What is has_expressions colum in projections table?

HyeontaeJu

What is has_expressions colum in projections table?
what's that mean? is useful for optimization?

Hibiki

Projection can have the columns defined by the expressions. HAS_EXPRESSIONS column in PROJECTIONS table tells you whether the projection has the columns defined by the expressions or not.

https://www.vertica.com/docs/10.0.x/HTML/Content/Authoring/AnalyzingData/AggregatedData/ExpressionsAggregateData.htm