Better documentation of speed characteristics and index usage for `Find` vs `Select`

[dimroc]

We've been writing some queries to later realize that Select and Query don't use indices.

https://github.com/asdine/storm/blob/dbd37722730b6cb703b5bd825c3f142d87358525/query.go#L9-L10

If that's correct, we have two scenarios that I'm hoping can leverage indices:

1. We want to Find by a particular index, but OrderBy another. Is there a way to do this that leverages indices? We used to do the following by are moving to Find and sorting ourselves.

err := orm.Select(q.Eq("JobID", jobID)).OrderBy("CreatedAt").Reverse().Find(&runs) // doesn't use index

moving to

_ := orm.Find("JobID", jobID, &runs) // Use Find to leverage db index
sort.Sort(jobRunSorterAscending(runs))

2. Find ing from a field with multiple matches (aka In). Would it be more perfomant for us to have multiple Finds? Seems unlikely.

err := orm.Select(q.In("Status", statuses)).Find(&runs) // doesn't use index

Thanks for any insight. We are considering a PR with this functionality if there's consensus.

[asdine]

There is currently no index support in the Select method. While it could be a great addition, it is complicated to add them with the current code, so i decided to focus on the Storm v3 rewrite #211.

If you are interested in contributing by adding the support for indexes to Select, i'd be more than interested to give any insight you need 👍

[dimroc]

I think we will be. Storm and bolt are critical pieces of our app so we would love to be involved in the discussion at https://github.com/asdine/storm/issues/211.

As for a concise takeaway regarding this issue, is it safe to say Find gives us O(log(N)) and Select is O(N) and to just deal with that for v2?

[asdine]

I think we will be. Storm and bolt are critical pieces of our app so we would love to be involved in the discussion at #211.

Actually i was proposing to add the support for indexes for v2 if you are interested (i'm glad you are interested in v3 though 👍 ) v3 is a complete rewrite and needs a lot of time to be ready, so i don't have time to focus on big features additions to v2, but i'm open to contributions.

Find gives us O(log(N)) and Select is O(N)

Yes exactly.