On 06/04/2015 12:17 PM, Andres Freund wrote:
> On 2015-06-04 11:51:44 +0300, Heikki Linnakangas wrote:
>> So, I'm all for refactoring and adding abstractions where it makes sense,
>> but it's not going to solve design problems.
>
> I personally don't really see the multixact changes being that bad on
> the overall design. It pretty much just extended an earlier design. Now
> that wasn't great, but I don't think too many people had realized that
> at that point. The biggest problem was underestimating the complexity.
Yeah, many of the issues were pre-existing, and would've been good to
fix anyway.
The multixact issues remind me of the another similar thing we did: the
visibility map. It too was non-critical when it was first introduced,
but later we started using it for index-only-scans, and it suddenly
became important that it's up-to-date and crash-safe. We did uncover
some bugs in that area when index-only-scans were introduced, similar to
the multixact bugs, only not as bad because it didn't lead to data loss.
I don't have any point to make with that comparison, but it was similar
in many ways.
- Heikki
