If I submit a series of SQL statements (each with GO in sqlcmd) that I want to make an reasonable attempt to run on an Azure SQL Data Warehouse, I've found in sqlcmd how to ignore errors. But I've seen if I want to abort a statement in that sequence of statements with:
KILL "SIDxxxxxxx";
The whole session ends:
Msg 111202, Level 16, State 1, Server adws_database, Line 1
111202;Query QIDyyyyyyyyyy has been cancelled.
Is there a way to not end a query session in Azure SQL Data Warehouse? Similar to how postgres's
pg_cancel_backend()
works?
In postgres the
pg_terminate_backed(<pid>)
seems to be working similarly to the ADW
KILL 'SIDxxxx'
command.
Yes, a client can cancel a running request without aborting the whole session. In SSMS this is what the red square does during query execution.
Sqlcmd doesn't expose any way to cancel a running request, though. Other client interfaces do, like the .NET SqlClient you can use SqlCommand.Cancel()
David
Related
Currently, I am working on a project to integrate mysql with the IOCP server to collect sensor data and verify the collected data from the client.
However, there is a situation where mysql misses a connection.
The query itself is a simple query that inserts a single row of records or gets the average value between date intervals.
The data of each sensor flows into the DB at the same time every 5 seconds. When the messages of the sensors come on occasionally or overlap with the message of the client, the connection is disconnected.
lost connection to mysql server during query
In relation to throwing the above message
max_allowed_packet Numbers changed.
interactive_timeout, net_read_timeout, net_write_timeout, wait_timeout
It seems that if there are overlapping queries, an error occurs.
Please let me know if you know the solution.
I had a similar issue in a MySQL server with very simple queries where the number of concurrent queries were high. I had to disable the query cache to solve the issue. You could try disabling the query cache using following statements.
SET GLOBAL query_cache_size = 0;
SET GLOBAL query_cache_type = 0;
Please note that a server restart will enable the query cache again. Please put the configuration in MySQL configuration file if you need to have it preserved.
Can you run below command and check the current timeouts?
SHOW VARIABLES LIKE '%timeout';
You can change the timeout, if needed -
SET GLOBAL <timeout_variable>=<value>;
Coldfusion 2016
Microsoft Server 2012
Oracle 12
ODBC connection
I turned on profiling and monitoring and now I can see that there are requests that are stuck and cannot be terminated by the CF monitor; Some are over 200k seconds.
I know I can increase the number of simultaneous requests but I want to solve the underlying problem. As I read the stack traces of these “zombie requests” they are getting stuck on and some are in but some are not. I ran the query in my oracle client and they resolve instantly.
Is there a way to terminate these requests or prevent this from happening at all?
EDIT: The server monitor does not treat these requests as slow or hung, the alerts are not triggering for any of these. Honestly, they should have be going off constantly considering how many of these there are.
Also, the execution time is a mere .003 seconds so what happened? Why doesn't ColdFusion know this?
An example of a "zombie"
The active query that is stuck
We have a similar situation with a different database engine - redbrick, which runs on a unix server. We solved it as follows.
We set up a cron job on the database server to run every 5 minutes. This job uses a combination of unix and awk commands.
This job runs a query against the system table that looks for queries that have been running for more than 120 seconds, where the database account is the one used by ColdFusion. Records are outputted to a file. Something like this:
print "alter system cancel user command userName process " $1 ";"
$1 comes from the query and is the process Id we want to stop.
Then we run the file, which executes all those alter system commands.
With a different database engine, and possible different OS for the database server, the details would be different, but the approach should work.
Edit Starts Here
To prevent recurrence, look at the pages that call the ones with the long running queries. If impatient users are able to repeatedly click something because nothing is happening, do something about that. You can use javascript to make the link/button go away. Alternatively, you can go to an intermediate page with a display for the user and something that carries them through to the real page.
I'm working on a system which uses versant object database.
We have functional tests which sends requests to the server, server performs requested operation on database and returns results.
Afterwards we send an opposite request which is supposed to restore db to previous state untill next test starts.
This is invalid approach, we try to restore db to previous state using the very same request we are testing.
Is there a feature similar to Oracle Flashback in Versant, if not what is the proper way to handle this problem?
I'm writing a C++ application that uses MySQL C API to connect to the database. MySQL server version is 5.6.19-log.
I need to run several SQL UPDATE, INSERT and DELETE statements in one transaction to make sure that either all changes or no changes are applied.
I found in the docs functions mysql_commit() and mysql_rollback() that finish the transaction (commit it or roll it back), but I can't find a corresponding function that starts a transaction.
Is there such a function? Am I missing something obvious?
I run UPDATE, INSERT and DELETE statements using mysql_real_query() function.
I guess I should be able to start the transaction by running START TRANSACTION SQL statement using same mysql_real_query() function. Then I should be able to commit the transaction by running COMMIT SQL statement using same mysql_real_query() function.
But then, what is the point of having dedicated mysql_commit() and mysql_rollback() functions in the API?
It looks like MySQL C API indeed doesn't have a dedicated function that is equivalent of the START TRANSACTION SQL statement.
The MySQL C API has mysql_commit() function that does the same as COMMIT SQL statement.
The MySQL C API has mysql_rollback() function that does the same as ROLLBACK SQL statement.
But, there is no function for starting the transaction in this API.
//connect to mysql server:
MYSQL *mysql = mysql_init(NULL);
mysql = mysql_real_connect(mysql, ......)
//turn off auto_commit
mysql_autocommit(mysql , false);
OR
//start a tranaction directly as follows
mysql_real_query(mysql,"BEGIN");
//run your commands:
mysql_real_query(mysql,"UPDATE...");
//commit your transaction
mysql_real_query(mysql, "COMMIT");
I'm working on a script that creates a MySQL dump via <cfexecute> and then FTPs the SQL script to another server. I've resorted to checking once per second to see if the filesize has changed, and if it has not changed within the past five seconds I assume it has completed.
This is fine for the current application, but eventually I would like to be able to import the SQL script on the second server and provide some sort of notification that it has completed.
Is there some way to track the status of a running process?
If not, is there a way to accomplish a full DB export and import via ColdFusion alone?
Actually you may not realize it, but when you call <cfexecute> without passing a timeout attribute it defaults to '0' timeout. And if you read the docs on <cfexecute> you'd see:
If the value is 0:
ColdFusion starts a process and returns immediately. ColdFusion may
return control to the calling page
before any program output displays. To
ensure that program output displays,
set the value to 2 or higher.
So I would suggest passing a higher value for timeout which will cause ColdFusion to wait for mysqldump to complete before moving on.
Reference
Check out Event Gateways[1] for one way to deal with asynchronous operations. There's a Directory Watcher gateway that comes with CF as an example.[2]
Barring that, create some sort of batch processing facility using CF Scheduled Tasks. Add the job to a database table and have a scheduled task periodically pull jobs out of the table and execute them, reporting on the result. A second scheduled task can detect that the first completed and carry out the next step of the process.
[1] http://help.adobe.com/en_US/ColdFusion/9.0/CFMLRef/WSc3ff6d0ea77859461172e0811cbec214e3-7fa7.html
[2] http://help.adobe.com/en_US/ColdFusion/9.0/Developing/WSc3ff6d0ea77859461172e0811cbec22c24-77f7.html