Faster Indexes using order by statement

Hello all,
I have a specific sql statement and I am looking to return the result
set a lot faster. Currently the setup is like so:
myTable schema:
Counterdecimal9 (pk)
Machinevarchar60
LogEntryvarchar1000
Activevarchar50
SysInfovarchar255
Idlevarchar50
IPvarchar15
KioskDatedatetime
KioskTimedatetime
ServerDatedatetime
ServerTimedatetime
Applicationvarchar15
WebDomainvarchar50
NSCodevarchar10
There is a Clustered index on Counter and two Non-clustered:
1) Counter & ServerDate - unique values, fill factor 90% on PRIMARY
2) Counter, Machine, NSCode, KioskDate, KioskTime - - unique values,
fill factor 90% on PRIMARY
sql statment:
select top 1000 machine, logentry,
convert(varchar(8),kioskdate,5) as Kiosk_date,
convert(varchar(8),kiosktime,8) as Kiosk_time,
convert(varchar(8),serverdate,5) as ServerDate,
convert(varchar(8),serverdate,8) as ServerTime,
application,
nscode,
webdomain
from myTable
where machine = 'machinename'
order by kioskdate desc, kiosktime desc
Currently the table holds over 18 million records and the above search
returns in under 3 seconds, however when I change the order by
statement to ServerDate desc only (which is what I need), it takes
over four minutes. I have tried altering/tweaking the indexes, but
have had no success.
Any ideas greatly appreciated.
Thanks
Scott
The only index that would be useful for that query is
Counter, Machine, NSCode, KioskDate, KioskTime
And that only for a scan as Counter is the first field.
How unique is machinename - if it's good then put an index on that.
Not sure how the optimiser would handle it but try an index
machinename, kioskdate desc, kiosktime desc
This will be in the oerder of the required resultset and the server could
take the top thousand entries for the machinename without any other
processing. Doubt if it will do that but it's worth a try.
You might be able to give it hint by finding the range of dates required and
using that.
"scott" wrote:

> Hello all,
> I have a specific sql statement and I am looking to return the result
> set a lot faster. Currently the setup is like so:
> myTable schema:
>
> Counterdecimal9 (pk)
> Machinevarchar60
> LogEntryvarchar1000
> Activevarchar50
> SysInfovarchar255
> Idlevarchar50
> IPvarchar15
> KioskDatedatetime
> KioskTimedatetime
> ServerDatedatetime
> ServerTimedatetime
> Applicationvarchar15
> WebDomainvarchar50
> NSCodevarchar10
> There is a Clustered index on Counter and two Non-clustered:
> 1) Counter & ServerDate - unique values, fill factor 90% on PRIMARY
> 2) Counter, Machine, NSCode, KioskDate, KioskTime - - unique values,
> fill factor 90% on PRIMARY
>
> sql statment:
> select top 1000 machine, logentry,
> convert(varchar(8),kioskdate,5) as Kiosk_date,
> convert(varchar(8),kiosktime,8) as Kiosk_time,
> convert(varchar(8),serverdate,5) as ServerDate,
> convert(varchar(8),serverdate,8) as ServerTime,
> application,
> nscode,
> webdomain
> from myTable
> where machine = 'machinename'
> order by kioskdate desc, kiosktime desc
>
> Currently the table holds over 18 million records and the above search
> returns in under 3 seconds, however when I change the order by
> statement to ServerDate desc only (which is what I need), it takes
> over four minutes. I have tried altering/tweaking the indexes, but
> have had no success.
>
> Any ideas greatly appreciated.
> Thanks
> Scott
>
|||Scott,
both your nonclustered indexes are not very useful (ever). This is
because Counter is a unique column and is already indexed.
As Nigel suggested, if "machine = 'machinename'" is highly selective
(returns just a few percent of all rows), then your query could benefit
from an index on (machinename, kioskdate, kiosktime). Specifying
ascending or descending in the index definition is not useful for your
query.
If the expression "machine = 'machinename'" returns a very high
percentage of all rows, then the query could benefit from an index on
(kioskdate, kiosktime, machinename).
You could also try the Index Tuning Wizard and see what that comes up
with.
Hope this helps,
Gert-Jan
scott wrote:
> Hello all,
> I have a specific sql statement and I am looking to return the result
> set a lot faster. Currently the setup is like so:
> myTable schema:
> Counter decimal 9 (pk)
> Machine varchar 60
> LogEntry varchar 1000
> Active varchar 50
> SysInfo varchar 255
> Idle varchar 50
> IP varchar 15
> KioskDate datetime
> KioskTime datetime
> ServerDate datetime
> ServerTime datetime
> Application varchar 15
> WebDomain varchar 50
> NSCode varchar 10
> There is a Clustered index on Counter and two Non-clustered:
> 1) Counter & ServerDate - unique values, fill factor 90% on PRIMARY
> 2) Counter, Machine, NSCode, KioskDate, KioskTime - - unique values,
> fill factor 90% on PRIMARY
> sql statment:
> select top 1000 machine, logentry,
> convert(varchar(8),kioskdate,5) as Kiosk_date,
> convert(varchar(8),kiosktime,8) as Kiosk_time,
> convert(varchar(8),serverdate,5) as ServerDate,
> convert(varchar(8),serverdate,8) as ServerTime,
> application,
> nscode,
> webdomain
> from myTable
> where machine = 'machinename'
> order by kioskdate desc, kiosktime desc
> Currently the table holds over 18 million records and the above search
> returns in under 3 seconds, however when I change the order by
> statement to ServerDate desc only (which is what I need), it takes
> over four minutes. I have tried altering/tweaking the indexes, but
> have had no success.
> Any ideas greatly appreciated.
> Thanks
> Scott
(Please reply only to the newsgroup)
|||Hi,
many thanks for all your replies, however I'm still have no joy on
this. Whatever non-clustered indexes I create, searching by kioskdate
and time (desc) is still way faster than searchig by serverdate (desc)
which is what I want.
Using the Index Tuning Wizard gives me nothing whichever way I do it
(create new indexes, or scan with existing indexes).
Back to the drawing board methinks!
Cheers
Scott