Github user liancheng commented on a diff in the pull request:
https://github.com/apache/spark/pull/12153#discussion_r58909434
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/FileSourceStrategy.scala
---
@@ -137,10 +140,14 @@ private[sql] object FileSourceStrategy extends
Strategy with Logging {
val splitFiles = selectedPartitions.flatMap { partition =>
partition.files.flatMap { file =>
+ val blockLocations = getBlockLocations(file)
(0L to file.getLen by maxSplitBytes).map { offset =>
val remaining = file.getLen - offset
val size = if (remaining > maxSplitBytes) maxSplitBytes
else remaining
- PartitionedFile(partition.values,
file.getPath.toUri.toString, offset, size)
+ // Finds out a list of location hosts where lives the
first block that contains the
+ // starting point the file block starts at `offset` with
length `size`.
+ val hosts = getBlockHosts(blockLocations, offset)
+ PartitionedFile(partition.values,
file.getPath.toUri.toString, offset, size, hosts)
--- End diff --
Each `FilePartition` derives their own preferred location in
`FileScanRDD.preferredLocations()` from location hosts of all its
`PartitionedFile`s.
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