Preventing Preview errors on SQL Server tables

[mglasser]

When I get new data from a dimension table we have in SQL Server I get an error that it is unable to preview the table because "the type of the current preview value is too complex to display".  It does not load the fields in the field list and when you edit the query you can see the table name with an exclamation ponit in a yellow triangle with the Preview Error shown.  I am attempting to do this with a DirectQuery, but it does not even ask that before the preview complains.

If I create a view of SELECT * FROM the same table, it loads fine.  If I create a view that lists all the columns in the SELECT, it also works fine.

I can fix the query with the code below, but I do not know what it is fixing or how to avoid it.  I certainly do not want to use this workaround every time I add a dimension to my queries.  The workaround involves showing the formula bar (from View menu) and replacing the existing formula with the following.  

= Table.RemoveColumns(Source{[Schema="Final",Item="DimTerm"]}[Data], Table.ColumnsOfType(Source{[Schema="Final",Item="DimTerm"]}[Data], {type record, type table}))

What exactly is it fixing?  How can I avoid this error?

[v-eachen-msft]

Hi @mglasser ,

I found a solved case which is similar to yours, you can refer to it.

https://community.powerbi.com/t5/Desktop/Preview-Error-The-type-of-the-current-preview-value-is-too/...

[mglasser]

Is your proprosed solution that I revert back to an older version of the product?  We just downloaded the latest version in an attempt test out Power BI functionality.  I do not even know how to get an older version of the product.  Is this a known issue that is going to be resolved soon or is this expected behavior?

[mglasser]

Instead of using my workaround using Table.RemoveColumns, I just used the Table.ColumnsOfType function to see what are the things being removed.  It returned a list of all the fact tables that have a foreign key connected with the dimension table I am trying to load.  When I remove those column types the dimension table returns all the columns from the table, so I am not sure exactly what this workaround is doing.  More importantly, is there something I need to do to all my foreign keys or fact tables to allow my dimension tables to preview?