Allow filtering labels by a single character

When we use Gitlab::SQL::Pattern, this typically relates to a trigram
index. As the 'tri' indicates, we need at least three characters to be
able to use that index.

Labels don't have a trigram index, because we never allow you to search
for them globally: it's always in the context of a project or a
group. In that context, it's just as fast to search for a single
character (in general) because there is already a pretty specific index
being used.

1 files changed, 7 insertions, 0 deletions

diff --git a/app/models/label.rb b/app/models/label.rb
index 1c3db3eb35d..96bdb7f17c5 100644
--- a/app/models/label.rb
+++ b/app/models/label.rb
@@ -126,6 +126,13 @@ class Label < ActiveRecord::Base
     fuzzy_search(query, [:title, :description])
   end
 
+  # Override Gitlab::SQL::Pattern.min_chars_for_partial_matching as
+  # label queries are never global, and so will not use a trigram
+  # index. That means we can have just one character in the LIKE.
+  def self.min_chars_for_partial_matching
+    1
+  end
+
   def open_issues_count(user = nil)
     issues_count(user, state: 'opened')
   end