Re: BitmapHeapScan streaming read user and prelim refactoring

On 4/6/24 23:34, Melanie Plageman wrote:
> ...
>>
>> I realized it makes more sense to add a FIXME (I used XXX. I'm not when
>> to use what) with a link to the message where Andres describes why he
>> thinks it is a bug. If we plan on fixing it, it is good to have a record
>> of that. And it makes it easier to put a clear and accurate comment.
>> Done in 0009.
>>
>>> OK, thanks. If think 0001-0008 are ready to go, with some minor tweaks
>>> per above (tuple vs. tuples etc.), and the question about the recheck
>>> flag. If you can do these tweaks, I'll get that committed today and we
>>> can try to get a couple more patches in tomorrow.
>
> Attached v19 rebases the rest of the commits from v17 over the first
> nine patches from v18. All patches 0001-0009 are unchanged from v18. I
> have made updates and done cleanup on 0010-0021.
>

I've pushed 0001-0005, I'll get back to this tomorrow and see how much
more we can get in for v17.

What bothers me on 0006-0008 is that the justification in the commit
messages is "future commit will do something". I think it's fine to have
a separate "prepareatory" patches (I really like how you structured the
patches this way), but it'd be good to have them right before that
"future" commit - I'd like not to have one in v17 and then the "future
commit" in v18, because that's annoying complication for backpatching,
(and probably also when implementing the AM?) etc.

AFAICS for v19, the "future commit" for all three patches (0006-0008) is
0012, which introduces the unified iterator. Is that correct?

Also, for 0008 I'm not sure we could even split it between v17 and v18,
because even if heapam did not use the iterator, what if some other AM
uses it? Without 0012 it'd be a problem for the AM, no?

Would it make sense to move 0009 before these three patches? That seems
like a meaningful change on it's own, right?

FWIW I don't think it's very likely I'll commit the UnifiedTBMIterator
stuff. I do agree with the idea in general, but I think I'd need more
time to think about the details. Sorry about that ...

regards

--
Tomas Vondra
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