ivy-read calls collection function on input change without dynamic-collection

[dminuoso]

Hi,

I'm currently chasing down a performance problem in counsel-projectile, which behaves rather sluggish on typing input inside counsel-projectile. After some debugging I found out, that ivy-read calls the collection function counsel-projectile--project-buffers-and-files each time an additional character was entered into ivy's input.

https://github.com/ericdanan/counsel-projectile/blob/06b03c1080d3ccc3fa9b9c41b1ccbcf13f058e4b/counsel-projectile.el#L1628-L1638

This is the call into ivy-read.

I'm not quite sure why that is, there's no dynamic-collection passed to ivy-read, even explicitly passing :dynamic-collection nil does not help.

Under what circumstance would ivy-read call the collection function repeatedly on input change? The documentation does not give any hint here.

[basil-conto]

Completion collections that are non-dynamic-collection functions are described in the Elisp manual: (info "(elisp) Programmed Completion").

Since Ivy's whole model is an instantly-updating list of all possible completions given the current input, it's only natural that it needs to call programmed completion functions with any change in input. IIUC, it's up to the completion table to cache its results or otherwise achieve acceptable performance, and AFAICT counsel-projectile has deliberately gone down this route.

So, unless I'm missing something, this discussion seems more fitting for the counsel-projectile issue tracker, no? Thanks.