Query_id is not being populated for all the pids - Mailing list pgsql-admin

Hello Admins,

When we query pg_stat_statements in Postgres, it has a column “query_id” which is not having any value for most of the
sessions. 

Compute_query_id is set to AUTO

Can someone please help me understand why the query_id is missing most of the sessions and how is it populated in the
background?

Thank you,
J. Teja.