

Ask HN: Efficiently store per-item unread count? - porker

Over at Newsblur there&#x27;s mild uproar about items automatically being marked read after 14 days (https:&#x2F;&#x2F;getsatisfaction.com&#x2F;newsblur&#x2F;topics&#x2F;do_unread_items_sunset_after_14_days). Google Reader used to mark items read after 30 days, so I&#x27;m guessing it&#x27;s a hard&#x2F;unsolved problem to store this data for a long time.<p>Has it been solved, and what&#x27;s the most space-efficient way to store the per-item unread state for all users? In my mind it forms a sparse matrix, but then you&#x27;d want to group people&#x27;s storage of unread status together (so you get some data compression) - until one person marks an item as read, and then you have to extract them from the compressed data set...<p>I have no practical experience but this intrigues me, and real world stories would be great!
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benologist
It might be easier to store references to what you have read and if you 'mark
all as read' you can remove the individual references below [date].

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porker
I like your thinking :)

Over time this could potentially grow, but given your 'remove below date' (and
I guess many people's behaviour of marking all read after a while) this sounds
good.

