Re: Increased storage size of jsonb in pg15

Follow-up:
Working with AWS, we found that starting in RDS Postgres 15, the
default_toast_compression parameter is set to use lz4 compression instead
of pglz. This resulted in the increased json storage size we were seeing.

I have been able to reproduce the increased storage size on RDS Postgres
and using my local docker instance of postgres 15.5 by changing the local
default_toast_compression value in postgresql.conf.

I have attached the test script we use to create a table, insert some test
records and a query to test the JSON data size on disk.

Kind regards,
Sean

On Fri, Dec 15, 2023 at 1:56 PM Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>
wrote:

> On 12/15/23 12:43, Sean Flaherty wrote:
> > We did a little more digging on our side, which I apologize for not
> > doing beforehand.
> >
> > We wrote a script to create a simple table with a jsonb column, inserted
> > some json data into the column and then used *pg_column_size* to test
> > the size of the jsonb data column.
> >
> > We ran the script against local docker versions of postgres 14.8 and
> > 15.5 and saw that the data in the jsonb column was the same size.
> >
> > We then ran the script on AWS RDS Postgres and saw a size difference for
> > the same json data between versions 14.8 and 15.4 (we also saw the
> > larger size on RDS postgres 15.5 and 16.1).
>
> This points at RDS Postgres being the issue. Since that is behind the
> AWS curtain, you will need to contact AWS technical support for
> information on what changed.
>
> >
> > *Version* *size (kb)* *notes *
> > RDS Postgres-14.8 1587 (the same size we were seeing
> locally)
> > RDS Postgres-15.4 2112
> >
> >
> > Thank you for your prompt responses and assistance.
> >
> > If you are curious, I can share the script we used with you.
> >
> >
> > Kind regards,
> > Sean
>
>
> --
> Adrian Klaver
> adrian(dot)klaver(at)aklaver(dot)com
>
>