unrestricted listing of events can require significant memory.
this patch implements mandatory limit on event-list
sql backend requires a little rewrite due to fact that we grab data
in two steps: first we grab all events matching query, then we grab
appropriate traits (we don't use orm relationships because it's slow).
we can not just append order_by and limit to first query because we
use query in second part as well and sqlite will complain about
order_by/limit coming before join. this patch changes it to use a
subquery. based on testing, this does not appear to degrade
performance.
DocImpact
ApiImpact
Change-Id: Ib8009d6e4ab6d066ba5fca43b824c24c8cb32d4e
Implements: blueprint mandatory-limit
50fc88183c