Library unloading has never been supported with its code removed in
ab02d702ef, and there were some comments still mentioning that it was
a possible operation.
ChangAo has noticed the incorrect references in dfmgr.c, while I have
noticed the other ones while scanning the rest of the tree for similar
mistakes.
Author: ChangAo Chen, Michael Paquier
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/tencent_1D09840A1632D406A610C8C4E2491D74DB0A@qq.com
The PostgreSQL contrib tree
---------------------------
This subtree contains porting tools, analysis utilities, and plug-in
features that are not part of the core PostgreSQL system, mainly
because they address a limited audience or are too experimental to be
part of the main source tree. This does not preclude their
usefulness.
User documentation for each module appears in the main SGML
documentation.
When building from the source distribution, these modules are not
built automatically, unless you build the "world" target. You can
also build and install them all by running "make all" and "make
install" in this directory; or to build and install just one selected
module, do the same in that module's subdirectory.
Some directories supply new user-defined functions, operators, or
types. To make use of one of these modules, after you have installed
the code you need to register the new SQL objects in the database
system by executing a CREATE EXTENSION command. In a fresh database,
you can simply do
CREATE EXTENSION module_name;
See the PostgreSQL documentation for more information about this
procedure.
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