docstrings for DatabricksClient interface

varun-edachali-dbx · varun-edachali-dbx · commit eecc67d102f9 · 2025-05-29T03:19:02.000Z
Signed-off-by: varun-edachali-dbx &lt;varun.edachali@databricks.com&gt;
diff --git a/src/databricks/sql/backend/databricks_client.py b/src/databricks/sql/backend/databricks_client.py
@@ -1,3 +1,15 @@
+"""
+Abstract client interface for interacting with Databricks SQL services.
+
+Implementations of this class are responsible for:
+- Managing connections to Databricks SQL services
+- Handling authentication
+- Executing SQL queries and commands
+- Retrieving query results
+- Fetching metadata about catalogs, schemas, tables, and columns
+- Managing error handling and retries
+"""
+
 from abc import ABC, abstractmethod
 from typing import Dict, Tuple, List, Optional, Any, Union
 
@@ -16,10 +28,42 @@ def open_session(
         catalog: Optional[str],
         schema: Optional[str],
     ) -> SessionId:
+        """
+        Opens a new session with the Databricks SQL service.
+        
+        This method establishes a new session with the server and returns a session
+        identifier that can be used for subsequent operations.
+        
+        Args:
+            session_configuration: Optional dictionary of configuration parameters for the session
+            catalog: Optional catalog name to use as the initial catalog for the session
+            schema: Optional schema name to use as the initial schema for the session
+            
+        Returns:
+            SessionId: A session identifier object that can be used for subsequent operations
+            
+        Raises:
+            Error: If the session configuration is invalid
+            OperationalError: If there's an error establishing the session
+            InvalidServerResponseError: If the server response is invalid or unexpected
+        """
         pass
 
     @abstractmethod
     def close_session(self, session_id: SessionId) -> None:
+        """
+        Closes an existing session with the Databricks SQL service.
+        
+        This method terminates the session identified by the given session ID and
+        releases any resources associated with it.
+        
+        Args:
+            session_id: The session identifier returned by open_session()
+            
+        Raises:
+            ValueError: If the session ID is invalid
+            OperationalError: If there's an error closing the session
+        """
         pass
 
     # == Query Execution, Command Management ==
@@ -37,18 +81,92 @@ def execute_command(
         async_op: bool,
         enforce_embedded_schema_correctness: bool,
     ) -> Any:
+        """
+        Executes a SQL command or query within the specified session.
+        
+        This method sends a SQL command to the server for execution and handles
+        the response. It can operate in both synchronous and asynchronous modes.
+        
+        Args:
+            operation: The SQL command or query to execute
+            session_id: The session identifier in which to execute the command
+            max_rows: Maximum number of rows to fetch in a single batch
+            max_bytes: Maximum number of bytes to fetch in a single batch
+            lz4_compression: Whether to use LZ4 compression for result data
+            cursor: The cursor object that will handle the results
+            use_cloud_fetch: Whether to use cloud fetch for retrieving large result sets
+            parameters: List of parameters to bind to the query
+            async_op: Whether to execute the command asynchronously
+            enforce_embedded_schema_correctness: Whether to enforce schema correctness
+            
+        Returns:
+            If async_op is False, returns an ExecuteResponse object containing the
+            query results and metadata. If async_op is True, returns None and the
+            results must be fetched later using get_execution_result().
+            
+        Raises:
+            ValueError: If the session ID is invalid
+            OperationalError: If there's an error executing the command
+            ServerOperationError: If the server encounters an error during execution
+        """
         pass
 
     @abstractmethod
     def cancel_command(self, command_id: CommandId) -> None:
+        """
+        Cancels a running command or query.
+        
+        This method attempts to cancel a command that is currently being executed.
+        It can be called from a different thread than the one executing the command.
+        
+        Args:
+            command_id: The command identifier to cancel
+            
+        Raises:
+            ValueError: If the command ID is invalid
+            OperationalError: If there's an error canceling the command
+        """
         pass
 
     @abstractmethod
     def close_command(self, command_id: CommandId) -> ttypes.TStatus:
+        """
+        Closes a command and releases associated resources.
+        
+        This method informs the server that the client is done with the command
+        and any resources associated with it can be released.
+        
+        Args:
+            command_id: The command identifier to close
+            
+        Returns:
+            ttypes.TStatus: The status of the close operation
+            
+        Raises:
+            ValueError: If the command ID is invalid
+            OperationalError: If there's an error closing the command
+        """
         pass
 
     @abstractmethod
     def get_query_state(self, command_id: CommandId) -> ttypes.TOperationState:
+        """
+        Gets the current state of a query or command.
+        
+        This method retrieves the current execution state of a command from the server.
+        
+        Args:
+            command_id: The command identifier to check
+            
+        Returns:
+            ttypes.TOperationState: The current state of the command
+            
+        Raises:
+            ValueError: If the command ID is invalid
+            OperationalError: If there's an error retrieving the state
+            ServerOperationError: If the command is in an error state
+            DatabaseError: If the command has been closed unexpectedly
+        """
         pass
 
     @abstractmethod
@@ -57,6 +175,23 @@ def get_execution_result(
         command_id: CommandId,
         cursor: Any,
     ) -> ExecuteResponse:
+        """
+        Retrieves the results of a previously executed command.
+        
+        This method fetches the results of a command that was executed asynchronously
+        or retrieves additional results from a command that has more rows available.
+        
+        Args:
+            command_id: The command identifier for which to retrieve results
+            cursor: The cursor object that will handle the results
+            
+        Returns:
+            ExecuteResponse: An object containing the query results and metadata
+            
+        Raises:
+            ValueError: If the command ID is invalid
+            OperationalError: If there's an error retrieving the results
+        """
         pass
 
