[unixODBC-support] unicode issues :/ st_fetch/SQLFetch (long truncated DBI attribute LongTruncOk not set and/or LongReadLen too small)

Daniel Kasak d.j.kasak.dk at gmail.com
Thu Mar 5 22:55:37 GMT 2015


I've installed DBD::ODBC from git just now and tested. Same error :/

On Fri, Mar 6, 2015 at 8:06 AM, Daniel Kasak <d.j.kasak.dk at gmail.com> wrote:

> Hi. Thanks for the responses :)
>
> I'm using DBD::ODBC version 1.50, which is the latest version I see on
> CPAN ( and my cpan client agrees ).
>
> I'm not using bound input parameters on this particular connection - I'm
> using it on other connections inside the app, but definitely not this
> connection. The window where this particular failure happens is a SQL
> client. Users can enter any SQL they want. I do very limited parsing to
> detect whether they've entered a 'select' query or not. If it's a select,
> the SQL gets passed to Gtk3::Ex::DBI ( which is also my code ) as a
> 'pass-through' query ... in which case no further parsing is done, and
> bound input parameters are not used. The SQL gets executed, and a datasheet
> is populated from the results of the query execution.
>
> I've just rebooted into Windows ... and yes I have DBD::ODBC version 1.50
> in Windows too.
>
> Dan
>
> On Fri, Mar 6, 2015 at 2:02 AM, Martin J. Evans <bohica at ntlworld.com>
> wrote:
>
>> On 05/03/15 13:47, Daniel Kasak wrote:
>>
>>> Hi all.
>>>
>>> I'm struggling to understand some issues I'm seeing talking to SQL
>>> Server. I'm pretty sure I've isolated the issue to unixODBC.
>>>
>>> I've loaded by Microsoft's AdventureWorksDW2014 database for testing
>>> purposes. To give an idea of the data, here's a query I've been testing. It
>>> fails in Linux, but runs and displays find in Windows:
>>>
>>> http://tesla.duckdns.org/images/windows_odbc.png
>>>
>>> As you can see, I'm substring-ing out each character ( I'm debugging yet
>>> other issues ), and also getting hex values for each character. Note the
>>> 6th character ( column S6 ), with hex value f3 ( column H6 ). Also note the
>>> complete string at the end.
>>>
>>> ---
>>>
>>> Issue 1)
>>>
>>> http://tesla.duckdns.org/images/linux_odbc_1.png
>>>
>>> Note in this screenshot, the last column - the complete string. That
>>> doesn't look right. It's difficult to say *why* it doesn't look right, but
>>> my feeling is that the driver is sending a multibyte character, and
>>> somewhere along the line it's being interpreted as 2 single-byte characters.
>>>
>>> Issue 2)
>>>
>>> You might have noticed I'd commented out the expression for S6 in the
>>> Linux query. If I run the query with the S6 expression, I get an empty
>>> recordset back, and the following in STDERR:
>>>
>>> DBD::ODBC::st fetchrow_array failed: st_fetch/SQLFetch (long truncated
>>> DBI attribute LongTruncOk not set and/or LongReadLen too small) (SQL-HY000)
>>>
>>> Now ... note that this is a single character ... and that things weren't
>>> too long when I selected the entire column at once. I've tried setting
>>> LongReadLen to various large values. That doesn't stop this error. If I
>>> also set LongTruncOk, the error disappears, *and* I get a recordset, but
>>> the S6 column is null.
>>>
>>> What's going on here? If this was related to the 1st issue ( and I feel
>>> it might be ) ... I'd say the driver manager was expecting a single byte
>>> character only for the entire field, but was receiving a multi-byte
>>> character.
>>>
>>> ---
>>>
>>> I built unixODBC-2.3.2 with the following configure options:
>>>   --enable-iconv --disable-drivers --disable-driverc
>>> --with-iconv-char-enc=UTF8 --with-iconv-ucode-enc=UTF16LE
>>>
>>> I've tested with freetds-0.91, *and* with Microsoft's native client for
>>> Linux. Interestingly, I get exactly the same behaviour with both.
>>>
>>> I've obviously also tested in Windows, which produced the 1st
>>> screenshot. Based on the fact that it works perfectly in Windows, I'd
>>> assume Microsoft's drivers, *and* DBD::ODBC, *and* my code are behaving
>>> well. And based on the fact that both freetds and MS's drivers produce
>>> exactly the same failure under Linux, I'm guessing the problem lies
>>> somewhere in unixODBC. I do concede that it's possible that the same bug
>>> exists in freetds and Microsoft's native client, and that unixODBC is
>>> completely innocent.
>>>
>>> An odbc trace is at ( pasting it in the message make the message too big
>>> to post, apparently ):
>>> http://tesla.duckdns.org/downloads/trace.log
>>>
>>> Note that this will have *two* executions of the query. My app 1st
>>> executes each query with the filter "where 0=1" ... to analyse the columns
>>> and decide how to go about things. Then it execute the 'real' query.
>>>
>>> Any help greatly appreciated.
>>>
>>> Dan
>>>
>>
>> Sounds like it could be this bug:
>>
>> 1.51_3 2015-01-17
>>
>>   [BUG FIXES]
>>
>>   RT101579 - using bound input parameters for numeric columns (e.g.,
>>   SQL_NUMERIC) only works the first time and will quite likey fail
>>   with "string data, right truncation" on the second and subsequent
>>   calls to execute. Thanks to Laura Cox for finding.
>>
>> What version of DBD::ODBC are you using?
>>
>> What does you perl code look like?
>>
>> Martin
>>
>>
>> _______________________________________________
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>> unixODBC-support at mailman.unixodbc.org
>> http://mailman.unixodbc.org/mailman/listinfo/unixodbc-support
>>
>
>
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