GAE datastore design to store "like" mechanism for user's status (like Facebook's "likes")

Question

I'm using Google App Engine's datastore and looking for a design solution for "like" functionality for user's status (similair to Facebook "likes")

I've gone through the Sharding Counters concepts (https://developers.google.com/appengine/articles/sharding_counters) and found its good and suitable for counting number of likes where you can increment or decrement the count. But I want to store the userId who liked the status. So I tried the same sharding concepts to store userIds but facing the below issues, * First of all is it good to shard userId list like count? * If so when the user dislike it, I have remove the user id from shared list. To achieve this I need to traverse all the sharded datastore and do a userId check and remove

Any suggestions on this or alternative solutions to achieve it?

score 0 · Accepted Answer · answered Oct 11 '13 at 14:20

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Sharding doesnt apply for that case. Sharding is to avoid many writes to the same object in short time periods. Makes sense for a 'likes' counter since many people like the same post. Not the same when sgoring who liked what. Those objects only change per-user, many users dont share the same object. Just store those in a non sharded table like you would in sql.

answered Oct 11 '13 at 14:20

Zig Mandel

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Ok. So we need another table with the structure like "user id"-"post id". But how can we effectively count post likes and how to get posts ordered by likes? – Ruslan Yanchyshyn Oct 30 '13 at 15:20
For large data you will need something based or similar to mapreduce – Zig Mandel Oct 30 '13 at 18:41

GAE datastore design to store "like" mechanism for user's status (like Facebook's "likes")

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