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Re: TopN on two metrics


For the vast majority of use cases, Yes! For example, lets say you have two
metrics "Cost" and "Taxes" as USD cents. When you add the two together you
get the total that was charged (or something similar).

To get the total that was charged across everything, you simply sum the
Cost and sum the Taxes as aggregators, then do what's called a
post-aggregator to sum those two aggregators.

The place where this DOESN'T work well is if Cost is is local monies, and
you want to convert every event to USD and then sum them. The easiest way I
know to handle such a thing is to do the conversion during your initial
data cleanup and processing. An example on a similar vein is if you want to
do "inflation adjusted USD". For these two scenarios I'd really have to
think about if there's a clean way to do the calculation; no immediate one
comes to mind. In these scenarios the way I can think of would be:

A) Do a topN (or groupBy) against the currency type, then do some client
side aggregation to convert the per-currency result into a constant
currency value
B) Do a timeseries, and do the per-time-bucket conversion on the client
side, then do the final aggregation on the client side as well.

Hopefully that clarifies things a bit.


On Thu, Oct 11, 2018 at 6:07 AM Abhishek Kaushik <akaushik079@xxxxxxxxx>
wrote:

> Hi,
> Suppose I have two metrics A and B in my dataset. I need to have a TopN
> query on the aggregated combination of both (here A+B). Is it possible in
> druid?
>