[development] Is "SELECT * FROM ..." ok?

Chris Johnson cxjohnson at gmail.com
Fri Feb 13 18:16:44 UTC 2009

I'm with Morbus on the clarity argument.

And I also argue for better performance.

It's not just the extra time the server needs to find the column
names, but all of the extra data being buffered and sent over the
wire.  On large sites with load-balanced web server front ends, and
mirrored or slaved database servers on the backend, operations people
are usually trying to squeeze out every inch of performance possible
from the site/database combined performance.  Even though it may add
only a millisecond per operation, when there are millions of
operations being done, it quickly adds up.

I'm well aware of the arguments against premature optimization, but
given the arguments which Morbus presented, there's very little reason
to not avoid "SELECT * " except when absolutely needed.


On Fri, Feb 13, 2009 at 9:15 AM, Morbus Iff <morbus at disobey.com> wrote:
> I give *little* regard for performance (in this case), and everything for my
> *expectations* and *documentation*. I could care less if it's faster or not.
> I care more about clarity.
> David Metzler wrote:
>> Although there are merits in this argument, I wouldn't classify it as  a
>> bug.  There's a lot of generic/abstracted data loading, and as long  as
>> there's code at there that dynamically adds columns, select *  actually is
>> the sanest way to do things.
>> Also, the performance costs are database dependent. Mysql may work  one
>> way, but other db's work another.   Any DB with precompiled  cached queries
>> is not going to carry significant parsing overhead.   The amount of data
>> transfered in most cases is dependent on the size  of the data in the column
>> and not the number of columns.  So in some  tables it may make sense.  You
>> might get the name of the image file  in drupal, but you're not likely to
>> get the image.
>> Finally in my experience, most database performance problems lie in  what
>> is in the WHERE or JOIN, and not what's in the column list.
> --
> Morbus Iff ( masochism-oriented recombinant bot (unlisted series) )
> Technical: http://www.oreillynet.com/pub/au/779
> Enjoy: http://www.disobey.com/ and http://www.videounderbelly.com/
> aim: akaMorbus / skype: morbusiff / icq: 2927491 / jabber.org: morbus

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