Re: Strange result using pg_dump gzip or split.

On 11/10/2014 03:34 AM, Condor wrote:
>
> Hello,
>
> I found strange result when I use pg_dump described on postgresql site:
> http://www.postgresql.org/docs/9.3/static/backup-dump.html
>
> I have a database with 30 gb data and decide to archive it, postgresql
> is 9.3.5 x64_86, ext4 file system, kernel 3.14.18 Slackware 14.2 (current)

How did you determine there is 30GB of data?

>
>
> First I use gzip with : pg_dump logdb | gzip > log.sql.gz
>
> After a few minute I have log.sql.gz with size 2 170 016 226
> Well, that is strange and I dump database again with:
>
> pg_dump logdb | split -b 1024m - log.sql
>
> 20 files is generated and I zip them with:
>
> zip -r log.sql.zip logdir (because I move them in logdir)
>
> file size is : 2 170 020 867
>
> Almost the same, but if I check size in archives there is a huge
> difference.

Any reason for not using pg_dump -Fc and get the built in compression?

>
>
> $ gzip -l log.sql.gz
> compressed uncompressed ratio uncompressed_name
> 2170016226 3060688725 29.1% log_to.sql
>
> and
>
>
> $ unzip -v log.sql.zip
> *** snip ***
> -------- ------- --- -------
> 20240557909 2170020867 89% 20 files
>
>
> Here is difference: with gzip I have 29.1% compress ratio and
> uncompressed size is 3 060 688 725 which means 3 GB
> and with zip I have 89% compress ratio and uncompressed size is 20 240
> 557 909 witch mean 20 GB. That is 7 times bigger.
>
> My question is: Is there some special config params that is not
> described in documentation here:
> http://www.postgresql.org/docs/9.3/static/backup-dump.html
> Or something need to be configured on my linux.
>
> And most important question for me is: Did the database dump is corrupt
> or not ?
>
>
>
> Regards,
>
> Hristo Simeonov
>
>

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