Backend Base Classes

BaseBackend

Bases: abc.ABC, _FileIOHandler

Base backend class.

All Ibis backends must subclass this class and implement all the required methods.

Attributes

current_database: str | None abstractmethod property

Return the name of the current database.

Backends that don't support different databases will return None.

Returns:

Type	Description
str | None	Name of the current database.

db_identity: str property cached

Return the identity of the database.

Multiple connections to the same database will return the same value for db_identity.

The default implementation assumes connection parameters uniquely specify the database.

Returns:

Type	Description
Hashable	Database identity

tables property cached

An accessor for tables in the database.

Tables may be accessed by name using either index or attribute access:

Examples:

>>> con = ibis.sqlite.connect("example.db")
>>> people = con.tables['people']  # access via index
>>> people = con.tables.people  # access via attribute

version: str abstractmethod property

Return the version of the backend engine.

For database servers, return the server version.

For others such as SQLite and pandas return the version of the underlying library or application.

Returns:

Type	Description
str	The backend version

Functions

add_operation(operation)

Add a translation function to the backend for a specific operation.

Operations are defined in ibis.expr.operations, and a translation function receives the translator object and an expression as parameters, and returns a value depending on the backend. For example, in SQL backends, a NullLiteral operation could be translated to the string "NULL".

Examples:

>>> @ibis.sqlite.add_operation(ibis.expr.operations.NullLiteral)
... def _null_literal(translator, expression):
...     return 'NULL'

compile(expr, params=None)

Compile an expression.

connect(*args, **kwargs)

Connect to the database.

Parameters:

Name	Type	Description	Default
*args		Mandatory connection parameters, see the docstring of do_connect for details.	()
**kwargs		Extra connection parameters, see the docstring of do_connect for details.	{}

Notes

This creates a new backend instance with saved args and kwargs, then calls reconnect and finally returns the newly created and connected backend instance.

Returns:

Type	Description
BaseBackend	An instance of the backend

create_database(name, force=False)

Create a new database.

Not all backends implement this method.

Parameters:

Name	Type	Description	Default
name	str	Name of the new database.	required
force	bool	If False, an exception is raised if the database already exists.	False

create_table(name, obj=None, *, schema=None, database=None, temp=False, overwrite=False) abstractmethod

Create a new table.

Parameters:

Name	Type	Description	Default
name	str	Name of the new table.	required
obj	pd.DataFrame | ir.Table | None	An Ibis table expression or pandas table that will be used to extract the schema and the data of the new table. If not provided, schema must be given.	None
schema	ibis.Schema | None	The schema for the new table. Only one of schema or obj can be provided.	None
database	str | None	Name of the database where the table will be created, if not the default.	None
temp	bool	Whether a table is temporary or not	False
overwrite	bool	Whether to clobber existing data	False

Returns:

Type	Description
Table	The table that was created.

create_view(name, obj, *, database=None, overwrite=False) abstractmethod

Create a new view from an expression.

Parameters:

Name	Type	Description	Default
name	str	Name of the new view.	required
obj	ir.Table	An Ibis table expression that will be used to create the view.	required
database	str | None	Name of the database where the view will be created, if not provided the database's default is used.	None
overwrite	bool	Whether to clobber an existing view with the same name	False

Returns:

Type	Description
Table	The view that was created.

database(name=None)

Return a Database object for the name database.

Parameters:

Name	Type	Description	Default
name	str | None	Name of the database to return the object for.	None

Returns:

Type	Description
Database	A database object for the specified database.

drop_table(name, *, database=None, force=False) abstractmethod

Drop a table.

Parameters:

Name	Type	Description	Default
name	str	Name of the table to drop.	required
database	str | None	Name of the database where the table exists, if not the default.	None
force	bool	If False, an exception is raised if the table does not exist.	False

drop_view(name, *, database=None, force=False) abstractmethod

Drop a view.

Parameters:

Name	Type	Description	Default
name	str	Name of the view to drop.	required
database	str | None	Name of the database where the view exists, if not the default.	None
force	bool	If False, an exception is raised if the view does not exist.	False

execute(expr)

Execute an expression.

has_operation(operation) classmethod

Return whether the backend implements support for operation.

Parameters:

Name	Type	Description	Default
operation	type[ops.Value]	A class corresponding to an operation.	required

Returns:

Type	Description
bool	Whether the backend implements the operation.

Examples:

>>> import ibis
>>> import ibis.expr.operations as ops
>>> ibis.sqlite.has_operation(ops.ArrayIndex)
False
>>> ibis.postgres.has_operation(ops.ArrayIndex)
True

list_databases(like=None) abstractmethod

List existing databases in the current connection.

Parameters:

Name	Type	Description	Default
like	str	A pattern in Python's regex format to filter returned database names.	None

Returns:

Type	Description
list[str]	The database names that exist in the current connection, that match the like pattern if provided.

list_tables(like=None, database=None) abstractmethod

Return the list of table names in the current database.

For some backends, the tables may be files in a directory, or other equivalent entities in a SQL database.

Parameters:

Name	Type	Description	Default
like	str, optional	A pattern in Python's regex format.	None
database	str, optional	The database to list tables of, if not the current one.	None

Returns:

Type	Description
list[str]	The list of the table names that match the pattern like.

register_options() classmethod

Register custom backend options.

table(name, database=None) abstractmethod

Construct a table expression.

Parameters:

Name	Type	Description	Default
name	str	Table name	required
database	str | None	Database name	None

Returns:

Type	Description
Table	Table expression

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Last update: January 4, 2023