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Re: pg_dump with compressible and non-compressible tables

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On 05/05/2018 12:41 PM, Ron wrote:
On 05/05/2018 12:13 PM, Adrian Klaver wrote:
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?

Very much so.  The ASCII hex representations of the PDF files are compressible, but take a *long* time to compress. Uncompressed backups are 50% faster.

Got it. The developers will need to comment on whether this is doable or not. The thing is that this would be a new feature. At this point version 11 is closed to new features, so you are looking at version 12 which means 1.5-2 years out. If it where me I would try piping a pg_dump plain text output to a compression program other then zlib(used in pg_dump compression) and see if you can get better performance.


These are different critters then bytea.

Ok.  I need the data in my backups anyway, so excluding them is 100% contrary to what I need.

I understand. What I was trying to say was that the blob you are referring to, bytea in a field, is not the same as what pg_dump is referring to, a large object stored in the pg_largeobject table:

https://www.postgresql.org/docs/10/static/lo-intro.html

So if you want to pursue this feature I think you need to come up with another name for it to avoid the confusion I mentioned above.


--
Angular momentum makes the world go 'round.


--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx




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