aokolnychyi opened a new pull request #29066:
URL: https://github.com/apache/spark/pull/29066
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### What changes were proposed in this pull request?
This WIP PR shows how we can implement first steps of the [design
doc](https://docs.google.com/document/d/1X0NsQSryvNmXBY9kcvfINeYyKC-AahZarUqg3nS1GQs/edit#)
for SPARK-23889.
**Important:** the purpose of this PR is to simplify the review of the
design doc and get early feedback on the proposal. The change is complementary
to the design doc and is not meant for a detailed review.
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### Why are the changes needed?
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Data sources should be able to request a specific distribution and ordering
of data on write. In particular, these scenarios are considered useful:
- global sort
- cluster data and sort within partitions
- local sort within partitions
- no sort
Please see the design doc above for a more detailed explanation of
requirements.
### Does this PR introduce _any_ user-facing change?
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This PR introduces public changes to the DS V2 by adding a logical write
abstraction as we have on the read path as well as additional interfaces to
represent distribution and ordering of data (please see the doc for
alternatives).
Important pieces:
- `Write` - a logical representation of a data source write
- `RequiresDistributionAndOrdering` - a write that requires a specific
distribution/ordering
- `V2Writes` - a rule that constructs a logical write
- `V2WriteRequirements` - a rule that inserts repartition/sort nodes
- `WriteDistributionAndOrderingSuite` - a test case with samples
The PR is split into 2 commits that are self-contained:
- Introduction of the logical write abstraction
- Required distribution and sort work
### How was this patch tested?
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Since this PR is just an example of what can be done, the patch comes with a
minimal test case.
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