fix: Assert chunks are equal after physical cast to prevent OOB

crates/polars-core/src/datatypes/dtype.rs

@@ -209,6 +209,27 @@ impl DataType {
         matches!(self, DataType::Boolean)
     }
 
+    /// Check if this [`DataType`] is a list
+    pub fn is_list(&self) -> bool {
+        matches!(self, DataType::List(_))
+    }
+
+    pub fn is_nested(&self) -> bool {
+        self.is_list() || self.is_struct()
+    }
+
+    /// Check if this [`DataType`] is a struct
+    pub fn is_struct(&self) -> bool {
+        #[cfg(feature = "dtype-struct")]
+        {
+            matches!(self, DataType::Struct(_))
+        }
+        #[cfg(not(feature = "dtype-struct"))]
+        {
+            false
+        }
+    }
+
     pub fn is_binary(&self) -> bool {
         matches!(self, DataType::Binary)
     }

crates/polars-ops/src/chunked_array/gather/chunked.rs

@@ -1,3 +1,6 @@
+use std::borrow::Cow;
+use std::fmt::Debug;
+
 use polars_core::prelude::gather::_update_gather_sorted_flag;
 use polars_core::prelude::*;
 use polars_core::series::IsSorted;
@@ -67,9 +70,24 @@ pub trait TakeChunked {
     unsafe fn take_opt_chunked_unchecked(&self, by: &[ChunkId]) -> Self;
 }
 
+fn prepare_series(s: &Series) -> Cow<Series> {
+    let phys = if s.dtype().is_nested() {
+        Cow::Borrowed(s)
+    } else {
+        s.to_physical_repr()
+    };
+    // If this is hit the cast rechunked the data and the gather will OOB
+    assert_eq!(
+        phys.chunks().len(),
+        s.chunks().len(),
+        "implementation error"
+    );
+    phys
+}
+
 impl TakeChunked for Series {
     unsafe fn take_chunked_unchecked(&self, by: &[ChunkId], sorted: IsSorted) -> Self {
-        let phys = self.to_physical_repr();
+        let phys = prepare_series(self);
         use DataType::*;
         let out = match phys.dtype() {
             dt if dt.is_numeric() => {
@@ -122,7 +140,7 @@ impl TakeChunked for Series {
 
     /// Take function that checks of null state in `ChunkIdx`.
     unsafe fn take_opt_chunked_unchecked(&self, by: &[NullableChunkId]) -> Self {
-        let phys = self.to_physical_repr();
+        let phys = prepare_series(self);
         use DataType::*;
         let out = match phys.dtype() {
             dt if dt.is_numeric() => {
@@ -177,6 +195,7 @@ impl TakeChunked for Series {
 impl<T> TakeChunked for ChunkedArray<T>
 where
     T: PolarsDataType,
+    T::Array: Debug,
 {
     unsafe fn take_chunked_unchecked(&self, by: &[ChunkId], sorted: IsSorted) -> Self {
         let arrow_dtype = self.dtype().to_arrow(true);

crates/polars-ops/src/frame/join/hash_join/mod.rs

@@ -173,11 +173,11 @@ pub trait JoinDispatch: IntoDf {
         args: JoinArgs,
         verbose: bool,
     ) -> PolarsResult<DataFrame> {
-        let ca_self = self.to_df();
+        let df_self = self.to_df();
         #[cfg(feature = "dtype-categorical")]
         _check_categorical_src(s_left.dtype(), s_right.dtype())?;
 
-        let mut left = ca_self.clone();
+        let mut left = df_self.clone();
         let mut s_left = s_left.clone();
         // Eagerly limit left if possible.
         if let Some((offset, len)) = args.slice {
@@ -188,16 +188,19 @@ pub trait JoinDispatch: IntoDf {
         }
 
         // Ensure that the chunks are aligned otherwise we go OOB.
-        let mut right = other.clone();
+        let mut right = Cow::Borrowed(other);
         let mut s_right = s_right.clone();
         if left.should_rechunk() {
             left.as_single_chunk_par();
             s_left = s_left.rechunk();
         }
         if right.should_rechunk() {
-            right.as_single_chunk_par();
+            let mut other = other.clone();
+            other.as_single_chunk_par();
+            right = Cow::Owned(other);
             s_right = s_right.rechunk();
         }
+
         let ids = sort_or_hash_left(&s_left, &s_right, verbose, args.validation, args.join_nulls)?;
         left._finish_left_join(ids, &right.drop(s_right.name()).unwrap(), args)
     }

crates/polars/tests/it/chunks/mod.rs

@@ -0,0 +1,2 @@
+#[cfg(feature = "parquet")]
+mod parquet;

crates/polars/tests/it/chunks/parquet.rs

@@ -0,0 +1,38 @@
+use std::io::{Seek, SeekFrom};
+
+use polars::prelude::*;
+
+#[test]
+fn test_cast_join_14872() {
+    let df1 = df![
+        "ints" => [1]
+    ]
+    .unwrap();
+
+    let mut df2 = df![
+        "ints" => [0, 1],
+        "strings" => vec![Series::new("", ["a"]); 2],
+    ]
+    .unwrap();
+
+    let mut buf = std::io::Cursor::new(vec![]);
+    ParquetWriter::new(&mut buf)
+        .with_row_group_size(Some(1))
+        .finish(&mut df2)
+        .unwrap();
+
+    let _ = buf.seek(SeekFrom::Start(0));
+    let df2 = ParquetReader::new(buf).finish().unwrap();
+
+    let out = df1
+        .join(&df2, ["ints"], ["ints"], JoinArgs::new(JoinType::Left))
+        .unwrap();
+
+    let expected = df![
+        "ints" => [1],
+        "strings" => vec![Series::new("", ["a"]); 1],
+    ]
+    .unwrap();
+
+    assert!(expected.equals(&out));
+}

crates/polars/tests/it/main.rs

@@ -7,5 +7,6 @@ mod schema;
 mod time;
 
 mod arrow;
+mod chunks;
 
 pub static FOODS_CSV: &str = "../../examples/datasets/foods1.csv";