zhengruifeng commented on code in PR #47328:
URL: https://github.com/apache/spark/pull/47328#discussion_r1676692203
##########
mllib/src/main/scala/org/apache/spark/ml/r/AFTSurvivalRegressionWrapper.scala:
##########
@@ -129,7 +129,9 @@ private[r] object AFTSurvivalRegressionWrapper extends
MLReadable[AFTSurvivalReg
val rMetadata = ("class" -> instance.getClass.getName) ~
("features" -> instance.features.toImmutableArraySeq)
val rMetadataJson: String = compact(render(rMetadata))
- sc.parallelize(Seq(rMetadataJson), 1).saveAsTextFile(rMetadataPath)
+ sparkSession.createDataFrame(
+ Seq(Tuple1(rMetadataJson))
+ ).repartition(1).write.text(rMetadataPath)
Review Comment:
No, the single partition is needed to avoid creating empty files, even
though there is only one row:
```
spark.range(1).select(sf.lit("123")).write.text("/tmp/test-test")
```
```
(base) ➜ runtime git:(master) ls /tmp/test-test
_SUCCESS
part-00011-e548682e-21a5-41ea-93bc-0089efccbf4f-c000.txt
part-00000-e548682e-21a5-41ea-93bc-0089efccbf4f-c000.txt
(base) ➜ runtime git:(master) wc -l /tmp/test-test/*
0 /tmp/test-test/_SUCCESS
0
/tmp/test-test/part-00000-e548682e-21a5-41ea-93bc-0089efccbf4f-c000.txt
1
/tmp/test-test/part-00011-e548682e-21a5-41ea-93bc-0089efccbf4f-c000.txt
1 total
```
I think we can use `coalesce(1)` to avoid this small shuffle
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