Re: Removing pg_pltemplate and creating "trustable" extensions

I wrote:
> Stephen Frost  writes:
>> On Tue, Jan 28, 2020 at 16:17 Tom Lane  wrote:
>>> On the other hand, there's the point that lots of people have probably
>>> given out schema-CREATE privilege to users whom they wouldn't necessarily
>>> wish to trust with INSTALL privilege.  Schema-CREATE is a pretty harmless
>>> privilege, INSTALL much less so.

>> CREATE doesn't just control the ability to create schemas these days- it
>> was extended to cover publications also not that long ago.

> Oh really ... hm, that does make it a much bigger deal than I was
> thinking.  Given that, I don't think there's any huge objection to
> attaching this to CREATE, at least till we get around to a more
> significant redesign.

Here's a v5 that drops the new predefined role and allows
trusted-extension installation when you have CREATE on the current
database.  There's no other changes except a bit of documentation
wordsmithing.

Barring further complaints, I'm going to push this fairly soon.

			regards, tom lane

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 85ac79f..a10b665 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -8519,7 +8519,15 @@ SCRAM-SHA-256$<iteration count>:&l
      
       superuser
       bool
-      True if only superusers are allowed to install this extension
+      True if only superusers are allowed to install this extension
+       (but see trusted)
+     
+
+     
+      trusted
+      bool
+      True if the extension can be installed by non-superusers
+       with appropriate privileges
      
 
      
diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
index 3546e39..8d3a0d1 100644
--- a/doc/src/sgml/ddl.sgml
+++ b/doc/src/sgml/ddl.sgml
@@ -1742,6 +1742,7 @@ REVOKE ALL ON accounts FROM PUBLIC;
      
       
        For databases, allows new schemas and publications to be created within
+       the database, and allows trusted extensions to be installed within
        the database.
       
       
@@ -1753,8 +1754,11 @@ REVOKE ALL ON accounts FROM PUBLIC;
       
        For tablespaces, allows tables, indexes, and temporary files to be
        created within the tablespace, and allows databases to be created that
-       have the tablespace as their default tablespace.  (Note that revoking
-       this privilege will not alter the placement of existing objects.)
+       have the tablespace as their default tablespace.
+      
+      
+       Note that revoking this privilege will not alter the existence or
+       location of existing objects.
       
      
     
diff --git a/doc/src/sgml/extend.sgml b/doc/src/sgml/extend.sgml
index a3046f2..ffe068b 100644
--- a/doc/src/sgml/extend.sgml
+++ b/doc/src/sgml/extend.sgml
@@ -576,6 +576,31 @@
         version.  If it is set to false, just the privileges
         required to execute the commands in the installation or update script
         are required.
+        This should normally be set to true if any of the
+        script commands require superuser privileges.  (Such commands would
+        fail anyway, but it's more user-friendly to give the error up front.)
+       
+      
+     
+
+     
+      trusted (boolean)
+      
+       
+        This parameter, if set to true (which is not the
+        default), allows some non-superusers to install an extension that
+        has superuser set to true.
+        Specifically, installation will be permitted for anyone who has
+        CREATE privilege on the current database.
+        When the user executing CREATE EXTENSION is not
+        a superuser but is allowed to install by virtue of this parameter,
+        then the installation or update script is run as the bootstrap
+        superuser, not as the calling user.
+        This parameter is irrelevant if superuser is
+        false.
+        Generally, this should not be set true for extensions that could
+        allow access to otherwise-superuser-only abilities, such as
+        filesystem access.
        
       
      
@@ -642,6 +667,18 @@
     
 
     
+     If the extension script contains the
+     string @extowner@, that string is replaced with the
+     (suitably quoted) name of the user calling CREATE
+     EXTENSION or ALTER EXTENSION.  Typically
+     this feature is used by extensions that are marked trusted to assign
+     ownership of selected objects to the calling user rather than the
+     bootstrap superuser.  (One should be careful about doing so, however.
+     For example, assigning ownership of a C-language function to a
+     non-superuser would create a privilege escalation path for that user.)
+    
+
+    
      While the script files can contain any characters allowed by the specified
      encoding, control files should contain only plain ASCII, because there
      is no way for PostgreSQL to know what encoding a
diff --git a/doc/src/sgml/ref/create_extension.sgml b/doc/src/sgml/ref/create_extension.sgml
index 36837f9..d76ac3e 100644
--- a/doc/src/sgml/ref/create_extension.sgml
+++ b/doc/src/sgml/ref/create_extension.sgml
@@ -47,14 +47,25 @@ CREATE EXTENSION [ IF NOT EXISTS ] extension_name
   
 
   
-   Loading an extension requires the same privileges that would be
-   required to create its component objects.  For most extensions this
-   means superuser or database owner privileges are needed.
    The user who runs CREATE EXTENSION becomes the
    owner of the extension for purposes of later privilege checks, as well
    as the owner of any objects created by the extension's script.
   
 
+  
+   Loading an extension ordinarily requires the same privileges that would
+   be required to create its component objects.  For many extensions this
+   means superuser privileges are needed.
+   However, if the extension is marked trusted in
+   its control file, then it can be installed by any user who has
+   CREATE privilege on the current database.
+   In this case the extension object itself will be owned by the calling
+   user, but the contained objects will be owned by the bootstrap superuser
+   (unless the extension's script explicitly assigns them to the calling
+   user).  This configuration gives the calling user the right to drop the
+   extension, but not to modify individual objects within it.
+  
+
  
 
  
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index c9e75f4..c9e6060 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -317,7 +317,8 @@ CREATE VIEW pg_available_extensions AS
 
 CREATE VIEW pg_available_extension_versions AS
     SELECT E.name, E.version, (X.extname IS NOT NULL) AS installed,
-           E.superuser, E.relocatable, E.schema, E.requires, E.comment
+           E.superuser, E.trusted, E.relocatable,
+           E.schema, E.requires, E.comment
       FROM pg_available_extension_versions() AS E
            LEFT JOIN pg_extension AS X
              ON E.name = X.extname AND E.version = X.extversion;
diff --git a/src/backend/commands/extension.c b/src/backend/commands/extension.c
index 01de398..ddd46f4 100644
--- a/src/backend/commands/extension.c
+++ b/src/backend/commands/extension.c
@@ -40,6 +40,7 @@
 #include "catalog/indexing.h"
 #include "catalog/namespace.h"
 #include "catalog/objectaccess.h"
+#include "catalog/pg_authid.h"
 #include "catalog/pg_collation.h"
 #include "catalog/pg_depend.h"
 #include "catalog/pg_extension.h"
@@ -84,6 +85,7 @@ typedef struct ExtensionControlFile
 	char	   *schema;			/* target schema (allowed if !relocatable) */
 	bool		relocatable;	/* is ALTER EXTENSION SET SCHEMA supported? */
 	bool		superuser;		/* must be superuser to install? */
+	bool		trusted;		/* allow becoming superuser on the fly? */
 	int			encoding;		/* encoding of the script file, or -1 */
 	List	   *requires;		/* names of prerequisite extensions */
 } ExtensionControlFile;
@@ -558,6 +560,14 @@ parse_extension_control_file(ExtensionControlFile *control,
 						 errmsg("parameter \"%s\" requires a Boolean value",
 								item->name)));
 		}
+		else if (strcmp(item->name, "trusted") == 0)
+		{
+			if (!parse_bool(item->value, &control->trusted))
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("parameter \"%s\" requires a Boolean value",
+								item->name)));
+		}
 		else if (strcmp(item->name, "encoding") == 0)
 		{
 			control->encoding = pg_valid_server_encoding(item->value);
@@ -614,6 +624,7 @@ read_extension_control_file(const char *extname)
 	control->name = pstrdup(extname);
 	control->relocatable = false;
 	control->superuser = true;
+	control->trusted = false;
 	control->encoding = -1;
 
 	/*
@@ -795,6 +806,27 @@ execute_sql_string(const char *sql)
 }
 
 /*
+ * Policy function: is the given extension trusted for installation by a
+ * non-superuser?
+ *
+ * (Update the errhint logic below if you change this.)
+ */
+static bool
+extension_is_trusted(ExtensionControlFile *control)
+{
+	AclResult	aclresult;
+
+	/* Never trust unless extension's control file says it's okay */
+	if (!control->trusted)
+		return false;
+	/* Allow if user has CREATE privilege on current database */
+	aclresult = pg_database_aclcheck(MyDatabaseId, GetUserId(), ACL_CREATE);
+	if (aclresult == ACLCHECK_OK)
+		return true;
+	return false;
+}
+
+/*
  * Execute the appropriate script file for installing or updating the extension
  *
  * If from_version isn't NULL, it's an update
@@ -806,35 +838,56 @@ execute_extension_script(Oid extensionOid, ExtensionControlFile *control,
 						 List *requiredSchemas,
 						 const char *schemaName, Oid schemaOid)
 {
+	bool		switch_to_superuser = false;
 	char	   *filename;
+	Oid			save_userid = 0;
+	int			save_sec_context = 0;
 	int			save_nestlevel;
 	StringInfoData pathbuf;
 	ListCell   *lc;
 
