1. Qube
2. A Primer for the pfx_dw Data Warehouse Schema

A Primer for the pfx_dw Data Warehouse Schema

The pfx_dw schema is a fairly textbook "star schema", with things like jobs and worker usage in fact tables, and the various things that you might use in a SQL WHERE clause in dimension tables.

The job dimension table, a typical "fact" table.

For example, to get reports about various jobs over time, you'll be querying the pfx_dw.job_fact table:

"*_sk" columns can be used to do INNER JOINs to a similarly named dimension table

Any column that is named with an _sk suffix is a Synthetic Key that points to a corresponding dimension table, named with the part of the column before the _sk; the dimension table will have a _dim suffix in the name. This way, it's easy to write the JOIN's, the column name is a clue to the dimension table, which will have a column of the same name. Almost every dimension table will consist of a *_sk PRIMARY KEY and a name column.

A typical dimension table, the "user_dim" table

For example, the user_sk column can be used to do a SQL INNER JOIN to the user_dim table.

Get a count of all jobs for a particular user:

The time dimension table

The pfx_dw.time_dim table is provided so that you don't have to perform date/time operations on every row in a fact table (since they can run into the 100's of millions of rows), instead you do a SQL INNER JOIN to it and use the values in the time_dim table in your WHERE clause. The time_sk column in every fact table has an identical value in the time_dim table which has a single row with a primary key time_sk.  The time_sk value is actually the unix epoch time in seconds:

The "job status" dimension table

The pfx_dw.jobstatus_dim table is one of the few exceptions to the normal dimension table structure; it provides a mapping between the integer and human-readable status values.

Get a count of all jobs for a particular user for January, 2014:

Get a count of all jobs for each user for all of 2013:

Get a count of all jobs for each user for all of 2013, broken down by month and the job's final status:

Get the sum total of cpu_seconds used for each user for the last 7 days, broken down by user, date, and the job's final status: