Special character issue connecting Mod lua to Sybase DB using Freetds

Dagobert Michelsen dam at opencsw.org
Fri Oct 21 10:17:54 CEST 2016

Hi Krishna,

Am 21.10.2016 um 09:29 schrieb Upadhay, Krishna - Kolkata <kupadhay at wiley.com>:
> We are trying to fetch data from sybase DB through mod lua (in apache 2.4.23) using the freetds(downloaded from
> https://www.opencsw.org/package/freetds/ <https://www.opencsw.org/package/freetds/>).
> OS details is: Oracle Solaris 10 8/11 s10s_u10wos_17b SPARC
> The lua module receives a key from the http request and looks up for the corresponding value from a sybase database table.
> The problem is in this database lookup. It's only a plain select query fetching a single value of type varchar.
> However, some random characters get appended to the retrieved value at the end when we recieve it in the lua module.
> We tried to gather a pattern of data for which we encountered the issue. If the character count of the string value that is fetched from DB is exactly 2^n, the data fetched is absolutely fine. Anything greater or less than that is appended with random characters at the end. Following are few examples:
> -- 9 character varchar value in DB -> 0021/2015
> -- Data received in lua code -> 0021/2015h
> -- 17 character varchar value in DB -> 0021/2015/06/18/7
> -- Data received in lua code -> 0021/2015/06/18/7\x07\xc1\xd4
> -- 33 character varchar value in DB -> 0021/2015/06/18/732/10.1002-2Fabc
> -- Data received in lua code -> 0021/2015/06/18/732/10.1002-2Fabc\x02h
> -- 65 character varchar value in DB -> 0021/2015/06/18/732/10.1002-2Fab0021/2015/06/18/732/10.1002-2Fabc
> -- Data received in lua code -> 0021/2015/06/18/732/10.1002-2Fab0021/2015/06/18/732/10.1002-2FabcY\x140
> Please note the following:
> 1. The issue do not happen in a RHEL system
> 2. The same functionality works fine if we lookup a similar table in MySQL.
> Any comments regarding the cause of this issue would be really helpful.

This doesn’t sound like a packaging issue, are you using the same version on RHEL?
Maybe the FreeTDS people can help.

Best regards

  — Dago

> Thanks & Regards,
> Krishna Upadhyay
> Tata Consultancy Services

"You don't become great by trying to be great, you become great by wanting to do something,
and then doing it so hard that you become great in the process." - xkcd #896

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