Using Reference in Power Query...

[Gusd8]

Thank you for looking...I wasn't sure how to succinctly ask my question...so I wasn't getting the answer I was looking for.

Very simply, the data source that I am pulling data from (teradata server) is notorious for killing connections because of "throttling" and "too many concurrent connections."

So I am hoping to understand...if I create a query called "tbl_data" that pulls data from teradata...

I then create a second query (tbl_option1) and use "= tbl_data" as the source...

When I refresh...will power bi create a single connection to teradata or will it create two connections to teradata...one for tbl_data and then a second for tbl_option1 because it is using a new instance of tbl_data?

I hope this is clear. I am hoping that the answer is a single connection...but I just have an uneasy feeling about it while I watch the refresh dialogue.

Thank you in advance for any insight you are able  to offer.

[lbendlin · Accepted solution]

It depends.  Not actually on your reference, but on the incredible chattiness of Power Query when it comes to meta data updates.

https://blog.crossjoin.co.uk/2020/07/05/why-is-power-bi-running-my-sql-query-twice/

You can prevent concurrent queries - but only in the Desktop. The service will always run as much as possible in parallel, if you want it or not.

[suparnababu8 · Accepted solution]

I think Power BI generally uses a single connection to the data source for queries that reference each other. This means that tbl_option1 referencing tbl_data should not create an additional connection.
if you need additional information pls follow the below links
Power Query Teradata database connector - Power Query | Microsoft Learn

Why does my query run multiple times - Power Query | Microsoft Learn
Thanks

[lbendlin · Accepted solution]

It depends.  Not actually on your reference, but on the incredible chattiness of Power Query when it comes to meta data updates.

https://blog.crossjoin.co.uk/2020/07/05/why-is-power-bi-running-my-sql-query-twice/

You can prevent concurrent queries - but only in the Desktop. The service will always run as much as possible in parallel, if you want it or not.