Ma77Ball commented on code in PR #5384: URL: https://github.com/apache/texera/pull/5384#discussion_r3368511619
########## common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/reservoirsampling/ReservoirSamplingOpExecSpec.scala: ########## @@ -0,0 +1,126 @@ +/* + * 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.texera.amber.operator.reservoirsampling + +import org.apache.texera.amber.core.tuple.{Attribute, AttributeType, Schema, Tuple} +import org.apache.texera.amber.util.JSONUtils.objectMapper +import org.scalatest.flatspec.AnyFlatSpec + +class ReservoirSamplingOpExecSpec extends AnyFlatSpec { + + private val schema: Schema = + Schema().add(new Attribute("v", AttributeType.INTEGER)) + + private def tuple(v: Int): Tuple = + Tuple.builder(schema).add(new Attribute("v", AttributeType.INTEGER), Integer.valueOf(v)).build() + + // LogicalOp is registered for polymorphic Jackson deserialization via the + // `operatorType` discriminator, so a hand-rolled `{"k":N}` string would fail + // to bind. Serialize a real `ReservoirSamplingOpDesc` to embed the discriminator. + private def desc(k: Int): String = { + val d = new ReservoirSamplingOpDesc() + d.k = k + objectMapper.writeValueAsString(d) + } + + private def newExec(k: Int, idx: Int = 0, workerCount: Int = 1): ReservoirSamplingOpExec = { + val exec = new ReservoirSamplingOpExec(desc(k), idx, workerCount) + exec.open() + exec + } + + /** Feed every value through processTuple, then drain onFinish into a list. */ + private def runFinish(exec: ReservoirSamplingOpExec, values: Seq[Int]): List[Tuple] = { + values.foreach(v => exec.processTuple(tuple(v), 0)) + exec.onFinish(0).map(_.asInstanceOf[Tuple]).toList + } + + "ReservoirSamplingOpExec.processTuple" should "buffer silently and emit nothing until onFinish" in { + val exec = newExec(k = 3) + val perTupleEmissions = (0 until 10).map(i => exec.processTuple(tuple(i), 0).toList) + assert( + perTupleEmissions.forall(_.isEmpty), + "processTuple should never emit; sampling emits on finish" + ) + } + + "ReservoirSamplingOpExec.onFinish" should "return all input tuples in order when input size == k" in { + val exec = newExec(k = 4) + val emitted = runFinish(exec, 0 until 4) + assert(emitted == List(tuple(0), tuple(1), tuple(2), tuple(3))) + } + + it should "keep exactly k tuples, all drawn from the input, when input size > k" in { + val exec = newExec(k = 5) + val input = 0 until 100 + val emitted = runFinish(exec, input) + + assert(emitted.size == 5, "reservoir must hold exactly k samples") + assert(!emitted.contains(null), "no null padding when the reservoir is fully filled") + val inputTuples = input.map(tuple).toSet + assert( + emitted.forall(inputTuples.contains), + "every sample must originate from the input stream" + ) + assert(emitted.distinct.size == emitted.size, "each input tuple is sampled at most once") + } + + it should "be deterministic across runs (RNG is seeded, so identical input yields identical samples)" in { + val input = 0 until 100 + val firstRun = runFinish(newExec(k = 7), input) + val secondRun = runFinish(newExec(k = 7), input) + assert(firstRun == secondRun) + // Sanity-check the sample is not simply the first k tuples, i.e. replacement happened. + assert(firstRun != (0 until 7).map(tuple).toList) + } + + it should "distribute k across workers via equallyPartitionGoal (k=10, 3 workers -> 4,3,3)" in { + // The remainder is handed to the lowest-indexed workers, so worker 0 keeps one extra. + val perWorkerSize = (0 until 3).map { idx => + runFinish(newExec(k = 10, idx = idx, workerCount = 3), 0 until 50).size + } + assert(perWorkerSize == Seq(4, 3, 3)) + assert(perWorkerSize.sum == 10, "the per-worker reservoirs together hold the requested k") + } + + "ReservoirSamplingOpExec.open" should "reset state so a reused executor re-samples from scratch" in { + val exec = newExec(k = 3) + runFinish(exec, 0 until 20) // first pass consumes the executor's state + exec.open() // reopen should clear n and the reservoir + val emitted = runFinish(exec, Seq(100, 101, 102)) + assert(emitted == List(tuple(100), tuple(101), tuple(102))) + } + + // Sharp edge worth a reviewer's attention: when fewer than k tuples arrive, the + // fixed-size reservoir is never fully filled, so onFinish emits the buffered + // tuples followed by null padding. Downstream operators receive null tuples. + // This test documents the current behavior; emitting nulls is very likely a bug + // (onFinish should probably be `reservoir.iterator.take(n)` / filter nulls). + it should "currently emit null padding when input size < k (documents a likely bug)" in { + val exec = newExec(k = 5) + val emitted = runFinish(exec, 0 until 3) + assert(emitted.size == 5) + assert(emitted.take(3) == List(tuple(0), tuple(1), tuple(2))) + assert( + emitted.drop(3) == List(null, null), + "trailing reservoir slots are emitted as null tuples" + ) Review Comment: done -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
