dianfu commented on code in PR #28998: URL: https://github.com/apache/flink/pull/28998#discussion_r3921731195
########## flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/plan/nodes/exec/utils/PythonCallCseResult.java: ########## @@ -0,0 +1,89 @@ +/* + * 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.flink.table.planner.plan.nodes.exec.utils; + +import org.apache.flink.annotation.Internal; + +import org.apache.calcite.rex.RexCall; + +import java.util.Collections; +import java.util.LinkedHashMap; +import java.util.List; +import java.util.Map; + +/** Encapsulates the result of Python UDF call Common Sub-expression Elimination (CSE). */ +@Internal +public class PythonCallCseResult { + + /** + * The deduplicated Python UDF calls to be evaluated, in execution order. + * + * <p>Nested call trees are flattened so that a sub-expression shared between calls appears + * exactly once. For example {@code SELECT udf1(x), udf2(udf1(x))} yields {@code [udf1(x), + * udf2(<ref to udf1(x)>)]}. + */ + private final List<RexCall> deduplicatedCalls; + + /** + * For each projection entry, the position in {@link #deduplicatedCalls} holding its result. + * + * <p>Flattening appends intermediate sub-expressions that must not be emitted, and post-order + * can leave a projected result before the end of the list, so this is not necessarily the + * identity. + */ + private final int[] outputIndices; + + /** + * Maps a call to the position in {@link #deduplicatedCalls} where its result is computed. + * + * <p>Derived from {@link #deduplicatedCalls}: since the list is already deduplicated, the first + * occurrence of a structurally equal call is the one that computes it. + */ + private final Map<RexCall, Integer> refMap; + + public PythonCallCseResult(List<RexCall> deduplicatedCalls, int[] outputIndices) { + this.deduplicatedCalls = deduplicatedCalls; + this.outputIndices = outputIndices; + this.refMap = buildRefMap(deduplicatedCalls); + } + + public List<RexCall> getDeduplicatedCalls() { + return deduplicatedCalls; + } + + public int[] getOutputIndices() { + return outputIndices; + } + + public Map<RexCall, Integer> getRefMap() { + return refMap; + } + + /** + * Indexes the deduplicated calls by structural equality, keeping the first occurrence so that a + * parent references its own child rather than a later structurally equal duplicate. + */ + private static Map<RexCall, Integer> buildRefMap(List<RexCall> deduplicatedCalls) { Review Comment: Not every entry in this list is safe to reference, e.g. non-deterministic calls. It makes `SELECT Nondet(s), Det(Nondet(s))` incorrectly reuse the first result. ########## flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/plan/nodes/exec/utils/PythonCallDeduplicator.java: ########## @@ -0,0 +1,120 @@ +/* + * 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.flink.table.planner.plan.nodes.exec.utils; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.table.planner.plan.utils.PythonUtil; +import org.apache.flink.table.planner.utils.ShortcutUtils; + +import org.apache.calcite.rex.RexCall; +import org.apache.calcite.rex.RexNode; + +import java.util.ArrayList; +import java.util.Collections; +import java.util.LinkedHashMap; +import java.util.List; + +/** + * Utility for Python UDF Common Sub-expression Elimination (CSE) of nested calls. + * + * <p>Nested Python UDF call trees are flattened in post-order and deduplicated by structural + * equivalence, so that a sub-expression shared between calls is evaluated only once by the Python + * worker. Duplicates between whole projection entries are already removed in the planner by {@code + * RemoteCalcProjectionCseRule}, so this only concerns sub-expressions. + */ +@Internal +public class PythonCallDeduplicator { + + /** + * Flattens the given Python UDF call trees and deduplicates the resulting calls. + * + * <p>Flattening all trees into a single list enables cross-subtree reuse: e.g. in {@code SELECT + * udf1(x), udf2(udf1(x))}, the inner {@code udf1(x)} is evaluated only once and {@code udf2} + * receives its result by reference. + */ + public static PythonCallCseResult deduplicate(List<RexCall> pythonRexCalls) { Review Comment: This flattens every deterministic nested call, even when no sub-expression is shared. As a result, `SELECT f(g(a))` switches to sequential worker execution and allocates a results list per row without any CSE benefit. ########## flink-table/flink-table-planner/src/test/scala/org/apache/flink/table/planner/plan/nodes/exec/utils/PythonCalcNestedCseInvariantTest.scala: ########## @@ -0,0 +1,170 @@ +/* + * 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.flink.table.planner.plan.nodes.exec.utils + +import org.apache.flink.table.api._ +import org.apache.flink.table.planner.plan.nodes.exec.ExecNode +import org.apache.flink.table.planner.plan.nodes.exec.common.CommonExecPythonCalc +import org.apache.flink.table.planner.plan.nodes.physical.stream.StreamPhysicalRel +import org.apache.flink.table.planner.runtime.utils.JavaUserDefinedScalarFunctions.PythonScalarFunction +import org.apache.flink.table.planner.utils.{TableTestBase, TableTestUtil} +import org.apache.flink.table.types.logical.RowType + +import org.apache.calcite.rel.RelNode +import org.apache.calcite.rex.{RexCall, RexNode} +import org.assertj.core.api.Assertions.assertThat +import org.junit.jupiter.api.{BeforeEach, Test} + +import scala.collection.JavaConverters._ + +/** + * Tests the invariants of nested Python UDF flattening, driven through the real SQL pipeline so + * that genuine Python [[RexCall]]s are used. + * + * <p>Flattening happens while translating the ExecNode into a transformation and is therefore not + * visible in the optimized plan, so these invariants are asserted here rather than in a plan test. + */ +class PythonCalcNestedCseInvariantTest extends TableTestBase { Review Comment: Could we rewrite this test as a Java test? -- This is an automated message from the Apache Git Service. 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