Querys that return large # of results can freeze / crash the app

[matthewmturner]

I ran a query on local context that returned a large number of rows and the app became unresponsive after completing. We need to paginate somehow

[matthewmturner]

@alamb FYI pagination also relevant for local context

[alamb]

@alamb FYI pagination also relevant for local context

I agree

One way to do this might be to wrap the SendableRecordBatchStream in an object that buffers past results and fetches next result on demand. Something like this perhaps

struct SendableRecordBatchStream {
  // currently executing stream
  inner: SendableRecordBatchStream,
  // any batches that have been buffered so far
  batches: Vec<RecordBatch>,
  // current batch being shown
  current_batch: usize,
}

impl SendableRecordBatchStream {
  /// return the next batch in the stream
  async fn next(&self) -> &RecordBatch {
    self.current_batch += 1;
    self.current()
  }

  /// go to current_index
 async fn current(&self) -> &RecordBatch{
    while self.batches.len()+1 < current_batch {
      // fetch next batch from inner and put into self.batches
    }
    self.batches[self.current_batch]
  }
}