 	/*
-	 * Enforce superuser-ness if appropriate.  We postpone this check until
-	 * here so that the flag is correctly associated with the right script(s)
-	 * if it's set in secondary control files.
+	 * Enforce superuser-ness if appropriate.  We postpone these checks until
+	 * here so that the control flags are correctly associated with the right
+	 * script(s) if they happen to be set in secondary control files.
 	 */
 	if (control->superuser && !superuser())
 	{
-		if (from_version == NULL)
+		if (extension_is_trusted(control))
+			switch_to_superuser = true;
+		else if (from_version == NULL)
 			ereport(ERROR,
 					(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 					 errmsg("permission denied to create extension \"%s\"",
 							control->name),
-					 errhint("Must be superuser to create this extension.")));
+					 control->trusted
+					 ? errhint("Must have CREATE privilege on current database to create this extension.")
+					 : errhint("Must be superuser to create this extension.")));
 		else
 			ereport(ERROR,
 					(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 					 errmsg("permission denied to update extension \"%s\"",
 							control->name),
-					 errhint("Must be superuser to update this extension.")));
+					 control->trusted
+					 ? errhint("Must have CREATE privilege on current database to update this extension.")
+					 : errhint("Must be superuser to update this extension.")));
 	}
 
 	filename = get_extension_script_filename(control, from_version, version);
 
 	/*
+	 * If installing a trusted extension on behalf of a non-superuser, become
+	 * the bootstrap superuser.  (This switch will be cleaned up automatically
+	 * if the transaction aborts, as will the GUC changes below.)
+	 */
+	if (switch_to_superuser)
+	{
+		GetUserIdAndSecContext(&save_userid, &save_sec_context);
+		SetUserIdAndSecContext(BOOTSTRAP_SUPERUSERID,
+							   save_sec_context | SECURITY_LOCAL_USERID_CHANGE);
+	}
+
+	/*
 	 * Force client_min_messages and log_min_messages to be at least WARNING,
 	 * so that we won't spam the user with useless NOTICE messages from common
 	 * script actions like creating shell types.
@@ -907,6 +960,22 @@ execute_extension_script(Oid extensionOid, ExtensionControlFile *control,
 										CStringGetTextDatum("ng"));
 
 		/*
+		 * If the script uses @extowner@, substitute the calling username.
+		 */
+		if (strstr(c_sql, "@extowner@"))
+		{
+			Oid			uid = switch_to_superuser ? save_userid : GetUserId();
+			const char *userName = GetUserNameFromId(uid, false);
+			const char *qUserName = quote_identifier(userName);
+
+			t_sql = DirectFunctionCall3Coll(replace_text,
+											C_COLLATION_OID,
+											t_sql,
+											CStringGetTextDatum("@extowner@"),
+											CStringGetTextDatum(qUserName));
+		}
+
+		/*
 		 * If it's not relocatable, substitute the target schema name for
 		 * occurrences of @extschema@.
 		 *
@@ -953,6 +1022,12 @@ execute_extension_script(Oid extensionOid, ExtensionControlFile *control,
 	 * Restore the GUC variables we set above.
 	 */
 	AtEOXact_GUC(true, save_nestlevel);
+
+	/*
+	 * Restore authentication state if needed.
+	 */
+	if (switch_to_superuser)
+		SetUserIdAndSecContext(save_userid, save_sec_context);
 }
 
 /*
@@ -2111,8 +2186,8 @@ get_available_versions_for_extension(ExtensionControlFile *pcontrol,
 	{
 		ExtensionVersionInfo *evi = (ExtensionVersionInfo *) lfirst(lc);
 		ExtensionControlFile *control;
-		Datum		values[7];
-		bool		nulls[7];
+		Datum		values[8];
+		bool		nulls[8];
 		ListCell   *lc2;
 
 		if (!evi->installable)
@@ -2133,24 +2208,26 @@ get_available_versions_for_extension(ExtensionControlFile *pcontrol,
 		values[1] = CStringGetTextDatum(evi->name);
 		/* superuser */
 		values[2] = BoolGetDatum(control->superuser);
+		/* trusted */
+		values[3] = BoolGetDatum(control->trusted);
 		/* relocatable */
-		values[3] = BoolGetDatum(control->relocatable);
+		values[4] = BoolGetDatum(control->relocatable);
 		/* schema */
 		if (control->schema == NULL)
-			nulls[4] = true;
+			nulls[5] = true;
 		else
-			values[4] = DirectFunctionCall1(namein,
+			values[5] = DirectFunctionCall1(namein,
 											CStringGetDatum(control->schema));
 		/* requires */
 		if (control->requires == NIL)
-			nulls[5] = true;
+			nulls[6] = true;
 		else
-			values[5] = convert_requires_to_datum(control->requires);
+			values[6] = convert_requires_to_datum(control->requires);
 		/* comment */
 		if (control->comment == NULL)
-			nulls[6] = true;
+			nulls[7] = true;
 		else
-			values[6] = CStringGetTextDatum(control->comment);
+			values[7] = CStringGetTextDatum(control->comment);
 
 		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
 
@@ -2178,16 +2255,18 @@ get_available_versions_for_extension(ExtensionControlFile *pcontrol,
 				values[1] = CStringGetTextDatum(evi2->name);
 				/* superuser */
 				values[2] = BoolGetDatum(control->superuser);
+				/* trusted */
+				values[3] = BoolGetDatum(control->trusted);
 				/* relocatable */
-				values[3] = BoolGetDatum(control->relocatable);
+				values[4] = BoolGetDatum(control->relocatable);
 				/* schema stays the same */
 				/* requires */
 				if (control->requires == NIL)
-					nulls[5] = true;
+					nulls[6] = true;
 				else
 				{
-					values[5] = convert_requires_to_datum(control->requires);
-					nulls[5] = false;
+					values[6] = convert_requires_to_datum(control->requires);
+					nulls[6] = false;
 				}
 				/* comment stays the same */
 
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index bef50c7..2228256 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -9496,9 +9496,9 @@
   proname => 'pg_available_extension_versions', procost => '10',
   prorows => '100', proretset => 't', provolatile => 's',
   prorettype => 'record', proargtypes => '',
-  proallargtypes => '{name,text,bool,bool,name,_name,text}',
-  proargmodes => '{o,o,o,o,o,o,o}',
-  proargnames => '{name,version,superuser,relocatable,schema,requires,comment}',
+  proallargtypes => '{name,text,bool,bool,bool,name,_name,text}',
+  proargmodes => '{o,o,o,o,o,o,o,o}',
+  proargnames => '{name,version,superuser,trusted,relocatable,schema,requires,comment}',
   prosrc => 'pg_available_extension_versions' },
 { oid => '3084', descr => 'list an extension\'s version update paths',
   proname => 'pg_extension_update_paths', procost => '10', prorows => '100',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 70e1e2f..2ab2115 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1311,11 +1311,12 @@ pg_available_extension_versions| SELECT e.name,
     e.version,
     (x.extname IS NOT NULL) AS installed,
     e.superuser,
+    e.trusted,
     e.relocatable,
     e.schema,
     e.requires,
     e.comment
-   FROM (pg_available_extension_versions() e(name, version, superuser, relocatable, schema, requires, comment)
+   FROM (pg_available_extension_versions() e(name, version, superuser, trusted, relocatable, schema, requires, comment)
      LEFT JOIN pg_extension x ON (((e.name = x.extname) AND (e.version = x.extversion))));
 pg_available_extensions| SELECT e.name,
     e.default_version,
diff --git a/src/pl/plperl/GNUmakefile b/src/pl/plperl/GNUmakefile
index 9b1c514..e4d0a0b 100644
--- a/src/pl/plperl/GNUmakefile
+++ b/src/pl/plperl/GNUmakefile
@@ -55,8 +55,10 @@ endif # win32
 
 SHLIB_LINK = $(perl_embed_ldflags)
 
-REGRESS_OPTS = --dbname=$(PL_TESTDB) --load-extension=plperl  --load-extension=plperlu
-REGRESS = plperl plperl_lc plperl_trigger plperl_shared plperl_elog plperl_util plperl_init plperlu plperl_array plperl_call plperl_transaction
+REGRESS_OPTS = --dbname=$(PL_TESTDB)
+REGRESS = plperl_setup plperl plperl_lc plperl_trigger plperl_shared \
+	plperl_elog plperl_util plperl_init plperlu plperl_array \
+	plperl_call plperl_transaction
 # if Perl can support two interpreters in one backend,
 # test plperl-and-plperlu cases
 ifneq ($(PERL),)
diff --git a/src/pl/plperl/expected/plperl_setup.out b/src/pl/plperl/expected/plperl_setup.out
new file mode 100644
index 0000000..faeb645
--- /dev/null
+++ b/src/pl/plperl/expected/plperl_setup.out
@@ -0,0 +1,66 @@
+--
+-- Install the plperl and plperlu extensions
+--
+-- Before going ahead with the to-be-tested installations, verify that
+-- a non-superuser is allowed to install plperl (but not plperlu) when
+-- suitable permissions have been granted.
+CREATE USER regress_user1;
+CREATE USER regress_user2;
+SET ROLE regress_user1;
+CREATE EXTENSION plperl;  -- fail
+ERROR:  permission denied to create extension "plperl"
+HINT:  Must have CREATE privilege on current database to create this extension.
+CREATE EXTENSION plperlu;  -- fail
+ERROR:  permission denied to create extension "plperlu"
+HINT:  Must be superuser to create this extension.
+RESET ROLE;
+DO $$
+begin
+  execute format('grant create on database %I to regress_user1',
+                 current_database());
+end;
+$$;
+SET ROLE regress_user1;
+CREATE EXTENSION plperl;
+CREATE EXTENSION plperlu;  -- fail
+ERROR:  permission denied to create extension "plperlu"
+HINT:  Must be superuser to create this extension.
+CREATE FUNCTION foo1() returns int language plperl as '1;';
+SELECT foo1();
+ foo1 
+------
+    1
+(1 row)
+
+-- Should be able to change privileges on the language
+revoke all on language plperl from public;
+SET ROLE regress_user2;
+CREATE FUNCTION foo2() returns int language plperl as '2;';  -- fail
+ERROR:  permission denied for language plperl
+SET ROLE regress_user1;
+grant usage on language plperl to regress_user2;
+SET ROLE regress_user2;
+CREATE FUNCTION foo2() returns int language plperl as '2;';
+SELECT foo2();
+ foo2 
+------
+    2
+(1 row)
+
+SET ROLE regress_user1;
+-- Should be able to drop the extension, but not the language per se
+DROP LANGUAGE plperl CASCADE;
+ERROR:  cannot drop language plperl because extension plperl requires it
+HINT:  You can drop extension plperl instead.
+DROP EXTENSION plperl CASCADE;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to function foo1()
+drop cascades to function foo2()
+-- Clean up
+RESET ROLE;
+DROP OWNED BY regress_user1;
+DROP USER regress_user1;
+DROP USER regress_user2;
+-- Now install the versions that will be used by subsequent test scripts.
+CREATE EXTENSION plperl;
+CREATE EXTENSION plperlu;
diff --git a/src/pl/plperl/plperl--1.0.sql b/src/pl/plperl/plperl--1.0.sql
index f716ba1..5ff31e7 100644
--- a/src/pl/plperl/plperl--1.0.sql
+++ b/src/pl/plperl/plperl--1.0.sql
@@ -1,11 +1,20 @@
 /* src/pl/plperl/plperl--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 plperl_call_handler() RETURNS language_handler
+  LANGUAGE c AS 'MODULE_PATHNAME';
 
