vim89 opened a new pull request, #16941:
URL: https://github.com/apache/datafusion/pull/16941
## Which issue does this PR close?
- Partially closes #15873
## Rationale for this change
`EmptyExec` previously returned **"unknown"** statistics for both global and
partition-level queries, which impacts planner accuracy. This change provides
exact-zero stats for EmptyExec, aligning with how other operators like
`AggregateExec` and `PlaceholderRowExec` handle partition statistics.
## What changes are included in this PR?
- Implemented `partition_statistics(...)` for `EmptyExec`:
- Sets `num_rows` and `total_byte_size` to `Precision::Exact(0)`
- Populates `column_statistics` with one `ColumnStatistics::new_unknown()`
per schema field
- Added unit test `empty_multi_partition_statistics`:
- Verifies default 1-partition behavior: global and partition 0 return
zero stats, invalid partition errors
- Verifies 2-partition behavior: partitions 0 and 1 return zero stats,
invalid partition errors
- Added a `TreeRender` branch to `DisplayAs` to provide informative display
of the operator:
`"EmptyExec: partitions=X, fields=Y"`
- No other execution plans or tests were modified
## Are these changes tested?
Yes.
- New test covers all relevant edge cases.
- The full test suite still passes without regressions.
## Are there any user-facing changes?
No.
This change affects internal planner behavior only; no public APIs or
outputs are changed.
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