我正在尝试反映一个基于 sqlite 的数据库（更具体地说是 plex 媒体服务器数据库）。
我可以连接到数据库：
import sqlalchemy as sa
from sqlalchemy.orm import create_session
from sqlalchemy.ext.automap import automap_base
from sqlalchemy.engine.reflection import Inspector
conn = 'sqlite:////..../com.plexapp.plugins.library.db-2016-07-17'
eng = sa.create_engine(conn)
plex = eng.connect()
我可以查询数据库：
s = create_session(plex)
r = s.execute('SELECT COUNT(*) FROM METADATA_ITEMS')
r.fetchall()
>>> [(55368,)]
我什至可以使用 SQLAlchemy 的 Inspector 检查所有表
i = Inspector.from_engine(plex)
i.get_sorted_table_and_fkc_names()
>>>> [('metadata_item_views', set()),
('cloudsync_files', set()),
('library_timeline_entries', set()),
('synced_ancestor_items', set()),
('schema_migrations', set()),
('fts4_tag_titles_stat', set()),
('spellfix_tag_titles', set()),
('metadata_items', set()),
('media_streams', set()),
('metadata_relations', set()),
('play_queue_generators', set()),
...
但是，我似乎无法反映整个数据库。我遇到了这个丑陋的大异常：
m = sa.MetaData(bind=plex)
m.reflect()
>>>>
---------------------------------------------------------------------------
OperationalError Traceback (most recent call last)
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/engine/base.py in _execute_context(self, dialect, constructor, statement, parameters, *args)
1138 parameters,
-> 1139 context)
1140 except Exception as e:
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/engine/default.py in do_execute(self, cursor, statement, parameters, context)
449 def do_execute(self, cursor, statement, parameters, context=None):
--> 450 cursor.execute(statement, parameters)
451
OperationalError: no such module: spellfix1
The above exception was the direct cause of the following exception:
OperationalError Traceback (most recent call last)
<ipython-input-58-8cb90bbdb0ad> in <module>()
1 m = sa.MetaData(bind=plex)
2
----> 3 m.reflect()
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/sql/schema.py in reflect(self, bind, schema, views, only, extend_existing, autoload_replace, **dialect_kwargs)
3653
3654 for name in load:
-> 3655 Table(name, self, **reflect_opts)
3656
3657 def append_ddl_listener(self, event_name, listener):
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/sql/schema.py in __new__(cls, *args, **kw)
414 except:
415 with util.safe_reraise():
--> 416 metadata._remove_table(name, schema)
417
418 @property
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/util/langhelpers.py in __exit__(self, type_, value, traceback)
58 exc_type, exc_value, exc_tb = self._exc_info
59 self._exc_info = None # remove potential circular references
---> 60 compat.reraise(exc_type, exc_value, exc_tb)
61 else:
62 if not compat.py3k and self._exc_info and self._exc_info[1]:
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/util/compat.py in reraise(tp, value, tb, cause)
184 if value.__traceback__ is not tb:
185 raise value.with_traceback(tb)
--> 186 raise value
187
188 else:
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/sql/schema.py in __new__(cls, *args, **kw)
409 metadata._add_table(name, schema, table)
410 try:
--> 411 table._init(name, metadata, *args, **kw)
412 table.dispatch.after_parent_attach(table, metadata)
413 return table
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/sql/schema.py in _init(self, name, metadata, *args, **kwargs)
482 # circular foreign keys
483 if autoload:
--> 484 self._autoload(metadata, autoload_with, include_columns)
485
486 # initialize all the column, etc. objects. done after reflection to
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/sql/schema.py in _autoload(self, metadata, autoload_with, include_columns, exclude_columns)
494 autoload_with.run_callable(
495 autoload_with.dialect.reflecttable,
--> 496 self, include_columns, exclude_columns
497 )
498 else:
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/engine/base.py in run_callable(self, callable_, *args, **kwargs)
1475
1476 """
-> 1477 return callable_(self, *args, **kwargs)
1478
1479 def _run_visitor(self, visitorcallable, element, **kwargs):
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/engine/default.py in reflecttable(self, connection, table, include_columns, exclude_columns)
362 self, connection, table, include_columns, exclude_columns):
363 insp = reflection.Inspector.from_engine(connection)
--> 364 return insp.reflecttable(table, include_columns, exclude_columns)
365
366 def get_pk_constraint(self, conn, table_name, schema=None, **kw):
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/engine/reflection.py in reflecttable(self, table, include_columns, exclude_columns)
561
