Allow non-superusers to create (some) extensions.

Remove the unconditional superuser permissions check in CREATE EXTENSION,
and instead define a "superuser" extension property, which when false
(not the default) skips the superuser permissions check.  In this case
the calling user only needs enough permissions to execute the commands
in the extension's installation script.  The superuser property is also
enforced in the same way for ALTER EXTENSION UPDATE cases.

In other ALTER EXTENSION cases and DROP EXTENSION, test ownership of
the extension rather than superuserness.  ALTER EXTENSION ADD/DROP needs
to insist on ownership of the target object as well; to do that without
duplicating code, refactor comment.c's big switch for permissions checks
into a separate function in objectaddress.c.

I also removed the superuserness checks in pg_available_extensions and
related functions; there's no strong reason why everybody shouldn't
be able to see that info.

Also invent an IF NOT EXISTS variant of CREATE EXTENSION, and use that
in pg_dump, so that dumps won't fail for installed-by-default extensions.
We don't have any of those yet, but we will soon.

This is all per discussion of wrapping the standard procedural languages
into extensions.  I'll make those changes in a separate commit; this is
just putting the core infrastructure in place.

doc/src/sgml/catalogs.sgml

@@ -6460,8 +6460,8 @@
 
   <para>
    The <structname>pg_available_extensions</structname> view lists the
-   extensions that are available for installation.  This view can only
-   be read by superusers.  See also the
+   extensions that are available for installation.
+   See also the
    <link linkend="catalog-pg-extension"><structname>pg_extension</structname></link>
    catalog, which shows the extensions currently installed.
   </para>
@@ -6522,8 +6522,8 @@
 
   <para>
    The <structname>pg_available_extension_versions</structname> view lists the
-   specific extension versions that are available for installation.  This view
-   can only be read by superusers.  See also the <link
+   specific extension versions that are available for installation.
+   See also the <link
    linkend="catalog-pg-extension"><structname>pg_extension</structname></link>
    catalog, which shows the extensions currently installed.
   </para>
@@ -6560,6 +6560,12 @@
        installed</entry>
      </row>
 
+     <row>
+      <entry><structfield>superuser</structfield></entry>
+      <entry><type>bool</type></entry>
+      <entry>True if only superusers are allowed to install this extension</entry>
+     </row>
+
      <row>
       <entry><structfield>relocatable</structfield></entry>
       <entry><type>bool</type></entry>

doc/src/sgml/extend.sgml

@@ -463,6 +463,19 @@
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><varname>superuser</varname> (<type>boolean</type>)</term>
+      <listitem>
+       <para>
+        If this parameter is <literal>true</> (which is the default),
+        only superusers can create the extension or update it to a new
+        version.  If it is set to <literal>false</>, just the privileges
+        required to execute the commands in the installation or update script
+        are required.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><varname>relocatable</varname> (<type>boolean</type>)</term>
       <listitem>

doc/src/sgml/ref/alter_extension.sgml

@@ -114,7 +114,9 @@ ALTER EXTENSION <replaceable class="PARAMETER">extension_name</replaceable> DROP
   </para>
 
   <para>
-   Only superusers can execute <command>ALTER EXTENSION</command>.
+   You must own the extension to use <command>ALTER EXTENSION</command>.
+   The <literal>ADD</>/<literal>DROP</> forms require ownership of the
+   added/dropped object as well.
   </para>
  </refsect1>
 

doc/src/sgml/ref/create_extension.sgml

@@ -21,7 +21,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-CREATE EXTENSION <replaceable class="parameter">extension_name</replaceable>
+CREATE EXTENSION [ IF NOT EXISTS ] <replaceable class="parameter">extension_name</replaceable>
     [ WITH ] [ SCHEMA <replaceable class="parameter">schema</replaceable> ]
              [ VERSION <replaceable class="parameter">version</replaceable> ]
              [ FROM <replaceable class="parameter">old_version</replaceable> ]
@@ -51,7 +51,12 @@ CREATE EXTENSION <replaceable class="parameter">extension_name</replaceable>
   </para>
 
   <para>
-   Only superusers can execute <command>CREATE EXTENSION</command>.
+   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 <command>CREATE EXTENSION</command> 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.
   </para>
 
