Prune mysql table - averaging records - mysql

Question

I have a MySQL table which stores real-time data from different devices. Data is recorded about every 20 seconds.
The table looks like this:
report_dt device value1 value2
2015-10-16 10:32:15 solar 34.4 67.8
2015-10-16 10:32:15 grid 56.9 23.5
2015-10-16 10:32:35 solar 45.6 34.3
Queries to get the recorded values per device are pretty CPU consuming. I have (report_dt,device) as primary key. Besides, after a few days I do not need the 20 second data anymore, but just the 10 minute average.
So either the same table setup or a table per device would be satisfactory, with this contents:
report_dt device value1
2015-10-16 10:00:00 solar avg(value1 over 10 mins)
2015-10-16 10:10:10 grid avg(value1 over 10 mins)
2015-10-16 10:20:20 solar avg(value1 over 10 mins)
The idea is to run the pruning action once every 24 hours.
The reason is that data containing averages must be retrieved fast. And because the data in a 20 second interval is extremely fluctuating, I must use averaging or the data is difficult to assess.
I could do this in an application. Retrieve the average values for 10 minutes at each 10 minute interval and write it back to a different table or different tables, one for each device.
But would something also be possible with a database function?

Answer 1

You can do this by Events in mysql. Suppose i have 2 tables in mysql. Table_1 store the data continiously per second or miunte as your application generate. Table_2 is your main table which contains the 10 min avg data. Now you need to create a stored procedure which calls once in 10 minutes (this can be done by Events or CRON in linux ). So whats contains the stored procedure ? These steps perform in Stored Procedure
BEGIN
SELECT avg(value) of last 10 min from Table_1
INSERT into Table_2 the avg record.
DELETE avg(value) of last 10 min from Table_1
END
Caution- I am not developing mysql code, i am just show the approach