sqlalchemy.ext.horizontal_shard.ShardedSession

class documentation

class ShardedSession(Session):

Undocumented

Method	`__init__`	Construct a ShardedSession.
Method	`connection_callable`	Provide a `_engine.Connection` to use in the unit of work flush process.
Method	`get_bind`	Return a "bind" to which this `.Session` is bound.
Method	`_choose_shard_and_assign`	Undocumented
Method	`_identity_lookup`	override the default `.Session._identity_lookup` method so that we search for a given non-token primary key identity across all possible identity tokens (e.g. shard ids).
Method	`bind_shard`	Undocumented
Instance Variable	`__binds`	Undocumented
Instance Variable	`execute_chooser`	Undocumented
Instance Variable	`id_chooser`	Undocumented
Instance Variable	`query_chooser`	Undocumented
Instance Variable	`shard_chooser`	Undocumented

Inherited from Session:

Method	`__contains__`	Return True if the instance is associated with this session.
Method	`__enter__`	Undocumented
Method	`__exit__`	Undocumented
Method	`__iter__`	Iterate over all pending or persistent instances within this Session.
Method	`_add_bind`	Undocumented
Method	`_after_attach`	Undocumented
Method	`_autobegin`	Undocumented
Method	`_autoflush`	Undocumented
Method	`_before_attach`	Undocumented
Method	`_bulk_save_mappings`	Undocumented
Method	`_close_impl`	Undocumented
Method	`_conditional_expire`	Expire a state if persistent, else expunge if pending
Method	`_connection_for_bind`	Undocumented
Method	`_contains_state`	Undocumented
Method	`_delete_impl`	Undocumented
Method	`_expire_state`	Undocumented
Method	`_expunge_states`	Undocumented
Method	`_flush`	Undocumented
Method	`_flush_warning`	Undocumented
Method	`_get_impl`	Undocumented
Method	`_is_clean`	Undocumented
Method	`_legacy_transaction`	Undocumented
Method	`_maker_context_manager`	Undocumented
Method	`_merge`	Undocumented
Method	`_register_altered`	Undocumented
Method	`_register_persistent`	Register all persistent objects from a flush.
Method	`_remove_newly_deleted`	Undocumented
Method	`_save_impl`	Undocumented
Method	`_save_or_update_impl`	Undocumented
Method	`_save_or_update_state`	Undocumented
Method	`_update_impl`	Undocumented
Method	`_validate_persistent`	Undocumented
Method	`add`	Place an object in the `Session`.
Method	`add_all`	Add the given collection of instances to this `Session`.
Method	`begin`	Begin a transaction, or nested transaction, on this `.Session`, if one is not already begun.
Method	`begin_nested`	Begin a "nested" transaction on this Session, e.g. SAVEPOINT.
Method	`bind_mapper`	Associate a `_orm.Mapper` or arbitrary Python class with a "bind", e.g. an `_engine.Engine` or `_engine.Connection`.
Method	`bind_table`	Associate a `_schema.Table` with a "bind", e.g. an `_engine.Engine` or `_engine.Connection`.
Method	`bulk_insert_mappings`	Perform a bulk insert of the given list of mapping dictionaries.
Method	`bulk_save_objects`	Perform a bulk save of the given list of objects.
Method	`bulk_update_mappings`	Perform a bulk update of the given list of mapping dictionaries.
Method	`close`	Close out the transactional resources and ORM objects used by this `_orm.Session`.
Method	`commit`	Flush pending changes and commit the current transaction.
Method	`connection`	Return a `_engine.Connection` object corresponding to this `.Session` object's transactional state.
Method	`delete`	Mark an instance as deleted.
Method	`enable_relationship_loading`	Associate an object with this `.Session` for related object loading.
Method	`execute`	Execute a SQL expression construct.
Method	`expire`	Expire the attributes on an instance.
Method	`expire_all`	Expires all persistent instances within this Session.
Method	`expunge`	Remove the `instance` from this `Session`.
Method	`expunge_all`	Remove all object instances from this `Session`.
Method	`flush`	Flush all the object changes to the database.
Method	`get`	Return an instance based on the given primary key identifier, or `None` if not found.
Method	`get_nested_transaction`	Return the current nested transaction in progress, if any.
Method	`get_transaction`	Return the current root transaction in progress, if any.
Method	`in_nested_transaction`	Return True if this `_orm.Session` has begun a nested transaction, e.g. SAVEPOINT.
Method	`in_transaction`	Return True if this `_orm.Session` has begun a transaction.
Method	`invalidate`	Close this Session, using connection invalidation.
Method	`is_modified`	Return `True` if the given instance has locally modified attributes.
Method	`merge`	Copy the state of a given instance into a corresponding instance within this `.Session`.
Method	`prepare`	Prepare the current transaction in progress for two phase commit.
Method	`query`	Return a new `_query.Query` object corresponding to this `_orm.Session`.
Method	`refresh`	Expire and refresh attributes on the given instance.
Method	`rollback`	Rollback the current transaction in progress.
Method	`scalar`	Execute a statement and return a scalar result.
Method	`scalars`	Execute a statement and return the results as scalars.
Class Variable	`_is_asyncio`	Undocumented
Class Variable	`_trans_context_manager`	Undocumented
Instance Variable	`_deleted`	Undocumented
Instance Variable	`_flushing`	Undocumented
Instance Variable	`_nested_transaction`	Undocumented
Instance Variable	`_new`	Undocumented
Instance Variable	`_query_cls`	Undocumented
Instance Variable	`_transaction`	Undocumented
Instance Variable	`_warn_on_events`	Undocumented
Instance Variable	`autocommit`	Undocumented
Instance Variable	`autoflush`	Undocumented
Instance Variable	`bind`	Undocumented
Instance Variable	`enable_baked_queries`	Undocumented
Instance Variable	`expire_on_commit`	Undocumented
Instance Variable	`future`	Undocumented
Instance Variable	`hash_key`	Undocumented
Instance Variable	`identity_map`	A mapping of object identities to objects themselves.
Instance Variable	`twophase`	Undocumented
Property	`_dirty_states`	The set of all persistent states considered dirty.
Property	`deleted`	The set of all instances marked as 'deleted' within this `Session`
Property	`dirty`	The set of all persistent instances considered dirty.
Property	`info`	A user-modifiable dictionary.
Property	`is_active`	True if this `.Session` not in "partial rollback" state.
Property	`new`	The set of all instances marked as 'new' within this `Session`.
Property	`no_autoflush`	Return a context manager that disables autoflush.
Property	`transaction`	The current active or inactive `.SessionTransaction`.

