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.klaver@aklaver.com