Rudder

at start of the web interface, we catch up with all reports sent when the web interface was stopped, with a granularity of one day
on very loaded system, this is simply infeasible: there aren't enough ram to fetch it all, and poor postgresql choke on query

2019-06-11 20:21:29 UTCLOG:  duration: 997284.994 ms  execute <unnamed>: select distinct
          T.nodeid, T.executiontimestamp, coalesce(C.keyvalue, '') as nodeconfigid, coalesce(C.iscomplete, false) as complete, T.insertionid
        from
          (select nodeid, executiontimestamp, min(id) as insertionid from ruddersysevents where id > $1 and id <= $2 group by nodeid, executiontimestamp) as T
        left join
          (select
            true as iscomplete, nodeid, executiontimestamp, keyvalue
          from
            ruddersysevents where id > $3 and id <= $4 and
            eventtype = 'control' and
            component = 'end'
          ) as C
        on T.nodeid = C.nodeid and T.executiontimestamp = C.executiontimestamp
2019-06-11 20:21:29 UTCDETAIL:  parameters: $1 = '1428065585', $2 = '1437233953', $3 = '1428065585', $4 = '1437233953'

We should:

1. be able to turn this feature off (or say: i catch up only xx minutes to avoid a gray compliance at start)
2. be able to catch all (when using advanced reporting plugin), but deal with it in batches of yy minutes
3. improve indexes

query

select
            true as iscomplete, nodeid, executiontimestamp, keyvalue
          from
            ruddersysevents where id >  1428065585 and id <= 1437233953 and
            eventtype = 'control' and
            component = 'end' ;

takes 36 seconds (see https://explain.depesz.com/s/T07l ) when there's no load on database

the index on component is used, but that's all.

Index on component is used only for that, we should use this index instead
CREATE INDEX endRun_control_idx ON RudderSysEvents (id) WHERE eventType = 'control' and component = 'end';

having this index results in 2,5s on a crazyly highly loaded system(load of 4 on a 2 CPU system)