SQLAlchemy 映射現有表（IBM Db2 問題）

Question

我一直在研究 SQLAlchemy，以此來簡化我擁有的一些數據庫工作。 我工作的表以前是由其他系統創建的，我通常具有只讀訪問權限。

我在這里閱讀了幾個問題和一些其他來源，以了解一些有關 SQLAlchemy 的信息，但沒有成功。 我相信這個錯誤與表相關，沒有主鍵，但我嘗試了幾種方法來繞過它而沒有成功。

更難的是，錯誤日志真的很難理解任何東西。

import sqlalchemy
    
engine = sqlalchemy.create_engine('ibm_db_sa://hjxXXXX:XXXXX.databases.appdomain.cloud:30756/BLUDB;security=SSL;', echo=True)

metadata = sqlalchemy.MetaData(bind=engine)

到這里為止它的工作原理。 我什至可以運行一些測試

insp = sqlalchemy.inspect(engine)
print(insp.get_table_names())

 Output : 022-05-12 00:15:47,915 INFO sqlalchemy.engine.Engine SELECT "SYSCAT"."TABLES"."TABNAME" 
FROM "SYSCAT"."TABLES" 
WHERE "SYSCAT"."TABLES"."TYPE" = ? AND "SYSCAT"."TABLES"."TABSCHEMA" = ? ORDER BY "SYSCAT"."TABLES"."TABNAME"
2022-05-12 00:15:47,915 INFO sqlalchemy.engine.Engine [dialect ibm_db_sa+ibm_db_sa does not support caching 0.00309s] (b'T', b'HJX16012')
['chicago_schools', 'chicago_socioeconomic_data', 'departments', 'employees', 'international_student_test_scores', 'jobs', 'job_history', 'locations', 'petsale', 'teste1']

但是，當我嘗試映射一張表時，我：

Schools = sqlalchemy.Table('CHICAGO_SCHOOLS', metadata, sqlalchemy.Column('FakePK', sqlalchemy.Integer, primary_key= True) , autoload = True, autoload_with = engine) 

我開始得到一些奇怪的日志，甚至不知道如何解釋它們。 抱歉復制所有日志，但我不知道在哪里看！

2022-05-12 00:18:24,283 INFO sqlalchemy.engine.Engine SELECT "SYSCAT"."COLUMNS"."COLNAME", "SYSCAT"."COLUMNS"."TYPENAME", "SYSCAT"."COLUMNS"."DEFAULT", "SYSCAT"."COLUMNS"."NULLS", "SYSCAT"."COLUMNS"."LENGTH", "SYSCAT"."COLUMNS"."SCALE", "SYSCAT"."COLUMNS"."IDENTITY", "SYSCAT"."COLUMNS"."GENERATED" 
FROM "SYSCAT"."COLUMNS" 
WHERE "SYSCAT"."COLUMNS"."TABSCHEMA" = ? AND "SYSCAT"."COLUMNS"."TABNAME" = ? ORDER BY "SYSCAT"."COLUMNS"."COLNO"
2022-05-12 00:18:24,285 INFO sqlalchemy.engine.Engine [dialect ibm_db_sa+ibm_db_sa does not support caching 0.00265s] (b'HJX16012', b'CHICAGO_SCHOOLS')
---------------------------------------------------------------------------
NotImplementedError                       Traceback (most recent call last)
Input In [5], in <module>
----> 1 Schools = sqlalchemy.Table('CHICAGO_SCHOOLS', metadata, sqlalchemy.Column('School ID', sqlalchemy.Integer, primary_key= True) , autoload = True, autoload_with = engine)

File <string>:2, in __new__(cls, *args, **kw)

File c:\Users\fabio\AppData\Local\Programs\Python\Python310\lib\site-packages\sqlalchemy\util\deprecations.py:309, in deprecated_params.<locals>.decorate.<locals>.warned(fn, *args, **kwargs)
    302     if m in kwargs:
    303         _warn_with_version(
    304             messages[m],
    305             versions[m],
    306             version_warnings[m],
    307             stacklevel=3,
    308         )
--> 309 return fn(*args, **kwargs)

File c:\Users\fabio\AppData\Local\Programs\Python\Python310\lib\site-packages\sqlalchemy\sql\schema.py:615, in Table.__new__(cls, *args, **kw)
    613     return table
    614 except Exception:
--> 615     with util.safe_reraise():
    616         metadata._remove_table(name, schema)

File c:\Users\fabio\AppData\Local\Programs\Python\Python310\lib\site-packages\sqlalchemy\util\langhelpers.py:70, in safe_reraise.__exit__(self, type_, value, traceback)
     68     self._exc_info = None  # remove potential circular references
     69     if not self.warn_only:
---> 70         compat.raise_(
     71             exc_value,
     72             with_traceback=exc_tb,
     73         )
     74 else:
     75     if not compat.py3k and self._exc_info and self._exc_info[1]:
     76         # emulate Py3K's behavior of telling us when an exception
     77         # occurs in an exception handler.

