Invent "trusted" extensions, and remove the pg_pltemplate catalog.

This patch creates a new extension property, "trusted".  An extension
that's marked that way in its control file can be installed by a
non-superuser who has the CREATE privilege on the current database,
even if the extension contains objects that normally would have to be
created by a superuser.  The objects within the extension will (by
default) be owned by the bootstrap superuser, but the extension itself
will be owned by the calling user.  This allows replicating the old
behavior around trusted procedural languages, without all the
special-case logic in CREATE LANGUAGE.  We have, however, chosen to
loosen the rules slightly: formerly, only a database owner could take
advantage of the special case that allowed installation of a trusted
language, but now anyone who has CREATE privilege can do so.

Having done that, we can delete the pg_pltemplate catalog, moving the
knowledge it contained into the extension script files for the various
PLs.  This ends up being no change at all for the in-core PLs, but it is
a large step forward for external PLs: they can now have the same ease
of installation as core PLs do.  The old "trusted PL" behavior was only
available to PLs that had entries in pg_pltemplate, but now any
extension can be marked trusted if appropriate.

This also removes one of the stumbling blocks for our Python 2 -> 3
migration, since the association of "plpythonu" with Python 2 is no
longer hard-wired into pg_pltemplate's initial contents.  Exactly where
we go from here on that front remains to be settled, but one problem
is fixed.

Patch by me, reviewed by Peter Eisentraut, Stephen Frost, and others.

Discussion: https://postgr.es/m/5889.1566415762@sss.pgh.pa.us

4 files changed, 37 insertions, 19 deletions

diff --git a/src/pl/plpython/plpy_main.c b/src/pl/plpython/plpy_main.c
index faaec559a22..882d69e14a1 100644
--- a/src/pl/plpython/plpy_main.c
+++ b/src/pl/plpython/plpy_main.c
@@ -29,7 +29,7 @@
  */
 
 #if PY_MAJOR_VERSION >= 3
-/* Use separate names to avoid clash in pg_pltemplate */
+/* Use separate names to reduce confusion */
 #define plpython_validator plpython3_validator
 #define plpython_call_handler plpython3_call_handler
 #define plpython_inline_handler plpython3_inline_handler
diff --git a/src/pl/plpython/plpython2u--1.0.sql b/src/pl/plpython/plpython2u--1.0.sql
index 661cc66a891..69f74775678 100644
--- a/src/pl/plpython/plpython2u--1.0.sql
+++ b/src/pl/plpython/plpython2u--1.0.sql
@@ -1,11 +1,17 @@
 /* src/pl/plpython/plpython2u--1.0.sql */
 
-/*
- * Currently, all the interesting stuff is done by CREATE LANGUAGE.
- * Later we will probably "dumb down" that command and put more of the
- * knowledge into this script.
- */
+CREATE FUNCTION plpython2_call_handler() RETURNS language_handler
+  LANGUAGE c AS 'MODULE_PATHNAME';
 
-CREATE LANGUAGE plpython2u;
+CREATE FUNCTION plpython2_inline_handler(internal) RETURNS void
+  STRICT LANGUAGE c AS 'MODULE_PATHNAME';
+
+CREATE FUNCTION plpython2_validator(oid) RETURNS void
+  STRICT LANGUAGE c AS 'MODULE_PATHNAME';
+
+CREATE LANGUAGE plpython2u
+  HANDLER plpython2_call_handler
+  INLINE plpython2_inline_handler
+  VALIDATOR plpython2_validator;
 
 COMMENT ON LANGUAGE plpython2u IS 'PL/Python2U untrusted procedural language';
diff --git a/src/pl/plpython/plpython3u--1.0.sql b/src/pl/plpython/plpython3u--1.0.sql
index c0d6ea82c2d..ba2e6ac076b 100644
--- a/src/pl/plpython/plpython3u--1.0.sql
+++ b/src/pl/plpython/plpython3u--1.0.sql
@@ -1,11 +1,17 @@
 /* src/pl/plpython/plpython3u--1.0.sql */
 
-/*
- * Currently, all the interesting stuff is done by CREATE LANGUAGE.
- * Later we will probably "dumb down" that command and put more of the
- * knowledge into this script.
- */
+CREATE FUNCTION plpython3_call_handler() RETURNS language_handler
+  LANGUAGE c AS 'MODULE_PATHNAME';
 
-CREATE LANGUAGE plpython3u;
+CREATE FUNCTION plpython3_inline_handler(internal) RETURNS void
+  STRICT LANGUAGE c AS 'MODULE_PATHNAME';
+
+CREATE FUNCTION plpython3_validator(oid) RETURNS void
+  STRICT LANGUAGE c AS 'MODULE_PATHNAME';
+
+CREATE LANGUAGE plpython3u
+  HANDLER plpython3_call_handler
+  INLINE plpython3_inline_handler
+  VALIDATOR plpython3_validator;
 
 COMMENT ON LANGUAGE plpython3u IS 'PL/Python3U untrusted procedural language';
diff --git a/src/pl/plpython/plpythonu--1.0.sql b/src/pl/plpython/plpythonu--1.0.sql
index 4a3e64aac50..4c6f7c3f140 100644
--- a/src/pl/plpython/plpythonu--1.0.sql
+++ b/src/pl/plpython/plpythonu--1.0.sql
@@ -1,11 +1,17 @@
 /* src/pl/plpython/plpythonu--1.0.sql */
 
-/*
- * Currently, all the interesting stuff is done by CREATE LANGUAGE.
- * Later we will probably "dumb down" that command and put more of the
- * knowledge into this script.
- */
+CREATE FUNCTION plpython_call_handler() RETURNS language_handler
+  LANGUAGE c AS 'MODULE_PATHNAME';
 
-CREATE LANGUAGE plpythonu;
+CREATE FUNCTION plpython_inline_handler(internal) RETURNS void
+  STRICT LANGUAGE c AS 'MODULE_PATHNAME';
+
+CREATE FUNCTION plpython_validator(oid) RETURNS void
+  STRICT LANGUAGE c AS 'MODULE_PATHNAME';
+
+CREATE LANGUAGE plpythonu
+  HANDLER plpython_call_handler
+  INLINE plpython_inline_handler
+  VALIDATOR plpython_validator;
 
 COMMENT ON LANGUAGE plpythonu IS 'PL/PythonU untrusted procedural language';