     # == Metadata Operations ==
@@ -68,6 +203,25 @@ def get_catalogs(
         max_bytes: int,
         cursor: Any,
     ) -> Any:
+        """
+        Retrieves a list of available catalogs.
+        
+        This method fetches metadata about the catalogs that are available
+        in the current session.
+        
+        Args:
+            session_id: The session identifier
+            max_rows: Maximum number of rows to fetch in a single batch
+            max_bytes: Maximum number of bytes to fetch in a single batch
+            cursor: The cursor object that will handle the results
+            
+        Returns:
+            ExecuteResponse: An object containing the catalog metadata
+            
+        Raises:
+            ValueError: If the session ID is invalid
+            OperationalError: If there's an error retrieving the catalogs
+        """
         pass
 
     @abstractmethod
@@ -80,6 +234,27 @@ def get_schemas(
         catalog_name: Optional[str] = None,
         schema_name: Optional[str] = None,
     ) -> Any:
+        """
+        Retrieves a list of available schemas.
+        
+        This method fetches metadata about the schemas that are available
+        in the specified catalog.
+        
+        Args:
+            session_id: The session identifier
+            max_rows: Maximum number of rows to fetch in a single batch
+            max_bytes: Maximum number of bytes to fetch in a single batch
+            cursor: The cursor object that will handle the results
+            catalog_name: Optional catalog name to filter schemas
+            schema_name: Optional schema pattern to filter schemas by name
+            
+        Returns:
+            ExecuteResponse: An object containing the schema metadata
+            
+        Raises:
+            ValueError: If the session ID is invalid
+            OperationalError: If there's an error retrieving the schemas
+        """
         pass
 
     @abstractmethod
@@ -94,6 +269,29 @@ def get_tables(
         table_name: Optional[str] = None,
         table_types: Optional[List[str]] = None,
     ) -> Any:
+        """
+        Retrieves a list of available tables.
+        
+        This method fetches metadata about the tables that are available
+        in the specified catalog and schema.
+        
+        Args:
+            session_id: The session identifier
+            max_rows: Maximum number of rows to fetch in a single batch
+            max_bytes: Maximum number of bytes to fetch in a single batch
+            cursor: The cursor object that will handle the results
+            catalog_name: Optional catalog name to filter tables
+            schema_name: Optional schema name to filter tables
+            table_name: Optional table pattern to filter tables by name
+            table_types: Optional list of table types to include (e.g., "TABLE", "VIEW")
+            
+        Returns:
+            ExecuteResponse: An object containing the table metadata
+            
+        Raises:
+            ValueError: If the session ID is invalid
+            OperationalError: If there's an error retrieving the tables
+        """
         pass
 
     @abstractmethod
@@ -108,29 +306,109 @@ def get_columns(
         table_name: Optional[str] = None,
         column_name: Optional[str] = None,
     ) -> Any:
+        """
+        Retrieves column metadata for tables.
+        
+        This method fetches metadata about the columns in the specified
+        catalog, schema, and table.
+        
+        Args:
+            session_id: The session identifier
+            max_rows: Maximum number of rows to fetch in a single batch
+            max_bytes: Maximum number of bytes to fetch in a single batch
+            cursor: The cursor object that will handle the results
+            catalog_name: Optional catalog name to filter columns
+            schema_name: Optional schema name to filter columns
+            table_name: Optional table name to filter columns
+            column_name: Optional column pattern to filter columns by name
+            
+        Returns:
+            ExecuteResponse: An object containing the column metadata
+            
+        Raises:
+            ValueError: If the session ID is invalid
+            OperationalError: If there's an error retrieving the columns
+        """
         pass
 
     # == Utility Methods ==
     @abstractmethod
     def handle_to_id(self, session_id: SessionId) -> Any:
+        """
+        Gets the raw session ID from a SessionId object.
+        
+        This method extracts the underlying protocol-specific identifier
+        from the SessionId abstraction.
+        
+        Args:
+            session_id: The session identifier
+            
+        Returns:
+            The raw session ID as used by the underlying protocol
+            
+        Raises:
+            ValueError: If the session ID is not valid for this client's backend type
+        """
         pass
 
     @abstractmethod
     def handle_to_hex_id(self, session_id: SessionId) -> str:
+        """
+        Gets a hexadecimal string representation of a session ID.
+        
+        This method converts the session ID to a human-readable hexadecimal string
+        that can be used for logging and debugging.
+        
+        Args:
+            session_id: The session identifier
+            
+        Returns:
+            str: A hexadecimal string representation of the session ID
+            
+        Raises:
+            ValueError: If the session ID is not valid for this client's backend type
+        """
         pass
 
     # Properties related to specific backend features
     @property
     @abstractmethod
     def staging_allowed_local_path(self) -> Union[None, str, List[str]]:
+        """
+        Gets the local path(s) allowed for staging data.
+        
+        This property returns the path or paths on the local filesystem that
+        are allowed to be used for staging data when uploading to the server.
+        
+        Returns:
+            Union[None, str, List[str]]: The allowed local path(s) or None if staging is not allowed
+        """
         pass
 
     @property
     @abstractmethod
     def ssl_options(self) -> SSLOptions:
+        """
+        Gets the SSL options used by this client.
+        
+        This property returns the SSL configuration options that are used
+        for secure communication with the server.
+        
+        Returns:
+            SSLOptions: The SSL configuration options
+        """
         pass
 
     @property
     @abstractmethod
     def max_download_threads(self) -> int:
-        pass
+        """
+        Gets the maximum number of threads for handling cloud fetch downloads.
+        
+        This property returns the maximum number of concurrent threads that
+        can be used for downloading result data when using cloud fetch.
+        
+        Returns:
+            int: The maximum number of download threads
+        """
+        pass
