alter user set local_preload_libraries.

Hello, This is about a document fix of local_preload_libraries
for the versions 9.3 and earlier to at least 8.4.

There's inconsistency between documentation about
local_preload_libraries for 9.3 and earlier and their behavior.

The 9.3 document for local_preload_libraries says that:

http://www.postgresql.org/docs/9.3/static/runtime-config-client.html

| For example, debugging could be enabled for all sessions under
| a given user name by setting this parameter with ALTER ROLE
| SET.

Ok, let's do that.

postgres=# alter user horiguti2 set local_preload_libraries='libname';
ERROR: parameter "local_preload_libraries" cannot be set after connection start

Back to 8.4 shows the same behavior.

session_preload_libraries works as expected since 9.4. It is
added at 9.4 vested the context PGC_SUSET so its setting in
pg_db_role_setting can complete its mission. On the other hand,
local_preload_libraries seems to continue to have the context
PCG_BACKEND and the behavior is same to the older versions, as
shown above. And the description about 'ALTER ROLE SET' has been
removed from config.sgml. These are done by the commit
070518ddab2.

I think we should regard the real behavior as right, right?

Eventually, local_preload_libraries seems to have almost the same
function to shared_preload_libraries, except a restriction on
load module directory.

Putting aside the meaning of its existence, anyway the third
paragraph of the description for local_preload_libraries should
be removed. The change made by the attached patch for 9.3 will
show in runtime-config-client.html "18.11. Client Connection
Defaults"

regards,

--
Kyotaro Horiguchi
NTT Open Source Software Center