Sometimes our fancy "run this agg as a Query" optimizations end up
slower than running the aggregation in the old way. We know that and use
heuristics to dissable the optimization in that case. But it turns out
that the process of running the heuristics itself can be slow, depending
on the query. Worse, changing the heuristics requires an upgrade, which
means waiting. If the heurisics make a terrible choice folks need a
quick way out. This adds such a way: a cluster level setting that
contains a list of queries that are considered "too expensive" to try
and optimize. If the top level query contains any of those queries we'll
disable the "run as Query" optimization.
The default for this settings is wildcard and term-in-set queries, which
is fairly conservative. There are certainly wildcard and term-in-set
queries that the optimization works well with, but there are other queries
of that type that it works very badly with. So we're being careful.
Better, you can modify this setting in a running cluster to disable the
optimization if we find a new type of query that doesn't work well.
Closes#73426
4b5aebe8b0