[RCU] What kind of search response time are you getting on full text search across all folders with dovecot with solr plugins installed?

[Steve Dondley]

MY SETUP: I'm using the Larry theme on Debian buster. Roundcube was 
installed with debian's package system. The package reports a roundcube 
core of 1.3.16+dfsg.1-1~deb10u1. I'm using dovecot. Roundcube is running 
on the same machine as the  mailstore.

THE PROBLEM: When I perform a search query across all folders, it takes 
about 10 seconds for any emails to get returned. This is better than the 
40 seconds it takes with dovecot's solr plugins turned off, but still 
pretty bad.

Queries with more results are taking longer. So a search result with 500 
results could take 10 seconds while a query with 10 results takes just a 
few seconds. If there are no results, the search terminates almost 
instantly in roundcube.

THE QUESTION: How do I find the bottleneck?

I've ruled out solr as the problem because when I run a query against 
solr running on a remote machine from the command line, I'm getting 
results returned in less than 1/2 a second.

When I run a query using telnet directly over imap on a single folder, 
search results are taking about 3 or 4 seconds, which indicates that 
IMAP/dovecot may be where the bottleneck is.

So I'm leaning toward thinking roundcube is not the culprit so this post 
may be a bit off topic but I'd like to know what kind of search speeds 
others are seeing and hoping someone can help point me in the right 
direction so I can nail this problem.

Thanks so much!