Add hashtag score for better sorting of autosuggestions (#11427)

* Add hashtag score for better sorting of autosuggestions

* Do not use `~<~` operator with no text_pattern_ops index

db/migrate/20190729185330_add_score_to_tags.rb

@@ -0,0 +1,5 @@
+class AddScoreToTags < ActiveRecord::Migration[5.2]
+  def change
+    add_column :tags, :score, :int
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2019_07_28_084117) do
+ActiveRecord::Schema.define(version: 2019_07_29_185330) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -659,6 +659,7 @@ ActiveRecord::Schema.define(version: 2019_07_28_084117) do
     t.string "name", default: "", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.integer "score"
     t.index "lower((name)::text)", name: "index_tags_on_name_lower", unique: true
   end