feat: expose peek next commit function to python

Author: PengLiVectra

crates/deltalake-core/src/errors.rs

@@ -76,6 +76,10 @@ pub enum DeltaTableError {
     #[error("Invalid table version: {0}")]
     InvalidVersion(i64),
 
+    /// Error returned when the DeltaTable has no delta log version.
+    #[error("Delta log not found for table version: {0}")]
+    DeltaLogNotFound(i64),
+
     /// Error returned when the DeltaTable has no data files.
     #[error("Corrupted table, cannot read data file {}: {}", .path, .source)]
     MissingDataFile {

crates/deltalake-core/src/table/mod.rs

@@ -484,6 +484,23 @@ impl DeltaTable {
         self.update().await
     }
 
+    /// Get the commit obj from the version
+    pub async fn get_obj_from_version(
+        &self,
+        current_version: i64,
+    ) -> Result<Bytes, DeltaTableError> {
+        let commit_uri = commit_uri_from_version(current_version);
+        let commit_log_bytes = self.storage.get(&commit_uri).await;
+        let commit_log_bytes = match commit_log_bytes {
+            Err(ObjectStoreError::NotFound { .. }) =>  {
+                return Err(DeltaTableError::DeltaLogNotFound(current_version));
+            },
+            Err(err) => Err(err),
+            Ok(result) => result.bytes().await,
+        }?;
+        Ok(commit_log_bytes)
+    }
+
     /// Get the list of actions for the next commit
     pub async fn peek_next_commit(
         &self,

python/deltalake/table.py

@@ -1,6 +1,7 @@
 import json
 import operator
 import warnings
+import logging
 from dataclasses import dataclass
 from datetime import datetime, timedelta
 from functools import reduce
@@ -36,7 +37,7 @@
 from ._internal import RawDeltaTable
 from ._util import encode_partition_value
 from .data_catalog import DataCatalog
-from .exceptions import DeltaProtocolError
+from .exceptions import DeltaError, DeltaProtocolError
 from .fs import DeltaStorageHandler
 from .schema import Schema
 
@@ -250,6 +251,7 @@ def __init__(
 
         """
         self._storage_options = storage_options
+        self._latest_version = -1
         self._table = RawDeltaTable(
             str(table_uri),
             version=version,
@@ -796,6 +798,31 @@ def update_incremental(self) -> None:
         """
         self._table.update_incremental()
 
+    def peek_next_commit(
+        self, version: int
+    ) -> Tuple[Optional[List[Dict[Any, Any]]], int]:
+        """
+        Peek next commit of the input version.
+        """
+        actions = []
+        next_version = version + 1
+        if next_version > self._latest_version:
+            self._latest_version = self._table.get_latest_version()
+        while next_version <= self._latest_version:
+            try:
+                commit_log_bytes = self._table.get_obj(next_version)
+                for commit_action in commit_log_bytes.split(b"\n"):
+                    if commit_action:
+                        actions.append(json.loads(commit_action))
+                return actions, next_version
+            except DeltaError as e:
+                if str(e) == f"Delta log not found for table version: {next_version}":
+                    next_version += 1
+                else:
+                    raise
+        logging.info(f"Provided Delta Version is up to date. Version: {version}")
+        return None, version
+
     def create_checkpoint(self) -> None:
         self._table.create_checkpoint()
 

python/src/lib.rs

@@ -154,6 +154,13 @@ impl RawDeltaTable {
         Ok(self._table.version())
     }
 
+    pub fn get_obj<'py>(&self, py: Python<'py>, version: i64) -> PyResult<&'py PyBytes> {
+        let commit_log_bytes = rt()?
+            .block_on(self._table.get_obj_from_version(version))
+            .map_err(PythonError::from)?;
+        return Ok(PyBytes::new(py, &commit_log_bytes));
+    }
+
     pub fn metadata(&self) -> PyResult<RawDeltaTableMetaData> {
         let metadata = self._table.get_metadata().map_err(PythonError::from)?;
         Ok(RawDeltaTableMetaData {

python/tests/test_table_read.py

@@ -495,6 +495,14 @@ def test_writer_fails_on_protocol():
         dt.to_pandas()
 
 
+@pytest.mark.parametrize("version, expected", [(2, (5, 3))])
+def test_peek_next_commit(version, expected):
+    table_path = "../rust/tests/data/simple_table"
+    dt = DeltaTable(table_path)
+    actions, current_version = dt.peek_next_commit(version=version)
+    assert (len(actions), current_version) == expected
+
+
 class ExcPassThroughThread(Thread):
     """Wrapper around `threading.Thread` that propagates exceptions."""