SQLite Forum

Shortcut to change a non changing update or upsert in a noop
> I would think that this might better be an option offered by a VFS. There is little point to doing work to avoid some byte writes if a page is dirtied elsewhere anyway and has to be written out.

I might be misunderstanding your point, but:

The VFS might not have enough information to optimize this.  If SQLite can determine that the a write is unnecessary from an index lookup, say, then skipping the write saves the VFS from having to determine if a non-index page is dirty in the first place.