Recall from Section 3.4 that the PostgreSQL
server provides a large number of run-time configuration variables.
You can set database-specific default values for many of these
settings.
For example, if for some reason you want to disable the
GEQO optimizer for a given database, you'd
ordinarily have to either disable it for all databases or make sure
that every connecting client is careful to issue SET geqo
TO off;. To make this setting the default you can
execute the command
ALTER DATABASE mydb SET geqo TO off;
This will save the setting (but not set it immediately) and in
subsequent connections it will appear as though SET geqo
TO off; had been called right before the session started.
Note that users can still alter this setting during the session; it
will only be the default. To undo any such setting, use
ALTER DATABASE dbname RESET
varname;.
