If a search is too long, we get a timeout and this results in an Internal page error displayed to the user.
It would be more appropriate to show an error page like "Your search timed out. you can retry at a less busy time or contact your administrator."

In order to reproduce, you can try:
With MS SQL server, a large database (18000 issues),
*set the database timeout to be 1s by modifying redmine/config/database.yml and adding
:timeout 1
in your production: section settings
Then restart and search for a very common word.
We get the following error in log/production.log:
ActiveRecord::StatementInvalid (TinyTds::Error: Adaptive Server connection timed out: EXEC sp_executesql...

We fixed the issue by increasing the timeout in the config, but still, getting Internal errors is not nice.