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Your strong statement about postgres doesn't sound right to me. You can't use an array values as foreign keys. Array column wouldn't be my first choice even it could do this: you're limited and constricted in usage overall for a little gain if any. Which imageboard/booru engines use array column for tags?

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Danbooru (and forks like Moebooru) and Philomena use string arrays in the database for tags.

Edit: nevermind, Philomena has a table for the many-to-many relationship and uses Elasticsearch for the heavy lifting.

Why arrays are preferable over m2m tables? What so special about pg arrays that makes anything but them inferior in "tagging" case? I genuinely don't get it.

Accodring to these rough benchmarks, it's faster to use arrays rather than joins:

https://shon.github.io/2015/12/21/postgres_array_performance...

https://gist.github.com/joevandyk/031cf5812bd656887623

To search for a post with multiple tags, you need to do a join for each tag. You don't have that problem with arrays.

Thanks, that looks cool.

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