[freetds] FreeTDS Digest, Vol 119, Issue 3

Discussion:

"Tony" Yu Jiang

2012-12-05 17:43:42 UTC

Hi Frediano,

That patch is almost exactly the same as mine - so I guess mine is
unnecessary anymore.

I think this patch is perfectly safe to backport to 0.91 since the change
is so small and so clearly defined. It shouldn't affect anything else.

Thanks!
Tony

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1. Enable freebcp to specify target database on command line
("Tony" Yu Jiang)
2. Re: Enable freebcp to specify target database on command line
(Frediano Ziglio)
3. Re: Memory problems with dbcmd (Frediano Ziglio)
4. Re: Memory problems with dbcmd (Alberto Pulvirenti)
----------------------------------------------------------------------
Message: 1
Date: Tue, 4 Dec 2012 10:24:27 -0800
From: "\"Tony\" Yu Jiang" <yujiang99 at gmail.com>
Subject: [freetds] Enable freebcp to specify target database on
command line
To: freetds at lists.ibiblio.org
<CAD9rgJ=
9HQjzYjAF-M0gUEg0QEFCf5+3MjDyHWdE_tg_OoPoLw at mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Hi there,
This patch allows the user to specify a target database on freebcp command
line. This is especially useful when accessing SQL Azure, which always
returns a connection to a system database.
https://github.com/tonyjiang/freetds/commit/4d50f8835f584b042fabe42510f1cede24e5d938
It'd be great if you can merge it into freebcp.
Cheers,
Tony
------------------------------
Message: 2
Date: Tue, 4 Dec 2012 19:27:59 +0000
From: Frediano Ziglio <freddy77 at gmail.com>
Subject: Re: [freetds] Enable freebcp to specify target database on
command line
To: FreeTDS Development Group <freetds at lists.ibiblio.org>
<CAHt6W4fuBAfg=
j+aJ7gUW5tC1HGCib2+Rvqtd-OdbGNMYM_sgw at mail.gmail.com>
Content-Type: text/plain; charset=UTF-8

Hi there,
This patch allows the user to specify a target database on freebcp

command

line. This is especially useful when accessing SQL Azure, which always
returns a connection to a system database.

https://github.com/tonyjiang/freetds/commit/4d50f8835f584b042fabe42510f1cede24e5d938

It'd be great if you can merge it into freebcp.
Cheers,
Tony

http://gitorious.org/freetds/freetds/commit/c34afafd2fec4cbba9b245e4f13a5471c6fb8041
Do you think we should backport it on 0.91branch? Usually we do not
backport new feature on stable branch but this seems quite safe to me.
James fixed the snapshot generation a week ago so snapshots have this
patch.
Regards,
Frediano
------------------------------
Message: 3
Date: Tue, 4 Dec 2012 19:30:58 +0000
From: Frediano Ziglio <freddy77 at gmail.com>
Subject: Re: [freetds] Memory problems with dbcmd
To: FreeTDS Development Group <freetds at lists.ibiblio.org>
<
CAHt6W4fLnOS3AuypN8pRALr1rRsQeHAcNxoyLBNx4quE0dqGNg at mail.gmail.com>
Content-Type: text/plain; charset=UTF-8

Dear all,
unfortunately, searching on google seemed to be unsuccessful for this,

and

I didn't find any help looking ad previous discussions (maybe since I
subscribed this mailing list).
I have manage to set up a connection to a MS SQL database server using
freeTDS, but it sometimes (seldom, fortunately) happens that a dbcmd

fails.

Looking at the various documentations, it should be a problem of memory
allocation, but this happened even for extremely simple queries like a
"begin transaction", and not always for the same query: it just happened

a given moment, and it was not either possible to reproduce this problem,
but I remained afraid that it can appear again.
I don't really understand how can dbcmd fail with such a simple query

when

the machine is not stuck (which I would think if it is a problem is so
serious that even such a small string cannot be allocated).
The MS SQL server stays in another machine to which I must connect

through

network, although it is a machine internal to the location where all this
stuff runs. Can it happen that a sudden and momentary communication

failure

causes dbcmd() to fail? Or its failure are only due to memory allocation
problems?
Is there any way I can adopt to deeper check this problem?
Thanks
Alberto

