如何獲得匹配的3元組的條件與SQLAlchemy的

Question

列表爲3元組列表，其中行：

[(a, b, c), (d, e, f)] 

我想檢索所有從一個表，其中3列中的元組相匹配的行。在這個例子中，查詢WHERE條款可以是這樣的：

(column_X = a AND column_Y = b AND column_Z = c) 
OR (column_X = d AND column_Y = e AND column_Z = f) 

如何創建使用的SQLAlchemy這樣的要求？在我的情況下，三元組列表將包含數百個元素，並且我正在尋找最好的可縮放解決方案。

感謝您的幫助，

Answer 1

最簡單的方法將使用的SQLAlchemy提供的tuple_功能：

from sqlalchemy import tuple_ 

session.query(Foo).filter(tuple_(Foo.a, Foo.b, Foo.c).in_(items)) 

這適用於PostgreSQL的，但休息的SQLite。不確定其他數據庫引擎。

幸運的是，有一種解決方法應該適用於所有數據庫。

開始通過與and_表情映射出的所有物品：

conditions = (and_(c1=x, c2=y, c3=z) for (x, y, z) in items) 

然後再創建一個or_過濾器包圍的所有條件：

q.filter(or_(*conditions)) 

這裏有一個簡單的例子：

#/usr/bin/env python 
from sqlalchemy import create_engine 
from sqlalchemy import Column, Integer 
from sqlalchemy.sql import and_, or_ 
from sqlalchemy.orm import sessionmaker 
from sqlalchemy.ext.declarative import declarative_base 

engine = create_engine('sqlite:///') 
session = sessionmaker(bind=engine)() 
Base = declarative_base() 

class Foo(Base): 
    __tablename__ = 'foo' 

    id = Column(Integer, primary_key=True) 
    a = Column(Integer) 
    b = Column(Integer) 
    c = Column(Integer) 

    def __init__(self, a, b, c): 
     self.a = a 
     self.b = b 
     self.c = c 

    def __repr__(self): 
     return '(%d %d %d)' % (self.a, self.b, self.c) 

Base.metadata.create_all(engine) 

session.add_all([Foo(1, 2, 3), Foo(3, 2, 1), Foo(3, 3, 3), Foo(1, 3, 4)]) 
session.commit() 
items = ((1, 2, 3), (3, 3, 3)) 
conditions = (and_(Foo.a==x, Foo.b==y, Foo.c==z) for (x, y, z) in items) 
q = session.query(Foo) 
print q.all() 
q = q.filter(or_(*conditions)) 
print q 
print q.all() 

輸出：

，我懷疑會很好地擴展

$ python test.py 
[(1 2 3), (3 2 1), (3 3 3), (1 3 4)] 
SELECT foo.id AS foo_id, foo.a AS foo_a, foo.b AS foo_b, foo.c AS foo_c 
FROM foo 
WHERE foo.a = :a_1 AND foo.b = :b_1 AND foo.c = :c_1 OR foo.a = :a_2 AND foo.b = :b_2 AND foo.c = :c_2 
[(1 2 3), (3 3 3)] 

Answer 2

一個不太常規的方法是創建所有元組的臨時表，然後對加盟：

import sqlalchemy 
from sqlalchemy.ext.declarative import declarative_base 
from sqlalchemy import Column, Integer, Table 
from sqlalchemy.orm import sessionmaker 
Base = declarative_base() 
engine = sqlalchemy.create_engine('sqlite:///:memory:') 
Session = sessionmaker(bind=engine) 
session = Session() 

class Triple(Base): 
    __tablename__ = 'triple' 
    id = Column(Integer(), primary_key=True) 
    x = Column(Integer()) 
    y = Column(Integer()) 
    z = Column(Integer()) 

ws_table = Table('where_sets', Base.metadata, 
     Column('x', Integer()), 
     Column('y', Integer()), 
     Column('z', Integer()), 
     prefixes = ['temporary'] 
    ) 

Base.metadata.create_all(engine) 

... 

where_sets = [(1, 2, 3), (3, 2, 1), (1, 1, 1)] 
ws_table.create(engine, checkfirst=True) 
session.execute(ws_table.insert(), [dict(zip('xyz', s)) for s in where_sets]) 
matches = session.query(Triple).join(ws_table, (Triple.x==ws_table.c.x) & (Triple.y==ws_table.c.y) & (Triple.z==ws_table.c.z)).all() 

其執行這樣的SQL：

INSERT INTO triple (x, y, z) VALUES (?, ?, ?) 
(1, 2, 3) 
INSERT INTO triple (x, y, z) VALUES (?, ?, ?) 
(3, 1, 2) 
INSERT INTO triple (x, y, z) VALUES (?, ?, ?) 
(1, 1, 1) 
SELECT triple.id AS triple_id, triple.x AS triple_x, triple.y AS triple_y, triple.z AS triple_z 
FROM triple JOIN where_sets ON triple.x = where_sets.x AND triple.y = where_sets.y AND triple.z = where_sets.z