Data engineering·Modelling for analysis
eight unrelated yes/no flags were collapsed into one small dimension of every combination, instead of eight columns on the fact.
Junk dimension
Also calledmystery dimension, flag dimension
A single dimension assembled from several low-cardinality flags and indicators that have no natural home. It keeps the fact table narrow and gives the flags somewhere to be described in words rather than as booleans. The name is unhelpful and the technique is sound, though on columnar storage the width saving matters much less than it did, so this is increasingly a readability argument.