Ask HN: How can a HN comment parent id be higher than it's id?

2 pointsyehosef5 comments

I'm doing some looking into HN data and I notice times where the parent field is higher than the comment id. Assuming this is a simple autoincrement id, the comment id should always be higher.

Any ideas how this happens? is this from merging stories? something else?

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Sometimes the mods merge the comments of a story and a close repost. For example: https://news.ycombinator.com/item?id=15137168

I'm not sure if that cover all your cases.

Could be - but I see examples without [dupe] in the title. But that's probably it.

Its interesting because I see plenty of times where they don't do this..

It's a manual decision [I guess they have a magical button to do the merge.] so sometimes they don't find out abbot the dupe or they may decide no to merge them, so it's quite random and arbitrary, but it looks very difficult to automate.

Parent is updated, perhaps?

I hope not - usually updates don't require a new primary id.

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