Add data source sinks for Polars LazyFrame (#791)

This commit adds four data sink methods for Polars LazyFrame:
- sink_parquet: Write LazyFrame to Parquet format
- sink_csv: Write LazyFrame to CSV format
- sink_ipc: Write LazyFrame to IPC/Feather format
- sink_ndjson: Write LazyFrame to NDJSON format

These sinks allow users to write LazyFrames directly without needing to call .collect() first, improving performance for large datasets.

Fixes #791

Author: Chowdhury-Anik

hamilton/plugins/polars_lazyframe_extensions.py

@@ -297,6 +297,166 @@ def name(cls) -> str:
         return "feather"
 
 
+
+@dataclasses.dataclass
+class PolarsSinkParquetWriter(DataLoader):
+    """
+    Class specifically to handle writing parquet files with Polars LazyFrame.
+    Should map to https://docs.pola.rs/api/python/stable/reference/lazyframe/api/polars.LazyFrame.sink_parquet.html
+    """
+    path: Union[str, Path]
+    # kwargs:
+    compression: str = "zstd"
+    compression_level: Optional[int] = None
+    statistics: bool = False
+    row_group_size: Optional[int] = None
+    data_page_size: Optional[int] = None
+    
+    @classmethod
+    def applicable_types(cls) -> Collection[Type]:
+        return [DATAFRAME_TYPE]
+    
+    def _get_writing_kwargs(self):
+        kwargs = {}
+        if self.compression is not None:
+            kwargs["compression"] = self.compression
+        if self.compression_level is not None:
+            kwargs["compression_level"] = self.compression_level
+        if self.statistics is not None:
+            kwargs["statistics"] = self.statistics
+        if self.row_group_size is not None:
+            kwargs["row_group_size"] = self.row_group_size
+        if self.data_page_size is not None:
+            kwargs["data_page_size"] = self.data_page_size
+        return kwargs
+    
+    def save_data(self, data: DATAFRAME_TYPE) -> Dict[str, Any]:
+        data.sink_parquet(self.path, **self._get_writing_kwargs())
+        metadata = utils.get_file_metadata(self.path)
+        return metadata
+    
+    @classmethod
+    def name(cls) -> str:
+        return "parquet"
+
+
+@dataclasses.dataclass
+class PolarsSinkCSVWriter(DataLoader):
+    """
+    Class specifically to handle writing CSV files with Polars LazyFrame.
+    Should map to https://docs.pola.rs/api/python/stable/reference/lazyframe/api/polars.LazyFrame.sink_csv.html
+    """
+    path: Union[str, Path]
+    # kwargs:
+    include_bom: bool = False
+    include_header: bool = True
+    separator: str = ","
+    line_terminator: str = "\n"
+    quote_char: str = '"'
+    batch_size: int = 1024
+    datetime_format: Optional[str] = None
+    date_format: Optional[str] = None
+    time_format: Optional[str] = None
+    float_precision: Optional[int] = None
+    null_value: Optional[str] = None
+    quote_style: Optional[str] = None
+    
+    @classmethod
+    def applicable_types(cls) -> Collection[Type]:
+        return [DATAFRAME_TYPE]
+    
+    def _get_writing_kwargs(self):
+        kwargs = {}
+        if self.include_bom is not None:
+            kwargs["include_bom"] = self.include_bom
+        if self.include_header is not None:
+            kwargs["include_header"] = self.include_header
+        if self.separator is not None:
+            kwargs["separator"] = self.separator
+        if self.line_terminator is not None:
+            kwargs["line_terminator"] = self.line_terminator
+        if self.quote_char is not None:
+            kwargs["quote_char"] = self.quote_char
+        if self.batch_size is not None:
+            kwargs["batch_size"] = self.batch_size
+        if self.datetime_format is not None:
+            kwargs["datetime_format"] = self.datetime_format
+        if self.date_format is not None:
+            kwargs["date_format"] = self.date_format
+        if self.time_format is not None:
+            kwargs["time_format"] = self.time_format
+        if self.float_precision is not None:
+            kwargs["float_precision"] = self.float_precision
+        if self.null_value is not None:
+            kwargs["null_value"] = self.null_value
+        if self.quote_style is not None:
+            kwargs["quote_style"] = self.quote_style
+        return kwargs
+    
+    def save_data(self, data: DATAFRAME_TYPE) -> Dict[str, Any]:
+        data.sink_csv(self.path, **self._get_writing_kwargs())
+        metadata = utils.get_file_metadata(self.path)
+        return metadata
+    
+    @classmethod
+    def name(cls) -> str:
+        return "csv"
+
+
+@dataclasses.dataclass
+class PolarsSinkIPCWriter(DataLoader):
+    """
+    Class specifically to handle writing IPC/Feather files with Polars LazyFrame.
+    Should map to https://docs.pola.rs/api/python/stable/reference/lazyframe/api/polars.LazyFrame.sink_ipc.html
+    """
+    path: Union[str, Path]
+    # kwargs:
+    compression: Optional[str] = "zstd"
+    
+    @classmethod
+    def applicable_types(cls) -> Collection[Type]:
+        return [DATAFRAME_TYPE]
+    
+    def _get_writing_kwargs(self):
+        kwargs = {}
+        if self.compression is not None:
+            kwargs["compression"] = self.compression
+        return kwargs
+    
+    def save_data(self, data: DATAFRAME_TYPE) -> Dict[str, Any]:
+        data.sink_ipc(self.path, **self._get_writing_kwargs())
+        metadata = utils.get_file_metadata(self.path)
+        return metadata
+    
+    @classmethod
+    def name(cls) -> str:
+        return "ipc"
+
+
+@dataclasses.dataclass
+class PolarsSinkNDJSONWriter(DataLoader):
+    """
+    Class specifically to handle writing NDJSON files with Polars LazyFrame.
+    Should map to https://docs.pola.rs/api/python/stable/reference/lazyframe/api/polars.LazyFrame.sink_ndjson.html
+    Note: Load support for NDJSON is not yet implemented.
+    """
+    path: Union[str, Path]
+    
+    @classmethod
+    def applicable_types(cls) -> Collection[Type]:
+        return [DATAFRAME_TYPE]
+    
+    def save_data(self, data: DATAFRAME_TYPE) -> Dict[str, Any]:
+        data.sink_ndjson(self.path)
+        metadata = utils.get_file_metadata(self.path)
+        return metadata
+    
+    @classmethod
+    def name(cls) -> str:
+        return "ndjson"
+
+
+
 def register_data_loaders():
     """Function to register the data loaders for this extension."""
     for loader in [
@@ -308,3 +468,17 @@ def register_data_loaders():
 
 
 register_data_loaders()
+
+
+def register_data_savers():
+    """Function to register the data savers for this extension."""
+    for saver in [
+        PolarsSinkParquetWriter,
+        PolarsSinkCSVWriter,
+        PolarsSinkIPCWriter,
+        PolarsSinkNDJSONWriter,
+    ]:
+        registry.register_adapter(saver)
+
+
+register_data_savers()