-CREATE LANGUAGE plperl;
+CREATE FUNCTION plperl_inline_handler(internal) RETURNS void
+  STRICT LANGUAGE c AS 'MODULE_PATHNAME';
+
+CREATE FUNCTION plperl_validator(oid) RETURNS void
+  STRICT LANGUAGE c AS 'MODULE_PATHNAME';
+
+CREATE TRUSTED LANGUAGE plperl
+  HANDLER plperl_call_handler
+  INLINE plperl_inline_handler
+  VALIDATOR plperl_validator;
+
+-- The language object, but not the functions, can be owned by a non-superuser.
+ALTER LANGUAGE plperl OWNER TO @extowner@;
 
 COMMENT ON LANGUAGE plperl IS 'PL/Perl procedural language';
diff --git a/src/pl/plperl/plperl.control b/src/pl/plperl/plperl.control
index 6faace1..3a2230a 100644
--- a/src/pl/plperl/plperl.control
+++ b/src/pl/plperl/plperl.control
@@ -4,4 +4,5 @@ default_version = '1.0'
 module_pathname = '$libdir/plperl'
 relocatable = false
 schema = pg_catalog
-superuser = false
+superuser = true
+trusted = true
diff --git a/src/pl/plperl/plperlu--1.0.sql b/src/pl/plperl/plperlu--1.0.sql
index 7efb4fb..10d7594 100644
--- a/src/pl/plperl/plperlu--1.0.sql
+++ b/src/pl/plperl/plperlu--1.0.sql
@@ -1,11 +1,17 @@
 /* src/pl/plperl/plperlu--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 plperlu_call_handler() RETURNS language_handler
+  LANGUAGE c AS 'MODULE_PATHNAME';
 
-CREATE LANGUAGE plperlu;
+CREATE FUNCTION plperlu_inline_handler(internal) RETURNS void
+  STRICT LANGUAGE c AS 'MODULE_PATHNAME';
+
+CREATE FUNCTION plperlu_validator(oid) RETURNS void
+  STRICT LANGUAGE c AS 'MODULE_PATHNAME';
+
+CREATE LANGUAGE plperlu
+  HANDLER plperlu_call_handler
+  INLINE plperlu_inline_handler
+  VALIDATOR plperlu_validator;
 
 COMMENT ON LANGUAGE plperlu IS 'PL/PerlU untrusted procedural language';
diff --git a/src/pl/plperl/sql/plperl_setup.sql b/src/pl/plperl/sql/plperl_setup.sql
new file mode 100644
index 0000000..ae48fea
--- /dev/null
+++ b/src/pl/plperl/sql/plperl_setup.sql
@@ -0,0 +1,64 @@
+--
+-- Install the plperl and plperlu extensions
+--
+
+-- Before going ahead with the to-be-tested installations, verify that
+-- a non-superuser is allowed to install plperl (but not plperlu) when
+-- suitable permissions have been granted.
+
+CREATE USER regress_user1;
+CREATE USER regress_user2;
+
+SET ROLE regress_user1;
+
+CREATE EXTENSION plperl;  -- fail
+CREATE EXTENSION plperlu;  -- fail
+
+RESET ROLE;
+
+DO $$
+begin
+  execute format('grant create on database %I to regress_user1',
+                 current_database());
+end;
+$$;
+
+SET ROLE regress_user1;
+
+CREATE EXTENSION plperl;
+CREATE EXTENSION plperlu;  -- fail
+
+CREATE FUNCTION foo1() returns int language plperl as '1;';
+SELECT foo1();
+
+-- Should be able to change privileges on the language
+revoke all on language plperl from public;
+
+SET ROLE regress_user2;
+
+CREATE FUNCTION foo2() returns int language plperl as '2;';  -- fail
+
+SET ROLE regress_user1;
+
+grant usage on language plperl to regress_user2;
+
+SET ROLE regress_user2;
+
+CREATE FUNCTION foo2() returns int language plperl as '2;';
+SELECT foo2();
+
+SET ROLE regress_user1;
+
+-- Should be able to drop the extension, but not the language per se
+DROP LANGUAGE plperl CASCADE;
+DROP EXTENSION plperl CASCADE;
+
+-- Clean up
+RESET ROLE;
+DROP OWNED BY regress_user1;
+DROP USER regress_user1;
+DROP USER regress_user2;
+
+-- Now install the versions that will be used by subsequent test scripts.
+CREATE EXTENSION plperl;
+CREATE EXTENSION plperlu;
diff --git a/src/pl/plpgsql/src/plpgsql--1.0.sql b/src/pl/plpgsql/src/plpgsql--1.0.sql
index ab6fa84..6e5b990 100644
--- a/src/pl/plpgsql/src/plpgsql--1.0.sql
+++ b/src/pl/plpgsql/src/plpgsql--1.0.sql
@@ -1,11 +1,20 @@
 /* src/pl/plpgsql/src/plpgsql--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 plpgsql_call_handler() RETURNS language_handler
+  LANGUAGE c AS 'MODULE_PATHNAME';
 
-CREATE LANGUAGE plpgsql;
+CREATE FUNCTION plpgsql_inline_handler(internal) RETURNS void
+  STRICT LANGUAGE c AS 'MODULE_PATHNAME';
+
+CREATE FUNCTION plpgsql_validator(oid) RETURNS void
+  STRICT LANGUAGE c AS 'MODULE_PATHNAME';
+
+CREATE TRUSTED LANGUAGE plpgsql
+  HANDLER plpgsql_call_handler
+  INLINE plpgsql_inline_handler
+  VALIDATOR plpgsql_validator;
+
+-- The language object, but not the functions, can be owned by a non-superuser.
+ALTER LANGUAGE plpgsql OWNER TO @extowner@;
 
 COMMENT ON LANGUAGE plpgsql IS 'PL/pgSQL procedural language';
diff --git a/src/pl/plpgsql/src/plpgsql.control b/src/pl/plpgsql/src/plpgsql.control
index b320227..42e764b 100644
--- a/src/pl/plpgsql/src/plpgsql.control
+++ b/src/pl/plpgsql/src/plpgsql.control
@@ -4,4 +4,5 @@ default_version = '1.0'
 module_pathname = '$libdir/plpgsql'
 relocatable = false
 schema = pg_catalog
-superuser = false
+superuser = true
+trusted = true
diff --git a/src/pl/plpython/plpython2u--1.0.sql b/src/pl/plpython/plpython2u--1.0.sql
index 661cc66..69f7477 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 c0d6ea8..ba2e6ac 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 4a3e64a..4c6f7c3 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';
diff --git a/src/pl/tcl/pltcl--1.0.sql b/src/pl/tcl/pltcl--1.0.sql
index 34a68c8..2ed2b92 100644
--- a/src/pl/tcl/pltcl--1.0.sql
+++ b/src/pl/tcl/pltcl--1.0.sql
@@ -1,11 +1,12 @@
 /* src/pl/tcl/pltcl--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 pltcl_call_handler() RETURNS language_handler
+  LANGUAGE c AS 'MODULE_PATHNAME';
 
-CREATE LANGUAGE pltcl;
+CREATE TRUSTED LANGUAGE pltcl
+  HANDLER pltcl_call_handler;
+
+-- The language object, but not the functions, can be owned by a non-superuser.
+ALTER LANGUAGE pltcl OWNER TO @extowner@;
 
 COMMENT ON LANGUAGE pltcl IS 'PL/Tcl procedural language';
diff --git a/src/pl/tcl/pltcl.control b/src/pl/tcl/pltcl.control
index b9dc1b8..1568c17 100644
--- a/src/pl/tcl/pltcl.control
+++ b/src/pl/tcl/pltcl.control
@@ -4,4 +4,5 @@ default_version = '1.0'
 module_pathname = '$libdir/pltcl'
 relocatable = false
 schema = pg_catalog
-superuser = false
+superuser = true
+trusted = true
diff --git a/src/pl/tcl/pltclu--1.0.sql b/src/pl/tcl/pltclu--1.0.sql
index e05b470..fca869f 100644
--- a/src/pl/tcl/pltclu--1.0.sql
+++ b/src/pl/tcl/pltclu--1.0.sql
@@ -1,11 +1,9 @@
 /* src/pl/tcl/pltclu--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 pltclu_call_handler() RETURNS language_handler
+  LANGUAGE c AS 'MODULE_PATHNAME';
 
