currently only support
+            // simple conditions of the form 'column </<= constant'.
+            // TODO: Support more complex situations in filter conditions.
+            Set<Expression> conjuncts = filter.getConjuncts();
+            if (conjuncts.size() != 1) {
+                return filter;
+            }

Review Comment:
   You can see the `TODO`. It maybe needs to normalize the filter conditions, for example if there is a condition contains `and` and `or`. We need to expand it. So I think it can be handled separate.



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