chamikaramj commented on code in PR #39372:
URL: https://github.com/apache/beam/pull/39372#discussion_r3619854382
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sdks/java/core/src/main/java/org/apache/beam/sdk/io/WriteFiles.java:
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@@ -553,29 +556,53 @@ public PCollection<List<ResultT>>
expand(PCollection<ResultT> input) {
// Reshuffle one more time to stabilize the contents of the bundle
lists to finalize.
.apply(Reshuffle.viaRandomKey());
} else {
- // Pass results via a side input rather than reshuffle, because we
need to get an empty
- // iterable to finalize if there are no results.
- return input
- .getPipeline()
- .apply(
- "AsPossiblyEmptyList",
- Reify.viewInGlobalWindow(
- // Insert a reshuffle before taking the view to
consolidate the (typically)
- // one-output-per-bundle writes.
- // This avoids producing a huge number of tiny files in
the case that side
- // inputs are materialized to disk bundle-by-bundle.
- input.apply("Consolidate",
Reshuffle.viaRandomKey()).apply(View.asIterable()),
Review Comment:
I think this is a significant behavior change that could have performance
implications and potential cost changes due to the extra shuffle (for batch and
streaming). Hence we should perform some large scale benchmarking as a part of
the solution to avoid potential regressions.
I think this probably require a dev list discussion as well.
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