562 for col_d in self.get_columns(
--> 563 table_name, schema, **table.dialect_kwargs):
564 found_table = True
565
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/engine/reflection.py in get_columns(self, table_name, schema, **kw)
367 col_defs = self.dialect.get_columns(self.bind, table_name, schema,
368 info_cache=self.info_cache,
--> 369 **kw)
370 for col_def in col_defs:
371 # make this easy and only return instances for coltype
<string> in get_columns(self, connection, table_name, schema, **kw)
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/engine/reflection.py in cache(fn, self, con, *args, **kw)
52 ret = info_cache.get(key)
53 if ret is None:
---> 54 ret = fn(self, con, *args, **kw)
55 info_cache[key] = ret
56 return ret
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/dialects/sqlite/base.py in get_columns(self, connection, table_name, schema, **kw)
1181 def get_columns(self, connection, table_name, schema=None, **kw):
1182 info = self._get_table_pragma(
-> 1183 connection, "table_info", table_name, schema=schema)
1184
1185 columns = []
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/dialects/sqlite/base.py in _get_table_pragma(self, connection, pragma, table_name, schema)
1478 qtable = quote(table_name)
1479 statement = "%s%s(%s)" % (statement, pragma, qtable)
-> 1480 cursor = connection.execute(statement)
1481 if not cursor._soft_closed:
1482 # work around SQLite issue whereby cursor.description
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/engine/base.py in execute(self, object, *multiparams, **params)
904 """
905 if isinstance(object, util.string_types[0]):
--> 906 return self._execute_text(object, multiparams, params)
907 try:
908 meth = object._execute_on_connection
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/engine/base.py in _execute_text(self, statement, multiparams, params)
1052 statement,
1053 parameters,
-> 1054 statement, parameters
1055 )
1056 if self._has_events or self.engine._has_events:
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/engine/base.py in _execute_context(self, dialect, constructor, statement, parameters, *args)
1144 parameters,
1145 cursor,
-> 1146 context)
1147
1148 if self._has_events or self.engine._has_events:
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/engine/base.py in _handle_dbapi_exception(self, e, statement, parameters, cursor, context)
1339 util.raise_from_cause(
1340 sqlalchemy_exception,
-> 1341 exc_info
1342 )
1343 else:
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/util/compat.py in raise_from_cause(exception, exc_info)
200 exc_type, exc_value, exc_tb = exc_info
201 cause = exc_value if exc_value is not exception else None
--> 202 reraise(type(exception), exception, tb=exc_tb, cause=cause)
203
204 if py3k:
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/util/compat.py in reraise(tp, value, tb, cause)
183 value.__cause__ = cause
184 if value.__traceback__ is not tb:
--> 185 raise value.with_traceback(tb)
186 raise value
187
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/engine/base.py in _execute_context(self, dialect, constructor, statement, parameters, *args)
1137 statement,
1138 parameters,
-> 1139 context)
1140 except Exception as e:
1141 self._handle_dbapi_exception(
/opt/anaconda3/lib/python3.5/site-packages/sqlalchemy/engine/default.py in do_execute(self, cursor, statement, parameters, context)
448
449 def do_execute(self, cursor, statement, parameters, context=None):
--> 450 cursor.execute(statement, parameters)
451
452 def do_execute_no_params(self, cursor, statement, context=None):
OperationalError: (sqlite3.OperationalError) no such module: spellfix1 [SQL: 'PRAGMA table_info("spellfix_metadata_titles")']
我知道spellfix1是sqlite的一个功能。但我找不到任何 python 支持/插件来正确反映它，或者我不完全理解引发的异常。
谢谢！
SQLite是一个嵌入式数据库，并且可以定制。 Plex媒体服务器添加了spellfix1扩展； 文档说：
spellfix1 虚拟表不包含在 SQLite 合并中，也不属于任何标准 SQLite 构建的一部分。这是一个可加载扩展。
为了能够访问此表，您必须自己编译此扩展，并将其加载到 Python 数据库连接中。
如果您实际上不需要进行拼写检查，您可以创建没有该虚拟表的数据库副本：
使用
sqlite3sqlite3 some/where/...library.db ".dump" > library.sql
（无需安装模块即可工作）；
从SQL脚本中删除虚拟表的创建；这是一条看起来像这样的线：
INSERT INTO sqlite_master(type,name,tbl_name,rootpage,sql)VALUES('table','xxx','xxx',0,'CREATE VIRTUAL TABLE xxx using spellfix1(...)');
从该脚本创建一个新数据库：
sqlite3 new.db < library.sql
我找到了一个很好的解决方法。
SQLAlchemy 允许元数据反射为“only”标志提供可调用函数。 这将忽略需要该插件的不受支持的表。 （感谢@CL。提示忽略这些！）
m = sa.MetaData(plex)
m.reflect(only=(lambda x, y: 'spellfix' not in x))
Base = automap_base(metadata=m)
Base.prepare(plex)
就像魅力一样！
“在为我的 Plex 媒体服务器设置反映 SQLite 数据库时，我遇到了类似的挑战。spellfix1 表添加了一个有趣的转折！如果您想优化媒体体验，请访问我的网站，了解有关选择 最佳流媒体服务的提示.这对我来说改变了游戏规则。