[MSM]

SQL Server has all this information saved (I'm not paid by Microsoft, I swear). I would suspect something is available for other engines as well.

For example, I can easily grab (what it thinks are) the top 10 most impactful missing indexes and create them. The big issue is that, well, they can be really dumb when looking at a macro level. Do I often query a 10 column table for 8 of the columns? It will likely recommend I index those 8 columns. In a vacuum that might be a great index for this specific query, but now I'm basically maintaining two copies of the full table.

To be able to weigh these pros and cons would be a really nice feat, then DBAs will have to abandon the "It Depends" mantra!

[pizza234]

I think indexing is ultimately a trade-off design; the end effect of it is a decision which belongs to a human - what do we make faster at the expense of what?

Probably the best thing a "machine" can do is to give tools to easily perform a reasonably accurate and extensive analysis, but I think any major RDBMS has "good enough" tools to do so.

Interestingly, I think it's important to think who is the target of such tools - the casual developer? the novice dba? the expert dba who works on large datasets? I think even theoretically advanced tools would help only the first case; the other two need to know very well what they're working with.