Re: unexpected result for wastedbytes query after vacuum full

On Fri, Dec 06, 2019 at 05:18:20PM +0000, Mike Schanne wrote:
> Hi all,
> 
> This question is somewhat related to my previous question:
> https://www.postgresql.org/message-id/0871fcf35ceb4caa8a2204ca9c38e330%40USEPRDEX1.corp.kns.com
> 
> I was attempting to measure the benefit of doing a VACUUM FULL on my database.  I was using the query found here:
> https://wiki.postgresql.org/wiki/Show_database_bloat
> 
> However, I got an unexpected result in that the "wastedbytes" value actually increased for some tables after doing the vacuum.

> I was wondering if the fact that we use a json column could be interfering with the wastedbytes calculation.  Can anyone explain how wastedbytes could increase from a vacuum?

Is it due to dropped columns, like Tom explained here ?
https://www.postgresql.org/message-id/18375.1520723971%40sss.pgh.pa.us