Inherited from _SessionClassMethods (via Session):

Class Method	`close_all`	Close all sessions in memory.
Class Method	`identity_key`	Return an identity key.
Class Method	`object_session`	Return the `.Session` to which an object belongs.

def __init__(self, shard_chooser, id_chooser, execute_chooser=None, shards=None, query_cls=ShardedQuery, **kwargs):

overrides sqlalchemy.orm.session.Session.__init__

Construct a ShardedSession.

Parameters
shard_chooser	A callable which, passed a Mapper, a mapped instance, and possibly a SQL clause, returns a shard ID. This id may be based off of the attributes present within the object, or on some round-robin scheme. If the scheme is based on a selection, it should set whatever state on the instance to mark it in the future as participating in that shard.
id_chooser	A callable, passed a query and a tuple of identity values, which should return a list of shard ids where the ID might reside. The databases will be queried in the order of this listing.
execute_chooser	For a given `.ORMExecuteState`, returns the list of shard_ids where the query should be issued. Results from all shards returned will be combined together into a single listing. Changed in version 1.4: The `execute_chooser` parameter supersedes the `query_chooser` parameter.
shards	A dictionary of string shard names to `~sqlalchemy.engine.Engine` objects.
query_cls	Undocumented
**kwargs	Undocumented

def connection_callable(self, mapper=None, instance=None, shard_id=None, **kwargs):

overrides sqlalchemy.orm.session.Session.connection_callable

Provide a _engine.Connection to use in the unit of work flush process.

def get_bind(self, mapper=None, shard_id=None, instance=None, clause=None, **kw):

overrides sqlalchemy.orm.session.Session.get_bind

Return a "bind" to which this .Session is bound.

The "bind" is usually an instance of _engine.Engine, except in the case where the .Session has been explicitly bound directly to a _engine.Connection.

For a multiply-bound or unbound .Session, the mapper or clause arguments are used to determine the appropriate bind to return.

Note that the "mapper" argument is usually present when .Session.get_bind is called via an ORM operation such as a .Session.query, each individual INSERT/UPDATE/DELETE operation within a .Session.flush, call, etc.

The order of resolution is:

if mapper given and :paramref:`.Session.binds` is present, locate a bind based first on the mapper in use, then on the mapped class in use, then on any base classes that are present in the __mro__ of the mapped class, from more specific superclasses to more general.
if clause given and Session.binds is present, locate a bind based on _schema.Table objects found in the given clause present in Session.binds.
if Session.binds is present, return that.
if clause given, attempt to return a bind linked to the _schema.MetaData ultimately associated with the clause.
if mapper given, attempt to return a bind linked to the _schema.MetaData ultimately associated with the _schema.Table or other selectable to which the mapper is mapped.
No bind can be found, ~sqlalchemy.exc.UnboundExecutionError is raised.

Note that the .Session.get_bind method can be overridden on a user-defined subclass of .Session to provide any kind of bind resolution scheme. See the example at :ref:`session_custom_partitioning`.

Parameters
mapper	Optional `.mapper` mapped class or instance of `_orm.Mapper`. The bind can be derived from a `_orm.Mapper` first by consulting the "binds" map associated with this `.Session`, and secondly by consulting the `_schema.MetaData` associated with the `_schema.Table` to which the `_orm.Mapper` is mapped for a bind.
shard_id	Undocumented
instance	Undocumented
clause	A `_expression.ClauseElement` (i.e. `_expression.select`, `_expression.text`, etc.). If the `mapper` argument is not present or could not produce a bind, the given expression construct will be searched for a bound element, typically a `_schema.Table` associated with bound `_schema.MetaData`.
**kw	Undocumented