  </refsect1>
@@ -60,6 +65,18 @@ CREATE EXTENSION <replaceable class="parameter">extension_name</replaceable>
   <title>Parameters</title>
 
     <variablelist>
+     <varlistentry>
+      <term><literal>IF NOT EXISTS</></term>
+      <listitem>
+       <para>
+        Do not throw an error if an extension with the same name already
+        exists.  A notice is issued in this case.  Note that there is no
+        guarantee that the existing extension is anything like the one that
+        would have been created.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><replaceable class="parameter">extension_name</replaceable></term>
       <listitem>

doc/src/sgml/ref/drop_extension.sgml

@@ -34,7 +34,7 @@ DROP EXTENSION [ IF EXISTS ] <replaceable class="PARAMETER">extension_name</repl
   </para>
 
   <para>
-   An extension can only be dropped by a superuser.
+   You must own the extension to use <command>DROP EXTENSION</command>.
   </para>
  </refsect1>
 

src/backend/catalog/aclchk.c

@@ -29,6 +29,7 @@
 #include "catalog/pg_conversion.h"
 #include "catalog/pg_database.h"
 #include "catalog/pg_default_acl.h"
+#include "catalog/pg_extension.h"
 #include "catalog/pg_foreign_data_wrapper.h"
 #include "catalog/pg_foreign_server.h"
 #include "catalog/pg_language.h"
@@ -3148,6 +3149,8 @@ static const char *const no_priv_msg[MAX_ACL_KIND] =
 	gettext_noop("permission denied for foreign server %s"),
 	/* ACL_KIND_FOREIGN_TABLE */
 	gettext_noop("permission denied for foreign table %s"),
+	/* ACL_KIND_EXTENSION */
+	gettext_noop("permission denied for extension %s"),
 };
 
 static const char *const not_owner_msg[MAX_ACL_KIND] =
@@ -3192,6 +3195,8 @@ static const char *const not_owner_msg[MAX_ACL_KIND] =
 	gettext_noop("must be owner of foreign server %s"),
 	/* ACL_KIND_FOREIGN_TABLE */
 	gettext_noop("must be owner of foreign table %s"),
+	/* ACL_KIND_EXTENSION */
+	gettext_noop("must be owner of extension %s"),
 };
 
 
@@ -4688,6 +4693,48 @@ pg_conversion_ownercheck(Oid conv_oid, Oid roleid)
 	return has_privs_of_role(roleid, ownerId);
 }
 
+/*
+ * Ownership check for an extension (specified by OID).
+ */
+bool
+pg_extension_ownercheck(Oid ext_oid, Oid roleid)
+{
+	Relation	pg_extension;
+	ScanKeyData entry[1];
+	SysScanDesc scan;
+	HeapTuple	tuple;
+	Oid			ownerId;
+
+	/* Superusers bypass all permission checking. */
+	if (superuser_arg(roleid))
+		return true;
+
+	/* There's no syscache for pg_extension, so do it the hard way */
+	pg_extension = heap_open(ExtensionRelationId, AccessShareLock);
+
+	ScanKeyInit(&entry[0],
+				ObjectIdAttributeNumber,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(ext_oid));
+
+	scan = systable_beginscan(pg_extension,
+							  ExtensionOidIndexId, true,
+							  SnapshotNow, 1, entry);
+
+	tuple = systable_getnext(scan);
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("extension with OID %u does not exist", ext_oid)));
+
+	ownerId = ((Form_pg_extension) GETSTRUCT(tuple))->extowner;
+
+	systable_endscan(scan);
+	heap_close(pg_extension, AccessShareLock);
+
+	return has_privs_of_role(roleid, ownerId);
+}
+
 /*
  * Fetch pg_default_acl entry for given role, namespace and object type
  * (object type must be given in pg_default_acl's encoding).

