`active' flag or not?

Question

OK, so practically every database based application has to deal with \"non-active\" records. Either, soft-deletions or marking something as \"to be ignored\". I\'m curious a

Answer 1

This is an old question but for those search for low cardinality/selectivity indexes, I'd like to propose the following approach that avoids partitioning, secondary tables, etc.:

The trick is to use "dateInactivated" column that stores the timestamp of when the record is inactivated/deleted. As the name implies, the value is NULL while the record is active, but once inactivated, write in the system datetime. Thus, an index on that column ends up having high selectivity as the number of "deleted" records grows since each record will have a unique (not strictly speaking) value.

Then your query becomes:

SELECT * FROM people WHERE dateInactivated is NULL;

The index will pull in just the right set of rows that you care about.