generated.md

Postgres introduce generated columns.

There are many usecases of generated column.

e.g. we want to create a unique index based on several columns. We can instead md5 all those columns and add a unique index to one single column to save storage. Of course it does not help with indexing soeed. E.g. is address table.

Generated columns immutable

Generated stored columns requires the generation of the column to be immutable. You can check which function returns an immutable column through this query

select * 
from pg_proc 
where provolatile = 'i' -- Immutable
and proname ilike 'array%'
order by proname;