Clear all old data within a feed

[OHarvey]

Not sure if this has been previously raised, if it has I apologise.

I would like the ability to clear data that has been logged in a feed.

A "clear all" would be very helpful to have in the feeds edit menu.

Thanks.

[Paul-Reed]

Agree, with the safeguard of a secondary check - 'This action is irreversible, are you sure that you want to delete this feed's data?' Y/N
This crops up regularly in the forum, and would be a nice addition.

Paul

[lxxl]

Yep +1 for this.

[robertsLando]

Any news about this feature? Is there any work in progress?

I need to delete data of a feed before a date, I also would like to know if there is a way to remove all values of a feed without remove and recreate the feed. I think this feature is a must have in a software like emon, the possibility to delete datas isn't supported in anyway, also an API to delete feeds data would be great for full feeds support.

[JacoFourie]

I also need this. I need to keep only one year of data. I asked in the past and was told it is not supported. Will it be looked at in future ? I need to look at cleaning up data in the near future.

[TrystanLea]

@emrysr a couple of pointers to help, we discussed two methods one for the clear all data for a particular feed and the other to delete data before a certain time.

These methods could be implemented in the feed engine's themselves, e.g PHPFina.php: https://github.com/emoncms/emoncms/blob/master/Modules/feed/engine/PHPFina.php

perhaps of the form:

public function clear($feedid) {
    // clear code...
    // 1. clear feedid.dat
    // 2. set start_time to 0 in feedid.meta, keep interval the same
}

public function trim($feedid,$start_time) {
    // trim code...
    // 1. system level trim command? as discussed?
    // 2. change start_time in feedid.meta to new $start_time
}

A corresponding entry needs to be created in all feed engines, however they can be left empty to be implemented later, the priority engines are PHPFina and PHPTimeSeries, these are ordered by time feeds and so a simple trim should work well.

An entry in feed_model.php and feed_controller.php is also needed to complete the chain. E.g:

get average in PHPFina:
https://github.com/emoncms/emoncms/blob/master/Modules/feed/engine/PHPFina.php#L836

get average in feed_model.php:
https://github.com/emoncms/emoncms/blob/master/Modules/feed/feed_model.php#L603

get average in feed_controller.php
https://github.com/emoncms/emoncms/blob/master/Modules/feed/feed_controller.php#L107

Implementing trim in PHPTimeSeries is a little more complicated than PHPFina as a binary search is required to find the file position that corresponds to the given time. This method can be found here:
https://github.com/emoncms/emoncms/blob/master/Modules/feed/engine/PHPTimeSeries.php#L562

The buffered writing of data on an emonpi may also need considering. Im not sure what the result will be of triming a file mid way through a buffer period. The trim method may need to clear the buffer..

thanks a lot!