Re: pg_dump with compressible and non-compressible tables

On 05/05/2018 07:14 AM, Ron wrote:
> Hi,
>
> v9.6
>
> We've got big databases where some of the tables are highly
> compressible, but some have many bytea fields containing PDF files.

Can you see a demonstrable difference?

>
> When the data format is custom, directory or tar, how feasible would a
> "--no-blob-compression" option be (where pg_dump just tells the zlib
> library to just Store tables with bytea columns, while compressing all
> other tables at the specified -Z level)?

In pg_dump blob refers to large objects:

https://www.postgresql.org/docs/10/static/app-pgdump.html
"
-b
--blobs

Include large objects in the dump. This is the default behavior
except when --schema, --table, or --schema-only is specified. The -b
switch is therefore only useful to add large objects to dumps where a
specific schema or table has been requested. Note that blobs are
considered data and therefore will be included when --data-only is used,
but not when --schema-only is.
"

These are different critters then bytea.

>
> Thanks
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com