Buffer web query request

[Bessonnizza1992]

Hello there,

I have function which i am using to get statistics from POST method: fnMotorModes_Get

let
    Source = (AuthorizationId as text, StatisticsId as text) => 
    let
        data = Json.FromValue([StatisticsSessionId=StatisticsId]),
        headers = [#"accept"="*/*", #"ScoutAuthorization"=AuthorizationId, #"Content-Type"="application/json"],
        web = Web.Contents("url", [ Content = data, Headers = headers, Timeout=#duration(0,0,0,10), ManualStatusHandling = {404, 400}]),
        source = ()=> Json.Document(web),
        result = Function.InvokeAfter(source, #duration(0,0,0,5))
in
    Source

This function i invoke like Custom Function only one time in MotorModes table:

Tables MotorModesTotal and MotorModesEvents are created via Reference button from MotorModes table. When i update data i check Fiddler Web Debugger and see that PowerQuery address to web service three times. One time for every table.

What do i need to add in query to make only one request to web service?

[edhans · Accepted solution]

I am not sure you can. It doesn't work top down, it works bottom up. So if you have 3 final tables in your model from a source, it starts at those 3 tables in Power Query then works backwards to the source, so you will get three refreshes. You can optimize it perhaps by turning off background data in settings.

There is a good video from Guys in a Cube with Chris Webb that will help explain this as well.

[Bessonnizza1992]

@edhans 
What about Tabble.Buffer?

Mb this function can help me.

[edhans]

No. As the docs indicate, it is for a specific purpose. "Buffers a table in memory, isolating it from external changes during evaluation."

A popular use of it is when sorting data. Additional data/transformations can cause sort order to change. Table.Buffer() isolates it from that. I also use it to purposfully break query folding in some instances. But it is not taking the table as is, and putting the whole thing in memory for all downstream transformations to use. 

If you go through the article to see how the queries are hitting that source data, you can wrap Table.Buffer() around whatever step you want, but it will still query the source table 3 times if you have 3 references to it.