Sessions

Sessions#

Note

Daft’s session APIs are early in their development and may change.

class Session[source]#

Session holds a connection’s state and orchestrates execution of DataFrame and SQL queries against catalogs.

attach(object: daft.catalog.Catalog | daft.catalog.Table, alias: Optional[str] = None) → None[source]#

Attaches a known attachable object like a Catalog or Table.

Parameters:: object (Catalog|Table) – object which is attachable to a session
Returns:: None

attach_catalog(catalog: daft.catalog.Catalog | object, alias: Optional[str] = None) → Catalog[source]#

Attaches an external catalog to this session.

Parameters:

catalog (object) – catalog instance or supported catalog object
alias (str|None) – optional alias for name resolution

Returns:

new daft catalog instance

Return type:

Catalog

attach_table(table: daft.catalog.Table | object, alias: Optional[str] = None) → Table[source]#

Attaches an external table instance to this session.

Parameters:

table (Table | object) – table instance or supported table object
alias (str | None) – optional alias for name resolution

Returns:

new daft table instance

Return type:

Table

create_namespace(identifier: daft.catalog.Identifier | str)[source]#: Creates a namespace in the current catalog.

create_table(identifier: daft.catalog.Identifier | str, source: daft.catalog.TableSource | object) → Table[source]#: Creates a table in the current catalog.

create_temp_table(identifier: str, source: Optional[Union[TableSource, object]] = None) → Table[source]#

Creates a temp table scoped to this session’s lifetime.

Example

>>> import daft
>>> from daft.session import Session
>>> sess = Session()
>>> sess.create_temp_table("T", daft.from_pydict({"x": [1, 2, 3]}))
>>> sess.create_temp_table("S", daft.from_pydict({"y": [4, 5, 6]}))
>>> sess.list_tables()
[Identifier(''T''), Identifier(''S'')]

Parameters:

identifier (str) – table identifier (name)
source (TableSource|object) – table source like a schema or dataframe

Returns:

new table instance

Return type:

Table

current_catalog() → daft.catalog.Catalog | None[source]#

Get the session’s current catalog or None.

Parameters:: None –
Returns:: current catalog or None if one is not set
Return type:: Catalog

current_namespace() → daft.catalog.Identifier | None[source]#

Get the session’s current namespace or None.

Parameters:: None –
Returns:: current namespace or none if one is not set
Return type:: Identifier

detach_catalog(alias: str)[source]#

Detaches the catalog from this session or raises if the catalog does not exist.

Parameters:: alias (str) – catalog alias to detach
Returns:: None

detach_table(alias: str)[source]#

Detaches the table from this session or raises if the table does not exist.

Parameters:: alias (str) – catalog alias to detach
Returns:: None

drop_namespace(identifier: daft.catalog.Identifier | str)[source]#

Drop the given namespace in the current catalog.

Parameters:: identifier (Identifier|str) – table identifier
Returns:: None

drop_table(identifier: daft.catalog.Identifier | str)[source]#

Drop the given table in the current catalog.

Parameters:: identifier (Identifier|str) – table identifier
Returns:: None

get_catalog(identifier: str) → Catalog[source]#

Returns the catalog or raises an exception if it does not exist.

Parameters:: identifier (str) – catalog identifier (name)
Returns:: The catalog object.
Return type:: Catalog
Raises:: ValueError – If the catalog does not exist.

get_table(identifier: daft.catalog.Identifier | str) → Table[source]#

Returns the table or raises an exception if it does not exist.

Parameters:: identifier (Identifier|str) – table identifier or identifier string
Returns:: The table object.
Return type:: Table
Raises:: ValueError – If the table does not exist.

has_catalog(identifier: str) → bool[source]#: Returns true if a catalog with the given identifier exists.

has_table(identifier: daft.catalog.Identifier | str) → bool[source]#: Returns true if a table with the given identifier exists.

list_catalogs(pattern: Optional[str] = None) → list[str][source]#

Returns a list of available catalogs matching the pattern.

This API currently returns a list of catalog names for backwards compatibility. In 0.5.0 this API will return a list of Catalog objects.

Parameters:: pattern (str) – catalog name pattern
Returns:: list of available catalog names
Return type:: list[str]

list_namespaces(pattern: Optional[str] = None) → list[daft.catalog.Identifier][source]#: Returns a list of matching namespaces in the current catalog.

list_tables(pattern: Optional[str] = None) → list[daft.catalog.Identifier][source]#

Returns a list of available tables.

Parameters:: pattern (str) – table name pattern
Returns:: list of available tables
Return type:: list[Identifier]

read_table(identifier: daft.catalog.Identifier | str, **options) → DataFrame[source]#

Returns the table as a DataFrame or raises an exception if it does not exist.

Parameters:: identifier (Identifier|str) – table identifier
Return type:: DataFrame
Raises:: ValueError – If the tables odes not exist.

set_catalog(identifier: str | None)[source]#

Set the given catalog as current_catalog or raises an err if it does not exist.

Parameters:: identifier (str) – sets the current catalog
Returns:: None
Raises:: ValueError – If the catalog does not exist.

set_namespace(identifier: daft.catalog.Identifier | str | None)[source]#

Set the given namespace as current_namespace for table resolution.

Parameters:: identifier (Identifier | str) – namespace identifier

sql(sql: str) → daft.dataframe.dataframe.DataFrame | None[source]#

Executes the SQL statement using this session.

Parameters:: sql (str) – input SQL statement
Returns:: dataframe instance if this was a data statement (DQL, DDL, DML).
Return type:: DataFrame

use(identifier: Optional[Union[Identifier, str]] = None)[source]#: Use sets the current catalog and namespace.

write_table(identifier: daft.catalog.Identifier | str, df: daft.dataframe.dataframe.DataFrame | object, mode: Literal['append', 'overwrite'] = 'append', **options)[source]#

Writes the DataFrame to the table specified by the identifier.

Parameters:

identifier (Identifier|str) – table identifier
df (DataFrame|object) – dataframe to write
mode ("append"|"overwrite") – write mode, defaults to “append”
options** – additional, format-specific write options

Returns:

None

Sessions

Contents

Sessions#