Removed unused fields from ChannelMemberHistory table, introduced new model.ChannelMemberHistoryResult object that includes those fields that are selected from a join on other tables

store/sqlstore/upgrade.go

@@ -346,6 +346,8 @@ func UpgradeDatabaseToVersion47(sqlStore SqlStore) {
 	if shouldPerformUpgrade(sqlStore, VERSION_4_6_0, VERSION_4_7_0) {
 		sqlStore.AlterColumnTypeIfExists("Users", "Position", "varchar(128)", "varchar(128)")
 		sqlStore.AlterColumnTypeIfExists("OAuthAuthData", "State", "varchar(1024)", "varchar(1024)")
+		sqlStore.RemoveColumnIfExists("ChannelMemberHistory", "Email")
+		sqlStore.RemoveColumnIfExists("ChannelMemberHistory", "Username")
 		saveSchemaVersion(sqlStore, VERSION_4_7_0)
 	}
 }