Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/18503#discussion_r129474900
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/state/HDFSBackedStateStoreProvider.scala
---
@@ -363,7 +363,11 @@ private[state] class HDFSBackedStateStoreProvider
extends StateStoreProvider wit
val valueRowBuffer = new Array[Byte](valueSize)
ByteStreams.readFully(input, valueRowBuffer, 0, valueSize)
val valueRow = new UnsafeRow(valueSchema.fields.length)
- valueRow.pointTo(valueRowBuffer, valueSize)
+ // If valueSize in existing file is not multiple of 8, floor
it to multiple of 8.
+ // This is work around for the following.
+ // Pre-Spark 2.3 mistakenly append 4 bytes to the value row in
+ // `FixedLengthRowBasedKeyValueBatch`, which gets persisted
into the checkpoint data
+ valueRow.pointTo(valueRowBuffer, (valueSize / 8) * 8)
--- End diff --
yes I'm absolutely sure, as we store aggregate buffers in checkpoint files.
BTW, I run [this
test](https://github.com/apache/spark/pull/18503/commits/01597010145f7769506cfa51c0450a2db779fc07#diff-b601a70172e88e90cea0020b978d0b5bL482)
without the workaround here, and it can still pass. Which means, after this
PR, `RowBasedKeyValueBatch` is fixed, and the generated checkpoint files have
corrected row length.
And I also run the test without the fix for `RowBasedKeyValueBatch`, and it
fails. I think this proves that `RowBasedKeyValueBatch` is the reason why we
have wrong row length in checkpoit files.
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