HN Explorer

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

2 points by yehosef ↗ HN
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?

5 comments

[ 3.4 ms ] story [ 14.4 ms ] thread
angersock
Parent is updated, perhaps?
yehosef
I hope not - usually updates don't require a new primary id.
gus_massa
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.

yehosef
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..

gus_massa
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.