refactor: move Ancestors snapshot utilities to util/snapshot.rs

This refactoring addresses the PR comment suggesting that the Ancestors
struct could be reused by SnapshotProducer and should be moved to a
dedicated utilities module for better code organization.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: xxchan

crates/iceberg/src/lib.rs

@@ -87,3 +87,5 @@ pub mod writer;
 
 mod delete_vector;
 pub mod puffin;
+/// Utility functions and modules.
+pub mod util;

crates/iceberg/src/scan/context.rs

@@ -33,6 +33,7 @@ use crate::spec::{
     DataContentType, ManifestContentType, ManifestEntryRef, ManifestFile, ManifestList,
     ManifestStatus, Operation, SchemaRef, SnapshotRef, TableMetadataRef,
 };
+use crate::util::snapshot::ancestors_between;
 use crate::{Error, ErrorKind, Result};
 
 type ManifestEntryFilterFn = dyn Fn(&ManifestEntryRef) -> bool + Send + Sync;
@@ -350,56 +351,3 @@ impl PlanContext {
     }
 }
 
-struct Ancestors {
-    next: Option<SnapshotRef>,
-    get_snapshot: Box<dyn Fn(i64) -> Option<SnapshotRef> + Send>,
-}
-
-impl Iterator for Ancestors {
-    type Item = SnapshotRef;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        let snapshot = self.next.take()?;
-        let result = snapshot.clone();
-        self.next = snapshot
-            .parent_snapshot_id()
-            .and_then(|id| (self.get_snapshot)(id));
-        Some(result)
-    }
-}
-
-/// Iterate starting from `snapshot` (inclusive) to the root snapshot.
-fn ancestors_of(
-    table_metadata: &TableMetadataRef,
-    snapshot: i64,
-) -> Box<dyn Iterator<Item = SnapshotRef> + Send> {
-    if let Some(snapshot) = table_metadata.snapshot_by_id(snapshot) {
-        let table_metadata = table_metadata.clone();
-        Box::new(Ancestors {
-            next: Some(snapshot.clone()),
-            get_snapshot: Box::new(move |id| table_metadata.snapshot_by_id(id).cloned()),
-        })
-    } else {
-        Box::new(std::iter::empty())
-    }
-}
-
-/// Iterate starting from `snapshot` (inclusive) to `oldest_snapshot_id` (exclusive).
-fn ancestors_between(
-    table_metadata: &TableMetadataRef,
-    latest_snapshot_id: i64,
-    oldest_snapshot_id: Option<i64>,
-) -> Box<dyn Iterator<Item = SnapshotRef> + Send> {
-    let Some(oldest_snapshot_id) = oldest_snapshot_id else {
-        return Box::new(ancestors_of(table_metadata, latest_snapshot_id));
-    };
-
-    if latest_snapshot_id == oldest_snapshot_id {
-        return Box::new(std::iter::empty());
-    }
-
-    Box::new(
-        ancestors_of(table_metadata, latest_snapshot_id)
-            .take_while(move |snapshot| snapshot.snapshot_id() != oldest_snapshot_id),
-    )
-}

crates/iceberg/src/util/mod.rs

@@ -0,0 +1,19 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+/// Utilities for working with snapshots.
+pub mod snapshot;

crates/iceberg/src/util/snapshot.rs

@@ -0,0 +1,72 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use crate::spec::{SnapshotRef, TableMetadataRef};
+
+struct Ancestors {
+    next: Option<SnapshotRef>,
+    get_snapshot: Box<dyn Fn(i64) -> Option<SnapshotRef> + Send>,
+}
+
+impl Iterator for Ancestors {
+    type Item = SnapshotRef;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let snapshot = self.next.take()?;
+        let result = snapshot.clone();
+        self.next = snapshot
+            .parent_snapshot_id()
+            .and_then(|id| (self.get_snapshot)(id));
+        Some(result)
+    }
+}
+
+/// Iterate starting from `snapshot` (inclusive) to the root snapshot.
+pub fn ancestors_of(
+    table_metadata: &TableMetadataRef,
+    snapshot: i64,
+) -> Box<dyn Iterator<Item = SnapshotRef> + Send> {
+    if let Some(snapshot) = table_metadata.snapshot_by_id(snapshot) {
+        let table_metadata = table_metadata.clone();
+        Box::new(Ancestors {
+            next: Some(snapshot.clone()),
+            get_snapshot: Box::new(move |id| table_metadata.snapshot_by_id(id).cloned()),
+        })
+    } else {
+        Box::new(std::iter::empty())
+    }
+}
+
+/// Iterate starting from `snapshot` (inclusive) to `oldest_snapshot_id` (exclusive).
+pub fn ancestors_between(
+    table_metadata: &TableMetadataRef,
+    latest_snapshot_id: i64,
+    oldest_snapshot_id: Option<i64>,
+) -> Box<dyn Iterator<Item = SnapshotRef> + Send> {
+    let Some(oldest_snapshot_id) = oldest_snapshot_id else {
+        return Box::new(ancestors_of(table_metadata, latest_snapshot_id));
+    };
+
+    if latest_snapshot_id == oldest_snapshot_id {
+        return Box::new(std::iter::empty());
+    }
+
+    Box::new(
+        ancestors_of(table_metadata, latest_snapshot_id)
+            .take_while(move |snapshot| snapshot.snapshot_id() != oldest_snapshot_id),
+    )
+}