Performance: ApplyMap in Preceding Map

[Anonymous]

Hi

I have noticed that this script runs about 4 times slower than the script at the bottom :

Load

ApplyMap ( 'MapSicknessHours' , [SCD Environment Date Employee Key] , 0 ) as [Sickness Hours] ,

*

;

Load

  [SCD Environment] & '|' &  [Date] & '|' &  [SCD Employee Number] as [SCD Environment Date Employee Key]  ,

  *

resident Temp10

;

Whereas eliminating the Preceding Load is 4 times faster :

Load

  ApplyMap ( 'MapSicknessHours' , [SCD Environment] & '|' &  [Date] & '|' &  [SCD Employee Number] , 0 ) as [Sickness Hours]
resident Temp10 

;

I am curious as to why is the case.  Any ideas anybody ?

Normally I love preceding loads, but not in this case.

Best Regards,     Bill

[rwunderlich]

Hi Bill,

The two scripts are not comparable.  In the preceding load, you are keeping the additional field "SCD Environment Date Employee Key".  It's a large string field, so could have significant impact on performance. An interesting comparison would be to not use * on the top load, but list the fields and don't keep "SCD Environment Date Employee Key".

In any case, I don't recommend using Preceding load in this scenario (adding one field). There is no benefit.

-Rob