Support TS.MRANGE/MREVRANGE GROUPBY <label> REDUCE <reducer>

[filipecosta90]

The following PR https://github.com/RedisTimeSeries/RedisTimeSeries/pull/617 added support for multi-series aggregations to RedisTimeSeries.

It adds GROUPBY <label> REDUCE <reducer> to TS.MRANGE/TS.MREVRANGE. It accepts SUM, MIN, MAX reducers and works with unaligned series.

Sample request:

TS.MRANGE 1451679382646 1451682982646 WITHLABELS 
AGGREGATION MAX 60000 
FILTER measurement=cpu 
      fieldname=usage_user 
      hostname=(host_9,host_3,host_5,host_1,host_7,host_2,host_8,host_4)
GROUPBY hostname REDUCE MAX

Reply labels array structure

Labels:

• <label>=<groupbyvalue>
• __reducer__=<reducer>
• __source__=key1,key2,key3

---

Sample output:

127.0.0.1:6379> ts.add ts1 1 90 labels metric cpu name system
(integer) 1
127.0.0.1:6379> ts.add ts1 2 45 labels metric cpu name system
(integer) 2
127.0.0.1:6379> ts.add ts2 2 99 labels metric cpu name user
(integer) 2
127.0.0.1:6379> ts.add ts3 2 02 labels metric cpu name system
(integer) 2

MAX reducer sample output

127.0.0.1:6379> ts.mrange - + withlabels filter metric=cpu groupby name reduce max
1) 1) "name=system"
   2) 1) 1) "name"
         2) "system"
      2) 1) "__reducer__"
         2) "max"
      3) 1) "__source__"
         2) "ts1,ts3"
   3) 1) 1) (integer) 1
         2) 90
      2) 1) (integer) 2
         2) 45
2) 1) "name=user"
   2) 1) 1) "name"
         2) "user"
      2) 1) "__reducer__"
         2) "max"
      3) 1) "__source__"
         2) "ts2"
   3) 1) 1) (integer) 2
         2) 99

MIN reducer sample output

127.0.0.1:6379> ts.mrange - + withlabels filter metric=cpu groupby name reduce min
1) 1) "name=system"
   2) 1) 1) "name"
         2) "system"
      2) 1) "__reducer__"
         2) "min"
      3) 1) "__source__"
         2) "ts1,ts3"
   3) 1) 1) (integer) 1
         2) 90
      2) 1) (integer) 2
         2) 2
2) 1) "name=user"
   2) 1) 1) "name"
         2) "user"
      2) 1) "__reducer__"
         2) "min"
      3) 1) "__source__"
         2) "ts2"
   3) 1) 1) (integer) 2
         2) 99