o y\u@s`dZddlmZddlmZddlmZddlmZddgZGdddeZ Gd ddeZ d S) aHorizontal sharding support. Defines a rudimental 'horizontal sharding' system which allows a Session to distribute queries and persistence operations across multiple databases. For a usage example, see the :ref:`examples_sharding` example included in the source distribution. )inspect)util)Query)SessionShardedSession ShardedQuerycsLeZdZfddZddZddZ  d fdd Zd fd d ZZS)rcs4tt|j|i||jj|_|jj|_d|_dSN)superr__init__session id_chooser query_chooser _shard_id)selfargskwargs __class__Q/var/www/html/env/lib/python3.10/site-packages/sqlalchemy/ext/horizontal_shard.pyr s   zShardedQuery.__init__cCs|}||_|S)zreturn a new query, limited to a single shard ID. all subsequent operations with the returned query will be against the single shard regardless of other state. )_cloner)rshard_idqrrr set_shard!szShardedQuery.set_shardcs`fdd}jdur|jSjdur|jSg}D] }|||q"t|S)Ncs:|jd<_j|djj}|S)Nr)mapperr) attributesidentity_token_connection_from_session _mapper_zeroexecute statement_params instances)rresultcontextrrriter_for_shard-s  z;ShardedQuery._execute_and_instances..iter_for_shard)rrr extenditer)rr%r&partialrrr$r_execute_and_instances,s    z#ShardedQuery._execute_and_instancesNc  s|durtt|j||fd|i|S|j|}|r ||}|||D]}tt|j||fd|i|}|dur?|Sq&dS)zoverride the default Query._identity_lookup method so that we search for a given non-token primary key identity across all possible identity tokens (e.g. shard ids). Nr)r r_identity_lookupr query_set_lazyload_fromr ) rrprimary_key_identityrlazy_loaded_fromkwrrobjrrrr+As0    zShardedQuery._identity_lookupcs<fdd}|durjdurj}ttj|||dS)zOverride the default Query._get_impl() method so that we emit a query to the DB for each possible identity token, if we don't have one already. csXjdur |St|}|D]}|}||}|dur)|SqdSr)rrto_listr r)r,r.identrro db_load_fnrrr _db_load_fnjs     z+ShardedQuery._get_impl.._db_load_fnN)r)rr r _get_impl)rr.r6rr7rr5rr8cs  zShardedQuery._get_impl)NNr) __name__ __module__ __qualname__r rr*r+r8 __classcell__rrrrrs  "csHeZdZdeffdd ZddZd ddZ d dd Zd d ZZ S) rNc sdtt|jdd|i|||_||_||_i|_|j|_|dur.|D] }| |||q#dSdS)aConstruct a ShardedSession. :param 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. :param 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. :param query_chooser: For a given Query, 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. :param shards: A dictionary of string shard names to :class:`~sqlalchemy.engine.Engine` objects. query_clsNr) r rr shard_chooserr r _ShardedSession__binds connectionconnection_callable bind_shard)rr>r r shardsr=rkrrrr szShardedSession.__init__cKsb|durt|}|jr|jd}|dusJ|S|jr|jS|j||fi|}|dur/||_|S)Nr)rkeyrr>)rrinstancer0statetokenrrrr_choose_shard_and_assigns  z'ShardedSession._choose_shard_and_assigncKsJ|dur |||}|jdur|jj||dS|j|||djdi|S)N)r)rrFr)rI transactionr@get_bindcontextual_connect)rrrFrrrrrr@s  zShardedSession.connectioncKs"|dur |j|||d}|j|S)N)clause)rIr?)rrrrFrMr0rrrrKs  zShardedSession.get_bindcCs||j|<dSr)r?)rrbindrrrrBszShardedSession.bind_shard)NNN) r9r:r;rr rIr@rKrBr<rrrrrs(   N) __doc__rr orm.queryr orm.sessionr__all__rrrrrrs   j