Search index cache?

[bakasora]

The first time when I do a search, it will go through 22,000 folders and 1,600,000 files, the search take about a few mins.
On the same directory, the 2nd search will only take a few seconds. When I restart my PC, the search will take longer again.
It's like there is some kind of search index cache that is cleared when I restart PC? Is it possible to retain that cache?
I looked at configuration, enabling "Cache search results" seem to do nothing for me.

[highend]

With that many files you'd be better off using Everything, e.g. with: viewtopic.php?f=7&t=23224&p=188977

[admin]

"Cache search results" is preserved across sessions, but it is bound to the search results tab, so you have to keep that tab in your tab bar to keep the cache (it doesn't have to be the selected tab). Tip: If you lock the tab it won't be accidentally overwritten.