src/backend/catalog/objectaddress.c

@@ -52,6 +52,8 @@
 #include "commands/proclang.h"
 #include "commands/tablespace.h"
 #include "commands/trigger.h"
+#include "libpq/be-fsstubs.h"
+#include "miscadmin.h"
 #include "nodes/makefuncs.h"
 #include "parser/parse_func.h"
 #include "parser/parse_oper.h"
@@ -78,6 +80,7 @@ static ObjectAddress get_object_address_opcf(ObjectType objtype, List *objname,
 						List *objargs);
 static bool object_exists(ObjectAddress address);
 
+
 /*
  * Translate an object name and arguments (as passed by the parser) to an
  * ObjectAddress.
@@ -688,3 +691,151 @@ object_exists(ObjectAddress address)
 	heap_close(rel, AccessShareLock);
 	return found;
 }
+
+
+/*
+ * Check ownership of an object previously identified by get_object_address.
+ */
+void
+check_object_ownership(Oid roleid, ObjectType objtype, ObjectAddress address,
+					   List *objname, List *objargs, Relation relation)
+{
+	switch (objtype)
+	{
+		case OBJECT_INDEX:
+		case OBJECT_SEQUENCE:
+		case OBJECT_TABLE:
+		case OBJECT_VIEW:
+		case OBJECT_FOREIGN_TABLE:
+		case OBJECT_COLUMN:
+		case OBJECT_RULE:
+		case OBJECT_TRIGGER:
+		case OBJECT_CONSTRAINT:
+			if (!pg_class_ownercheck(RelationGetRelid(relation), roleid))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
+							   RelationGetRelationName(relation));
+			break;
+		case OBJECT_DATABASE:
+			if (!pg_database_ownercheck(address.objectId, roleid))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_DATABASE,
+							   NameListToString(objname));
+			break;
+		case OBJECT_TYPE:
+		case OBJECT_DOMAIN:
+		case OBJECT_ATTRIBUTE:
+			if (!pg_type_ownercheck(address.objectId, roleid))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_TYPE,
+							   format_type_be(address.objectId));
+			break;
+		case OBJECT_AGGREGATE:
+		case OBJECT_FUNCTION:
+			if (!pg_proc_ownercheck(address.objectId, roleid))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_PROC,
+							   NameListToString(objname));
+			break;
+		case OBJECT_OPERATOR:
+			if (!pg_oper_ownercheck(address.objectId, roleid))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_OPER,
+							   NameListToString(objname));
+			break;
+		case OBJECT_SCHEMA:
+			if (!pg_namespace_ownercheck(address.objectId, roleid))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_NAMESPACE,
+							   NameListToString(objname));
+			break;
+		case OBJECT_COLLATION:
+			if (!pg_collation_ownercheck(address.objectId, roleid))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_COLLATION,
+							   NameListToString(objname));
+			break;
+		case OBJECT_CONVERSION:
+			if (!pg_conversion_ownercheck(address.objectId, roleid))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CONVERSION,
+							   NameListToString(objname));
+			break;
+		case OBJECT_EXTENSION:
+			if (!pg_extension_ownercheck(address.objectId, roleid))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_EXTENSION,
+							   NameListToString(objname));
+			break;
+		case OBJECT_FOREIGN_SERVER:
+			if (!pg_foreign_server_ownercheck(address.objectId, roleid))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_FOREIGN_SERVER,
+							   NameListToString(objname));
+			break;
+		case OBJECT_LANGUAGE:
+			if (!pg_language_ownercheck(address.objectId, roleid))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_LANGUAGE,
+							   NameListToString(objname));
+			break;
+		case OBJECT_OPCLASS:
+			if (!pg_opclass_ownercheck(address.objectId, roleid))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_OPCLASS,
+							   NameListToString(objname));
+			break;
+		case OBJECT_OPFAMILY:
+			if (!pg_opfamily_ownercheck(address.objectId, roleid))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_OPFAMILY,
+							   NameListToString(objname));
+			break;
+		case OBJECT_LARGEOBJECT:
+			if (!lo_compat_privileges &&
+				!pg_largeobject_ownercheck(address.objectId, roleid))
+				ereport(ERROR,
+						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+						 errmsg("must be owner of large object %u",
+							address.objectId)));
+			break;
+		case OBJECT_CAST:
+			{
+				/* We can only check permissions on the source/target types */
+				TypeName *sourcetype = (TypeName *) linitial(objname);
+				TypeName *targettype = (TypeName *) linitial(objargs);
+				Oid sourcetypeid = typenameTypeId(NULL, sourcetype);
+				Oid targettypeid = typenameTypeId(NULL, targettype);
+
+				if (!pg_type_ownercheck(sourcetypeid, roleid)
+					&& !pg_type_ownercheck(targettypeid, roleid))
+					ereport(ERROR,
+							(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+							 errmsg("must be owner of type %s or type %s",
+									format_type_be(sourcetypeid),
+									format_type_be(targettypeid))));
+			}
+			break;
+		case OBJECT_TABLESPACE:
+			if (!pg_tablespace_ownercheck(address.objectId, roleid))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_TABLESPACE,
+							   NameListToString(objname));
+			break;
+		case OBJECT_ROLE:
+			if (!has_privs_of_role(roleid, address.objectId))
+				ereport(ERROR,
+						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+						 errmsg("must be member of role \"%s\"",
+								NameListToString(objname))));
+			break;
+		case OBJECT_TSDICTIONARY:
+			if (!pg_ts_dict_ownercheck(address.objectId, roleid))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_TSDICTIONARY,
+							   NameListToString(objname));
+			break;
+		case OBJECT_TSCONFIGURATION:
+			if (!pg_ts_config_ownercheck(address.objectId, roleid))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_TSCONFIGURATION,
+							   NameListToString(objname));
+			break;
+		case OBJECT_FDW:
+		case OBJECT_TSPARSER:
+		case OBJECT_TSTEMPLATE:
+			/* We treat these object types as being owned by superusers */
+			if (!superuser_arg(roleid))
+				ereport(ERROR,
+						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+						 errmsg("must be superuser")));
+			break;
+		default:
+			elog(ERROR, "unrecognized object type: %d",
+				 (int) objtype);
+	}
+}

