How to get only the jsonb of specific keys from postgres?

Question

I\'m aware that you can remove keys from a jsonb in postgres using something like this

select \'{\"a\": 1, \"b\": 2, \"c\":3}\'::jsonb -\'a\';
 ?column?
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Answer 1

If you want to filter multiple rows with JSONB documents in each of them:

-- Let's generate rows with JSONB column:
WITH s AS (SELECT generate_series(1, 100) num),
g AS (SELECT num, jsonb_build_object('a', s.num, 'b', s.num * 2) obj FROM s),

-- A "filter" adding (in my example only keys of "filter" document remain in result rows)
j AS (SELECT '{"a": "int", "c": "string"}'::jsonb AS filter),
a AS (SELECT (ARRAY(SELECT jsonb_object_keys(filter))) AS ar FROM j),

-- Useless keys removing
o AS (SELECT jsonb_object_agg(l.key, l.value) obj
        FROM g, LATERAL jsonb_each(g.obj) l, a 
        WHERE l.key = ANY(a.ar)
        GROUP BY num)

SELECT * FROM o ORDER BY obj->'a';