Add Purpose as a searchable field (#8067)

* Add Purpose as a searchable field

* Add New Index and Remove old for Channels

* Include Purpose in FullTextSearch Clause

* Move removeIndex for Channels into upgrade.go

store/sqlstore/channel_store.go

@@ -298,7 +298,7 @@ func (s SqlChannelStore) CreateIndexesIfNotExists() {
 	s.CreateIndexIfNotExists("idx_channelmembers_channel_id", "ChannelMembers", "ChannelId")
 	s.CreateIndexIfNotExists("idx_channelmembers_user_id", "ChannelMembers", "UserId")
 
-	s.CreateFullTextIndexIfNotExists("idx_channels_txt", "Channels", "Name, DisplayName")
+	s.CreateFullTextIndexIfNotExists("idx_channel_search_txt", "Channels", "Name, DisplayName, Purpose")
 }
 
 func (s SqlChannelStore) Save(channel *model.Channel, maxChannelsPerTeam int64) store.StoreChannel {
@@ -1573,7 +1573,7 @@ func (s SqlChannelStore) SearchMore(userId string, teamId string, term string) s
 
 func (s SqlChannelStore) buildLIKEClause(term string) (likeClause, likeTerm string) {
 	likeTerm = term
-	searchColumns := "Name, DisplayName"
+	searchColumns := "Name, DisplayName, Purpose"
 
 	// These chars must be removed from the like query.
 	for _, c := range ignoreLikeSearchChar {
@@ -1608,7 +1608,7 @@ func (s SqlChannelStore) buildFulltextClause(term string) (fulltextClause, fullt
 	// Copy the terms as we will need to prepare them differently for each search type.
 	fulltextTerm = term
 
-	searchColumns := "Name, DisplayName"
+	searchColumns := "Name, DisplayName, Purpose"
 
 	// These chars must be treated as spaces in the fulltext query.
 	for _, c := range spaceFulltextSearchChar {

store/sqlstore/upgrade.go

@@ -446,6 +446,8 @@ func UpgradeDatabaseToVersion50(sqlStore SqlStore) {
 		sqlStore.GetMaster().Exec("UPDATE Roles SET SchemeManaged=false WHERE Name NOT IN ('system_user', 'system_admin', 'team_user', 'team_admin', 'channel_user', 'channel_admin')")
 		sqlStore.CreateColumnIfNotExists("IncomingWebhooks", "ChannelLocked", "boolean", "boolean", "0")
 
+		sqlStore.RemoveIndexIfExists("idx_channels_txt", "Channels")
+
 		saveSchemaVersion(sqlStore, VERSION_5_0_0)
 	}
 }