src/backend/catalog/system_views.sql

@@ -161,7 +161,7 @@ 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.relocatable, E.schema, E.requires, E.comment
+           E.superuser, 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;

src/backend/commands/comment.c

@@ -22,25 +22,11 @@
 #include "catalog/pg_shdescription.h"
 #include "commands/comment.h"
 #include "commands/dbcommands.h"
-#include "libpq/be-fsstubs.h"
 #include "miscadmin.h"
-#include "parser/parse_func.h"
-#include "parser/parse_type.h"
-#include "utils/acl.h"
 #include "utils/builtins.h"
 #include "utils/fmgroids.h"
-#include "utils/rel.h"
 #include "utils/tqual.h"
 
-/*
- * For most object types, the permissions-checking logic is simple enough
- * that it makes sense to just include it in CommentObject().  However, a few
- * object types require something more complex; for those, we define helper
- * functions.
- */
-static void CheckAttributeComment(Relation relation);
-static void CheckCastComment(List *qualname, List *arguments);
-
 
 /*
  * CommentObject --
@@ -76,143 +62,41 @@ CommentObject(CommentStmt *stmt)
 	}
 
 	/*
-	 * Translate the parser representation which identifies this object into
-	 * an ObjectAddress. get_object_address() will throw an error if the
+	 * Translate the parser representation that identifies this object into
+	 * an ObjectAddress.  get_object_address() will throw an error if the
 	 * object does not exist, and will also acquire a lock on the target
      * to guard against concurrent DROP operations.
 	 */
 	address = get_object_address(stmt->objtype, stmt->objname, stmt->objargs,
 								 &relation, ShareUpdateExclusiveLock);
 
