Thank you Rafal for your answer!
We do not use threads, it's a single threaded program. So we cannot set
a flag to exec the KILL QUERY later on in another thread.
The only flag I use is to avoid subsequent KILL QUERY attempts when one
has already been sent...
The code in the sigint handler is quite simple, basic mysql_ calls and
debug messages (fprintfs):
if (currConn && currConn->canInterrupt) {
char cmd[50];
MYSQL *h;
currConn->canInterrupt = 0;
h = mysql_init(NULL);
if (!mysql_real_connect(h, currConn->c_host, currConn->c_user,
currConn->c_auth, currConn->c_dbnm,
currConn->c_port, currConn->c_sock,
CLIENT_FOUND_ROWS)) {
DBGMSGINT(2, "Interrupt: Could not connect to database: %d.",
mysql_errno(h));
return 0;
}
sprintf(cmd, "KILL QUERY %ld", currConn->threadId);
if (mysql_query(h, cmd) != 0) {
DBGMSGSTR(2, "Could not execute %s.", cmd);
}
mysql_close(h);
}
Should do the job...
Thanks.
Seb
On 12/12/2014 12:12 PM, rafal somla wrote:
Hello Sebastein,
On 2014-12-03 17:25, Sebastien FLAESCH wrote:
Hi all,
I have a similar question regarding KILL QUERY usage:
We have a C client program using libmysqlclient.so, it is a
single-threaded program.
When running a long query, how can I send the KILL QUERY command when a
SIGINT (CTRL-C)
is caught? (of course we implement a signal handler, so we keep the
control)
=> Is is safe to establish a new connection to the server in the signal
handler, using
mysql_init() + mysql_real_connect(), and execute the KILL QUERY with the
mysql thread
id I got from the initial mysql_init() / mysql_real_connect()?
I made some tests, and it seems to work fine, the long query returns SQL
error -1317:
"Query execution was interrupted" (which is expected)
We want to support SQL interruption properly, so please someone from the
dev team,
give me a clear answer... I don't want to use a side effect or
undocumented feature.
Issuing KILL QUERY from a separate connection is the way to do it. We do not currently
have any CAPI "abort" function - introducing such functionality
would require changes on the protocol level.
Doing all this stuff in a signal handler is certainly risky... no?
Whether it is safe to do I/O extensive work inside a signal handler is another
topic, not related to MySQL client library. Depends on your particular
case and how careful you are about writing handler code which can be executed
at any time. One safe option is that signal handler only sets a flag
informing about the signal and then either the main logic of your application
detects the flag and performs KILL operation, or you have a separate
dedicated thread to do this job.
Rafal (from Connectors/C team @ MySQL)
I could not find the information in the documentation (mysql_real_connect).
I wish there would be an API like mysql_cancel_query(), similar to
Oracle's OCI
OCIBreak().
Thanks!
Seb
On 12/02/2014 05:13 PM, walter harms wrote:
hi list,
when i use CTRL-C to break a query that works fine in interactive mode.
mysql> select sleep(10) ;
^CCtrl-C -- sending "KILL QUERY 24289" to server ...
Ctrl-C -- query aborted.
+-----------+
| sleep(10) |
+-----------+
+-----------+
1 row in set (0.86 sec)
but when i use the noninteractive mode
timeout 5 mysql -BAN -e "select now(); select sleep (100) ; select
now() "
i looks like that but "show full processlist;" shows otherwise and
that is true
as a list of long running querys showed.
Is there a way to make it behave like the interactive version ?
Now it is a bit confusing for everyone.
re,
wh
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