"Unbuffer" - List/Table

[Anonymous]

Hey everyone,

I have a question regarding the Buffer() function in M. So after loading a List or Table into memory, is there away to unload it after it is not required anymore? That would be potentially be helpful to reduce Query Performance, or is my understanding wrong here?

Example:

So I have below case, where I have a parent child relationship. Meaning that in my case I want to filter out all values in my Child column that appear in the Parent column. So "A" in the Child column should be filtered out.

Child	Parent
A
B	A
C

parentlist = List.Buffer(List.Distinct(Table.Column(Fact.Table, "Parent"))),
filteroutparents = Table.SelectRows(Fact.Table, each List.Contains(parentlist, [Child])=false),

The above code does precisley this within the same query without reavaulating the parentlist statments for each row, I believe. So after I have filtered them out, this list becomes useless and only takes up memory, hence is there a way to drop it in subsequent steps?

Regards,

Christian

[v-eachen-msft · Accepted solution]

Hi @Anonymous ,

After my tests and research, I don't find a way like "unbuffer" to release memory manually.

When Power Query run the above query, it will actually takes memory, but after the data imported into dataset, Power Query will release this part of memory. 

[Anonymous]

Hi @v-eachen-msft , 

thank you for the reply. Ok, understood - that answers it.

Yes my idea was to release the list from memory in my case to free up memory for the subsequent transformation steps of the query to potentially increase the query execution performance. 

Best regards,

Christian