update Claude.md

Author: allisonwang-db

CLAUDE.md

@@ -135,40 +135,57 @@ stream = spark.readStream.format("fake").load()
 Primary abstract base class for custom data sources supporting read/write operations.
 
 **Key Methods:**
-- `__init__(self, options: Dict[str, str])` - Initialize with user options
-- `name() -> str` - Return format name (defaults to class name)
-- `schema() -> StructType` - Define data source schema
-- `reader(schema: StructType) -> DataSourceReader` - Create batch reader
-- `writer(schema: StructType, overwrite: bool) -> DataSourceWriter` - Create batch writer
-- `streamReader(schema: StructType) -> DataSourceStreamReader` - Create streaming reader
-- `streamWriter(schema: StructType, overwrite: bool) -> DataSourceStreamWriter` - Create streaming writer
-- `simpleStreamReader(schema: StructType) -> SimpleDataSourceStreamReader` - Create simple streaming reader
+- `__init__(self, options: Dict[str, str])` - Initialize with user options (Optional; base class provides default)
+- `name() -> str` - Return format name (Optional to override; defaults to class name)
+- `schema() -> StructType` - Define data source schema (Required)
+- `reader(schema: StructType) -> DataSourceReader` - Create batch reader (Required if batch read is supported)
+- `writer(schema: StructType, overwrite: bool) -> DataSourceWriter` - Create batch writer (Required if batch write is supported)
+- `streamReader(schema: StructType) -> DataSourceStreamReader` - Create streaming reader (Required if streaming read is supported and `simpleStreamReader` is not implemented)
+- `streamWriter(schema: StructType, overwrite: bool) -> DataSourceStreamWriter` - Create streaming writer (Required if streaming write is supported)
+- `simpleStreamReader(schema: StructType) -> SimpleDataSourceStreamReader` - Create simple streaming reader (Required if streaming read is supported and `streamReader` is not implemented)
 
 #### DataSourceReader
 Abstract base class for reading data from sources.
 
 **Key Methods:**
-- `read(partition) -> Iterator` - Read data from partition, returns tuples/Rows/pyarrow.RecordBatch
-- `partitions() -> List[InputPartition]` - Return input partitions for parallel reading
+- `read(partition) -> Iterator` - Read data from partition, returns tuples/Rows/pyarrow.RecordBatch (Required)
+- `partitions() -> List[InputPartition]` - Return input partitions for parallel reading (Optional; defaults to a single partition)
 
 #### DataSourceStreamReader
 Abstract base class for streaming data sources with offset management.
 
 **Key Methods:**
-- `initialOffset() -> Offset` - Return starting offset
-- `latestOffset() -> Offset` - Return latest available offset
-- `partitions(start: Offset, end: Offset) -> List[InputPartition]` - Get partitions for offset range
-- `read(partition) -> Iterator` - Read data from partition
-- `commit(end: Offset)` - Mark offsets as processed
-- `stop()` - Clean up resources
+- `initialOffset() -> dict` - Return starting offset (Required)
+- `latestOffset() -> dict` - Return latest available offset (Required)
+- `partitions(start: dict, end: dict) -> List[InputPartition]` - Get partitions for offset range (Required)
+- `read(partition) -> Iterator` - Read data from partition (Required)
+- `commit(end: dict) -> None` - Mark offsets as processed (Optional)
+- `stop() -> None` - Clean up resources (Optional)
+
+#### SimpleDataSourceStreamReader
+Simplified streaming reader interface without partition planning.
+
+**Key Methods:**
+- `initialOffset() -> dict` - Return starting offset (Required)
+- `read(start: dict) -> Tuple[Iterator, dict]` - Read from start offset; return an iterator and the next start offset (Required)
+- `readBetweenOffsets(start: dict, end: dict) -> Iterator` - Deterministic replay between offsets for recovery (Optional; recommended for reliable recovery)
+- `commit(end: dict) -> None` - Mark offsets as processed (Optional)
 
 #### DataSourceWriter
 Abstract base class for writing data to external sources.
 
 **Key Methods:**
-- `write(iterator) -> WriteResult` - Write data from iterator
-- `abort(messages: List[WriterCommitMessage])` - Handle write failures
-- `commit(messages: List[WriterCommitMessage]) -> WriteResult` - Commit successful writes
+- `write(iterator) -> WriteResult` - Write data from iterator (Required)
+- `abort(messages: List[WriterCommitMessage])` - Handle write failures (Optional)
+- `commit(messages: List[WriterCommitMessage]) -> WriteResult` - Commit successful writes (Required)
+
+#### DataSourceStreamWriter
+Abstract base class for writing data to external sinks in streaming queries.
+
+**Key Methods:**
+- `write(iterator) -> WriterCommitMessage` - Write data for a partition and return a commit message (Required)
+- `commit(messages: List[WriterCommitMessage], batchId: int) -> None` - Commit successful microbatch writes (Required)
+- `abort(messages: List[WriterCommitMessage], batchId: int) -> None` - Handle write failures for a microbatch (Optional)
 
 #### DataSourceArrowWriter
 Optimized writer using PyArrow RecordBatch for improved performance.