pg_toast oid limits

Hi all,

I am seeing some performance issues that I'm trying to track down on a large database. One of the things I'm beginning
tosuspect is a particularly large table with many columns, about 200 of which (type text) contain large chunks of data.
Now,for a given row, maybe 10-30 of those columns contain data, so not all 200 for each row, but the data can still be
prettysizable. There are currently around 750 million records in this table (and is about 22TB in size). I was trying
tolearn more about toast, and I see some references in the wiki and the hackers list to performance issues when you
approachthe 4 billion oids for a single table (which, I gather, are used when the data is toasted). Given my
rudimentaryunderstanding of how the whole toast thing works, I was wondering if there is a way to see how many oids are
usedfor a table, or another way to know if we're running into toast limits for a single table. 

What I was reading, for reference:
https://wiki.postgresql.org/wiki/TOAST
http://osdir.com/ml/postgresql-pgsql-hackers/2015-01/msg01901.html

Also, we are running postgres 9.5.4.

Many thanks!
Natalie