Postgres compression of jsonb

Postgres supports JSON data since loong time ago, but until jsonb (9.4) all solutions were somewhat limited in features.  Jsonb gives you most of what a document storage engine would give you, but...  what about performance? and space efficiency? Unfortunately I don't have real answers to those questions, but I've started doing some research, and for now, here's a nice takeaway:

First of all you should be aware of "\dt+", which gives us the size of a table and "\d+" which describes a table. The "+" suffix adds more info to the descriptions.

CREATE TABLE foo AS SELECT '{"f":true}'::jsonb FROM generate_series(1,1e6);

CREATE TABLE bar AS SELECT '{"f":true}'::text FROM generate_series(1,1e6);

\dt+ foo;

\dt+ bar;  

We see that the text field takes about half of the size of the jsonb. So if you don't need json features in a field (you're only archiving data that happens to be json), think twice when giving it the jsonb type.


Jsonb is TOAST-able, but will probably be toasted  (and compressed) when it's bigger than a page, so don't count on that if you're jsons are <4kb .="" p="">
References:

• https://dba.stackexchange.com/questions/161864/do-long-names-for-jsonb-keys-use-more-storage
• https://stackoverflow.com/questions/23120072/how-to-check-if-toast-is-working-on-a-particular-table-in-postgres
• https://postgrespro.com/list/thread-id/1849114

So, don't think spacewise it comes for free. If you're concerned about space, there's a big impact on the size of the table.