To: pgsql-sql@postgresql.org
From: Jasen Betts <jasen@xnet.co.nz>
Subject: Re: Understanding Binary Data Type
Date: 24 May 2012 06:09:32 GMT
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On 2012-05-22, Carlos Mennens <carlos.mennens@gmail.com> wrote:
> Hello everyone! I wanted to ask the list a question about the 'bytea'
> data type & how I can picture this in my head. I've been reading SQL
> for about a few months now and since then, I've only been working with
> textual data. Basically I'm familiar with storing text and numerical
> characters into tables but my friend told me that databases can hold
> much more than just ASCI text. In so I've read up on some pages that
> describe the bytea data type:
>
> http://en.wikipedia.org/wiki/Binary_large_object
>
> http://www.postgresql.org/docs/9.1/static/datatype-binary.html
>
> So my question is can and in fact does PostgreSQL and most other RDBMS
> have the ability to store large binary files like photos, music, etc
> etc into an actual table? I'm guessing the data is dumped into the
> table but rather linked or parsed through the file system store path
> into the database itself, right? I would just like to know in a basic
> round about way how databases store and handle large files like .jpg
> or .png files & regardless how relative this term is, how common is it
> to use these files or 'bytea' data in tables?
>
> Thanks for any info!

postgres has a maximum logical row size just under 2GiB so there's plenty of
room there for photos etc (DVD images might not fit).  

postgres uses a strategy called TOAST to move "wide" values out of the
file that holds the main table.

implementation detals:
  http://www.postgresql.org/docs/9.1/static/storage-toast.html

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