alamb commented on code in PR #16342:
URL: https://github.com/apache/datafusion/pull/16342#discussion_r2138987979
##########
datafusion/core/src/datasource/file_format/csv.rs:
##########
@@ -795,6 +796,25 @@ mod tests {
Ok(())
}
+ #[tokio::test]
+ async fn test_csv_write_empty_file() -> Result<()> {
Review Comment:
Can you please also add a test of what happens if we are writing into a
directory (aka a partitioned file)?
Like a test that targets a path of `/foo`
In this case, I think I would expect that no files are created when the data
stream is empty
##########
datafusion/datasource/src/file_sink_config.rs:
##########
@@ -77,13 +79,32 @@ pub trait FileSink: DataSink {
.runtime_env()
.object_store(&config.object_store_url)?;
let (demux_task, file_stream_rx) = start_demuxer_task(config, data,
context);
- self.spawn_writer_tasks_and_join(
- context,
- demux_task,
- file_stream_rx,
- object_store,
- )
- .await
+ let mut num_rows = self
+ .spawn_writer_tasks_and_join(
+ context,
+ demux_task,
+ file_stream_rx,
+ Arc::clone(&object_store),
+ )
+ .await?;
+ if num_rows == 0 {
Review Comment:
I think it would help here to add some comments with context about what it
is doing. For example, something like
```suggestion
// If no rows were written, then no files are output either. In this
case
// send an empty record batch through to ensure the output file is
generated
if num_rows == 0 {
```
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