Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/14864#discussion_r77117501
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/DataSourceScanExec.scala
---
@@ -156,24 +156,56 @@ case class FileSourceScanExec(
false
}
- override val outputPartitioning: Partitioning = {
+ override val (outputPartitioning, outputOrdering): (Partitioning,
Seq[SortOrder]) = {
val bucketSpec = if
(relation.sparkSession.sessionState.conf.bucketingEnabled) {
relation.bucketSpec
} else {
None
}
- bucketSpec.map { spec =>
- val numBuckets = spec.numBuckets
- val bucketColumns = spec.bucketColumnNames.flatMap { n =>
- output.find(_.name == n)
- }
- if (bucketColumns.size == spec.bucketColumnNames.size) {
- HashPartitioning(bucketColumns, numBuckets)
- } else {
- UnknownPartitioning(0)
- }
- }.getOrElse {
- UnknownPartitioning(0)
+ bucketSpec match {
+ case Some(spec) =>
+ val numBuckets = spec.numBuckets
+ val bucketColumns = spec.bucketColumnNames.flatMap { n =>
+ output.find(_.name == n)
+ }
+ if (bucketColumns.size == spec.bucketColumnNames.size) {
+ val partitioning = HashPartitioning(bucketColumns, numBuckets)
+
+ val sortOrder = if (spec.sortColumnNames.nonEmpty) {
+ // In case of bucketing, its possible to have multiple files
belonging to the
+ // same bucket in a given relation. Each of these files are
locally sorted
+ // but those files combined together are not globally sorted.
Given that,
+ // the RDD partition will not be sorted even if the relation
has sort columns set
+ // Current solution is to check if all the buckets have a
single file in it
+
+ val files =
+
relation.location.listFiles(partitionFilters).flatMap(partition =>
partition.files)
+ val bucketToFilesGrouping =
+ files.map(_.getPath.getName).groupBy(file =>
BucketingUtils.getBucketId(file))
+ val singleFilePartitions = bucketToFilesGrouping.forall(p =>
p._2.length <= 1)
--- End diff --
listing files and grouping by bucket id can be expensive, if there are a
lot of files. What's worse, we will do it again in `createBucketedReadRDD`.
Instead of doing this, I'd like to fix the sorting problem for bucketed
table first, then we don't need to scan file names to get the `outputOrdering`
---
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