-CREATE LANGUAGE pltclu;
+CREATE LANGUAGE pltclu
+  HANDLER pltclu_call_handler;
 
 COMMENT ON LANGUAGE pltclu IS 'PL/TclU untrusted procedural language';
diff --git a/doc/src/sgml/ref/create_language.sgml b/doc/src/sgml/ref/create_language.sgml
index 13b28b1..af9d115 100644
--- a/doc/src/sgml/ref/create_language.sgml
+++ b/doc/src/sgml/ref/create_language.sgml
@@ -21,9 +21,9 @@ PostgreSQL documentation
 
  
 
-CREATE [ OR REPLACE ] [ PROCEDURAL ] LANGUAGE name
 CREATE [ OR REPLACE ] [ TRUSTED ] [ PROCEDURAL ] LANGUAGE name
     HANDLER call_handler [ INLINE inline_handler ] [ VALIDATOR valfunction ]
+CREATE [ OR REPLACE ] [ TRUSTED ] [ PROCEDURAL ] LANGUAGE name
 
  
 
@@ -37,21 +37,6 @@ CREATE [ OR REPLACE ] [ TRUSTED ] [ PROCEDURAL ] LANGUAGE 
-    not CREATE LANGUAGE.  Direct use of
-    CREATE LANGUAGE should now be confined to
-    extension installation scripts.  If you have a bare
-    language in your database, perhaps as a result of an upgrade,
-    you can convert it to an extension using
-    CREATE EXTENSION langname FROM
-    unpackaged.
-   
-  
-
   
    CREATE LANGUAGE effectively associates the
    language name with handler function(s) that are responsible for executing
@@ -60,53 +45,32 @@ CREATE [ OR REPLACE ] [ TRUSTED ] [ PROCEDURAL ] LANGUAGE pg_pltemplate
-   system catalog to determine the correct parameters.  In the second form,
-   the user supplies the language parameters along with the language name.
-   The second form can be used to create a language that is not defined in
-   pg_pltemplate, but this approach is considered obsolescent.
-  
-
-  
-   When the server finds an entry in the pg_pltemplate catalog
-   for the given language name, it will use the catalog data even if the
-   command includes language parameters.  This behavior simplifies loading of
-   old dump files, which are likely to contain out-of-date information
-   about language support functions.
+   CREATE OR REPLACE LANGUAGE will either create a
+   new language, or replace an existing definition.  If the language
+   already exists, its parameters are updated according to the command,
+   but the language's ownership and permissions settings do not change,
+   and any existing functions written in the language are assumed to still
+   be valid.
   
 
   
-   Ordinarily, the user must have the
+   One must have the
    PostgreSQL superuser privilege to
-   register a new language.  However, the owner of a database can register
-   a new language within that database if the language is listed in
-   the pg_pltemplate catalog and is marked
-   as allowed to be created by database owners (tmpldbacreate
-   is true).  The default is that trusted languages can be created
-   by database owners, but this can be adjusted by superusers by modifying
-   the contents of pg_pltemplate.
-   The creator of a language becomes its owner and can later
-   drop it, rename it, or assign it to a new owner.
+   register a new language or change an existing language's parameters.
+   However, once the language is created it is valid to assign ownership of
+   it to a non-superuser, who may then drop it, change its permissions,
+   rename it, or assign it to a new owner.  (Do not, however, assign
+   ownership of the underlying C functions to a non-superuser; that would
+   create a privilege escalation path for that user.)
   
 
   
-   CREATE OR REPLACE LANGUAGE will either create a
-   new language, or replace an existing definition.  If the language
-   already exists, its parameters are updated according to the values
-   specified or taken from pg_pltemplate,
-   but the language's ownership and permissions settings do not change,
-   and any existing functions written in the language are assumed to still
-   be valid.  In addition to the normal privilege requirements for creating
-   a language, the user must be superuser or owner of the existing language.
-   The REPLACE case is mainly meant to be used to
-   ensure that the language exists.  If the language has a
-   pg_pltemplate entry then REPLACE
-   will not actually change anything about an existing definition, except in
-   the unusual case where the pg_pltemplate entry
-   has been modified since the language was created.
+   The form of CREATE LANGUAGE that does not supply
+   any handler function is obsolete.  For backwards compatibility with
+   old dump files, it is interpreted as CREATE EXTENSION.
+   That will work if the language has been packaged into an extension of
+   the same name, which is the conventional way to set up procedural
+   languages.
   
  
 
@@ -218,12 +182,6 @@ CREATE [ OR REPLACE ] [ TRUSTED ] [ PROCEDURAL ] LANGUAGE 
@@ -255,18 +213,6 @@ CREATE [ OR REPLACE ] [ TRUSTED ] [ PROCEDURAL ] LANGUAGE Examples
 
   
-   The preferred way of creating any of the standard procedural languages
-   is just:
-
-CREATE LANGUAGE plperl;
-
-  
-
-  
-   For a language not known in the pg_pltemplate catalog, a
-   sequence such as this is needed:
+   A minimal sequence for creating a new procedural language is:
 
 CREATE FUNCTION plsample_call_handler() RETURNS language_handler
     AS '$libdir/plsample'
     LANGUAGE C;
 CREATE LANGUAGE plsample
     HANDLER plsample_call_handler;
-
+
+   Typically that would be written in an extension's creation script,
+   and users would do this to install the extension:
+
+CREATE EXTENSION plsample;
+
+  
  
 
  
diff --git a/src/backend/commands/extension.c b/src/backend/commands/extension.c
index 01de398..ddd46f4 100644
--- a/src/backend/commands/extension.c
+++ b/src/backend/commands/extension.c
@@ -2277,6 +2277,64 @@ get_available_versions_for_extension(ExtensionControlFile *pcontrol,
 }
 
 /*
+ * Test whether the given extension exists (not whether it's installed)
+ *
+ * This checks for the existence of a matching control file in the extension
+ * directory.  That's not a bulletproof check, since the file might be
+ * invalid, but this is only used for hints so it doesn't have to be 100%
+ * right.
+ */
+bool
+extension_file_exists(const char *extensionName)
+{
+	bool		result = false;
+	char	   *location;
+	DIR		   *dir;
+	struct dirent *de;
+
+	location = get_extension_control_directory();
+	dir = AllocateDir(location);
+
+	/*
+	 * If the control directory doesn't exist, we want to silently return
+	 * false.  Any other error will be reported by ReadDir.
+	 */
+	if (dir == NULL && errno == ENOENT)
+	{
+		/* do nothing */
+	}
+	else
+	{
+		while ((de = ReadDir(dir, location)) != NULL)
+		{
+			char	   *extname;
+
+			if (!is_extension_control_filename(de->d_name))
+				continue;
+
+			/* extract extension name from 'name.control' filename */
+			extname = pstrdup(de->d_name);
+			*strrchr(extname, '.') = '\0';
+
+			/* ignore it if it's an auxiliary control file */
+			if (strstr(extname, "--"))
+				continue;
+
+			/* done if it matches request */
+			if (strcmp(extname, extensionName) == 0)
+			{
+				result = true;
+				break;
+			}
+		}
+
+		FreeDir(dir);
+	}
+
+	return result;
+}
+
+/*
  * Convert a list of extension names to a name[] Datum
  */
 static Datum
diff --git a/src/backend/commands/functioncmds.c b/src/backend/commands/functioncmds.c
index c31c57e..0f40c9e 100644
--- a/src/backend/commands/functioncmds.c
+++ b/src/backend/commands/functioncmds.c
@@ -49,6 +49,7 @@
 #include "catalog/pg_type.h"
 #include "commands/alter.h"
 #include "commands/defrem.h"
+#include "commands/extension.h"
 #include "commands/proclang.h"
 #include "executor/execdesc.h"
 #include "executor/executor.h"
@@ -991,7 +992,7 @@ CreateFunction(ParseState *pstate, CreateFunctionStmt *stmt)
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_OBJECT),
 				 errmsg("language \"%s\" does not exist", language),
-				 (PLTemplateExists(language) ?
+				 (extension_file_exists(language) ?
 				  errhint("Use CREATE EXTENSION to load the language into the database.") : 0)));
 
 	languageStruct = (Form_pg_language) GETSTRUCT(languageTuple);
@@ -2225,7 +2226,7 @@ ExecuteDoStmt(DoStmt *stmt, bool atomic)
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_OBJECT),
 				 errmsg("language \"%s\" does not exist", language),
-				 (PLTemplateExists(language) ?
+				 (extension_file_exists(language) ?
 				  errhint("Use CREATE EXTENSION to load the language into the database.") : 0)));
 
 	languageStruct = (Form_pg_language) GETSTRUCT(languageTuple);
diff --git a/src/backend/commands/proclang.c b/src/backend/commands/proclang.c
index cdff43d..9d72edb 100644
--- a/src/backend/commands/proclang.c
+++ b/src/backend/commands/proclang.c
@@ -13,329 +13,110 @@
  */
 #include "postgres.h"
 
