如何对 sqlalchemy association_proxy 属性进行不区分大小写的查询？

Question

我有两个课程，一个曲目和一个专辑。 为了从曲目轻松访问专辑字段，我创建了一个关联代理。

class Track(MusicItem, Base):
    __tablename__ = "tracks"

    _id = Column(Integer, primary_key=True)
    _album_id = Column(Integer, ForeignKey("albums._id"))
    artist = Column(String, nullable=False, default="")
    path = Column(_PathType, nullable=False, unique=True)
    title = Column(String, nullable=False, default="")

    _album_obj = relationship("Album", back_populates="tracks")

    album = association_proxy('_album_obj', 'title')

class Album(MusicItem, Base):
    __tablename__ = "albums"

    _id = Column(Integer, primary_key=True)
    artist = Column(String, nullable=False, default="")
    title = Column(String, nullable=False, default="")

    tracks = relationship("Track", back_populates="_album_obj", cascade="all, delete")

但是，我在尝试对曲目或专辑进行不区分大小写的查询时遇到问题。

创建查询过滤器时，以下内容适用于轨道的正常（非关联代理）属性。

attr = getattr(Track, field)
attr = sqlalchemy.func.lower(attr)

但是，当attr是关联代理属性时，会出现以下错误：

moe/core/query.py:187: in query
    items = session.query(query_cls).filter(*query_filters).all()
.venv/lib/python3.8/site-packages/sqlalchemy/orm/query.py:3346: in all
    return list(self)
.venv/lib/python3.8/site-packages/sqlalchemy/orm/query.py:3508: in __iter__
    return self._execute_and_instances(context)
.venv/lib/python3.8/site-packages/sqlalchemy/orm/query.py:3533: in _execute_and_instances
    result = conn.execute(querycontext.statement, self._params)
.venv/lib/python3.8/site-packages/sqlalchemy/engine/base.py:1011: in execute
    return meth(self, multiparams, params)
.venv/lib/python3.8/site-packages/sqlalchemy/sql/elements.py:298: in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)
.venv/lib/python3.8/site-packages/sqlalchemy/engine/base.py:1124: in _execute_clauseelement
    ret = self._execute_context(
.venv/lib/python3.8/site-packages/sqlalchemy/engine/base.py:1316: in _execute_context
    self._handle_dbapi_exception(
.venv/lib/python3.8/site-packages/sqlalchemy/engine/base.py:1510: in _handle_dbapi_exception
    util.raise_(
.venv/lib/python3.8/site-packages/sqlalchemy/util/compat.py:182: in raise_
    raise exception
.venv/lib/python3.8/site-packages/sqlalchemy/engine/base.py:1276: in _execute_context
    self.dialect.do_execute(
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <sqlalchemy.dialects.sqlite.pysqlite.SQLiteDialect_pysqlite object at 0x7f54a0692430>
cursor = <sqlite3.Cursor object at 0x7f54a0638b90>
statement = 'SELECT tracks._id AS tracks__id, tracks._album_id AS tracks__album_id, tracks.artist AS tracks_artist, tracks.path AS tracks_path, tracks.title AS tracks_title \nFROM tracks \nWHERE lower(?) = ?'
parameters = (ColumnAssociationProxyInstance(AssociationProxy('_album_obj', 'title')), 'tmp')
context = <sqlalchemy.dialects.sqlite.base.SQLiteExecutionContext object at 0x7f54a05b7fa0>

    def do_execute(self, cursor, statement, parameters, context=None):
>       cursor.execute(statement, parameters)
E       sqlalchemy.exc.InterfaceError: (sqlite3.InterfaceError) Error binding parameter 0 - probably unsupported type.
E       [SQL: SELECT tracks._id AS tracks__id, tracks._album_id AS tracks__album_id, tracks.artist AS tracks_artist, tracks.path AS tracks_path, tracks.title AS tracks_title 
E       FROM tracks 
E       WHERE lower(?) = ?]
E       [parameters: (ColumnAssociationProxyInstance(AssociationProxy('_album_obj', 'title')), 'tmp')]
E       (Background on this error at: http://sqlalche.me/e/13/rvf5)

.venv/lib/python3.8/site-packages/sqlalchemy/engine/default.py:593: InterfaceError

不确定是否有帮助，但这里有一些关于查询的更简化的代码。 如果需要，我可以对此进行扩展。

query_filters = [attr == query_value]
items = session.query(Track).filter(*query_filters).all()

我也在创建自定义比较器的文档中看到了这个相关的部分，但我不知道如何将它应用到我的代码中。 我将它与 Track/Album 类一起添加，但它没有任何帮助，并且发生了相同的错误。

Answer 1

从 1.3.19 版开始，sqlalchemy 不允许将 SQL 函数应用于关联代理属性。 这是一个跟踪该问题的问题。

对于不区分大小写查找的具体情况，可以使用ilike()

session.query(Track).filter(somecolumn.ilike("value"))

ilike()适用于关联代理属性和普通属性。