thinkharderdev opened a new issue, #2270:
URL: https://github.com/apache/arrow-rs/issues/2270
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The current (non-public) API for skipping records has some shortcomings when
trying to implement predicate pushdown from DataFusion. It assumes that we have
the entire `VecDequeue<RowSelection>` for an entire row group when construction
the `ParquetRecordBatchReader` which makes doing streaming filtering a
challenge.
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I wrote a prototype of row-level filtering in DataFusion that required a few
changes to the API here. Two main things:
1. Add a method to `ParquetRecordBatchStream`
```
pub fn next_selection(
&mut self,
selection: &mut VecDeque<RowSelection>,
) -> Option<ArrowResult<RecordBatch>>
```
which mimics `poll_next` but applies a selection to the next batch.
2. Add a method to `ParquetRecordBatchReader`
```
pub fn next_selection(
&mut self,
selection: &mut VecDeque<RowSelection>,
) -> Option<ArrowResult<RecordBatch>>
```
which mimics `next` but applies a selection and, importantly, emits a single
batch containing all selected rows in `selection`. The current implementation
just emits the next `RowSelection` that selects and stops.
See
https://github.com/coralogix/arrow-datafusion/blob/row-filtering/datafusion/core/src/physical_plan/file_format/parquet.rs
for the (very hacky) protoype in DataFusion built on
https://github.com/coralogix/arrow-rs/tree/row-filtering.
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