spark-reviews mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From yhuai <...@git.apache.org>
Subject [GitHub] spark pull request: [SPARK-9858][SPARK-9859][SPARK-9861][SQL] Add ...
Date Sun, 01 Nov 2015 01:16:36 GMT
Github user yhuai commented on a diff in the pull request:

    https://github.com/apache/spark/pull/9276#discussion_r43577949
  
    --- Diff: sql/core/src/main/scala/org/apache/spark/sql/execution/ExchangeCoordinator.scala
---
    @@ -0,0 +1,251 @@
    +/*
    + * 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.spark.sql.execution
    +
    +import java.util.{Map => JMap, HashMap => JHashMap}
    +
    +import scala.collection.mutable.ArrayBuffer
    +
    +import org.apache.spark.sql.catalyst.plans.physical.HashPartitioning
    +import org.apache.spark.{Logging, SimpleFutureAction, ShuffleDependency, MapOutputStatistics}
    +import org.apache.spark.rdd.RDD
    +import org.apache.spark.sql.catalyst.InternalRow
    +
    +/**
    + * A coordinator used to determines how we shuffle data between stages generated by Spark
SQL.
    + * Right now, the work of this coordinator is to determine the number of post-shuffle
partitions
    + * for a stage that needs to fetch shuffle data from one or multiple stages.
    + *
    + * A coordinator is constructed with two parameters, `numExchanges` and
    + * `targetPostShuffleInputSize`. `numExchanges` is used to indicated that how many [[Exchange]]s
    + * that will be registered to this coordinator. So, when we start to do any actual work,
we have
    + * a way to make sure that we have got expected number of [[Exchange]]s.
    + * `targetPostShuffleInputSize` is the targeted size of a post-shuffle partition's input
data size.
    + * With this parameter, we can estimate the number of post-shuffle partitions. This parameter
    + * is configured through `spark.sql.adaptive.shuffle.targetPostShuffleInputSize`.
    + *
    + * The workflow of this coordinator is described as follows:
    + *  - Before the execution of a [[SparkPlan]], for an [[Exchange]] operator,
    + *    if an [[ExchangeCoordinator]] is assigned to it, it registers itself to this coordinator.
    + *    This happens in the `doPrepare` method.
    + *  - Once we start to execute a physical plan, an [[Exchange]] registered to this coordinator
will
    + *    call `postShuffleRDD` to get its corresponding post-shuffle [[RDD]]. If this coordinator
has
    + *    made the decision on how to shuffle data, this [[Exchange]] will immediately get
its
    + *    corresponding post-shuffle [[RDD]].
    + *  - If this coordinator has not made the decision on how to shuffle data, it will ask
those
    + *    registered [[Exchange]]s to submit their pre-shuffle stages. Then, based on the
the size
    + *    statistics of pre-shuffle partitions, this coordinator will determine the number
of
    + *    post-shuffle partitions and pack multiple pre-shuffle partitions with continuous
indices
    + *    to a post-shuffle partition whenever necessary.
    + *  - Finally, this coordinator will create post-shuffle [[RDD]]s for all registered
[[Exchange]]s.
    + *    So, when an [[Exchange]] calls `postShuffleRDD`, this coordinator can lookup the
    + *    corresponding [[RDD]].
    + *
    + * The strategy used to determine the number of post-shuffle partitions is described
as follows.
    + * To determine the number of post-shuffle partitions, we have a target input size for
a
    + * post-shuffle partition. Once we have size statistics of pre-shuffle partitions from
stages
    + * corresponding to the registered [[Exchange]]s, we will do a pass of those statistics
and
    + * pack pre-shuffle partitions with continuous indices to a single post-shuffle partition
until
    + * the size of a post-shuffle partition is equal or greater than the target size.
    + * For example, we have two stages with the following pre-shuffle partition size statistics:
    + * stage 1: [100 MB, 20 MB, 100 MB, 10MB, 30 MB]
    + * stage 2: [10 MB,  10 MB, 70 MB,  5 MB, 5 MB]
    + * assuming the target input size is 128 MB, we will have three post-shuffle partitions,
    + * which are:
    + *  - post-shuffle partition 0: pre-shuffle partition 0 and 1
    + *  - post-shuffle partition 1: pre-shuffle partition 2
    + *  - post-shuffle partition 2: pre-shuffle partition 3 and 4
    + *
    + * If `minNumPostShufflePartitions` is defined. This ExchangeCoordinator will try to
enforce
    + * the minimal number of post-shuffle partitions to this number.
    + */
    +private[sql] class ExchangeCoordinator(
    +    numExchanges: Int,
    +    advisoryTargetPostShuffleInputSize: Long,
    +    minNumPostShufflePartitions: Option[Int] = None)
    +  extends Logging {
    --- End diff --
    
    Done


---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastructure@apache.org or file a JIRA ticket
with INFRA.
---

---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscribe@spark.apache.org
For additional commands, e-mail: reviews-help@spark.apache.org


Mime
View raw message