Re: WIP: Avoid creation of the free space map for small tables

On Wed, Jan 30, 2019 at 2:11 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> This is much better than the earlier version of test and there is no
> dependency on the vacuum.  However, I feel still there is some
> dependency on how the rows will fit in a page and we have seen some
> related failures due to alignment stuff.  By looking at the test, I
> can't envision any such problem, but how about if we just write some
> simple tests where we can check that the FSM won't be created for very
> small number of records say one or two and then when we increase the
> records FSM gets created, here if we want, we can even use vacuum to
> ensure FSM gets created.  Once we are sure that the main patch passes
> all the buildfarm tests, we can extend the test to something advanced
> as you are proposing now.  I think that will reduce the chances of
> failure, what do you think?

That's probably a good idea to limit risk. I just very basic tests
now, and vacuum before every relation size check to make sure any FSM
extension (whether desired or not) is invoked. Also, in my last patch
I forgot to implement explicit checks of the block number instead of
assuming how many rows will fit on a page. I've used a plpgsql code
block to do this.

-- 
John Naylor                https://www.2ndQuadrant.com/
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