Get all keys of jsonb object in postgresql table where value is true

Question

I have a postgresql table customers with name and features columns.

features contains jsonb objects like {"featureA": true, "featureB": false, "featureC":true}

What I'd like to get is an array of those keys in features where the value is true for each name, like:

name      | features
----------|---------------------
customerA | [featureA, featureC]
customerB | [featureB, featureC]

From this post, I learnt that

SELECT key
FROM jsonb_each()
WHERE value = jsonb 'true'

is how you get keys that are true, but how do I do that for my table customers?

Something like

SELECT array_agg(key)
FROM   jsonb_each((select features from customers))
WHERE  value = jsonb 'true'

returns SQL Error [21000]: ERROR: more than one row returned by a subquery used as an expression.

Any help would be appreciated.

Answer 1

You are describing a lateral join:

select c.name, x.keys
from customers c
cross join lateral (
    select array_agg(x.key) keys
    from jsonb_each(c.features) x
    where x.value = jsonb 'true'
) x