Personally I would exclude a memory problem. If the system fails to
allocate few bytes of memory you should note other problems (unless
you set some limits on your program for instance using PHP module
which limit memory itself).
It's possible that connection got broken for some reason (a simple
service restart or a backup schedule which put database in some
particular state). Or even that server disconnect you cause you where
idle for too time (see recent keepalive discussion).
Frediano
------------------------------
Message: 4
Date: Wed, 5 Dec 2012 10:38:18 +0100
From: Alberto Pulvirenti <alberto.pulvirenti at crowdengineering.com>
Subject: Re: [freetds] Memory problems with dbcmd
To: FreeTDS Development Group <freetds at lists.ibiblio.org>
<
CAJNp6N3tbXidcTW9iaEM6Lo+wxCLOFTTCHL9n1BsH+7zGx6u+w at mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Hi,
maybe I forgot to clarify a point. The failure I mention refers to the
function dbcmd().
I checked with a personal MS SQL Server I use for testing and I saw that
when the connection is faulty or the DB server is down, what happens is
that either the dbsqlsend() fails (and then I catch it) or the dbsqlok()
stays pending for a long time.
Whenever I try to switch off the server, it stops always there, never at
the dbcmd() level.
In all the documentations I see, when dbcmd fails it is always explained as
a memory problem, and it happens before one tries to send to the server
itself. That's what confused me.
It is surely possible that in a moment a memory occupancy spike took place
which caused this momentary failure (because, maybe I didn't stress this
point, but this failure was not a persistent condition, it happened just
once or twice and then the communication succeeded).
Thanks for any advice.
Alberto
2012/12/4 Frediano Ziglio <freddy77 at gmail.com>

Dear all,
unfortunately, searching on google seemed to be unsuccessful for this,

and

fails.

happened

a given moment, and it was not either possible to reproduce this

problem,

but I remained afraid that it can appear again.
I don't really understand how can dbcmd fail with such a simple query

when

the machine is not stuck (which I would think if it is a problem is so
serious that even such a small string cannot be allocated).
The MS SQL server stays in another machine to which I must connect

through

network, although it is a machine internal to the location where all

this

stuff runs. Can it happen that a sudden and momentary communication

failure

causes dbcmd() to fail? Or its failure are only due to memory

allocation

problems?
Is there any way I can adopt to deeper check this problem?
Thanks
Alberto

------------------------------
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End of FreeTDS Digest, Vol 119, Issue 3
***************************************

Frediano Ziglio

2012-12-06 14:12:06 UTC

Permalink

Went into stable (ftp://ftp.freetds.org/pub/freetds/stable/)

Post by "Tony" Yu Jiang
Hi Frediano,
That patch is almost exactly the same as mine - so I guess mine is
unnecessary anymore.
I think this patch is perfectly safe to backport to 0.91 since the change
is so small and so clearly defined. It shouldn't affect anything else.
Thanks!
Tony

Hi there,
This patch allows the user to specify a target database on freebcp

command

line. This is especially useful when accessing SQL Azure, which always
returns a connection to a system database.

https://github.com/tonyjiang/freetds/commit/4d50f8835f584b042fabe42510f1cede24e5d938

It'd be great if you can merge it into freebcp.
Cheers,
Tony

Dear all,
unfortunately, searching on google seemed to be unsuccessful for this,

and

fails.

a given moment, and it was not either possible to reproduce this problem,
but I remained afraid that it can appear again.
I don't really understand how can dbcmd fail with such a simple query

when

the machine is not stuck (which I would think if it is a problem is so
serious that even such a small string cannot be allocated).
The MS SQL server stays in another machine to which I must connect

through

network, although it is a machine internal to the location where all this
stuff runs. Can it happen that a sudden and momentary communication

failure

causes dbcmd() to fail? Or its failure are only due to memory allocation
problems?
Is there any way I can adopt to deeper check this problem?
Thanks
Alberto

Dear all,
unfortunately, searching on google seemed to be unsuccessful for this,

and

fails.

happened

a given moment, and it was not either possible to reproduce this

problem,

but I remained afraid that it can appear again.
I don't really understand how can dbcmd fail with such a simple query

when

the machine is not stuck (which I would think if it is a problem is so
serious that even such a small string cannot be allocated).
The MS SQL server stays in another machine to which I must connect

through

network, although it is a machine internal to the location where all

this

stuff runs. Can it happen that a sudden and momentary communication

failure

causes dbcmd() to fail? Or its failure are only due to memory

allocation

problems?
Is there any way I can adopt to deeper check this problem?
Thanks
Alberto

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James K. Lowden

2012-12-08 19:50:20 UTC

Permalink

On Thu, 6 Dec 2012 14:12:06 +0000

Post by Frediano Ziglio
Went into stable (ftp://ftp.freetds.org/pub/freetds/stable/)

Updated doc/freebcp.1.in in master.

--jkl