On Mon, May 23, 2016 at 11:49 AM, Lars Helge Øverland <l...@dhis2.org> wrote:
> Hi Vanya, > > thanks for raising this issue - it's a good question. Having program > indicators based on a data element / attributes dates instead of event date > has come up earlier and something we will have to support. > > Short story: Currently this is not possible. > > Long story: The current event analytics solution has a compromise between > query performance and flexibility around dates. If you have a look at the > event analytics tables (e.g. "analytics_event_2015_ebayegv0exc") you will > see two things: > > - The tables are partitioned by year (one analytics table with events per > year per program) based on event date. This reduces query time since the > indexes and tables become smaller instead of growing longer infinitely as > times goes. > > - The tables have columns for all period types based on event date. This > makes it possible to aggregate all periods in a query through group-bys on > those columns, instead of having to do one query per period, and hence > improves performance a lot. > > All this is great for performance but limits the analysis to be based on > event date. To partition data one needs a partition key and event date is > pretty much the only suitable candidate (in addition to program). > > So to support aggregation / analytics based on any date from data > elements/attributes of the events, one must sacrifice some of this and > basically have one analytics table per program, and have one query per > aggregation period. This will soon be a very popular requirement so we will > have to support it - still pondering how to solve this in a way which > offers required performance and flexibility. > > > best regards, > > Lars > > I have created a blueprint for this here: https://blueprints.launchpad.net/dhis2/+spec/event-analytics-date-flexibility Lars
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