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https://issues.apache.org/jira/browse/SPARK-22357?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-22357:
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Assignee: (was: Apache Spark)
> SparkContext.binaryFiles ignore minPartitions parameter
> -------------------------------------------------------
>
> Key: SPARK-22357
> URL: https://issues.apache.org/jira/browse/SPARK-22357
> Project: Spark
> Issue Type: Bug
> Components: Spark Core
> Affects Versions: 2.1.2, 2.2.0
> Reporter: Weichen Xu
> Priority: Major
>
> this is a bug in binaryFiles - even though we give it the partitions,
> binaryFiles ignores it.
> This is a bug introduced in spark 2.1 from spark 2.0, in file
> PortableDataStream.scala the argument “minPartitions” is no longer used (with
> the push to master on 11/7/6):
> {code}
> /**
> Allow minPartitions set by end-user in order to keep compatibility with old
> Hadoop API
> which is set through setMaxSplitSize
> */
> def setMinPartitions(sc: SparkContext, context: JobContext, minPartitions:
> Int) {
> val defaultMaxSplitBytes =
> sc.getConf.get(config.FILES_MAX_PARTITION_BYTES)
> val openCostInBytes = sc.getConf.get(config.FILES_OPEN_COST_IN_BYTES)
> val defaultParallelism = sc.defaultParallelism
> val files = listStatus(context).asScala
> val totalBytes = files.filterNot(.isDirectory).map(.getLen +
> openCostInBytes).sum
> val bytesPerCore = totalBytes / defaultParallelism
> val maxSplitSize = Math.min(defaultMaxSplitBytes,
> Math.max(openCostInBytes, bytesPerCore))
> super.setMaxSplitSize(maxSplitSize)
> }
> {code}
> The code previously, in version 2.0, was:
> {code}
> def setMinPartitions(context: JobContext, minPartitions: Int) {
> val totalLen =
> listStatus(context).asScala.filterNot(.isDirectory).map(.getLen).sum
> val maxSplitSize = math.ceil(totalLen / math.max(minPartitions,
> 1.0)).toLong
> super.setMaxSplitSize(maxSplitSize)
> }
> {code}
> The new code is very smart, but it ignores what the user passes in and uses
> the data size, which is kind of a breaking change in some sense
> In our specific case this was a problem, because we initially read in just
> the files names and only after that the dataframe becomes very large, when
> reading in the images themselves – and in this case the new code does not
> handle the partitioning very well.
> I’m not sure if it can be easily fixed because I don’t understand the full
> context of the change in spark (but at the very least the unused parameter
> should be removed to avoid confusion).
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