Efcore: SQLite Query: Simplify composed DateTime functions

[bricelam]

Today (pun intended) when we generate SQL for DateTime.Now.Date, for example, we generate this:

strftime('%Y-%m-%d %H:%M:%f', strftime('%Y-%m-%d %H:%M:%f', 'now', 'localtime'), 'start of day')

However, it can simplify to just this: (not surprisingly the same SQL we generate for DateTime.Today)

strftime('%Y-%m-%d %H:%M:%f', 'now', 'localtime', 'start of day')

The logic to do this is fairly simple. Whenever we generate a strftime(format, timestring, modifier...) call, if the timestring argument is another strftime() call:

1. Ignore its format parameter
2. Use its timestring parameter directly in its place
3. Prepend its modifier arguments (if any) to the current call

[Muppets]

@bricelam Threw together a PR for this, it's not super slick but it does the job. Let me know if you have any thoughts on ways of making less verbose.

[bricelam]

It's more robust than I would've made it. (probably a good thing) 😉 Thanks! Will merge when I get a chance...

[bricelam]

The rtrim calls force it to be a bit verbose. I can't think of any obvious ways to simplify it.

[bricelam]

Thanks, @Muppets! There's just something cool about seeing an O/RM generate such tidy SQL...