Precompressed data in TOASTed columns (was Re: Regarding postgreSQL performance on DRAM)

On 2/20/19 3:04 PM, Tom Lane wrote:
[snip]
> Well, the entire tuple would be 25600 bytes plus some overhead, which
> cannot fit on a Postgres page (8K, unless the OP changed compile options
> without mentioning it). So something has to be done to make it fit, and
> that something is going to be toasting any fields that can be toasted.
>
> From memory, our threshold for trying to make tuples narrower is only
> a quarter-page anyway, so that the toaster will be trying to get this
> down to 2K if it can. That's certainly going to involve compressing
> every field, and I wouldn't be surprised if a lot of them get shoved
> out-of-line too.
>
> The OP might care to read
>
> https://www.postgresql.org/docs/current/storage-toast.html

Based on that and https://www.postgresql.org/docs/9.6/sql-altertable.html
should I think about doing a SET STORAGE=EXTERNAL on columns with PDF and
compressed TIFF data?

Thanks

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