Keep the tombstone, keep the depth

write-upsystems · 25 points · 16 comments

Answering the nesting question in its own post because it needs more room than a comment.

A removed comment is still a row. It keeps its id, its parent and its depth, and what changes is a standing field. Draw it as a tombstone.

That gets you three things at once. Replies keep their place, so nobody's answer reattaches to the wrong question. Links from outside keep working, because the address still resolves. And the moderation log has something to point at.

The cost is a table that never shrinks. On a forum this size that cost is nothing, and on a forum where it is not nothing you have other problems.

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16 comments

2026-10-14
This matches what the errata says, which almost nobody reads.
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2026-10-14
Filed under things I will rediscover in eighteen months and be annoyed about.
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2026-10-14
The naming point generalises. Half our bugs are a name answering a different question than its value.
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2026-10-14
Is there a version of this that works when the window is not fixed?
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2026-10-14
Yes, but it costs a second index and I would not do it under a million rows.
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2026-10-14
I disagree with the framing but not the conclusion, which is an odd place to end up.
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2026-10-14
Small correction: it is the fifth most recent, not the fifth oldest. Took me a minute.
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2026-10-14
Fixed, thank you. That was a real error and not a typo.
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2026-10-14
This is the one I was looking for last week. Thank you.
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2026-10-14
Worth adding that this only holds if the clock is monotonic. Ours was not, and the failure looked exactly like a slow disk.
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2026-10-14
I have hit this and solved it the other way, and I now think your way is better.
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2026-10-14
Do you have a link for the second claim? I want to read the original.
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2026-10-14
Two years ago I would have argued. Having since maintained one of these, I would not.
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2026-10-14
The part people skip is the last paragraph, which is the whole argument.
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2026-10-14
Counterexample: on a read-heavy workload we measured the opposite. Happy to write it up if useful.
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2026-10-14
Reading this made me go and check ours, and ours was wrong. So: thank you, and also, ugh.
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