-	/* Privilege and integrity checks. */
+	/* Require ownership of the target object. */
+	check_object_ownership(GetUserId(), stmt->objtype, address,
+						   stmt->objname, stmt->objargs, relation);
+
+	/* Perform other integrity checks as needed. */
 	switch (stmt->objtype)
 	{
-		case OBJECT_INDEX:
-		case OBJECT_SEQUENCE:
-		case OBJECT_TABLE:
-		case OBJECT_VIEW:
-		case OBJECT_FOREIGN_TABLE:
-			if (!pg_class_ownercheck(RelationGetRelid(relation), GetUserId()))
-				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
-							   RelationGetRelationName(relation));
-			break;
 		case OBJECT_COLUMN:
-			CheckAttributeComment(relation);
-			break;
-		case OBJECT_DATABASE:
-			if (!pg_database_ownercheck(address.objectId, GetUserId()))
-				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_DATABASE,
-							   strVal(linitial(stmt->objname)));
-			break;
-		case OBJECT_TYPE:
-		case OBJECT_DOMAIN:
-			if (!pg_type_ownercheck(address.objectId, GetUserId()))
-				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_TYPE,
-							   format_type_be(address.objectId));
-			break;
-		case OBJECT_AGGREGATE:
-		case OBJECT_FUNCTION:
-			if (!pg_proc_ownercheck(address.objectId, GetUserId()))
-				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_PROC,
-							   NameListToString(stmt->objname));
-			break;
-		case OBJECT_OPERATOR:
-			if (!pg_oper_ownercheck(address.objectId, GetUserId()))
-				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_OPER,
-							   NameListToString(stmt->objname));
-			break;
-		case OBJECT_RULE:
-		case OBJECT_TRIGGER:
-		case OBJECT_CONSTRAINT:
-			if (!pg_class_ownercheck(RelationGetRelid(relation), GetUserId()))
-				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
-							   RelationGetRelationName(relation));
-			break;
-		case OBJECT_SCHEMA:
-			if (!pg_namespace_ownercheck(address.objectId, GetUserId()))
-				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_NAMESPACE,
-							   strVal(linitial(stmt->objname)));
-			break;
-		case OBJECT_COLLATION:
-			if (!pg_collation_ownercheck(address.objectId, GetUserId()))
-				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_COLLATION,
-							   NameListToString(stmt->objname));
-			break;
-		case OBJECT_CONVERSION:
-			if (!pg_conversion_ownercheck(address.objectId, GetUserId()))
-				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CONVERSION,
-							   NameListToString(stmt->objname));
-			break;
-		case OBJECT_LANGUAGE:
-			if (!superuser())
-				ereport(ERROR,
-						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-					 errmsg("must be superuser to comment on procedural language")));
-			break;
-		case OBJECT_EXTENSION:
-			if (!superuser())
-				ereport(ERROR,
-						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-						 errmsg("must be superuser to comment on extension")));
-			break;
-		case OBJECT_OPCLASS:
-			if (!pg_opclass_ownercheck(address.objectId, GetUserId()))
-				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_OPCLASS,
-							   NameListToString(stmt->objname));
-			break;
-		case OBJECT_OPFAMILY:
-			if (!pg_opfamily_ownercheck(address.objectId, GetUserId()))
-				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_OPFAMILY,
-							   NameListToString(stmt->objname));
-			break;
-		case OBJECT_LARGEOBJECT:
-			if (!lo_compat_privileges &&
-				!pg_largeobject_ownercheck(address.objectId, GetUserId()))
-				ereport(ERROR,
-						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-						 errmsg("must be owner of large object %u",
-							address.objectId)));
-			break;
-		case OBJECT_CAST:
-			CheckCastComment(stmt->objname, stmt->objargs);
-			break;
-		case OBJECT_TABLESPACE:
-			if (!pg_tablespace_ownercheck(address.objectId, GetUserId()))
-				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_TABLESPACE,
-							   strVal(linitial(stmt->objname)));
-			break;
-		case OBJECT_ROLE:
-			if (!has_privs_of_role(GetUserId(), address.objectId))
-				ereport(ERROR,
-						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-				  errmsg("must be member of role \"%s\" to comment upon it",
-						 strVal(linitial(stmt->objname)))));
-			break;
-		case OBJECT_TSPARSER:
-			if (!superuser())
+			/*
+			 * Allow comments only on columns of tables, views, composite
+			 * types, and foreign tables (which are the only relkinds for
+			 * which pg_dump will dump per-column comments).  In particular we
+			 * wish to disallow comments on index columns, because the naming
+			 * of an index's columns may change across PG versions, so dumping
+			 * per-column comments could create reload failures.
+			 */
+			if (relation->rd_rel->relkind != RELKIND_RELATION &&
+				relation->rd_rel->relkind != RELKIND_VIEW &&
+				relation->rd_rel->relkind != RELKIND_COMPOSITE_TYPE &&
+				relation->rd_rel->relkind != RELKIND_FOREIGN_TABLE)
 				ereport(ERROR,
-						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-					  errmsg("must be superuser to comment on text search parser")));
-			break;
-		case OBJECT_TSDICTIONARY:
-			if (!pg_ts_dict_ownercheck(address.objectId, GetUserId()))
-				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_TSDICTIONARY,
-							   NameListToString(stmt->objname));
-			break;
-		case OBJECT_TSTEMPLATE:
-			if (!superuser())
-				ereport(ERROR,
-						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-					errmsg("must be superuser to comment on text search template")));
-			break;
-		case OBJECT_TSCONFIGURATION:
-			if (!pg_ts_config_ownercheck(address.objectId, GetUserId()))
-				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_TSCONFIGURATION,
-							   NameListToString(stmt->objname));
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("\"%s\" is not a table, view, composite type, or foreign table",
+								RelationGetRelationName(relation))));
 			break;
 		default:
-			elog(ERROR, "unrecognized object type: %d",
-				 (int) stmt->objtype);
+			break;
 	}
 
