javascript - Counting transitions (rising edges) of boolean metric in Druid query -


i'm getting feet wet nosql queries , druid , came across interesting query case i'm not sure how solve.

how write druid timeseries query count rising-edge transitions granularity of 1 second?

two issues i'm aware of:

  1. aggregations stateless. have input of current floating point aggregation value, , can return updated floating point aggregation value. see "javascript aggregator" in druid aggregation docs
  2. queries aware of current segment , must have separate aggregations formula on different segments. see "sharding-the-data" in druid docs.

simplified data looks like:

seconds  metric 0.0      0 0.3      1 0.6      1 1.0      1 1.3      1 1.6      0 2.0      1 2.3      0 2.6      1 3.0      0 3.3      0

desired output:

seconds  rising-edge-count 0.0      1 1.0      0 2.0      2 3.0      0

here's best shot using floating point's negativity store previous-value's state, it's super hacky , doesn't seem give desired result...

{    "querytype": "timeseries",    "datasource": "data-store",    "granularity": "hour",    "intervals": ["2015-01-01/2019-01-01"],    "filter": { "type": "in",                 "dimension": "switchx",                 "values": ["0","1"]              },    "aggregations": [      { "type": "javascript",         "name": "rising-edge",        "fieldnames"  : ["switchx"],        "fnaggregate" : "function(current, a)         { return (1 - 2*a) * (math.abs(current) + (a > (current<0))); }",        "fncombine"   : "function(partiala, partialb) { return partiala + partialb; }",        "fnreset"     : "function()                   { return 0; }"      }    ] }


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