How to ensure only a single row with a certain value

All we need is an easy explanation of the problem, so here it is.

Given this table:

    id           UUID        PRIMARY KEY DEFAULT gen_random_uuid(),
    device_id    TEXT        NOT NULL,

How can I ensure that for a given device_id, there is only ever one active rollout? Multiple inactive ones are fine, so a simple unique index doesn’t cut it.

How to solve :

I know you bored from this bug, So we are here to help you! Take a deep breath and look at the explanation of your problem. We have many solutions to this problem, But we recommend you to use the first method because it is tested & true method that will 100% work for you.

Method 1

You can use a partial unique index:

create unique index on rollouts (device_id) 
where is_active;

Note: Use and implement method 1 because this method fully tested our system.
Thank you 🙂

All methods was sourced from or, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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