 	/*
@@ -574,63 +458,3 @@ GetComment(Oid oid, Oid classoid, int32 subid)
 
 	return comment;
 }
-
-/*
- * Check whether the user is allowed to comment on an attribute of the
- * specified relation.
- */
-static void
-CheckAttributeComment(Relation relation)
-{
-	if (!pg_class_ownercheck(RelationGetRelid(relation), GetUserId()))
-		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
-					   RelationGetRelationName(relation));
-
-	/*
-	 * Allow comments only on columns of tables, views, composite types, and
-	 * foreign tables (which are the only relkinds for which pg_dump will dump
-	 * per-column comments).  In particular we wish to disallow comments on
-	 * index columns, because the naming of an index's columns may change
-	 * across PG versions, so dumping per-column comments could create reload
-	 * failures.
-	 */
-	if (relation->rd_rel->relkind != RELKIND_RELATION &&
-		relation->rd_rel->relkind != RELKIND_VIEW &&
-		relation->rd_rel->relkind != RELKIND_COMPOSITE_TYPE &&
-		relation->rd_rel->relkind != RELKIND_FOREIGN_TABLE)
-		ereport(ERROR,
-				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-				 errmsg("\"%s\" is not a table, view, composite type, or foreign table",
-						RelationGetRelationName(relation))));
-}
-
-/*
- * Check whether the user is allowed to comment on the specified cast.
- */
-static void
-CheckCastComment(List *qualname, List *arguments)
-{
-	TypeName   *sourcetype;
-	TypeName   *targettype;
-	Oid			sourcetypeid;
-	Oid			targettypeid;
-
-	Assert(list_length(qualname) == 1);
-	sourcetype = (TypeName *) linitial(qualname);
-	Assert(IsA(sourcetype, TypeName));
-	Assert(list_length(arguments) == 1);
-	targettype = (TypeName *) linitial(arguments);
-	Assert(IsA(targettype, TypeName));
-
-	sourcetypeid = typenameTypeId(NULL, sourcetype);
-	targettypeid = typenameTypeId(NULL, targettype);
-
-	/* Permission check */
-	if (!pg_type_ownercheck(sourcetypeid, GetUserId())
-		&& !pg_type_ownercheck(targettypeid, GetUserId()))
-		ereport(ERROR,
-				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-				 errmsg("must be owner of type %s or type %s",
-						format_type_be(sourcetypeid),
-						format_type_be(targettypeid))));
-}

src/backend/nodes/copyfuncs.c

@@ -3289,6 +3289,7 @@ _copyCreateExtensionStmt(CreateExtensionStmt *from)
 	CreateExtensionStmt *newnode = makeNode(CreateExtensionStmt);
 
