Do merge operations like Append store data twice?

Question

I am trying to understand how Power BI stores data.

If I append Table A to Table B to create Table C:
Does Power Query / Power BI duplicate the data from A & B to create C and store it twice thereby doubling the size of the file / data model?

( I am asking because I cannot disable the load of my tables, as I use SSMS to load data via XMLA endpoints. This is because the dataset is to large to publish, and it times out if I attempt to refresh it using native functionality in Power BI Service)

mlsx4 · Answer

Hi&nbsp;Anonymous&nbsp;&nbsp;As far as I know, you're right. It stores data twice.

anonymous · Answer

Thanks for your response!&nbsp;&nbsp;Do you have a link to any documentation on the matter per chance?

mlsx4 · Answer

Hi&nbsp;Anonymous&nbsp;&nbsp;The own documentation of Microsoft:&nbsp;https://learn.microsoft.com/en-us/power-query/append-queries&nbsp;Also, if you try to remove one of the appended tables it will give you an error. The only solution may be to apply SQL to join them before importing data into Power BI. There are lot of links on how to do it. For instance:https://community.fabric.microsoft.com/t5/Power-Query/Join-data-sources-before-importing-data/td-p/3182325)https://www.youtube.com/watch?v=UQJAHUUFK-o

anonymous · Answer

I appreciate your effort, unfortunately I did not see anything about the storing of data in the Microsoft documentation.I don't have any issues or questions regarding how to Append or the behaviors, just the storage.Thanks for your time 🙂

anonymous · Answer

Just as a follow up - i use XMLA endpoints in SSMS, not SQL.&nbsp;

Forum Discussion

Do merge operations like Append store data twice?

5 Replies

Related content

Dataflow - Append

Appending Data

Optimize Transpose and append operations query

Copy Job Triggered Twice When Executed from Pipeline (Foreach)

SQL Operator with multiple destinations