BGWORKER_BACKEND_DATABASE_CONNECTION can only be used if
BGWORKER_SHMEM_ACCESS is also used.
Michael Paquier, with some tweaks by me.
<literal>BGWORKER_SHMEM_ACCESS</literal> (requesting shared memory access)
and <literal>BGWORKER_BACKEND_DATABASE_CONNECTION</literal> (requesting the
ability to establish a database connection, through which it can later run
- transactions and queries).
+ transactions and queries). A background worker using
+ <literal>BGWORKER_BACKEND_DATABASE_CONNECTION</literal> to connect to
+ a database must also attach shared memory using
+ <literal>BGWORKER_SHMEM_ACCESS</literal>, or worker start-up will fail.
</para>
<para>