将列从 integer[] 更新为 jsonb[]

Question

First off, for this I'm using Elixir (Ecto) but I think I'll be better off running a raw SQL statement on the migration.

I have a column which is an array of integers; due to requirement changes I need to convert this array of integers to an array of objects, jsonb[] in this case. This isn't looking quite right for me since converting from integer[] to jsonb[] is not possible (At least not automatically)

I've been trying to cast both types but its just not resulting; I've even tried to convert to string then to jsonb but that doesn't seem to work.

Now I'm looking for the best way to do this, not the simplest, just the best or correct way to do this. I was thinking about creating a temp column, copying the values from the old column there and renaming maybe? What would be the correct SQL statement for this?

By the way, I'm getting hit by this hint too hint: You might need to specify "USING table_name::jsonb[]" but using USING column_name::jsonb[] does not do the trick, neither CAST (column_name as jsonb) .

If it was as simple as I thought it would work with ALTER TABLE table_name ALTER COLUMN column_name TYPE jsonb[] USING column_name::jsonb[] . Let me know if I've not provided enough information, thanks.

Answer 1

One option is to use array_to_json() and then cast to jsonb or just to_jsonb() :

select x.*, array_to_json(ari)::jsonb,
       to_jsonb(ari)
from (select array[1, 2, 3] as ari) x;

If you want to change the type in place, use alter table :

alter table t alter column ari type jsonb using to_jsonb(ari);

Here is a db<>fiddle.

Answer 2

The below construct will work to get you a JSONB[] from INT[]. But technically what you get is not an array of JSON objects (which refers specifically to the hash-table like thingies), it just an array of JSON thingies which each contain a scalar with the JSON type of "number". If that isn't what you want, you will have to describe what you want.

ALTER TABLE table_name ALTER COLUMN column_name TYPE jsonb[] USING column_name::text::jsonb[]