Perseus commented on code in PR #47:
URL: https://github.com/apache/datafusion-iceberg/pull/47#discussion_r4203858452
##########
crates/datafusion/src/physical_plan/metadata_scan.rs:
##########
@@ -80,28 +92,40 @@ impl ExecutionPlan for IcebergMetadataScan {
fn apply_expressions(
&self,
- _f: &mut dyn FnMut(
- &Arc<dyn PhysicalExpr>,
- ) -> datafusion::error::Result<TreeNodeRecursion>,
- ) -> datafusion::error::Result<TreeNodeRecursion> {
+ _f: &mut dyn FnMut(&Arc<dyn PhysicalExpr>) ->
Result<TreeNodeRecursion>,
+ ) -> Result<TreeNodeRecursion> {
Ok(TreeNodeRecursion::Continue)
}
fn with_new_children(
self: Arc<Self>,
_children: Vec<Arc<dyn ExecutionPlan>>,
- ) -> datafusion::error::Result<Arc<dyn ExecutionPlan>> {
+ ) -> Result<Arc<dyn ExecutionPlan>> {
Ok(self)
}
fn execute(
&self,
_partition: usize,
_context: Arc<datafusion::execution::TaskContext>,
- ) ->
datafusion::error::Result<datafusion::execution::SendableRecordBatchStream> {
+ ) -> Result<datafusion::execution::SendableRecordBatchStream> {
let fut = self.provider.clone().scan();
- let stream = futures::stream::once(fut).try_flatten();
- let schema = self.provider.schema();
- Ok(Box::pin(RecordBatchStreamAdapter::new(schema, stream)))
+ let projection = self.projection.clone();
+
+ let stream =
+ futures::stream::once(fut)
+ .try_flatten()
+ .map(move |result| -> Result<_> {
+ let batch = result?;
+ match &projection {
+ Some(indices) => Ok(batch.project(indices)?),
+ None => Ok(batch),
+ }
+ });
Review Comment:
I did try to see if I could push this projection down further into the scan
so that we don't have to manually project them *after* reading all of the
columns, but it looks like iceberg-rust doesn't support this - the scan of the
tables happens [here
](https://github.com/apache/datafusion-iceberg/blob/main/crates/datafusion/src/table/metadata_table.rs#L95-L97)
which calls [this in
iceberg-rust](https://github.com/apache/iceberg-rust/blob/main/crates/iceberg/src/inspect/snapshots.rs#L82)
and that doesn't seem to take projections
Admittedly, I'm still trying to build a mental model of all of this and
might be missing something so I can spend some more time trying to make this
work (or open PRs on iceberg-rust to add support for this)
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