Re: Index Tuning Features

Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> - Virtual Indexes

> An index which only exists in the catalog, so is visible to the planner
> but not the executor.

Say what? What would that possibly be useful for, other than crashing
any bit of code that failed to know about it?

> - RECOMMEND command

> Similar in usage to an EXPLAIN, the RECOMMEND command would return a
> list of indexes that need to be added to get the cheapest plan for a
> particular query (no explain plan result though).

Both of these seem to assume that EXPLAIN results, without EXPLAIN
ANALYZE results to back them up, are sufficient for tuning. I find
this idea a bit dubious, particularly for cases of "marginal" indexes.

> Specifically, multi-column indexes are not considered very heavily in
> RECOMMEND.

That seems like a bad idea as well --- multicol indexes are exactly the
sort of thing a novice DBA might fail to consider. If you're going to
do this then you should consider all cases.

regards, tom lane