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Drop Mapping Table

blaise
Partner - Specialist
Partner - Specialist

Drop Mapping Table

Sometimes when you use large mapping tables, or using mapping tables inside a loop it would be good if the mapping table could be dropped. There is no reason to keep a huge mapping table in memory if is not to be used anymore (i do know mapping tables are dropped at the end of script execution).

So my suggestion is one of the following;

* Enable drop of mapping table with the Drop Table(s) cmd;

* Create a new Drop Mapping Table(s) statement

I initially thought that UnMap could be used to drop mapping tables but that one only works on fields names used for map.. using

 

11 Comments
Patric_Nordstrom
Employee
Employee

Thank you for your feedback on ways to improve our product. While this is something we understand would be useful, it's not on the short-term roadmap. Please continue to show your support for this idea.

Thanks,

Patric

Status changed to: Open - Collecting Feedback
mdescamps
Partner - Contributor
Partner - Contributor

Definitely a functionality IQVIA is looking for as well !

AronC
Partner - Creator II
Partner - Creator II

I would like to create a mapping-table within a loop witch would be causing trobble now when I cant drop it. It would have been nice to be able to use mappingtables in loops but would require possibility to drop it.

 

 

AlexOmetis
Partner Ambassador
Partner Ambassador

@AronC - when I need to loop through creating non-concatenated tables (including mapping tables), I put a variable into the map name - e.g. something like:

for vNumber = 0 to 10

Map_$(vNumber):
mapping load x, y resident table;

next vNumber

christopherkramer
Partner - Contributor III
Partner - Contributor III

@AlexOmetis that works but is basically a memory leak. Our maps currently have about 4 million rows and we loop 12 times, so we get about 50 million rows in memory and only need 4 of them. We estimate that it wastes something like 60GB of memory during reload. So it strongly limits us how far we can scale, as looping 50 times is just not feasible.

So please: Introduce support to drop mapping tables.

AlexOmetis
Partner Ambassador
Partner Ambassador

@christopherkramer - yes, we've had the same issue - we ended up reloading the same app multiple times with different loop configuration each time to minimise the number of mapping loads in memory on each run. We found a significant improvement in performance and reduction in memory usage by doing that. 

So yes, would be so nice to be able to drop them like you can normal tables.  

MichelLalancette

This is something I've been thinking about recently as my data grows and more business logic is added.

+1 vote from me!

KL1
Contributor III
Contributor III

Allowing dropping of Mapping tables makes sense, this gives control to the developer. And mainly minimises substantial memory leaks, a concept not a lot of QS/QV developers understand. I cringe every time I suspect memory leak in qlik programs/code, as managing memory leaks is something etched into my brain coming from C/C++ background. To be frank Qlik is very poor in managing memory leaks, in the middle of execution itself.

simonaubert
Partner - Specialist II
Partner - Specialist II

I have exactly this issue today,  dropping useless tables is a huge improvement of a script.

Best regards,

Simon

Meghann_MacDonald

From now on, please track this idea from the Ideation portal. 

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