Re: JSONB index not in use, but is TOAST the real cause of slow query?

 

Turn on track_io_timing, and then do explain (analyse, buffers).  This won't distinguish TOAST from main table IO, but will at least confirm if a large amount of IO is happening and how long it is taking.  

You can look at pg_statio_user_tables before the after the query to distinguish TOAST, but this won't give you the timing, just the block counts.  And the counts might also get incremented by concurrent users, so on a busy system it is hard to interpret.