-#include "access/genam.h"
-#include "access/htup_details.h"
 #include "access/table.h"
 #include "catalog/catalog.h"
 #include "catalog/dependency.h"
 #include "catalog/indexing.h"
 #include "catalog/objectaccess.h"
-#include "catalog/pg_authid.h"
 #include "catalog/pg_language.h"
 #include "catalog/pg_namespace.h"
-#include "catalog/pg_pltemplate.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
-#include "commands/dbcommands.h"
 #include "commands/defrem.h"
 #include "commands/proclang.h"
 #include "miscadmin.h"
 #include "parser/parse_func.h"
-#include "parser/parser.h"
-#include "utils/acl.h"
 #include "utils/builtins.h"
-#include "utils/fmgroids.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
 #include "utils/syscache.h"
 
 
-typedef struct
-{
-	bool		tmpltrusted;	/* trusted? */
-	bool		tmpldbacreate;	/* db owner allowed to create? */
-	char	   *tmplhandler;	/* name of handler function */
-	char	   *tmplinline;		/* name of anonymous-block handler, or NULL */
-	char	   *tmplvalidator;	/* name of validator function, or NULL */
-	char	   *tmpllibrary;	/* path of shared library */
-} PLTemplate;
-
-static ObjectAddress create_proc_lang(const char *languageName, bool replace,
-									  Oid languageOwner, Oid handlerOid, Oid inlineOid,
-									  Oid valOid, bool trusted);
-static PLTemplate *find_language_template(const char *languageName);
-
 /*
  * CREATE LANGUAGE
  */
 ObjectAddress
 CreateProceduralLanguage(CreatePLangStmt *stmt)
 {
-	PLTemplate *pltemplate;
-	ObjectAddress tmpAddr;
+	const char *languageName = stmt->plname;
+	Oid			languageOwner = GetUserId();
 	Oid			handlerOid,
 				inlineOid,
 				valOid;
 	Oid			funcrettype;
 	Oid			funcargtypes[1];
+	Relation	rel;
+	TupleDesc	tupDesc;
+	Datum		values[Natts_pg_language];
+	bool		nulls[Natts_pg_language];
+	bool		replaces[Natts_pg_language];
+	NameData	langname;
+	HeapTuple	oldtup;
+	HeapTuple	tup;
+	Oid			langoid;
+	bool		is_update;
+	ObjectAddress myself,
+				referenced;
 
 	/*
-	 * If we have template information for the language, ignore the supplied
-	 * parameters (if any) and use the template information.
+	 * Check permission
 	 */
-	if ((pltemplate = find_language_template(stmt->plname)) != NULL)
-	{
-		List	   *funcname;
-
-		/*
-		 * Give a notice if we are ignoring supplied parameters.
-		 */
-		if (stmt->plhandler)
-			ereport(NOTICE,
-					(errmsg("using pg_pltemplate information instead of CREATE LANGUAGE parameters")));
-
-		/*
-		 * Check permission
-		 */
-		if (!superuser())
-		{
-			if (!pltemplate->tmpldbacreate)
-				ereport(ERROR,
-						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-						 errmsg("must be superuser to create procedural language \"%s\"",
-								stmt->plname)));
-			if (!pg_database_ownercheck(MyDatabaseId, GetUserId()))
-				aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_DATABASE,
-							   get_database_name(MyDatabaseId));
-		}
-
-		/*
-		 * Find or create the handler function, which we force to be in the
-		 * pg_catalog schema.  If already present, it must have the correct
-		 * return type.
-		 */
-		funcname = SystemFuncName(pltemplate->tmplhandler);
-		handlerOid = LookupFuncName(funcname, 0, NULL, true);
-		if (OidIsValid(handlerOid))
-		{
-			funcrettype = get_func_rettype(handlerOid);
-			if (funcrettype != LANGUAGE_HANDLEROID)
-				ereport(ERROR,
-						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-						 errmsg("function %s must return type %s",
-								NameListToString(funcname), "language_handler")));
-		}
-		else
-		{
-			tmpAddr = ProcedureCreate(pltemplate->tmplhandler,
-									  PG_CATALOG_NAMESPACE,
-									  false,	/* replace */
-									  false,	/* returnsSet */
-									  LANGUAGE_HANDLEROID,
-									  BOOTSTRAP_SUPERUSERID,
-									  ClanguageId,
-									  F_FMGR_C_VALIDATOR,
-									  pltemplate->tmplhandler,
-									  pltemplate->tmpllibrary,
-									  PROKIND_FUNCTION,
-									  false,	/* security_definer */
-									  false,	/* isLeakProof */
-									  false,	/* isStrict */
-									  PROVOLATILE_VOLATILE,
-									  PROPARALLEL_UNSAFE,
-									  buildoidvector(funcargtypes, 0),
-									  PointerGetDatum(NULL),
-									  PointerGetDatum(NULL),
-									  PointerGetDatum(NULL),
-									  NIL,
-									  PointerGetDatum(NULL),
-									  PointerGetDatum(NULL),
-									  InvalidOid,
-									  1,
-									  0);
-			handlerOid = tmpAddr.objectId;
-		}
-
-		/*
-		 * Likewise for the anonymous block handler, if required; but we don't
-		 * care about its return type.
-		 */
-		if (pltemplate->tmplinline)
-		{
-			funcname = SystemFuncName(pltemplate->tmplinline);
-			funcargtypes[0] = INTERNALOID;
-			inlineOid = LookupFuncName(funcname, 1, funcargtypes, true);
-			if (!OidIsValid(inlineOid))
-			{
-				tmpAddr = ProcedureCreate(pltemplate->tmplinline,
-										  PG_CATALOG_NAMESPACE,
-										  false,	/* replace */
-										  false,	/* returnsSet */
-										  VOIDOID,
-										  BOOTSTRAP_SUPERUSERID,
-										  ClanguageId,
-										  F_FMGR_C_VALIDATOR,
-										  pltemplate->tmplinline,
-										  pltemplate->tmpllibrary,
-										  PROKIND_FUNCTION,
-										  false,	/* security_definer */
-										  false,	/* isLeakProof */
-										  true, /* isStrict */
-										  PROVOLATILE_VOLATILE,
-										  PROPARALLEL_UNSAFE,
-										  buildoidvector(funcargtypes, 1),
-										  PointerGetDatum(NULL),
-										  PointerGetDatum(NULL),
-										  PointerGetDatum(NULL),
-										  NIL,
-										  PointerGetDatum(NULL),
-										  PointerGetDatum(NULL),
-										  InvalidOid,
-										  1,
-										  0);
-				inlineOid = tmpAddr.objectId;
-			}
-		}
-		else
-			inlineOid = InvalidOid;
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("must be superuser to create custom procedural language")));
 
+	/*
+	 * Lookup the PL handler function and check that it is of the expected
+	 * return type
+	 */
+	Assert(stmt->plhandler);
+	handlerOid = LookupFuncName(stmt->plhandler, 0, NULL, false);
+	funcrettype = get_func_rettype(handlerOid);
+	if (funcrettype != LANGUAGE_HANDLEROID)
+	{
 		/*
-		 * Likewise for the validator, if required; but we don't care about
-		 * its return type.
+		 * We allow OPAQUE just so we can load old dump files.  When we see a
+		 * handler function declared OPAQUE, change it to LANGUAGE_HANDLER.
+		 * (This is probably obsolete and removable?)
 		 */
-		if (pltemplate->tmplvalidator)
+		if (funcrettype == OPAQUEOID)
 		{
-			funcname = SystemFuncName(pltemplate->tmplvalidator);
-			funcargtypes[0] = OIDOID;
-			valOid = LookupFuncName(funcname, 1, funcargtypes, true);
-			if (!OidIsValid(valOid))
-			{
-				tmpAddr = ProcedureCreate(pltemplate->tmplvalidator,
-										  PG_CATALOG_NAMESPACE,
-										  false,	/* replace */
-										  false,	/* returnsSet */
-										  VOIDOID,
-										  BOOTSTRAP_SUPERUSERID,
-										  ClanguageId,
-										  F_FMGR_C_VALIDATOR,
-										  pltemplate->tmplvalidator,
-										  pltemplate->tmpllibrary,
-										  PROKIND_FUNCTION,
-										  false,	/* security_definer */
-										  false,	/* isLeakProof */
-										  true, /* isStrict */
-										  PROVOLATILE_VOLATILE,
-										  PROPARALLEL_UNSAFE,
-										  buildoidvector(funcargtypes, 1),
-										  PointerGetDatum(NULL),
-										  PointerGetDatum(NULL),
-										  PointerGetDatum(NULL),
-										  NIL,
-										  PointerGetDatum(NULL),
-										  PointerGetDatum(NULL),
-										  InvalidOid,
-										  1,
-										  0);
-				valOid = tmpAddr.objectId;
-			}
+			ereport(WARNING,
+					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+					 errmsg("changing return type of function %s from %s to %s",
+							NameListToString(stmt->plhandler),
+							"opaque", "language_handler")));
+			SetFunctionReturnType(handlerOid, LANGUAGE_HANDLEROID);
 		}
 		else
-			valOid = InvalidOid;
+			ereport(ERROR,
+					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+					 errmsg("function %s must return type %s",
+							NameListToString(stmt->plhandler), "language_handler")));
+	}
 
-		/* ok, create it */
-		return create_proc_lang(stmt->plname, stmt->replace, GetUserId(),
-								handlerOid, inlineOid,
-								valOid, pltemplate->tmpltrusted);
+	/* validate the inline function */
+	if (stmt->plinline)
+	{
+		funcargtypes[0] = INTERNALOID;
+		inlineOid = LookupFuncName(stmt->plinline, 1, funcargtypes, false);
+		/* return value is ignored, so we don't check the type */
 	}
 	else
-	{
-		/*
-		 * No template, so use the provided information.  If there's no
-		 * handler clause, the user is trying to rely on a template that we
-		 * don't have, so complain accordingly.
-		 */
-		if (!stmt->plhandler)
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_OBJECT),
-					 errmsg("unsupported language \"%s\"",
-							stmt->plname),
-					 errhint("The supported languages are listed in the pg_pltemplate system catalog.")));
+		inlineOid = InvalidOid;
 
