Re: snapshot too old issues, first around wraparound and then more.

Hi,

On 2021-06-15 21:59:45 -0700, Noah Misch wrote:
> Hackers are rather wise, but the variety of PostgreSQL use is enormous. We
> see that, among other ways, when regression fixes spike in each vN.1. The
> $SUBJECT feature was born in response to a user experience; a lack of hacker
> interest doesn't invalidate that user experience. We face these competing
> interests, at least:
>
> 1) Some users want the feature kept so their application can use a certain
> pattern of long-running, snapshot-bearing transactions.

This is obviously true. However, given that the feature practically did
not work at all before 55b7e2f4d78d8aa7b4a5eae9a0a810601d03c563 and
still cannot really be described to work (e..g index scans returning
wrong query results), and there have been two complaints about it as far
as I know leads me to believe that it does not have a great many
features.

> 2) (a) Some hackers want the feature gone so they can implement changes
> without making those changes cooperate with this feature. (b) Bugs in this
> feature make such cooperation materially harder.

I think the a) part is a large problem. Primarily because it's so
unclear what one exactly has to do where (no docs/comments explaining
that) and because there's no usable test framework.

Greetings,

Andres Freund