feat: Add IPC source node for new streaming engine

crates/polars-arrow/src/io/ipc/read/reader.rs

@@ -66,6 +66,10 @@ impl<R: Read + Seek> FileReader<R> {
         self.reader
     }
 
+    pub fn set_current_block(&mut self, idx: usize) {
+        self.current_block = idx;
+    }
+
     /// Get the inner memory scratches so they can be reused in a new writer.
     /// This can be utilized to save memory allocations for performance reasons.
     pub fn get_scratches(&mut self) -> (Vec<u8>, Vec<u8>) {

crates/polars-io/src/utils/other.rs

@@ -45,7 +45,7 @@ pub fn get_reader_bytes<R: Read + MmapBytesReader + ?Sized>(
     feature = "parquet",
     feature = "avro"
 ))]
-pub(crate) fn apply_projection(schema: &ArrowSchema, projection: &[usize]) -> ArrowSchema {
+pub fn apply_projection(schema: &ArrowSchema, projection: &[usize]) -> ArrowSchema {
     projection
         .iter()
         .map(|idx| schema.get_at_index(*idx).unwrap())
@@ -59,14 +59,14 @@ pub(crate) fn apply_projection(schema: &ArrowSchema, projection: &[usize]) -> Ar
     feature = "avro",
     feature = "parquet"
 ))]
-pub(crate) fn columns_to_projection(
-    columns: &[String],
+pub fn columns_to_projection<T: AsRef<str>>(
+    columns: &[T],
     schema: &ArrowSchema,
 ) -> PolarsResult<Vec<usize>> {
     let mut prj = Vec::with_capacity(columns.len());
 
     for column in columns {
-        let i = schema.try_index_of(column)?;
+        let i = schema.try_index_of(column.as_ref())?;
         prj.push(i);
     }