-		/*
-		 * Check permission
-		 */
-		if (!superuser())
-			ereport(ERROR,
-					(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-					 errmsg("must be superuser to create custom procedural language")));
-
-		/*
-		 * Lookup the PL handler function and check that it is of the expected
-		 * return type
-		 */
-		handlerOid = LookupFuncName(stmt->plhandler, 0, NULL, false);
-		funcrettype = get_func_rettype(handlerOid);
-		if (funcrettype != LANGUAGE_HANDLEROID)
-		{
-			/*
-			 * We allow OPAQUE just so we can load old dump files.  When we
-			 * see a handler function declared OPAQUE, change it to
-			 * LANGUAGE_HANDLER.  (This is probably obsolete and removable?)
-			 */
-			if (funcrettype == OPAQUEOID)
-			{
-				ereport(WARNING,
-						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-						 errmsg("changing return type of function %s from %s to %s",
-								NameListToString(stmt->plhandler),
-								"opaque", "language_handler")));
-				SetFunctionReturnType(handlerOid, LANGUAGE_HANDLEROID);
-			}
-			else
-				ereport(ERROR,
-						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-						 errmsg("function %s must return type %s",
-								NameListToString(stmt->plhandler), "language_handler")));
-		}
-
-		/* validate the inline function */
-		if (stmt->plinline)
-		{
-			funcargtypes[0] = INTERNALOID;
-			inlineOid = LookupFuncName(stmt->plinline, 1, funcargtypes, false);
-			/* return value is ignored, so we don't check the type */
-		}
-		else
-			inlineOid = InvalidOid;
-
-		/* validate the validator function */
-		if (stmt->plvalidator)
-		{
-			funcargtypes[0] = OIDOID;
-			valOid = LookupFuncName(stmt->plvalidator, 1, funcargtypes, false);
-			/* return value is ignored, so we don't check the type */
-		}
-		else
-			valOid = InvalidOid;
-
-		/* ok, create it */
-		return create_proc_lang(stmt->plname, stmt->replace, GetUserId(),
-								handlerOid, inlineOid,
-								valOid, stmt->pltrusted);
+	/* validate the validator function */
+	if (stmt->plvalidator)
+	{
+		funcargtypes[0] = OIDOID;
+		valOid = LookupFuncName(stmt->plvalidator, 1, funcargtypes, false);
+		/* return value is ignored, so we don't check the type */
 	}
-}
-
-/*
- * Guts of language creation.
- */
-static ObjectAddress
-create_proc_lang(const char *languageName, bool replace,
-				 Oid languageOwner, Oid handlerOid, Oid inlineOid,
-				 Oid valOid, bool trusted)
-{
-	Relation	rel;
-	TupleDesc	tupDesc;
-	Datum		values[Natts_pg_language];
-	bool		nulls[Natts_pg_language];
-	bool		replaces[Natts_pg_language];
-	NameData	langname;
-	HeapTuple	oldtup;
-	HeapTuple	tup;
-	Oid			langoid;
-	bool		is_update;
-	ObjectAddress myself,
-				referenced;
+	else
+		valOid = InvalidOid;
 
+	/* ok to create it */
 	rel = table_open(LanguageRelationId, RowExclusiveLock);
 	tupDesc = RelationGetDescr(rel);
 
@@ -348,7 +129,7 @@ create_proc_lang(const char *languageName, bool replace,
 	values[Anum_pg_language_lanname - 1] = NameGetDatum(&langname);
 	values[Anum_pg_language_lanowner - 1] = ObjectIdGetDatum(languageOwner);
 	values[Anum_pg_language_lanispl - 1] = BoolGetDatum(true);
-	values[Anum_pg_language_lanpltrusted - 1] = BoolGetDatum(trusted);
+	values[Anum_pg_language_lanpltrusted - 1] = BoolGetDatum(stmt->pltrusted);
 	values[Anum_pg_language_lanplcallfoid - 1] = ObjectIdGetDatum(handlerOid);
 	values[Anum_pg_language_laninline - 1] = ObjectIdGetDatum(inlineOid);
 	values[Anum_pg_language_lanvalidator - 1] = ObjectIdGetDatum(valOid);
@@ -362,13 +143,17 @@ create_proc_lang(const char *languageName, bool replace,
 		Form_pg_language oldform = (Form_pg_language) GETSTRUCT(oldtup);
 
 		/* There is one; okay to replace it? */
-		if (!replace)
+		if (!stmt->replace)
 			ereport(ERROR,
 					(errcode(ERRCODE_DUPLICATE_OBJECT),
 					 errmsg("language \"%s\" already exists", languageName)));
+
+		/* This is currently pointless, since we already checked superuser */
+#ifdef NOT_USED
 		if (!pg_language_ownercheck(oldform->oid, languageOwner))
 			aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_LANGUAGE,
 						   languageName);
+#endif
 
 		/*
 		 * Do not change existing oid, ownership or permissions.  Note
@@ -451,83 +236,6 @@ create_proc_lang(const char *languageName, bool replace,
 }
 
 /*
- * Look to see if we have template information for the given language name.
- */
-static PLTemplate *
-find_language_template(const char *languageName)
-{
-	PLTemplate *result;
-	Relation	rel;
-	SysScanDesc scan;
-	ScanKeyData key;
-	HeapTuple	tup;
-
-	rel = table_open(PLTemplateRelationId, AccessShareLock);
-
-	ScanKeyInit(&key,
-				Anum_pg_pltemplate_tmplname,
-				BTEqualStrategyNumber, F_NAMEEQ,
-				CStringGetDatum(languageName));
-	scan = systable_beginscan(rel, PLTemplateNameIndexId, true,
-							  NULL, 1, &key);
-
-	tup = systable_getnext(scan);
-	if (HeapTupleIsValid(tup))
-	{
-		Form_pg_pltemplate tmpl = (Form_pg_pltemplate) GETSTRUCT(tup);
-		Datum		datum;
-		bool		isnull;
-
-		result = (PLTemplate *) palloc0(sizeof(PLTemplate));
-		result->tmpltrusted = tmpl->tmpltrusted;
-		result->tmpldbacreate = tmpl->tmpldbacreate;
-
-		/* Remaining fields are variable-width so we need heap_getattr */
-		datum = heap_getattr(tup, Anum_pg_pltemplate_tmplhandler,
-							 RelationGetDescr(rel), &isnull);
-		if (!isnull)
-			result->tmplhandler = TextDatumGetCString(datum);
-
-		datum = heap_getattr(tup, Anum_pg_pltemplate_tmplinline,
-							 RelationGetDescr(rel), &isnull);
-		if (!isnull)
-			result->tmplinline = TextDatumGetCString(datum);
-
-		datum = heap_getattr(tup, Anum_pg_pltemplate_tmplvalidator,
-							 RelationGetDescr(rel), &isnull);
-		if (!isnull)
-			result->tmplvalidator = TextDatumGetCString(datum);
-
-		datum = heap_getattr(tup, Anum_pg_pltemplate_tmpllibrary,
-							 RelationGetDescr(rel), &isnull);
-		if (!isnull)
-			result->tmpllibrary = TextDatumGetCString(datum);
-
-		/* Ignore template if handler or library info is missing */
-		if (!result->tmplhandler || !result->tmpllibrary)
-			result = NULL;
-	}
-	else
-		result = NULL;
-
-	systable_endscan(scan);
-
-	table_close(rel, AccessShareLock);
-
-	return result;
-}
-
-
-/*
- * This just returns true if we have a valid template for a given language
- */
-bool
-PLTemplateExists(const char *languageName)
-{
-	return (find_language_template(languageName) != NULL);
-}
-
-/*
  * Guts of language dropping.
  */
 void
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index ba5916b..1b0edf5 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -4324,14 +4324,17 @@ NumericOnly_list:	NumericOnly						{ $$ = list_make1($1); }
 CreatePLangStmt:
 			CREATE opt_or_replace opt_trusted opt_procedural LANGUAGE NonReservedWord_or_Sconst
 			{
-				CreatePLangStmt *n = makeNode(CreatePLangStmt);
-				n->replace = $2;
-				n->plname = $6;
-				/* parameters are all to be supplied by system */
-				n->plhandler = NIL;
-				n->plinline = NIL;
-				n->plvalidator = NIL;
-				n->pltrusted = false;
+				/*
+				 * We now interpret parameterless CREATE LANGUAGE as
+				 * CREATE EXTENSION.  "OR REPLACE" is silently translated
+				 * to "IF NOT EXISTS", which isn't quite the same, but
+				 * seems more useful than throwing an error.  We just
+				 * ignore TRUSTED, as the previous code would have too.
+				 */
+				CreateExtensionStmt *n = makeNode(CreateExtensionStmt);
+				n->if_not_exists = $2;
+				n->extname = $6;
+				n->options = NIL;
 				$$ = (Node *)n;
 			}
 			| CREATE opt_or_replace opt_trusted opt_procedural LANGUAGE NonReservedWord_or_Sconst
diff --git a/src/include/commands/extension.h b/src/include/commands/extension.h
index 6f10707..7923cdc 100644
--- a/src/include/commands/extension.h
+++ b/src/include/commands/extension.h
@@ -47,6 +47,7 @@ extern ObjectAddress ExecAlterExtensionContentsStmt(AlterExtensionContentsStmt *
 
 extern Oid	get_extension_oid(const char *extname, bool missing_ok);
 extern char *get_extension_name(Oid ext_oid);
+extern bool extension_file_exists(const char *extensionName);
 
 extern ObjectAddress AlterExtensionNamespace(const char *extensionName, const char *newschema,
 											 Oid *oldschema);
diff --git a/src/include/commands/proclang.h b/src/include/commands/proclang.h
index 9a4bc75..c70f8ec 100644
--- a/src/include/commands/proclang.h
+++ b/src/include/commands/proclang.h
@@ -1,11 +1,12 @@
-/*
- * src/include/commands/proclang.h
- *
- *-------------------------------------------------------------------------
+/*-------------------------------------------------------------------------
  *
  * proclang.h
  *	  prototypes for proclang.c.
  *
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/commands/proclang.h
  *
  *-------------------------------------------------------------------------
  */
@@ -17,7 +18,7 @@
 
 extern ObjectAddress CreateProceduralLanguage(CreatePLangStmt *stmt);
 extern void DropProceduralLanguageById(Oid langOid);
-extern bool PLTemplateExists(const char *languageName);
+
 extern Oid	get_language_oid(const char *langname, bool missing_ok);
 
