不能在 sqlite3 blob 字段上使用 pony orm

Question

只是尝试使用 pony ORM（和 python3.5，sqlite3）进行一些基本练习。我只想打印 select 查询我拥有的一些数据，而无需进一步处理。 Pony orm 好像一点都不喜欢....

sqlite 数据库转储

PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
CREATE TABLE sums (t text, path BLOB, name BLOB, sum text, primary key (path,name));
INSERT INTO "sums" VALUES('directory','','','');
INSERT INTO "sums" VALUES('file','','sums-backup-f.db','6859b35f9f026317c5df48932f9f2a91');
INSERT INTO "sums" VALUES('file','','md5-tree.py','c7af81d4aad9d00e88db7af950c264c2');
INSERT INTO "sums" VALUES('file','','test.db','a403e9b46e54d6ece851881a895b1953');
INSERT INTO "sums" VALUES('file','','sirius-alexa.db','22a20434cec550a83c675acd849002fa');
INSERT INTO "sums" VALUES('file','','sums-reseau-y.db','1021614f692b5d7bdeef2a45b6b1af5b');
INSERT INTO "sums" VALUES('file','','.md5-tree.py.swp','1c3c195b679e99ef18b3d46044f6e6c5');
INSERT INTO "sums" VALUES('file','','compare-md5.py','cfb4a5b3c7c4e62346aa5e1affef210a');
INSERT INTO "sums" VALUES('file','','charles.local.db','9c50689e8185e5a79fd9077c14636405');
COMMIT;

这是我在 python3.5 上尝试运行的代码 shell:

from pony.orm import *
db = Database()
class File(db.Entity) :
    _table_ = 'sums'
    t = Required(str)
    path = Required(bytes)
    name = Required(bytes)
    sum = Required(str)
    PrimaryKey(path,name)
db.bind('sqlite','/some/edited/path/test.db')
db.generate_mapping()

File.select().show()

它像这样失败了:

Traceback (most recent call last):
  File "/usr/lib/python3.5/site-packages/pony/orm/core.py", line 5149, in _fetch
    try: result = cache.query_results[query_key]
KeyError: (('f', 0, ()), (<pony.orm.ormtypes.SetType object at 0x7fd2d2701708>,), False, None, None, None, False, False, False, ())

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 2, in show
  File "/usr/lib/python3.5/site-packages/pony/utils/utils.py", line 75, in cut_traceback
    raise exc  # Set "pony.options.CUT_TRACEBACK = False" to see full traceback
  File "/usr/lib/python3.5/site-packages/pony/utils/utils.py", line 60, in cut_traceback
    try: return func(*args, **kwargs)
  File "/usr/lib/python3.5/site-packages/pony/orm/core.py", line 5256, in show
    query._fetch().show(width)
  File "/usr/lib/python3.5/site-packages/pony/orm/core.py", line 5155, in _fetch
    used_attrs=translator.get_used_attrs())
  File "/usr/lib/python3.5/site-packages/pony/orm/core.py", line 3859, in _fetch_objects
    real_entity_subclass, pkval, avdict = entity._parse_row_(row, attr_offsets)
  File "/usr/lib/python3.5/site-packages/pony/orm/core.py", line 3889, in _parse_row_
    avdict[attr] = attr.parse_value(row, offsets)
  File "/usr/lib/python3.5/site-packages/pony/orm/core.py", line 1922, in parse_value
    val = attr.validate(row[offset], None, attr.entity, from_db=True)
  File "/usr/lib/python3.5/site-packages/pony/orm/core.py", line 2218, in validate
    val = Attribute.validate(attr, val, obj, entity, from_db)
  File "/usr/lib/python3.5/site-packages/pony/orm/core.py", line 1894, in validate
    if from_db: return converter.sql2py(val)
  File "/usr/lib/python3.5/site-packages/pony/orm/dbapiprovider.py", line 619, in sql2py
    if not isinstance(val, buffer): val = buffer(val)
TypeError: string argument without an encoding

我是不是用错了，或者这是一个错误？我不介意提交错误，但这是我第一次使用这个 orm，所以我认为先检查一下可能会更好...

Answer 1

SQLite 有一个（错误的）特性，它允许列存储任意值而不管列类型。每个 SQLite 列都具有亲和力，而不是严格的数据类型，而每个值都有一个存储 class，在同一列中可以不同。例如，您可以将文本值存储在整数列中，反之亦然。有关详细信息，请参阅 Datatypes In SQLite Version 3。

错误的原因是 table 在其 BLOB 列中包含 "wrong" 类型的值。更正 SQLite 二进制文字 looks，如 x'abcdef'。您使用的 INSERT 命令改为插入 UTF8 字符串。

这个问题在 latest version of Pony 中得到了一定程度的修复，您可以从 GitHub 中获取。现在，如果 Pony 从 BLOB 列接收到一个字符串值，它只会保留该值而不会抛出异常。

如果您使用 Pony 填充 table，它会将 BLOB 数据写入正确的二进制值，因此稍后可以毫无问题地读取它们。

不能在 sqlite3 blob 字段上使用 pony orm

can't use pony orm on sqlite3 blob fields

python

sqlite

ponyorm