This answer motivated think again my following tables but I am still uncertain how to store statistic data for quick selection. I think it is well done with partial indexes because only a subset of data is required in my application described here. I have three tables: measurements, events and headers where all have some static (never changes) columns about sizes in bytes:

• originalMeasurementSizeInBytes in measurements - static, size of original .raw -file
• measurementHeaderSizeInBytes in headers - static, never changes

Example of my table schema measurements without names

SERIAL                     | NOT NULL
INTEGER                    | NOT NULL
INTEGER                    | NOT NULL
TIMESTAMP WITH TIME ZONE   | DEFAULT CURRENT_TIMESTAMP

where I am worried about increasing the schema size by INTEGER fields because of my need in statistics. I do not want to store in the main tables variables which are used rarely (just this intuition). I do not want cause my indexes not being used as described in the book PostgreSQL Up & Running and this article Why is my index not being indexed?

How can static/dynamic statistics be stored efficiently in partial indexes of PostgeSQL? For instance, removal of one event would decrease the measurement size which includes events and header.