So basically I realize there are ways to generate index suggestions (or even generate indices automatically) by observing query patterns, keeping stats on cardi

So basically I realize there are ways to generate index suggestions (or even generate indices automatically) by observing query patterns, keeping stats on cardinality of various columns, etc. We actually did that at Parse; we would observe query patterns and generate indices (including compound indices) at runtime that seemed to benefit the application's query pattern. There wasn't an option for this, it was just enabled by default. However we ran into the problem that users still made many queries which were essentially impossible to index. On many of the DB nodes, the resources used by these unindexable queries dominated the resources used by all of the easily indexed queries. I left the experience thinking that there really wasn't any good solution to the problem for general users other than making the query language force users to only make queries that can be obviously satisfied by common index types.