yunchipang opened a new pull request, #7100:
URL: https://github.com/apache/datafusion-comet/pull/7100
## Which issue does this PR close?
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Part of #6959.
## Rationale for this change
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the issue then this section is not needed.
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Today the native writer falls back whenever the write schema has a v3
`unknown` column. iceberg-java writes no Parquet column for a top-level
`unknown` field, so the native writer can support it by doing the same.
## What changes are included in this PR?
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- Native: drop top-level `unknown` fields when parsing the schema, and skip
the matching `Null` columns before writing.
- JVM: a top-level `unknown` no longer falls back. A nested `unknown` (in a
struct, list or map) still falls back:
- struct: Comet shuffle panics on a `Null` field inside a struct (the
field-major path in `row.rs`). Looks like
https://github.com/apache/datafusion-comet/pull/7099 will fix this bug.
- list/map: iceberg-java cannot write these either.
- Docs: update the supported column types.
## How are these changes tested?
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- Rust unit test: `decorate_batch_drops_null_columns`.
- `CometIcebergWriteActionSuite`: writes the same v3 table with the native
writer and with iceberg-java, then checks that the rows, the Parquet footer
columns and the manifest metrics match.
- `CometIcebergWriteDetectionSuite`: an `unknown` inside a struct falls back.
- Verified on Spark 4.1 / Iceberg 1.11. The other Iceberg versions are left
to the `run-iceberg-tests` label.
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