In PostgreSQL, user defaults for config parameters can be changed by
ALTER ROLE .. SET statements. We wish to propagate those defaults
accross the Citus cluster so that the behaviour will be similar in
different workers.
The defaults can either be set in a specific database, or the whole
cluster, similarly they can be set for a single role or all roles.
We propagate the ALTER ROLE .. SET if all the conditions below are met:
- The query affects the current database, or all databases
- The user is already created in worker nodes
New stack memory can contain anything including passwords/private keys.
In these functions we return structs that can have their padding
bytes uninitialized. By first zeroing out the struct fully, we try to
ensure that any data that is in these padding bytes is at least
overwritten once. It might not be zero anymore after setting the fields,
but at least it shouldn't be private data anymore.
Semmle reported quite some places where we use a value that could be NULL. Most of these are not actually a real issue, but better to be on the safe side with these things and make the static analysis happy.