Primary Keys and DAX Query Performance

Phil Seamark explains why including primary keys in summarize statements can be a bad thing:

When writing DAX queries, performance tuning often comes down to small design decisions that have big consequences. One such decision is whether to include Primary Key columns from Dimension tables in your SUMMARIZECOLUMNS statements. This is particularly important when those Dimension tables use DUAL or IMPORT storage modes.

This article explains why doing so can lead to inefficient query plans. It describes what happens under the hood. It also shows how to avoid this common pitfall.

Read on to learn more.