 	COPY_STRING_FIELD(extname);
+	COPY_SCALAR_FIELD(if_not_exists);
 	COPY_NODE_FIELD(options);
 
 	return newnode;

src/backend/nodes/equalfuncs.c

@@ -1650,6 +1650,7 @@ static bool
 _equalCreateExtensionStmt(CreateExtensionStmt *a, CreateExtensionStmt *b)
 {
 	COMPARE_STRING_FIELD(extname);
+	COMPARE_SCALAR_FIELD(if_not_exists);
 	COMPARE_NODE_FIELD(options);
 
 	return true;

src/backend/parser/gram.y

@@ -3240,9 +3240,18 @@ CreateExtensionStmt: CREATE EXTENSION name opt_with create_extension_opt_list
 				{
 					CreateExtensionStmt *n = makeNode(CreateExtensionStmt);
 					n->extname = $3;
+					n->if_not_exists = false;
 					n->options = $5;
 					$$ = (Node *) n;
 				}
+				| CREATE EXTENSION IF_P NOT EXISTS name opt_with create_extension_opt_list
+				{
+					CreateExtensionStmt *n = makeNode(CreateExtensionStmt);
+					n->extname = $6;
+					n->if_not_exists = true;
+					n->options = $8;
+					$$ = (Node *) n;
+				}
 		;
 
 create_extension_opt_list:

src/bin/pg_dump/pg_dump.c

@@ -45,6 +45,7 @@
 
 #include "access/attnum.h"
 #include "access/sysattr.h"
+#include "access/transam.h"
 #include "catalog/pg_cast.h"
 #include "catalog/pg_class.h"
 #include "catalog/pg_default_acl.h"
@@ -7041,6 +7042,19 @@ dumpExtension(Archive *fout, ExtensionInfo *extinfo)
 	if (!extinfo->dobj.dump || dataOnly)
 		return;
 
+	/*
+	 * In a regular dump, we use IF NOT EXISTS so that there isn't a problem
+	 * if the extension already exists in the target database; this is
+	 * essential for installed-by-default extensions such as plpgsql.
+	 *
+	 * In binary-upgrade mode, that doesn't work well, so instead we skip
+	 * extensions with OIDs less than FirstNormalObjectId; those were
+	 * presumably installed by initdb, and we assume they'll exist in the
+	 * target installation too.
+	 */
+	if (binary_upgrade && extinfo->dobj.catId.oid < (Oid) FirstNormalObjectId)
+		return;
+
 	q = createPQExpBuffer();
 	delq = createPQExpBuffer();
 	labelq = createPQExpBuffer();
@@ -7051,7 +7065,7 @@ dumpExtension(Archive *fout, ExtensionInfo *extinfo)
 
 	if (!binary_upgrade)
 	{
-		appendPQExpBuffer(q, "CREATE EXTENSION %s WITH SCHEMA %s;\n",
+		appendPQExpBuffer(q, "CREATE EXTENSION IF NOT EXISTS %s WITH SCHEMA %s;\n",
 						  qextname, fmtId(extinfo->namespace));
 	}
 	else

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201103032
+#define CATALOG_VERSION_NO	201103041
 
 #endif

src/include/catalog/objectaddress.h

@@ -27,7 +27,11 @@ typedef struct ObjectAddress
 	int32		objectSubId;	/* Subitem within object (eg column), or 0 */
 } ObjectAddress;
 
-ObjectAddress get_object_address(ObjectType objtype, List *objname,
+extern ObjectAddress get_object_address(ObjectType objtype, List *objname,
 				   List *objargs, Relation *relp, LOCKMODE lockmode);
 
+extern void check_object_ownership(Oid roleid,
+					   ObjectType objtype, ObjectAddress address,
+					   List *objname, List *objargs, Relation relation);
+
 #endif   /* PARSE_OBJECT_H */