 #endif							/* PROCLANG_H */
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 85ac79f..a10b665 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -226,11 +226,6 @@
      
 
      
-      pg_pltemplate
-      template data for procedural languages
-     
-
-     
       pg_policy
       row-security policies
      
@@ -4911,113 +4906,6 @@ SCRAM-SHA-256$<iteration count>:&l
  
 
 
- 
-  <structname>pg_pltemplate</structname>
-
-  
-   pg_pltemplate
-  
-
-  
-   The catalog pg_pltemplate stores
-   template information for procedural languages.
-   A template for a language allows the language to be created in a
-   particular database by a simple CREATE LANGUAGE command,
-   with no need to specify implementation details.
-  
-
-  
-   Unlike most system catalogs, pg_pltemplate
-   is shared across all databases of a cluster: there is only one
-   copy of pg_pltemplate per cluster, not
-   one per database.  This allows the information to be accessible in
-   each database as it is needed.
-  
-
-  
-   <structname>pg_pltemplate</structname> Columns
-
-   
-    
-     
-      Name
-      Type
-      Description
-     
-    
-
-    
-     
-      tmplname
-      name
-      Name of the language this template is for
-     
-
-     
-      tmpltrusted
-      boolean
-      True if language is considered trusted
-     
-
-     
-      tmpldbacreate
-      boolean
-      True if language may be created by a database owner
-     
-
-     
-      tmplhandler
-      text
-      Name of call handler function
-     
-
-     
-      tmplinline
-      text
-      Name of anonymous-block handler function, or null if none
-     
-
-     
-      tmplvalidator
-      text
-      Name of validator function, or null if none
-     
-
-     
-      tmpllibrary
-      text
-      Path of shared library that implements language
-     
-
-     
-      tmplacl
-      aclitem[]
-      Access privileges for template (not actually used)
-     
-
-    
-   
-  
-
-  
-   There are not currently any commands that manipulate procedural language
-   templates; to change the built-in information, a superuser must modify
-   the table using ordinary INSERT, DELETE,
-   or UPDATE commands.
-  
-
-  
-   
-    It is likely that pg_pltemplate will be removed in some
-    future release of PostgreSQL, in favor of
-    keeping this knowledge about procedural languages in their respective
-    extension installation scripts.
-   
-  
-
- 
-
-
  
   <structname>pg_policy</structname>
 
diff --git a/doc/src/sgml/plpython.sgml b/doc/src/sgml/plpython.sgml
index 7bdaf76..1921915 100644
--- a/doc/src/sgml/plpython.sgml
+++ b/doc/src/sgml/plpython.sgml
@@ -153,7 +153,7 @@
      
       Daredevils, who want to build a Python-3-only operating system
       environment, can change the contents of
-      pg_pltemplate
+      plpythonu's extension control and script files
       to make plpythonu be equivalent
       to plpython3u, keeping in mind that this
       would make their installation incompatible with most of the rest
diff --git a/doc/src/sgml/xplang.sgml b/doc/src/sgml/xplang.sgml
index 60e0430..e647e2d 100644
--- a/doc/src/sgml/xplang.sgml
+++ b/doc/src/sgml/xplang.sgml
@@ -190,7 +190,7 @@ CREATE FUNCTION plperl_call_handler() RETURNS language_handler AS
 
 
 CREATE FUNCTION plperl_inline_handler(internal) RETURNS void AS
-    '$libdir/plperl' LANGUAGE C;
+    '$libdir/plperl' LANGUAGE C STRICT;
 
 CREATE FUNCTION plperl_validator(oid) RETURNS void AS
     '$libdir/plperl' LANGUAGE C STRICT;
diff --git a/src/backend/catalog/Makefile b/src/backend/catalog/Makefile
index d5da81c..f8f0b48 100644
--- a/src/backend/catalog/Makefile
+++ b/src/backend/catalog/Makefile
@@ -58,7 +58,7 @@ CATALOG_HEADERS := \
 	pg_statistic_ext.h pg_statistic_ext_data.h \
 	pg_statistic.h pg_rewrite.h pg_trigger.h pg_event_trigger.h pg_description.h \
 	pg_cast.h pg_enum.h pg_namespace.h pg_conversion.h pg_depend.h \
-	pg_database.h pg_db_role_setting.h pg_tablespace.h pg_pltemplate.h \
+	pg_database.h pg_db_role_setting.h pg_tablespace.h \
 	pg_authid.h pg_auth_members.h pg_shdepend.h pg_shdescription.h \
 	pg_ts_config.h pg_ts_config_map.h pg_ts_dict.h \
 	pg_ts_parser.h pg_ts_template.h pg_extension.h \
@@ -84,7 +84,7 @@ POSTGRES_BKI_DATA = $(addprefix $(top_srcdir)/src/include/catalog/,\
 	pg_cast.dat pg_class.dat pg_collation.dat pg_conversion.dat \
 	pg_database.dat pg_language.dat \
 	pg_namespace.dat pg_opclass.dat pg_operator.dat pg_opfamily.dat \
-	pg_pltemplate.dat pg_proc.dat pg_range.dat pg_tablespace.dat \
+	pg_proc.dat pg_range.dat pg_tablespace.dat \
 	pg_ts_config.dat pg_ts_config_map.dat pg_ts_dict.dat pg_ts_parser.dat \
 	pg_ts_template.dat pg_type.dat \
 	)
diff --git a/src/backend/catalog/catalog.c b/src/backend/catalog/catalog.c
index 16cb6d8..7d6acae 100644
--- a/src/backend/catalog/catalog.c
+++ b/src/backend/catalog/catalog.c
@@ -33,7 +33,6 @@
 #include "catalog/pg_database.h"
 #include "catalog/pg_db_role_setting.h"
 #include "catalog/pg_namespace.h"
-#include "catalog/pg_pltemplate.h"
 #include "catalog/pg_replication_origin.h"
 #include "catalog/pg_shdepend.h"
 #include "catalog/pg_shdescription.h"
@@ -242,7 +241,6 @@ IsSharedRelation(Oid relationId)
 	if (relationId == AuthIdRelationId ||
 		relationId == AuthMemRelationId ||
 		relationId == DatabaseRelationId ||
-		relationId == PLTemplateRelationId ||
 		relationId == SharedDescriptionRelationId ||
 		relationId == SharedDependRelationId ||
 		relationId == SharedSecLabelRelationId ||
@@ -258,7 +256,6 @@ IsSharedRelation(Oid relationId)
 		relationId == AuthMemMemRoleIndexId ||
 		relationId == DatabaseNameIndexId ||
 		relationId == DatabaseOidIndexId ||
-		relationId == PLTemplateNameIndexId ||
 		relationId == SharedDescriptionObjIndexId ||
 		relationId == SharedDependDependerIndexId ||
 		relationId == SharedDependReferenceIndexId ||
@@ -278,8 +275,6 @@ IsSharedRelation(Oid relationId)
 		relationId == PgDatabaseToastIndex ||
 		relationId == PgDbRoleSettingToastTable ||
 		relationId == PgDbRoleSettingToastIndex ||
-		relationId == PgPlTemplateToastTable ||
-		relationId == PgPlTemplateToastIndex ||
 		relationId == PgReplicationOriginToastTable ||
 		relationId == PgReplicationOriginToastIndex ||
 		relationId == PgShdescriptionToastTable ||
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 799b698..ec3e2c6 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -11396,9 +11396,9 @@ dumpProcLang(Archive *fout, ProcLangInfo *plang)
 	}
 
