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Compressed Columns

5 posts in General Discussion (old) Last posting was on 2008-08-14 06:29:42.0Z
Markus KARG Posted on 2008-08-13 10:32:02.0Z
From: "Markus KARG" <karg@quipsy.de>
Newsgroups: sybase.public.sqlanywhere
Subject: Compressed Columns
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I have seen that SQL Anywhere can use "compressed columns" to save space.
I do not have any space problems, but I want to optimize the performance of
SELECTs.
Is compressing columns beneficial or harmful to performance of SELECTs?


Jeff Albion (Sybase iAnywhere) Posted on 2008-08-13 15:50:31.0Z
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Definitely harmful. We will have to uncompress the columns every time we
read the data (thus using up CPU time), then recompress them when
storing them again.

See:
http://www.ianywhere.com/developer/product_manuals/sqlanywhere/1001/en/html/dbugen10/ug-design-s-5092374.html

Regards,

Markus KARG wrote:
> I have seen that SQL Anywhere can use "compressed columns" to save space.
> I do not have any space problems, but I want to optimize the performance of
> SELECTs.
> Is compressing columns beneficial or harmful to performance of SELECTs?

--
Jeff Albion, Product Support Analyst
Sybase iAnywhere

iAnywhere Developer Community :
http://www.sybase.com/developer/library/sql-anywhere-techcorner
iAnywhere Documentation : http://www.ianywhere.com/developer/product_manuals
SQL Anywhere Patches and EBFs :
http://downloads.sybase.com/swd/summary.do?baseprod=144&client=ianywhere&timeframe=0


"Frank Ploessel" <fpl... Posted on 2008-08-13 17:02:32.0Z
Subject: Re: Compressed Columns
From: "Frank Ploessel" <fpl...@d_e.i_m_s_h_e_a_l_t_h.c_o_m>
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Jeff,

So you assume the CPU will take more time to uncompress than you save in
I/O time?

Frank

On Wed, 13 Aug 2008 17:50:31 +0200, Jeff Albion (Sybase iAnywhere)

<firstname.lastname@ianywhere.com> wrote:

> Definitely harmful. We will have to uncompress the columns every time we
> read the data (thus using up CPU time), then recompress them when
> storing them again.
>
> See:
> http://www.ianywhere.com/developer/product_manuals/sqlanywhere/1001/en/html/dbugen10/ug-design-s-5092374.html
>
> Regards,
>
> Markus KARG wrote:
>> I have seen that SQL Anywhere can use "compressed columns" to save
>> space.
>> I do not have any space problems, but I want to optimize the
>> performance of SELECTs.
>> Is compressing columns beneficial or harmful to performance of SELECTs?
>


Jeff Albion (Sybase iAnywhere) Posted on 2008-08-13 18:03:12.0Z
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Frank,

I suppose I am assuming that, yes. :)

---

Actually, it really depends on the available resources and what else is
happening on the server. If you're working with a large database cache
and lots of database pages are in memory, then yes, many queries will be
CPU-bound, and having compressed columns will result in a performance
penalty when retrieving them from disk on the select due to the
competition for that time.

If the database had a small cache however and was mostly I/O-bound in
its operation, I could see where performing less I/O at a cost of more
CPU might be beneficial.

A well-designed performance test would be the best way to figure out if
such a setting actually improved the performance for your specific
application.

---

I'll have to revise my original statement upon more reflection: "it
depends!"

Cheers,

Frank Ploessel wrote:
> Jeff,
>
> So you assume the CPU will take more time to uncompress than you save in
> I/O time?
>
> Frank

--
Jeff Albion, Product Support Analyst
Sybase iAnywhere

iAnywhere Developer Community :
http://www.sybase.com/developer/library/sql-anywhere-techcorner
iAnywhere Documentation : http://www.ianywhere.com/developer/product_manuals
SQL Anywhere Patches and EBFs :
http://downloads.sybase.com/swd/summary.do?baseprod=144&client=ianywhere&timeframe=0


Markus KARG Posted on 2008-08-14 06:29:42.0Z
From: "Markus KARG" <karg@quipsy.de>
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Article PK: 866564

Thanks, Jeff and Frank, for this interesting insights!

Markus

"Markus KARG" <karg@quipsy.de> schrieb im Newsbeitrag
news:48a2b822@forums-1-dub...

>I have seen that SQL Anywhere can use "compressed columns" to save space.
> I do not have any space problems, but I want to optimize the performance
> of SELECTs.
> Is compressing columns beneficial or harmful to performance of SELECTs?
>