src/include/catalog/pg_proc.h

@@ -4282,7 +4282,7 @@ DESCR("less-equal-greater");
 /* Extensions */
 DATA(insert OID = 3082 (  pg_available_extensions		PGNSP PGUID 12 10 100 0 f f f t t s 0 0 2249 "" "{19,25,25}" "{o,o,o}" "{name,default_version,comment}" _null_ pg_available_extensions _null_ _null_ _null_ ));
 DESCR("list available extensions");
-DATA(insert OID = 3083 (  pg_available_extension_versions	PGNSP PGUID 12 10 100 0 f f f t t s 0 0 2249 "" "{19,25,16,19,1003,25}" "{o,o,o,o,o,o}" "{name,version,relocatable,schema,requires,comment}" _null_ pg_available_extension_versions _null_ _null_ _null_ ));
+DATA(insert OID = 3083 (  pg_available_extension_versions	PGNSP PGUID 12 10 100 0 f f f t t s 0 0 2249 "" "{19,25,16,16,19,1003,25}" "{o,o,o,o,o,o,o}" "{name,version,superuser,relocatable,schema,requires,comment}" _null_ pg_available_extension_versions _null_ _null_ _null_ ));
 DESCR("list available extension versions");
 DATA(insert OID = 3084 (  pg_extension_update_paths		PGNSP PGUID 12 10 100 0 f f f t t s 1 0 2249 "19" "{19,25,25,25}" "{i,o,o,o}" "{name,source,target,path}" _null_ pg_extension_update_paths _null_ _null_ _null_ ));
 DESCR("list an extension's version update paths");

src/include/nodes/parsenodes.h

@@ -1557,6 +1557,7 @@ typedef struct CreateExtensionStmt
 {
 	NodeTag		type;
 	char	   *extname;
+	bool		if_not_exists;	/* just do nothing if it already exists? */
 	List	   *options;		/* List of DefElem nodes */
 } CreateExtensionStmt;
 

src/include/utils/acl.h

@@ -196,6 +196,7 @@ typedef enum AclObjectKind
 	ACL_KIND_FDW,				/* pg_foreign_data_wrapper */
 	ACL_KIND_FOREIGN_SERVER,	/* pg_foreign_server */
 	ACL_KIND_FOREIGN_TABLE,		/* pg_foreign_table */
+	ACL_KIND_EXTENSION,			/* pg_extension */
 	MAX_ACL_KIND				/* MUST BE LAST */
 } AclObjectKind;
 
@@ -315,5 +316,6 @@ extern bool pg_conversion_ownercheck(Oid conv_oid, Oid roleid);
 extern bool pg_ts_dict_ownercheck(Oid dict_oid, Oid roleid);
 extern bool pg_ts_config_ownercheck(Oid cfg_oid, Oid roleid);
 extern bool pg_foreign_server_ownercheck(Oid srv_oid, Oid roleid);
+extern bool pg_extension_ownercheck(Oid ext_oid, Oid roleid);
 
 #endif   /* ACL_H */

src/test/regress/expected/rules.out

@@ -1279,7 +1279,7 @@ SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schem
             viewname             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              definition                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
 ---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  iexit                           | SELECT ih.name, ih.thepath, interpt_pp(ih.thepath, r.thepath) AS exit FROM ihighway ih, ramp r WHERE (ih.thepath ## r.thepath);
- pg_available_extension_versions | SELECT e.name, e.version, (x.extname IS NOT NULL) AS installed, e.relocatable, e.schema, e.requires, e.comment FROM (pg_available_extension_versions() e(name, version, relocatable, schema, requires, comment) LEFT JOIN pg_extension x ON (((e.name = x.extname) AND (e.version = x.extversion))));
+ pg_available_extension_versions | SELECT e.name, e.version, (x.extname IS NOT NULL) AS installed, e.superuser, e.relocatable, e.schema, e.requires, e.comment FROM (pg_available_extension_versions() e(name, version, superuser, 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, x.extversion AS installed_version, e.comment FROM (pg_available_extensions() e(name, default_version, comment) LEFT JOIN pg_extension x ON ((e.name = x.extname)));
  pg_cursors                      | SELECT c.name, c.statement, c.is_holdable, c.is_binary, c.is_scrollable, c.creation_time FROM pg_cursor() c(name, statement, is_holdable, is_binary, is_scrollable, creation_time);
  pg_group                        | SELECT pg_authid.rolname AS groname, pg_authid.oid AS grosysid, ARRAY(SELECT pg_auth_members.member FROM pg_auth_members WHERE (pg_auth_members.roleid = pg_authid.oid)) AS grolist FROM pg_authid WHERE (NOT pg_authid.rolcanlogin);