Views

Creating a view

views are built on top of the immutable tables found in sources. In fact, you can think of a view as a layered stack of data transformations that have been performed on top of one or more tables.

Each view is ultimately described by a SQL query. You can view and edit this query by expanding the SQL Editor box at the top of a dataset view.

Example

Let’s imagine a table with an id field that we want to drop.

After dropping this field, we save the dataset by clicking the Save button in the upper-right corner. Because tables cannot be modified, this creates a new view. Clicking Save will prompt us to name our new view and select from a list of spaces where it will be stored.

Chaining Datasets

It is possible to create views based on other views or tables.

There are a few considerations when chaining datasets:

• If a column that is used in the child dataset (either direct column reference or select *) is dropped from the parent dataset, the child dataset must be updated. It is invalid until this is corrected.
• If a column is added to a parent dataset, it does not show up in the child dataset (even when using select *) until it is updated.

History

When viewing a dataset, you can see a history of all the applied transformations by hovering over the vertical row of dots on the right hand side. The latest transformation is represented by an orange dot at the top of the list. Clicking on earlier transformations returns you to a previous state of the dataset, where you can inspect the contents and even save a new dataset that takes a divergent transformation timeline.

In this way Dremio’s dataset history can provide a number of functions, such as:

• A tool for inspecting how a dataset was created
• A visual ‘undo’
• A method for ‘forking’ earlier versions of datasets and taking them down different analysis pathways

Exploring Data Lineage

You can click the Graph button above the contents of a dataset on the upper right to inspect how it’s related to other datasets. Parent datasets and data sources are shown on the left, with child datasets located to the right.

Clicking on datasets in the graph moves the view left and right along the chain of inheritance, allowing you to inspect the relationship of the selected dataset to others on your Dremio cluster. You can refocus the graph on the selected dataset at any time by hitting the target icon.