See this attached video. Just entering "gecko" actually shows the right result, but finishing with "gecko hook" takes 2 or 3 seconds for something to appear. This started happening to me all the time for different queries and I am starting to dread searching for something in the awesome bar. I recently pruned my history before October last year in the hope of improving this, but it has only helped temporarily. I am happy to help debugging this is any way, ping me on irc.
hm, that could happen if the result has a really low frecency value... but it should not happen often... Maybe you could try (after a backup) to run https://addons.mozilla.org/en-US/firefox/addon/places-maintenance/
also, please check the frecency value of that entry in the database, you can use Sqlite Manager add-on.
Ok just tried Places Maintenance and it seemed to have helped a lot in this case. Sadly it's still not as quick as it used to be. I will continue using this profile and report if there any new problems.
Yeah, so I used this profile for two days and I am back to square one. I am using my fresh profile now, because it just feels so much smoother.
Unfortunately, while we will keep working on performance, this bug by itself is not actionable. We introduced a bunch of improvements in 49 and 50 for the problem, and we are actively working on shrinking places.sqlite. We are also again investigating the possibility of a fulltextindex that would definitely solve this.