A bit ago I wrote a blog post that was supposed to show how to keep number of rows in table to N per some category.
Unfortunately, I overlooked a problem related to concurrency.
Continue reading How to limit rows to at most N per category – fix
Tag: n-rows
How to limit rows to at most N per category
The question was asked relatively recently on irc. And it proved to be non-trivial.
Surely, if you want to have one row per category (one address per user), it's trivial – add user_id column to addresses, make it unique, and we're done. But what if we want to allow five addresses? Or five thousands?
Let's see.
Continue reading How to limit rows to at most N per category