使用 FreeTDS 查询 MS SqlServer 时，Python 在 255 个字符处截断

问题描述

我想我错过了在 Debian 机器上通过 FreeTDS 使用 pyodbc 进行的 Python 查询中的某些内容.我不能超过前 255 个字符.

i think i have miss something in a query from python using pyodbc over a FreeTDS on a Debian machine. I can not manage to have more than the first 255 characters.

如果我尝试 CAST SQL 数据，如下所述:MS SQL Server 上的 ODBC 查询仅在 PHP PDO (FreeTDS) 中返回前 255 个字符 使用:SELECT CAST(myText as TEXT) FROM mytable我得到空/零长度字符串，

if i try to CAST SQL data as describe here: ODBC query on MS SQL Server returning first 255 characters only in PHP PDO (FreeTDS) with :SELECT CAST(myText as TEXT) FROM mytablei get empty/zero length string,

我也进行了测试，但没有成功:按照下面的配置描述更改大小，我只能得到前 255 个字符(例如，在我的 Win 框中 pyodbc 可以得到 279 个字符).

i have also test with no more success to : change size as describe with the config below, i only get first 255 characters (while on my Win box pyodbc can get 279 characters, for example).

这是一个示例查询:

SET TEXTSIZE 2147483647;
SELECT [id], myText , LEN(myText)
FROM    mytable

这是我的/etc/freetds/freetds/conf:(;@行首是什么意思?)

here is my /etc/freetds/freetds/conf:(what is the meaning of the ; @ beginning of line ?)

[global]
    # TDS protocol version
;   tds version = 4.2


#!!!added by me
client charset = UTF-8
text size = 4294967295
#!!!/added by me

    # Whether to write a TDSDUMP file for diagnostic purposes
    # (setting this to /tmp is insecure on a multi-user system)
;   dump file = /tmp/freetds.log
;   debug flags = 0xffff

    # Command and connection timeouts
;   timeout = 10
;   connect timeout = 10

    # If you get out-of-memory errors, it may mean that your client
    # is trying to allocate a huge buffer for a TEXT field.
    # Try setting 'text size' to a more reasonable limit
    #!!!changed by me
    #text size = 64512

其他配置文件是:

> cat /etc/odbc.ini #/etc/odbc.ini is empty! is it ok?
> cat /etc/odbcinst.ini
[FreeTDS]
Description=TDS driver (Sybase/MS SQL)
Driver=/usr/lib/odbc/libtdsodbc.so
Setup=/usr/lib/odbc/libtdsS.so
CPTimeout=
CPReuse=

我的 SQL 服务器在 192.168.1.2 上，我使用以下方式连接:

my SQL server is on 192.168.1.2, and i connect by using :

cnstr = 'DRIVER={FreeTDS};SERVER=192.168.1.2;DATABASE=MyDBName;UID=MyUID;PWD=MYPASSWD'
cursor = cnxn.cursor()
cursor.execute(SQL)
# etc.

感谢您的帮助，

最好的问候

推荐答案

它开始评论.ma​​n freetds.conf 是您的朋友.:-)

It starts a comment. man freetds.conf is your friend. :-)

我不能超过前 255 个字符.

我怀疑您使用的是协议版本 4.2，因为您使用的是无 DSN 连接并且没有提到设置默认值.还因为 TDS 4.2 将 VARCHAR 列限制为 255 个字符.

I suspect you are using protocol version 4.2, because you're using a DSN-less connection and did not mention setting the default. Also because TDS 4.2 limits VARCHAR columns to 255 characters.

您可以将协议版本添加到您的连接字符串中，参见.http://www.freetds.org/userguide/odbcconnattr.htm.

You can add the protocol version to your connection string, cf. http://www.freetds.org/userguide/odbcconnattr.htm.

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