title: When are data sets realized in Azure Data Factory data flows?
body: <p>If I create a dataset with no schema, and then use it in a flow, where I have a <code>Select</code> schema modifier, when is the retrieval from the database done? Is it done on the full dataset including the complete schema and then the <code>select</code> projection is done or is it done in a just-in-time fashion, where the retrieval is done at the latest possible time in order to minimize the amount data retrieved?</p>