File c:\Users\fabio\AppData\Local\Programs\Python\Python310\lib\site-packages\sqlalchemy\util\compat.py:207, in raise_(***failed resolving arguments***)
    204     exception.__cause__ = replace_context
    206 try:
--> 207     raise exception
    208 finally:
    209     # credit to
    210     # https://cosmicpercolator.com/2016/01/13/exception-leaks-in-python-2-and-3/
    211     # as the __traceback__ object creates a cycle
    212     del exception, replace_context, from_, with_traceback

File c:\Users\fabio\AppData\Local\Programs\Python\Python310\lib\site-packages\sqlalchemy\sql\schema.py:611, in Table.__new__(cls, *args, **kw)
    609 metadata._add_table(name, schema, table)
    610 try:
--> 611     table._init(name, metadata, *args, **kw)
    612     table.dispatch.after_parent_attach(table, metadata)
    613     return table

File c:\Users\fabio\AppData\Local\Programs\Python\Python310\lib\site-packages\sqlalchemy\sql\schema.py:686, in Table._init(self, name, metadata, *args, **kwargs)
    682 # load column definitions from the database if 'autoload' is defined
    683 # we do it after the table is in the singleton dictionary to support
    684 # circular foreign keys
    685 if autoload:
--> 686     self._autoload(
    687         metadata,
    688         autoload_with,
    689         include_columns,
    690         _extend_on=_extend_on,
    691         resolve_fks=resolve_fks,
    692     )
    694 # initialize all the column, etc. objects.  done after reflection to
    695 # allow user-overrides
    697 self._init_items(
    698     *args,
    699     allow_replacements=extend_existing or keep_existing or autoload
    700 )

File c:\Users\fabio\AppData\Local\Programs\Python\Python310\lib\site-packages\sqlalchemy\sql\schema.py:721, in Table._autoload(self, metadata, autoload_with, include_columns, exclude_columns, resolve_fks, _extend_on)
    719 insp = inspection.inspect(autoload_with)
    720 with insp._inspection_context() as conn_insp:
--> 721     conn_insp.reflect_table(
    722         self,
    723         include_columns,
    724         exclude_columns,
    725         resolve_fks,
    726         _extend_on=_extend_on,
    727     )

File c:\Users\fabio\AppData\Local\Programs\Python\Python310\lib\site-packages\sqlalchemy\engine\reflection.py:791, in Inspector.reflect_table(self, table, include_columns, exclude_columns, resolve_fks, _extend_on)
    788 if not found_table and not self.has_table(table_name, schema):
    789     raise exc.NoSuchTableError(table_name)
--> 791 self._reflect_pk(
    792     table_name, schema, table, cols_by_orig_name, exclude_columns
    793 )
    795 self._reflect_fk(
    796     table_name,
    797     schema,
   (...)
    803     reflection_options,
    804 )
    806 self._reflect_indexes(
    807     table_name,
    808     schema,
   (...)
    813     reflection_options,
    814 )

File c:\Users\fabio\AppData\Local\Programs\Python\Python310\lib\site-packages\sqlalchemy\engine\reflection.py:920, in Inspector._reflect_pk(self, table_name, schema, table, cols_by_orig_name, exclude_columns)
    917 def _reflect_pk(
    918     self, table_name, schema, table, cols_by_orig_name, exclude_columns
    919 ):
--> 920     pk_cons = self.get_pk_constraint(
    921         table_name, schema, **table.dialect_kwargs
    922     )
    923     if pk_cons:
    924         pk_cols = [
    925             cols_by_orig_name[pk]
    926             for pk in pk_cons["constrained_columns"]
    927             if pk in cols_by_orig_name and pk not in exclude_columns
    928         ]

File c:\Users\fabio\AppData\Local\Programs\Python\Python310\lib\site-packages\sqlalchemy\engine\reflection.py:528, in Inspector.get_pk_constraint(self, table_name, schema, **kw)
    508 """Return information about primary key constraint on `table_name`.
    509 
    510 Given a string `table_name`, and an optional string `schema`, return
   (...)
    525 
    526 """
    527 with self._operation_context() as conn:
--> 528     return self.dialect.get_pk_constraint(
    529         conn, table_name, schema, info_cache=self.info_cache, **kw
    530     )

File c:\Users\fabio\AppData\Local\Programs\Python\Python310\lib\site-packages\sqlalchemy\engine\interfaces.py:285, in Dialect.get_pk_constraint(self, connection, table_name, schema, **kw)
    270 def get_pk_constraint(self, connection, table_name, schema=None, **kw):
    271     """Return information about the primary key constraint on
    272     table_name`.
    273 
   (...)
    283 
    284     """
--> 285     raise NotImplementedError()

NotImplementedError: 

Answer 1

正如 snakecharmerb 評論的那樣，這是 IBM_DB_SA 適配器中的一個錯誤：

https://github.com/ibmdb/python-ibmdbsa/issues/104