topic Re: Lookup vs Applymap in App Development

Lookup vs Applymap

Tanish — Wed, 12 Oct 2022 09:47:26 GMT

Hello,

Can anyone explain why Applymap function is faster than Lookup function ?

Re: Lookup vs Applymap

_Iswarya_ — Wed, 12 Oct 2022 10:02:17 GMT

Hi @Tanish ,

ApplyMap() is more practical since:

even though you have to load the table, it will be dropped automatically.
it makes code easier to understand
Executed on the distinct values only, not per table record.

Pls find the link below:

https://support.qlik.com/articles/000042949

Re: Lookup vs Applymap

marcus_sommer — Wed, 12 Oct 2022 11:45:58 GMT

Lookup() has more parameter as applymap() and could look into each table including the currently loaded one. The description within the provided link just explained the performance-impact but not really the cause.

I don't know how it's technically implemented but I wouldn't be surprised as if an applymap() worked like an exists() against the symbol-tables and doesn't break the load-execution while lookup() is applied against the data-tables and may be evaluated separately for each single record.

Beside this is the usage-hint within the description not the whole truth because applymap() could be used with combined and/or sorted fields and also horizontally + vertically nested with a bit advanced scripting. Therefore, there won't be much scenarios in which joins or lookup() are necessary or having a benefit against a mapping.

- Marcus