Add support for “Logical Datasets” (query-defined entities / view definitions)

[mullinsms]

Many semantic layers allow defining an entity/dataset as a logical relation backed by an inline SQL query (or a view definition), not only as a reference to an existing physical table/view. The dataset spec says the source can be a query, but provides no examples and appears to be missing required elements like a SQL dialect declaration.

[khush-bhatia]

@mullinsms Great catch about missing dialect. The "source" field in the spec needs to be enhanced further, it is also missing a reference to a catalog currently.

There is an active working group that is figuring out the details for the catalog part of the spec. cc shubhambatlan

It will be nice introduce a catalog or connection object to the spec and then have the source field refer to catalog object or a query on catalog objects.