Query folding in Snowflake DirectQuery is failing

[Anonymous]

I have a query with DirectQuery.  It has 4 steps:

1. Source (Connet to snowflake)

2. Navigation (navigate to the table and define warehouse)

3. Rename some columns

4. Remove some columns.

When I check on the queries executed on Snowflake, I see two queries.  I would expect that one query is executed with only the columns that are remaining.  Any ideas why there is no query folding happeining?

Thanks

[v-yiruan-msft · Accepted solution]

Hi @Anonymous ,

Are you using a native database query when connecting to Snowflake, and if so, there are some limitation on query folding:

Query folding while using a native database query is limited to the PostgreSQL connector only. No other connectors support query folding if you use a native database query. Also, for folding to work in the PostgreSQL connector, the native database query you enter has to work as a subquery.

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Also, in this case below, it is mentioned that query folding does not work if there are arrays involved in the data source query.

Does Snowflake support query folding when used as a data source by Power BI?

Power BI Incremental Refresh with Snowflake

Best Regards

[Greg_Deckler]

@Anonymous In Power Query Editor, right-click each step of the query and see when View Native Query gets greyed out. That is the step that is negating query folding.

[Anonymous]

@Greg_Deckler "View native query" is not supported with Snowflake.  Even if query folding is working, this feature is always greyed out.

[Greg_Deckler]

@Anonymous Well then you answered your own question? View native query is present when query folding is occurring so if Snowflake doesn't support view native query then it doesn't support query folding...yes?

[Anonymous]

No... 

if "View Native Query" is enabled, then query folding is working.

If "View Native Query" is disabled then you cannot draw any conclusions.