sadikovi opened a new pull request, #37419:
URL: https://github.com/apache/spark/pull/37419
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### What changes were proposed in this pull request?
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This PR patches an issue in Parquet data source when a user tries to count
records for a Parquet table where file schema columns overlap with partition
columns and with filter on those columns.
```
root/
col0=0/
part-0001.parquet (schema: COL0)
```
When projection overlaps with partition columns, the output schema
(`requiredSchema`) becomes empty. In Parquet, when the predicate is provided
and column index is enabled, we would try to filter row ranges to figure out
what the count should be. Unfortunately, there is an issue that if the
projection is empty, any checks on columns would fail and 0 rows are returned
(`RowRanges.EMPTY`) even though there is data matching the filter.
This case is rare and only happens when doing count on a DataFrame that
results in empty projection (most of the cases would include the filtered
column which would work) but it is still good to fix.
This is a quick fix, the actual fix needs to go into Parquet-MR:
https://issues.apache.org/jira/browse/PARQUET-2170. Once that is fixed and
updated in Spark, we can remove the change.
### Why are the changes needed?
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Fixes a rare correctness issue when running `count` on a filtered Parquet
DataFrame.
### Does this PR introduce _any_ user-facing change?
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No.
### How was this patch tested?
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I added a unit test that reproduces this behaviour. The test fails without
the fix and passes with the fix.
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