Re: Freeze avoidance of very large table.

On 7 July 2015 at 15:18, Sawada Masahiko <sawada(dot)mshk(at)gmail(dot)com> wrote:

> > I would also like to see the visibilitymap_test function exposed in SQL,
> > so we can write code to examine the map contents for particular ctids.
> > By doing that we can then write a formal test that shows the evolution
> of tuples from insertion,
> > vacuuming and freezing, testing the map has been set correctly at each
> stage.
> > I guess that needs to be done as an isolationtest so we have an observer
> that contrains the xmin in various ways.
> > In light of multixact bugs, any code that changes the on-disk tuple
> metadata needs formal tests.
>
> Attached patch adds a few function to contrib/pg_freespacemap to
> explore the inside of visibility map, which I used for my test.
> I hope it helps for testing this feature.
>

I don't think pg_freespacemap is the right place.

I'd prefer to add that as a single function into core, so we can write
formal tests. I would not personally commit this feature without rigorous
and easily repeatable verification.

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