[英]python inserting and retrieving binary data into mysql
I'm using the MySQLdb package for interacting with MySQL.我正在使用 MySQLdb 包与 MySQL 交互。 I'm having trouble getting the proper type conversions.
我无法获得正确的类型转换。
I am using a 16-byte binary uuid as a primary key for the table and have a mediumblob holding zlib compressed json information.我使用 16 字节的二进制 uuid 作为表的主键,并有一个 mediumblob 保存 zlib 压缩的 json 信息。
I'm using the following schema:我正在使用以下架构:
CREATE TABLE repositories (
added_id int auto_increment not null,
id binary(16) not null,
data mediumblob not null,
create_date int not null,
update_date int not null,
PRIMARY KEY (added_id),
UNIQUE(id)
) DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci ENGINE=InnoDB;
Then I create a new row in the table using the following code:然后我使用以下代码在表中创建一个新行:
data = zlib.compress(json.dumps({'hello':'how are you :D'})
row_id = uuid.uuid(4).hex
added_id = cursor.execute('
INSERT INTO repositories (id, data, create_date, update_date)
VALUES (%s, %s, %s, %s)',
binascii.a2b_hex(row_id),
data,
time.time(),
time.time()
)
Then to retrieve data I use a similar query:然后为了检索数据,我使用了一个类似的查询:
query = cursor.execute('SELECT added_id, id, data, create_date, update_date ' \
'FROM repositories WHERE id = %s',
binascii.a2b_hex(row_id)
)
Then the query returns an empty result.然后查询返回一个空结果。
Any help would be appreciated.任何帮助,将不胜感激。 Also, as an aside, is it better to store unix epoch dates as integers or TIMESTAMP?
另外,顺便说一句,将unix纪元日期存储为整数还是TIMESTAMP更好?
NOTE: I am not having problems inserting the data, just trying to retrieve it from the database.注意:我在插入数据时没有问题,只是试图从数据库中检索它。 The row exists when I check via mysqlclient.
当我通过 mysqlclient 检查时,该行存在。
Thanks Alot!@多谢!@
One tip: you should be able to call uuid.uuid4().bytes
to get the raw bytes.一个提示:您应该能够调用
uuid.uuid4().bytes
来获取原始字节。 As for timestamps, if you want to perform time/date manipulation in SQL it's often easier to deal with real TIMESTAMP types.至于时间戳,如果您想在 SQL 中执行时间/日期操作,处理真正的 TIMESTAMP 类型通常更容易。
I created a test table to try to reproduce what you're seeing:我创建了一个测试表来尝试重现您所看到的内容:
CREATE TABLE xyz (
added_id INT AUTO_INCREMENT NOT NULL,
id BINARY(16) NOT NULL,
PRIMARY KEY (added_id),
UNIQUE (id)
) DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci ENGINE=InnoDB;
My script is able to insert and query for the rows using the binary field as a key without problem.我的脚本能够使用二进制字段作为键插入和查询行,没有问题。 Perhaps you are incorrectly fetching / iterating over the results returned by the cursor?
也许您错误地获取/迭代游标返回的结果?
import binascii
import MySQLdb
import uuid
conn = MySQLdb.connect(host='localhost')
key = uuid.uuid4()
print 'inserting', repr(key.bytes)
r = conn.cursor()
r.execute('INSERT INTO xyz (id) VALUES (%s)', key.bytes)
conn.commit()
print 'selecting', repr(key.bytes)
r.execute('SELECT added_id, id FROM xyz WHERE id = %s', key.bytes)
for row in r.fetchall():
print row[0], binascii.b2a_hex(row[1])
Output:输出:
% python qu.py
inserting '\x96\xc5\xa4\xc3Z+L\xf0\x86\x1e\x05\xebt\xf7\\\xd5'
selecting '\x96\xc5\xa4\xc3Z+L\xf0\x86\x1e\x05\xebt\xf7\\\xd5'
1 96c5a4c35a2b4cf0861e05eb74f75cd5
% python qu.py
inserting '\xac\xc9,jn\xb2O@\xbb\xa27h\xcd<B\xda'
selecting '\xac\xc9,jn\xb2O@\xbb\xa27h\xcd<B\xda'
2 acc92c6a6eb24f40bba23768cd3c42da
To supplement existing answers, there's also an issue with the following warning when dealing with binary strings in queries:为了补充现有答案,在处理查询中的二进制字符串时还存在以下警告问题:
Warning: (1300, "Invalid utf8 character string: 'ABCDEF'")
It is reproduced by the following:它是通过以下方式复制的:
cursor.execute('''
CREATE TABLE `table`(
bin_field` BINARY(16) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
''')
bin_value = uuid.uuid4().bytes
cursor.execute('INSERT INTO `table`(bin_field) VALUES(%s)', (bin_value,))
Whenever MySQL sees that a string literal in a query isn't valid against current character_set_connection
it will emit the warning.每当 MySQL 发现查询中的字符串文字对当前
character_set_connection
无效时,它会发出警告。 There are several solutions to it:有几种解决方案:
Explicitly set _binary
charset literal显式设置
_binary
字符集文字
INSERT INTO `table`(bin_field) VALUES(_binary %s)
Manually construct queries with hexadecimal literals使用十六进制文字手动构造查询
INSERT INTO `table`(bin_field) VALUES(x'abcdef')
Changeconnection charset if you're only working with binary strings如果您只使用二进制字符串,请更改连接字符集
For more details see MySQL Bug 79317 .有关更多详细信息,请参阅MySQL 错误 79317 。
As @charlax pointed out, there's binary_prefix
flag which can be passed to the connection's initialiser to automatically prepend _binary
prefix when interpolating arguments.正如@charlax 指出的那样,可以将
binary_prefix
标志传递给连接的初始化程序,以在插入参数时自动添加_binary
前缀。 It's supported by recent versions of both, mysql-client and pymysql . mysql-client和pymysql的最新版本都支持它。
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