Created question in FIWARE Q/A platform on 13-02-2021 at 13:02
Please, ANSWER this question AT https://stackoverflow.com/questions/66184982/how-to-define-which-time-index-attribute-is-used-when-notifing-quantumleap

Question:
How to define which time_index attribute is used when notifing Quantumleap?

Description:
I am using FIWARE for some time-series data of heat-pumps. I use Orion 2.5.2 and Quantumleap 0.7.6.
My entities have a lot of attributes which are reported in batches. Those data-batches have individual time-stamps for each attribute, so the exact time of a measurement is known (this is also rather important). I use a little python tool to split these batches and send them to the iot-agent seperately via http, using the time-stamp parameter.
I end up with an entity like this:
...

"attrs": {
"temp_outdoor": {
"value": "-6.6",
"type": "Number",
"md": {
"TimeInstant":

},
"mdNames": [
"TimeInstant"
],
"creDate": 1612780352.3855166,
"modDate": 1613148716.1449544
},
"temp_return_flow": {
"value": "40.8",
"type": "Number",
"md": {
"TimeInstant":

},
"mdNames": [
"TimeInstant"
],
"creDate": 1612780352.3855166,
"modDate": 1613149021.5991328
},
"TimeInstant":

,

...

I don't really care about the creDate and modDate but about the TimeInstant in "md" of each attribute. Also the bottom "TimeInstant" attribute is just the value of the last Data-Point I think? I would like to use the "md" TimeInstant to create the time_index in CrateDB. Hence, the reported time has to be the custom-metadata one. I tried some different values while subscribing to Quantumleap but can't get it right.
Can someone tell me how to specify md->TimeInstant as value for time_index?
I find the documentation to be rather unconclusive on that topic and hope that someone has already solved that mistery and might let me in on it
Thanks!