Обсуждение: Performance

Hello all!

I need to setup high performance DB server. Some time ago I red
there about processor cache influence on query execution
performance.
A question:
What system would perform better?
lh6000 with two xeon 7000Mhz 2MB cache
or
with four xeon 7000Mhz 1MB cache

Mark

On Friday, January 18, 2002, at 02:00 AM, Martins Zarins wrote:

> Hello all!
>
> I need to setup high performance DB server. Some time ago I red
> there about processor cache influence on query execution
> performance.
> A question:
> What system would perform better?
> lh6000 with two xeon 7000Mhz 2MB cache
> or
> with four xeon 7000Mhz 1MB cache

It's more than just processor cache, it's your whole I/O subsystem.
How fast are your drives?  How fast is the drive controller?  How much
cache is on each drive?  How much cache is on the drive controller?
Are you going to use a RAID?  If so, what type?  Do you have enough
memory for the size of the database and type of queries you're going to
run?

As far as processor cache goes, your goal is to avoid cache misses...so
it
depends on how many connections you're expecting, what those connections
will be doing, etc.  The best advice is to run your own benchmarks and
find
out for yourself.

--Jeremy

On 18 Jan 2002, at 9:22, Jeremy Buchmann wrote:
>
> It's more than just processor cache, it's your whole I/O subsystem.
> How fast are your drives?  How fast is the drive controller?  How much
> cache is on each drive?  How much cache is on the drive controller?
> Are you going to use a RAID?  If so, what type?  Do you have enough
> memory for the size of the database and type of queries you're going
> to run?
Is there any good doc about this on net?
(About disc cache, raid cache processor cache and queries - how
they influence each other?)

Mark

See techdocs performance article:

    http://techdocs.postgresql.org

Martins Zarins wrote:
> On 18 Jan 2002, at 9:22, Jeremy Buchmann wrote:
> >
> > It's more than just processor cache, it's your whole I/O subsystem.
> > How fast are your drives?  How fast is the drive controller?  How much
> > cache is on each drive?  How much cache is on the drive controller?
> > Are you going to use a RAID?  If so, what type?  Do you have enough
> > memory for the size of the database and type of queries you're going
> > to run?
> Is there any good doc about this on net?
> (About disc cache, raid cache processor cache and queries - how
> they influence each other?)
>
> Mark
>
>
>
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 Hai every body,

I want to know how the--where condition--is executed in a sql query.

e.g., select aa,bb,cc from ttt where aa=100 and bb = 200 and cc =300.

my doubt is , will psql leave the record as on when it fails to satisfy a record having aa !=100 

or will it chect for bb = 200 and cc = 300 also.

ie will it work like C-language if condition or not.

If i give paranthesis, will it change the execution plan accordingly.

Thanks in advance.

c u

raja

raja kumar thatte <trajakumar@yahoo.com> writes:
> I want to know how the--where condition--is executed in a sql query.
> e.g., select aa,bb,cc from ttt where aa=100 and bb = 200 and cc =300.
> my doubt is , will psql leave the record as on when it fails to satisfy a record having aa !=100
> or will it chect for bb = 200 and cc = 300 also.
> ie will it work like C-language if condition or not.
> If i give paranthesis, will it change the execution plan accordingly.

The planner will make its own decisions about which query plan to
follow; it's quite impervious to parentheses, clause order, or any
other semantically-insignificant details in the WHERE clause.

You may care to read the chapter on performance tips in the User's
Guide.

            regards, tom lane