 	/*
-	 * If the functions are dumpable then emit a traditional CREATE LANGUAGE
-	 * with parameters.  Otherwise, we'll write a parameterless command, which
-	 * will rely on data from pg_pltemplate.
+	 * If the functions are dumpable then emit a complete CREATE LANGUAGE with
+	 * parameters.  Otherwise, we'll write a parameterless command, which will
+	 * be interpreted as CREATE EXTENSION.
 	 */
 	useParams = (funcInfo != NULL &&
 				 (inlineInfo != NULL || !OidIsValid(plang->laninline)) &&
@@ -11431,11 +11431,11 @@ dumpProcLang(Archive *fout, ProcLangInfo *plang)
 		/*
 		 * If not dumping parameters, then use CREATE OR REPLACE so that the
 		 * command will not fail if the language is preinstalled in the target
-		 * database.  We restrict the use of REPLACE to this case so as to
-		 * eliminate the risk of replacing a language with incompatible
-		 * parameter settings: this command will only succeed at all if there
-		 * is a pg_pltemplate entry, and if there is one, the existing entry
-		 * must match it too.
+		 * database.
+		 *
+		 * Modern servers will interpret this as CREATE EXTENSION IF NOT
+		 * EXISTS; perhaps we should emit that instead?  But it might just add
+		 * confusion.
 		 */
 		appendPQExpBuffer(defqry, "CREATE OR REPLACE PROCEDURAL LANGUAGE %s",
 						  qlanname);
diff --git a/src/bin/pg_upgrade/function.c b/src/bin/pg_upgrade/function.c
index 28638e9..d163cb2 100644
--- a/src/bin/pg_upgrade/function.c
+++ b/src/bin/pg_upgrade/function.c
@@ -214,13 +214,9 @@ check_loadable_libraries(void)
 			 * plpython2u language was created with library name plpython2.so
 			 * as a symbolic link to plpython.so.  In Postgres 9.1, only the
 			 * plpython2.so library was created, and both plpythonu and
-			 * plpython2u pointing to it.  For this reason, any reference to
+			 * plpython2u point to it.  For this reason, any reference to
 			 * library name "plpython" in an old PG <= 9.1 cluster must look
 			 * for "plpython2" in the new cluster.
-			 *
-			 * For this case, we could check pg_pltemplate, but that only
-			 * works for languages, and does not help with function shared
-			 * objects, so we just do a general fix.
 			 */
 			if (GET_MAJOR_VERSION(old_cluster.major_version) < 901 &&
 				strcmp(lib, "$libdir/plpython") == 0)
diff --git a/src/include/catalog/indexing.h b/src/include/catalog/indexing.h
index 13e07fc..8be3038 100644
--- a/src/include/catalog/indexing.h
+++ b/src/include/catalog/indexing.h
@@ -206,9 +206,6 @@ DECLARE_UNIQUE_INDEX(pg_opfamily_am_name_nsp_index, 2754, on pg_opfamily using b
 DECLARE_UNIQUE_INDEX(pg_opfamily_oid_index, 2755, on pg_opfamily using btree(oid oid_ops));
 #define OpfamilyOidIndexId	2755
 
-DECLARE_UNIQUE_INDEX(pg_pltemplate_name_index, 1137, on pg_pltemplate using btree(tmplname name_ops));
-#define PLTemplateNameIndexId  1137
-
 DECLARE_UNIQUE_INDEX(pg_proc_oid_index, 2690, on pg_proc using btree(oid oid_ops));
 #define ProcedureOidIndexId  2690
 DECLARE_UNIQUE_INDEX(pg_proc_proname_args_nsp_index, 2691, on pg_proc using btree(proname name_ops, proargtypes oidvector_ops, pronamespace oid_ops));
diff --git a/src/include/catalog/pg_pltemplate.dat b/src/include/catalog/pg_pltemplate.dat
deleted file mode 100644
index 1c96b30..0000000
--- a/src/include/catalog/pg_pltemplate.dat
+++ /dev/null
@@ -1,51 +0,0 @@
-#----------------------------------------------------------------------
-#
-# pg_pltemplate.dat
-#    Initial contents of the pg_pltemplate system catalog.
-#
-# Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
-# Portions Copyright (c) 1994, Regents of the University of California
-#
-# src/include/catalog/pg_pltemplate.dat
-#
-#----------------------------------------------------------------------
-
-[
-
-{ tmplname => 'plpgsql', tmpltrusted => 't', tmpldbacreate => 't',
-  tmplhandler => 'plpgsql_call_handler', tmplinline => 'plpgsql_inline_handler',
-  tmplvalidator => 'plpgsql_validator', tmpllibrary => '$libdir/plpgsql',
-  tmplacl => '_null_' },
-{ tmplname => 'pltcl', tmpltrusted => 't', tmpldbacreate => 't',
-  tmplhandler => 'pltcl_call_handler', tmplinline => '_null_',
-  tmplvalidator => '_null_', tmpllibrary => '$libdir/pltcl',
-  tmplacl => '_null_' },
-{ tmplname => 'pltclu', tmpltrusted => 'f', tmpldbacreate => 'f',
-  tmplhandler => 'pltclu_call_handler', tmplinline => '_null_',
-  tmplvalidator => '_null_', tmpllibrary => '$libdir/pltcl',
-  tmplacl => '_null_' },
-{ tmplname => 'plperl', tmpltrusted => 't', tmpldbacreate => 't',
-  tmplhandler => 'plperl_call_handler', tmplinline => 'plperl_inline_handler',
-  tmplvalidator => 'plperl_validator', tmpllibrary => '$libdir/plperl',
-  tmplacl => '_null_' },
-{ tmplname => 'plperlu', tmpltrusted => 'f', tmpldbacreate => 'f',
-  tmplhandler => 'plperlu_call_handler', tmplinline => 'plperlu_inline_handler',
-  tmplvalidator => 'plperlu_validator', tmpllibrary => '$libdir/plperl',
-  tmplacl => '_null_' },
-{ tmplname => 'plpythonu', tmpltrusted => 'f', tmpldbacreate => 'f',
-  tmplhandler => 'plpython_call_handler',
-  tmplinline => 'plpython_inline_handler',
-  tmplvalidator => 'plpython_validator', tmpllibrary => '$libdir/plpython2',
-  tmplacl => '_null_' },
-{ tmplname => 'plpython2u', tmpltrusted => 'f', tmpldbacreate => 'f',
-  tmplhandler => 'plpython2_call_handler',
-  tmplinline => 'plpython2_inline_handler',
-  tmplvalidator => 'plpython2_validator', tmpllibrary => '$libdir/plpython2',
-  tmplacl => '_null_' },
-{ tmplname => 'plpython3u', tmpltrusted => 'f', tmpldbacreate => 'f',
-  tmplhandler => 'plpython3_call_handler',
-  tmplinline => 'plpython3_inline_handler',
-  tmplvalidator => 'plpython3_validator', tmpllibrary => '$libdir/plpython3',
-  tmplacl => '_null_' },
-
-]
diff --git a/src/include/catalog/pg_pltemplate.h b/src/include/catalog/pg_pltemplate.h
deleted file mode 100644
index b930730..0000000
--- a/src/include/catalog/pg_pltemplate.h
+++ /dev/null
@@ -1,52 +0,0 @@
-/*-------------------------------------------------------------------------
- *
- * pg_pltemplate.h
- *	  definition of the "PL template" system catalog (pg_pltemplate)
- *
- *
- * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
- * Portions Copyright (c) 1994, Regents of the University of California
- *
- * src/include/catalog/pg_pltemplate.h
- *
- * NOTES
- *	  The Catalog.pm module reads this file and derives schema
- *	  information.
- *
- *-------------------------------------------------------------------------
- */
-#ifndef PG_PLTEMPLATE_H
-#define PG_PLTEMPLATE_H
-
-#include "catalog/genbki.h"
-#include "catalog/pg_pltemplate_d.h"
-
-/* ----------------
- *		pg_pltemplate definition.  cpp turns this into
- *		typedef struct FormData_pg_pltemplate
- * ----------------
- */
-CATALOG(pg_pltemplate,1136,PLTemplateRelationId) BKI_SHARED_RELATION
-{
-	NameData	tmplname;		/* name of PL */
-	bool		tmpltrusted;	/* PL is trusted? */
-	bool		tmpldbacreate;	/* PL is installable by db owner? */
-
-#ifdef CATALOG_VARLEN			/* variable-length fields start here */
-	text		tmplhandler BKI_FORCE_NOT_NULL; /* name of call handler
-												 * function */
-	text		tmplinline;		/* name of anonymous-block handler, or NULL */
-	text		tmplvalidator;	/* name of validator function, or NULL */
-	text		tmpllibrary BKI_FORCE_NOT_NULL; /* path of shared library */
-	aclitem		tmplacl[1];		/* access privileges for template */
-#endif
-} FormData_pg_pltemplate;
-
-/* ----------------
- *		Form_pg_pltemplate corresponds to a pointer to a row with
- *		the format of pg_pltemplate relation.
- * ----------------
- */
-typedef FormData_pg_pltemplate *Form_pg_pltemplate;
-
-#endif							/* PG_PLTEMPLATE_H */
diff --git a/src/include/catalog/toasting.h b/src/include/catalog/toasting.h
index 3281dbd..51491c4 100644
--- a/src/include/catalog/toasting.h
+++ b/src/include/catalog/toasting.h
@@ -86,9 +86,6 @@ DECLARE_TOAST(pg_database, 4177, 4178);
 DECLARE_TOAST(pg_db_role_setting, 2966, 2967);
 #define PgDbRoleSettingToastTable 2966
 #define PgDbRoleSettingToastIndex 2967
-DECLARE_TOAST(pg_pltemplate, 4179, 4180);
-#define PgPlTemplateToastTable 4179
-#define PgPlTemplateToastIndex 4180
 DECLARE_TOAST(pg_replication_origin, 4181, 4182);
 #define PgReplicationOriginToastTable 4181
 #define PgReplicationOriginToastIndex 4182
diff --git a/src/pl/plpython/plpy_main.c b/src/pl/plpython/plpy_main.c
index faaec55..882d69e 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/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index 070de78..f0cd40b 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -134,7 +134,6 @@ pg_opclass|t
 pg_operator|t
 pg_opfamily|t
 pg_partitioned_table|t
-pg_pltemplate|t
 pg_policy|t
 pg_proc|t
 pg_publication|t