I’ve generally had pretty good luck with Spotlight on iOS, but I’ve long noticed that results are delayed or nonexistent after not using it for a little while, particularly if I haven’t rebooted my phone recently. I thought I was losing my head a little bit, until I found a tip on Twitter from Anand Iyer:
Settings > General > Spotlight Search > toggle Slack off
Just like that, Spotlight seems to be running quickly again. Every query I’ve tried is fast and reliable, even if I don’t use my phone for a while. I don’t know why Slack, in particular, seems to make Spotlight perform so poorly — other apps surely index thousands of messages and require network lookups to complete — but this one weird trick seems to make Spotlight performance issues disappear.
Update: John Gruber:
Sounds like there might widespread problems with Spotlight indexing on iOS 10, because a bunch of readers have written to say they have the same problem but don’t even have Slack installed.
I’ve seen this Slack trick working for a few other people, so I wonder what the common thread is between those of us with Slack installed and those without. Perhaps there are issues with indexing large numbers of items, or perhaps toggling a setting simply rebuilds the Spotlight cache.
Update: I’ve seen reports that 10.3.2 fixes this bug altogether. Daniel Shockley says that he improved Spotlight performance by toggling languages, which makes me think that it is — or was — a bug that can be worked around by clearing a cache.