Merge queries painfully slow

[KenHardwick]

Hello,

I am writing a new report in Power BI that requires me to merge two tables/queries together which I have done via the merge as new function.

When I do a refresh the data the standard tables load rapidly but when it comes to the merge query, it sits for a few minutes "waiting for dsn...". The image below shows what I am loading which isn't a large amount of data. The first four queries load in 8 seconds but the merge took 5 minutes before completing.

I have spent the weekend trying to figure this out and have deselected "Allow data preview to download in the background", this being a common thing to do to improve performance.

Does anyone know why the merge is reducing the refresh to a crawl?

[Anonymous]

I do facing same kind of scenarion. Merging 6 tables and each tables is having 4 coulms and date,text and number type colums exist. when i make small change then merge query is taking lot time for evalution and waiting for DSN.

How to improve the performace.

[tex628]

What is the dataformat on the columns that you are using for your merge?

[KenHardwick]

Currently, the tables are still in their original formats within our ERP system so will be various formats.

[tex628]

But I mean you're doing the merge in power query right? 

[KenHardwick]

Thats right. 

[tex628]

In that case you are using 2 or more columns to perform that merge. What I'm interested in is which datatype these columns have prior to the merge, as that can greatly affect the performance. 🙂