alamb commented on a change in pull request #789:
URL: https://github.com/apache/arrow-datafusion/pull/789#discussion_r678247263
##########
File path: datafusion/src/dataframe.rs
##########
@@ -222,6 +223,21 @@ pub trait DataFrame: Send + Sync {
/// ```
async fn collect(&self) -> Result<Vec<RecordBatch>>;
+ /// Executes this DataFrame and returns a stream over a single partition
+ ///
+ /// ```
+ /// # use datafusion::prelude::*;
+ /// # use datafusion::error::Result;
+ /// # #[tokio::main]
+ /// # async fn main() -> Result<()> {
+ /// let mut ctx = ExecutionContext::new();
+ /// let df = ctx.read_csv("tests/example.csv", CsvReadOptions::new())?;
+ /// let stream = df.collect_stream().await?;
+ /// # Ok(())
+ /// # }
+ /// ```
+ async fn collect_stream(&self) -> Result<SendableRecordBatchStream>;
Review comment:
What if we called this something like `execute` rather than
`collect_stream`?
```
async fn execute_stream(&self) -> Result<SendableRecordBatchStream>;
```
This would mirror the naming of `ExecutionPlan::execute` and might make it
clearer that `collect` means collect into a Vec and `execute` means get a stream
##########
File path: datafusion/src/execution/dataframe_impl.rs
##########
@@ -149,8 +152,19 @@ impl DataFrame for DataFrameImpl {
Ok(collect(plan).await?)
}
- // Convert the logical plan represented by this DataFrame into a physical
plan and
- // execute it
+ /// Convert the logical plan represented by this DataFrame into a physical
plan and
+ /// execute it, returning a stream over a single partition
+ async fn collect_stream(&self) -> Result<SendableRecordBatchStream> {
+ let state = self.ctx_state.lock().unwrap().clone();
+ let ctx = ExecutionContext::from(Arc::new(Mutex::new(state)));
+ let plan = ctx.optimize(&self.plan)?;
+ let plan = ctx.create_physical_plan(&plan)?;
+ collect_stream(plan).await
+ }
+
+ /// Convert the logical plan represented by this DataFrame into a physical
plan and
+ /// execute it, collecting all resulting batches into memory while
maintaining
+ /// partitioning
async fn collect_partitioned(&self) -> Result<Vec<Vec<RecordBatch>>> {
let state = self.ctx_state.lock().unwrap().clone();
Review comment:
You could probably rewrite `collect_partitioned` to be in terms of
`collect_stream_partitioned`:
```rust
collect(self.collect_stream_partitioned().await?)
```
or something like that
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