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Anonymous
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Join Types not supported by Query Folding

Hi,

 

Been struggling with this for a while as there seems to be very limited documentation on Query Folding, but from what I've read it seems like all types of joins should be supported by query folding. However in practice I've found that only Left Outer joins will query fold, with all other types disabling it ( view native query is disabled and it starts downloading rows for the preview ).

 

I'm connecting via SQL server to our data warehouse so I can't see why this would be occuring. Currently I'm having to always use Left Outer join then expand and filter out nulls to achieve what I want which seems to be the long way round when I would like to be using inner joins.

 

Thanks for any help

1 ACCEPTED SOLUTION

I came across this issue today as well and found a surprising solution: https://www.thebiccountant.com/2019/04/18/query-folding-joinkind-inner-gotcha-power-bi-power-query/

Imke Feldmann (The BIccountant)

If you liked my solution, please give it a thumbs up. And if I did answer your question, please mark this post as a solution. Thanks!

How to integrate M-code into your solution -- How to get your questions answered quickly -- How to provide sample data -- Check out more PBI- learning resources here -- Performance Tipps for M-queries

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4 REPLIES 4
v-piga-msft
Resident Rockstar
Resident Rockstar

Hi @Anonymous,

 

You could have a reference of this blog which introduces the query folding in more details.

 

Best Regards,

Cherry

Community Support Team _ Cherry Gao
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.
Anonymous
Not applicable

Hi Cherry,

 

I have read through the blogs a few times to find the solution, but none of them I could find mention there being issues with certain join types. Can't see any mention of why a Left Outer would query fold while no others would?

 

Thanks,

I came across this issue today as well and found a surprising solution: https://www.thebiccountant.com/2019/04/18/query-folding-joinkind-inner-gotcha-power-bi-power-query/

Imke Feldmann (The BIccountant)

If you liked my solution, please give it a thumbs up. And if I did answer your question, please mark this post as a solution. Thanks!

How to integrate M-code into your solution -- How to get your questions answered quickly -- How to provide sample data -- Check out more PBI- learning resources here -- Performance Tipps for M-queries

Anonymous
Not applicable

Hi Imke,

 

Sorry I only saw your reply today. It is correct though, it does Query fold at the end!. The individual step itself still doesn't though, very odd. If creating the steps one by one this was an issue as it had to download all the rows before I could continue. Not sure whether to use inner joins with this issue or continue with left join, expand and filter. Will probably need to test which returns best performance.

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