use gin for user search indexes

refs #CORE-1447

Change-Id: I92a2ca98b16aedec3a956d18287a82f0b6ccf1aa
Reviewed-on: https://gerrit.instructure.com/152192
Tested-by: Jenkins
Reviewed-by: Cody Cutrer <[email protected]>
Product-Review: James Williams  <[email protected]>
QA-Review: James Williams  <[email protected]>

db/migrate/20180601153421_replace_user_search_indexes_with_gin.rb

@@ -0,0 +1,49 @@
+#
+# Copyright (C) 2014 - present Instructure, Inc.
+#
+# This file is part of Canvas.
+#
+# Canvas is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Affero General Public License as published by the Free
+# Software Foundation, version 3 of the License.
+#
+# Canvas is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along
+# with this program. If not, see <http://www.gnu.org/licenses/>.
+
+class ReplaceUserSearchIndexesWithGin < ActiveRecord::Migration[5.1]
+  tag :postdeploy
+  disable_ddl_transaction!
+
+  def up
+    if (schema = connection.extension_installed?(:pg_trgm))
+      add_index :users, "lower(name) #{schema}.gin_trgm_ops", name: "index_gin_trgm_users_name", using: :gin, algorithm: :concurrently
+      add_index :pseudonyms, "lower(sis_user_id) #{schema}.gin_trgm_ops", name: "index_gin_trgm_pseudonyms_sis_user_id", using: :gin, algorithm: :concurrently
+      add_index :communication_channels, "lower(path) #{schema}.gin_trgm_ops", name: "index_gin_trgm_communication_channels_path", using: :gin, algorithm: :concurrently
+      add_index :pseudonyms, "lower(unique_id) #{schema}.gin_trgm_ops", name: "index_gin_trgm_pseudonyms_unique_id", using: :gin, algorithm: :concurrently
+
+      remove_index :users, name: "index_trgm_users_name"
+      remove_index :pseudonyms, name: "index_trgm_pseudonyms_sis_user_id"
+      remove_index :communication_channels, name: "index_trgm_communication_channels_path"
+      remove_index :pseudonyms, name: "index_trgm_pseudonyms_unique_id"
+    end
+  end
+
+  def down
+    if  (schema = connection.extension_installed?(:pg_trgm))
+      add_index :users, "lower(name) #{schema}.gist_trgm_ops", name: "index_trgm_users_name", using: :gist, algorithm: :concurrently
+      add_index :pseudonyms, "lower(sis_user_id) #{schema}.gist_trgm_ops", name: "index_trgm_pseudonyms_sis_user_id", using: :gist, algorithm: :concurrently
+      add_index :communication_channels, "lower(path) #{schema}.gist_trgm_ops", name: "index_trgm_communication_channels_path", using: :gist, algorithm: :concurrently
+      add_index :pseudonyms, "lower(unique_id) #{schema}.gist_trgm_ops", name: "index_trgm_pseudonyms_unique_id", using: :gist, algorithm: :concurrently
+
+      remove_index :users, name: "index_gin_trgm_users_name"
+      remove_index :pseudonyms, name: "index_gin_trgm_pseudonyms_sis_user_id"
+      remove_index :communication_channels, name: "index_gin_trgm_communication_channels_path"
+      remove_index :pseudonyms, name: "index_gin_trgm_pseudonyms_unique_id"
+    end
+  end
+end