system.tag.queryTagHistory can't access the tag created by system.tag.storeTagHistory

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1

Hi every one,

I use this code to store "data" (which is a real-time calculated value) as a history tag (tag5):

paths = ["folder/tag5"]
system.tag.storeTagHistory(histProv, tagProv, paths, data)

Then I try to query the created history tag's values using this:

endTime = system.date.now()
startTime = system.date.addHours(endTime, -24)
Hist_Tag_Paths = ["[tagProv]folder/tag5"]
Cols = ["data_query"]
result = system.tag.queryTagHistory(paths=Hist_Tag_Paths,
startDate=startTime, endDate=endTime, returnSize=0, aggregationMode="Average", returnFormat='Wide', columnNames = Cols)

I have also added tag5 as a pen to a PowerChart and I can see its values plotted as a graph, but the "result" returned by system.tag.queryTagHistory is an empty dataset.

Does anyone have any idea why system.tag.queryTagHistory can't find this history tag?

Thanks

2

Does the tag exist? And have history turned on?

(.storeTagHistory() is not intended to be the primary path to store history, but is a tool to backfill missing history for a tag that otherwise records normally.)

3

This was the issue. I enabled the tag's history and now I can get the values using system.tag.queryTagHistory.

Thank you for your help @pturmel

4

Another issue I’ve noticed with this implementation is that when the Designer or any session is not open, the script does not seem to historize data to tag5 properly — likely because it is not being executed at all.

The script is designed to run in real time as a transform on an expression binding to a main view parameter (see attached screenshot). It calculates the "data" value using system.tag.queryTagCalculations based on another history tag’s values, and then stores the result to tag5 as described earlier.

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Any idea regarding this is appreciated

5

Correct, if its a binding on a view then it's not being run if there is no session. It also means it's being run on EVERY session that is open. Tha's probably filling your history with a bunch of duplicates.

Make an expression tag that calculates this value and enable history on that tag. Or if the calculation is too complex for an expression, make a gateway timer event and do the calculation in there.

6

Thanks for your response, Ryan.

I initially wanted to implement the calculation as an expression tag, but my calculation requires taking the average of historical values over a predefined period. I couldn’t find a way to do this with an expression tag, as it seems expression tags don’t support historical queries — or at least I'm not aware of a way to accomplish it.

Using a gateway timer script is a great idea. Thank you for the suggestion!