[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
Fri Mar 6 22:55:32 GMT 2015


Actually I have to correct myself ... when selecting the entire column at
once, I *am* getting the correct data, at least as far as Perl is
concerned. It seems I have multiple bugs ... Gtk3 is not displaying unicode
stuff correctly. Anyway, the substring() bug remains.

Dan

On Sat, Mar 7, 2015 at 9:26 AM, Daniel Kasak <d.j.kasak.dk at gmail.com> wrote:

> Excellent :) Thanks for helping out.
>
> Code:
> http://tesla.duckdns.org/downloads/odbc_test.pl
>
> Table DDL:
> http://tesla.duckdns.org/downloads/DimCustomer.sql
>
> Data:
> http://tesla.duckdns.org/downloads/DimCustomerData.csv
>
> If it's easier for you, I can set up port forwarding to my SQL Server
> instance ( it's purely for testing this kind of thing ). Let me know ...
>
> The database is Microsoft's AdventureWorksDW2014 demo database:
> https://msftdbprodsamples.codeplex.com/releases/view/125550
>
> It may ( or may not ) be easier for you to just download that demo - it
> comes as a SQL Server backup file, and you don't have to mess around with
> loading the CSV ( I exported it from SQL Server Management Studio ). To be
> honest, I haven't used SQL Server for about 15 years, so I'm not sure what
> he easiest way of loading data is these days.
>
> If what I'm seeing is correct though, you can define a table with a single
> nvarchar column, insert any non-ASCII character, as dummy data to trigger
> this bug.
>
> 2 things to note in Linux:
>
> 1) If you use a substring() function on the column ( selecting *only* to
> non-ASCII character ), you'll get zero records back, and the truncation
> warnings.
>
> 2) If you *don't* substring() the column, you get data back, but it's
> corrupted.
>
> In Windows, the above behaves as expected.
>
> Let me know if there is anything else you need ...
>
> Dan
>
> On Sat, Mar 7, 2015 at 12:31 AM, Martin J. Evans <bohica at ntlworld.com>
> wrote:
>
>> On 05/03/15 22:55, Daniel Kasak wrote:
>>
>>> I've installed DBD::ODBC from git just now and tested. Same error :/
>>>
>>
>> ok, that rules that out.
>>
>> Can you give us a small example bit of perl which demonstrates the
>> problem.
>>
>> The schema for the table would be useful too.
>>
>> Martin
>>
>>  On Fri, Mar 6, 2015 at 8:06 AM, Daniel Kasak <d.j.kasak.dk at gmail.com
>>> <mailto: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
>>> <mailto: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 <
>>> 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 <
>>> 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 <
>>> 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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>>>
>>>
>>>
>>>
>>
>
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