Add more accurate hashtag search (#11579)

* Add more accurate hashtag search

Using ElasticSearch to index hashtags with edge n-grams and score
them by usage within the last 7 days since last activity. Only
hashtags that have been reviewed and are listable can appear in
searches, unless they match the query exactly

* Fix search analyzer dropping non-ascii characters

2 files changed, 9 insertions, 1 deletions

diff --git a/db/migrate/20190815225426_add_last_status_at_to_tags.rb b/db/migrate/20190815225426_add_last_status_at_to_tags.rb
new file mode 100644
index 000000000..d83537c47
--- /dev/null
+++ b/db/migrate/20190815225426_add_last_status_at_to_tags.rb
@@ -0,0 +1,6 @@
+class AddLastStatusAtToTags < ActiveRecord::Migration[5.2]
+  def change
+    add_column :tags, :last_status_at, :datetime
+    add_column :tags, :last_trend_at, :datetime
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index f8fc6a821..0da20d62f 100644
--- a/db/schema.rb
+++ b/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_08_07_135426) do
+ActiveRecord::Schema.define(version: 2019_08_15_225426) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -667,6 +667,8 @@ ActiveRecord::Schema.define(version: 2019_08_07_135426) do
     t.boolean "listable"
     t.datetime "reviewed_at"
     t.datetime "requested_review_at"
+    t.datetime "last_status_at"
+    t.datetime "last_trend_at"
     t.index "lower((name)::text)", name: "index_tags_on_name_lower", unique: true
   end