Single part checkpoint write api

acceptance/tests/other.rs

@@ -3,15 +3,15 @@
 /// Since each new `.rs` file in this directory results in increased build and link time, it is
 /// important to only add new files if absolutely necessary for code readability or test
 /// performance.
-use delta_kernel::snapshot::CheckpointMetadata;
+use delta_kernel::snapshot::LastCheckpointHint;
 
 #[test]
 fn test_checkpoint_serde() {
     let file = std::fs::File::open(
         "./tests/dat/out/reader_tests/generated/with_checkpoint/delta/_delta_log/_last_checkpoint",
     )
     .unwrap();
-    let cp: CheckpointMetadata = serde_json::from_reader(file).unwrap();
+    let cp: LastCheckpointHint = serde_json::from_reader(file).unwrap();
     assert_eq!(cp.version, 2)
 }
 

ffi/src/expressions/kernel.rs

@@ -65,6 +65,8 @@ pub struct EngineExpressionVisitor {
     pub visit_literal_int: VisitLiteralFn<i32>,
     /// Visit a 64bit `long`  belonging to the list identified by `sibling_list_id`.
     pub visit_literal_long: VisitLiteralFn<i64>,
+    /// Visit a 64bit unsigned `long`  belonging to the list identified by `sibling_list_id`.
+    pub visit_literal_uint: VisitLiteralFn<u32>,
     /// Visit a 16bit `short` belonging to the list identified by `sibling_list_id`.
     pub visit_literal_short: VisitLiteralFn<i16>,
     /// Visit an 8bit `byte` belonging to the list identified by `sibling_list_id`.

kernel/Cargo.toml

@@ -49,7 +49,7 @@ thiserror = "1"
 # only for structured logging
 tracing = { version = "0.1", features = ["log"] }
 url = "2"
-uuid = "1.10.0"
+uuid = { version = "1.10.0", features = ["v4", "fast-rng"] }
 z85 = "3.0.5"
 
 # bring in our derive macros
@@ -118,8 +118,6 @@ default-engine-base = [
   "need_arrow",
   "object_store",
   "tokio",
-  "uuid/v4",
-  "uuid/fast-rng",
 ]
 
 # the default-engine use the reqwest crate with default features which uses native-tls. if you want

kernel/src/actions/mod.rs

@@ -544,6 +544,19 @@ pub(crate) struct SetTransaction {
     pub(crate) last_updated: Option<i64>,
 }
 
+/// The CheckpointMetadata action describes details about a checkpoint following the V2 specification.
+///
+/// [More info]: https://github.com/delta-io/delta/blob/master/PROTOCOL.md#checkpoint-metadata
+#[derive(Schema, Debug, PartialEq)]
+#[cfg_attr(feature = "developer-visibility", visibility::make(pub))]
+pub(crate) struct CheckpointMetadata {
+    /// The version of the V2 spec checkpoint.
+    pub(crate) version: i64,
+
+    /// Map containing any additional metadata about the V2 spec checkpoint.
+    pub(crate) tags: Option<HashMap<String, String>>,
+}
+
 /// The sidecar action references a sidecar file which provides some of the checkpoint's
 /// file actions. This action is only allowed in checkpoints following the V2 spec.
 ///

kernel/src/actions/schemas.rs

@@ -8,6 +8,15 @@ pub(crate) trait ToSchema {
     fn to_schema() -> StructType;
 }
 
+/// Implement ToSchema for StructType to enable its use within Option<T> fields
+/// in schema-derived structs. This follows the system pattern where schema types
+/// implement ToSchema rather than directly implementing ToDataType.
+impl ToSchema for StructType {
+    fn to_schema() -> StructType {
+        StructType::new(vec![])
+    }
+}
+
 pub(crate) trait ToDataType {
     fn to_data_type() -> DataType;
 }