I need to access feed items based on Topic. As in salesforce chatter we post feed, with that we can add #Topic to the feed. There is a field called "ParentId" on Feeditem which is reference to many objects including "Topic" object. But if I am querying as follows I am not getting any result.
SELECT TYPEOF Parent WHEN Topic THEN Id,Name ELSE Name,Id END FROM FeedItem where ParentId = '0TO90000000TzS9GAK'
instead of there is a feed item with Topic(Id = 0TO90000000TzS9GAK).