[freetds] FreeTDS hangs when running a select
Hildo.Biersma at morganstanley.com
Tue Apr 8 08:05:44 EDT 2008
Brian Johnson wrote:
> We have a Windows system on the same network that uses the same firewall
> going through the same VPN tunnel. The Windoze system works great (returns
> all the rows). But both linux systems choke. I'm truely stumped. The log
> created when setting TDSDUMP did indeed seem to indicate that there was no
> problem, data just stopped flowing. I also looked into the ODBC logs, and
> there was no clues there either.
> Any ideas? Any where I can point a finger and say, "Aha! I have something
> to update!"?
> For the record, I did try compiling .82RC4 but saw the same results. So I
> am thinking you must be correct in that it's not FreeTDS. :(
Check the selective ACK (SACK) network setting on your Linux system. If
you have a bad firewall, turning off SACK may help.
> On Mon, Apr 7, 2008 at 1:03 PM, James K. Lowden <jklowden at freetds.org>
>> Brian Johnson wrote:
>>> Let me start by saying that the following numbers are somewhat made up,
>>> but demonstrate the problem accurately. Anyway, lets say we have a
>>> table with 5 columns, and 100 rows. If we do a "select * from foo", we
>>> would expect to get 100 rows returned. We don't. Instead we get say 25
>>> rows, and the select hangs. I can print out the results of those 25
>>> rows in perl, but the 26th row never gets returned.
>>> So, we modified the select to be "SELECT col1 FROM foo", and we got all
>>> 100 rows of that column. So we did "SELECT col1, col2 FROM foo", and
>>> then we got 75 rows and it hung. So we tried "SELECT col1, col2, col3"
>>> FROM foo", and ended up getting 50 rows.
>>> Of course, the numbers were not so nice and round. As for how we are
>>> connecting, I have tried DSN and DNS-less connections with dbi::ODBC,
>>> and of course have tried with sqsh. For sqsh I added an entry to
>>> freetds.conf, and then ran sqsh -S ENTRYNAME -U USER -P PASS. I was
>>> able to do very small selects, but any time I did a select that returned
>>> large numbers of rows it hung.
>> There's nothing in FreeTDS that would explain what you're seeing. It sure
>> sounds to me like there's something on your network -- perhaps a firewall?
>> Some sort of traffic shaper? -- between you and your server.
>> You can use TDSDUMP to create a log of the session and show it to your
>> network folks. I think you'll see the server seems to stop sending in
>> mid-packet. If you can show a successful log with the old server, that
>> might convince them to track it down.
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