I was wondering if its possible to the same event on MySQL overlap its execution:
eg:
I have this event scheduled to execute every 2 seconds:
BEGIN
DELETE FROM RouteDatabase3.route_fast WHERE TIMESTAMPDIFF(minute, updated_at, now()) > 5;
END
What happens if this event takes 10 seconds? MySQL server will execute the same event overlaping the last one?
Its possible to lock the event execution, so MySQL will execute only one at time?
I was able to find a solution using the GET_LOCK and RELEASE_LOCK functions from MySQL,
BEGIN
IF GET_LOCK('lock', 5) THEN
DELETE FROM RouteDatabase3.route_fast WHERE TIMESTAMPDIFF(minute, updated_at, now()) > 5;
SELECT RELEASE_LOCK('lock');
END IF;
END
Related
How can i make the following query execute each hour automatically?
SELECT count(*)
FROM user_tab_columns
WHERE table_name='MYTABLE'
Usually in a DBMS exist some schedule of instrument. In Oracle the instrument is DBMS_SCHEDULER.
MySQL same have scheduler. You should check global variable event_scheduler=1. Then you can create schedule:
CREATE EVENT 'new_event'
ON SCHEDULE EVERY 1 HOUR STARTS CURRENT_TIMESTAMP
ON COMPLETION NOT PRESERVE
ENABLE
COMMENT '' DO
call new_proc();
where new_proc() is procedure with your query.
Sorry, don't really know much about this stuff!
I have a table with a few columns, one of them is called 'expirationday' and every row has its unix timestamp for this column.
I would like to know, if at all possible, how to delete a row when the time in the 'expirationday' column (for that row) is reached.
Please note that it does not need to delete rows accurately to the second, a couple of hours is fine.
script.sh
Create a shell script like this:
#!/bin/bash
mysql --user=[username] --password=[password] --database=[db name] --execute="DELETE FROM tbl_name WHERE expiration_date < NOW()
Create a cron job that executes the (it will run every 30 min)
type
crontab -e
Add:
0,30 * * * * /path/script.sh
It's worth looking at the MySQL event scheduler. You could schedule a job to run for example every half hour.
It could then call a DELETE statement directly or to call a MySQL Function or Procedure.
DELIMITER $$
CREATE
EVENT `deleteExpire`
ON SCHEDULE EVERY 1 HOUR STARTS '2015-01-01 00:00:00'
DO BEGIN
DELETE FROM mytable
WHERE expirationday < UNIX_TIMESTAMP();
END */$$
DELIMITER ;
Also see this for more example usage.
I need to delete rows from table 14 days after the DELETE query has been made. Is it possible to do this using MySQL?
You can use the built-in MySQL Event Scheduler to schedule a query or a stored routine to run at an arbitrary point in time:
This is an example of a minimal CREATE EVENT statement:
CREATE EVENT myevent
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
DO
UPDATE myschema.mytable SET mycol = mycol + 1;
Please mind, the Event Scheduler is disabled by default.
Let's say I have rows of information in an SQL database.
I want to have rows of information that are older than 30 days to be automatically removed.
Is this possible?
Additional information:
I am using the SQL date function provided to collect the dates.
This problem has two aspects:
How to schedule
Actual SQL Statement
How to Schedule
You have multiple options, but all of this revolves around whether you will schedule, or whether you will have a stored procedure triggered.
Three options
Use MySql event scheduling: http://dev.mysql.com/doc/refman/5.1/en/events-overview.html
Schedule through an operating system (CRON, SCHEDULED TASK) the execution of an app using SQL (either PHP script, java etc)
Have a trigger that is executes a stored procedure every time a change is made to a table.
I would propose options 1 and 2 are the best.
SQL Statement
The actual SQL statement is quite easy provided you have a field (e.g. dateField) that represents insertDate...
delete from myTable where insertDate < DATE_SUB(NOW(), INTERVAL 1 MONTH);
You can easily generate this value using the NOW() function within an insert statement, for example:
insert into myTable values (NOW(), 'value1', 'value2', ... , 'valueN');
Scheduling Using Event Scheduler at End of Day
If you have the CREATE EVENT privilege this will work through PHP MyAdmin.
See also: http://www.sitepoint.com/how-to-create-mysql-events/
CREATE EVENT `clean_up2`
ON SCHEDULE EVERY 1 DAY STARTS CURRENT_DATE
DO
delete from `data` where updated_on < DATE_SUB(NOW(), INTERVAL 1 MONTH);
END;
Yes. In SQL Server you could create a stored procedure to perform the delete, and create a SQL Agent job that runs every day (or a schedule of your choosing)
Can any one help me how to create an event in MySQL so that it has to be executed for every 10 seconds?
I have tried with the following code but it is inserting only once but when i see whether the event is running of not in process list it is in running state
create event e_insert on schedule at 'timestamp' + interval 1 second do insert into 'table_name' values (now());
You should write -
ON SCHEDULE EVERY '10' SECOND
instead of on schedule at...
Using the Event Scheduler.
Edit:
CREATE EVENT event1
ON SCHEDULE EVERY '10' SECOND
STARTS CURRENT_TIMESTAMP
ON COMPLETION PRESERVE
DO
BEGIN
INSERT INTO...
END
set global event_scheduler = 1;
check this here