Edit File: horizontal_shard.cpython-37.pyc
B ��4]�# � @ sp d Z ddlmZ ddlmZ ddlmZ ddlmZ ddgZG dd� de�Z G d d � d e �Z G d d� de�Z d S ) a Horizontal 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)�Session�ShardedSession� ShardedQueryc sP e Zd Z� fdd�Zdd� Zdd� Zdd� Zd� fd d � Zd� fd d � Z� Z S )r c s0 t t| �j||� | jj| _| jj| _d | _d S )N)�superr �__init__�session� id_chooser� query_chooser� _shard_id)�self�args�kwargs)� __class__� �R/opt/alt/python37/lib64/python3.7/site-packages/sqlalchemy/ext/horizontal_shard.pyr s zShardedQuery.__init__c C s | � � }||_|S )z�return 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. )Z_cloner )r �shard_id�qr r r � set_shard" s zShardedQuery.set_shardc sh � �fdd�}� j d k r"|� j �S �jd k r6|�j�S g }x ����D ]}|�||�� qFW t|�S d S )Nc s: | � j d< � _�j��� | d��� j�j�}��|� �S )Nr )�mapperr )Z attributes�identity_token�_connection_from_sessionZ _bind_mapper�execute� statement�_paramsZ instances)r �result)�contextr r r �iter_for_shard. s z;ShardedQuery._execute_and_instances.<locals>.iter_for_shard)r r r �extend�iter)r r r �partialr r )r r r �_execute_and_instances- s z#ShardedQuery._execute_and_instancesc sj � ��fdd�}�j d k r$|�j �S d}g }x.����D ] }||�}||j7 }|�|� q8W t||�S d S )Nc s$ �j � | �dd�}|���j�}|S )NT)r r �clauseZclose_with_result)r r r )r Zconnr )r r �stmtr r �exec_for_shardC s z2ShardedQuery._execute_crud.<locals>.exec_for_shard� )r r �rowcount�append� ShardedResult)r r% r r& r( �resultsr r r )r r r% r � _execute_crudB s zShardedQuery._execute_crudNc s� |dk r&t t| �j||fd|i|��S | j�|�}|r@|�|�}x>| �||�D ].}t t| �j||fd|i|��}|dk rN|S qNW dS dS )z�override 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 �queryZ_set_lazyload_fromr ) r r �primary_key_identityr Zlazy_loaded_from�kwr r �obj)r r r r- Y s z ShardedQuery._identity_lookupc s< � �fdd�}|dkr&�j dk r&�j }tt��j|||d�S )z�Override 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. c s\ �j d k r� �|�S t�|�}x8���|�D ]$}��|�}� ||�}|d k r,|S q,W d S d S )N)r r Zto_listr r )r. r/ �identr r �o)� db_load_fnr r r � _db_load_fn� s z+ShardedQuery._get_impl.<locals>._db_load_fnN)r )r r r � _get_impl)r r/ r4 r r5 )r )r4 r r r6 { s zShardedQuery._get_impl)NN)N) �__name__� __module__� __qualname__r r r# r, r- r6 � __classcell__r r )r r r s c @ s( e Zd ZdZdZdd� Zedd� �ZdS )r* a� A value object that represents multiple :class:`.ResultProxy` objects. This is used by the :meth:`.ShardedQuery._execute_crud` hook to return an object that takes the place of the single :class:`.ResultProxy`. Attribute include ``result_proxies``, which is a sequence of the actual :class:`.ResultProxy` objects, as well as ``aggregate_rowcount`` or ``rowcount``, which is the sum of all the individual rowcount values. .. versionadded:: 1.3 )�result_proxies�aggregate_rowcountc C s || _ || _d S )N)r; r< )r r; r< r r r r � s zShardedResult.__init__c C s | j S )N)r< )r r r r r( � s zShardedResult.rowcountN)r7 r8 r9 �__doc__� __slots__r �propertyr( r r r r r* � s r* c sF e Zd Zdef� fdd� Zdd� Zd dd�Zd dd �Zd d � Z� Z S )r Nc sd t t| �jf d|i|�� || _|| _|| _i | _| j| _|dk r`x |D ]}| � ||| � qHW dS )a Construct 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_clsN) r r r � shard_chooserr r �_ShardedSession__binds� connectionZconnection_callable� bind_shard)r rA r r Zshardsr@ r �k)r r r r � s zShardedSession.__init__c K s^ |d k r<t |�}|jr0|jd }|d k s,t�|S |jr<|jS | j||f|�}|d k rZ||_|S )Nr )r �key�AssertionErrorr rA )r r �instancer0 �state�tokenr r r r �_choose_shard_and_assign� s z'ShardedSession._choose_shard_and_assignc K sJ |d kr| � ||�}| jd k r.| jj||d�S | j|||d�jf |�S d S )N)r )r rH )rK Z transactionrC �get_bindZ_contextual_connect)r r rH r r r r r rC � s zShardedSession.connectionc K s" |d kr| j |||d�}| j| S )N)r$ )rK rB )r r r rH r$ r0 r r r rL � s zShardedSession.get_bindc C s || j |< d S )N)rB )r r �bindr r r rD s zShardedSession.bind_shard)NNN)NNN) r7 r8 r9 r r rK rC rL rD r: r r )r r r � s " N) r= � r r Z orm.queryr Z orm.sessionr �__all__r �objectr* r r r r r �<module> s