Allow CURRENT/SESSION_USER to be used in certain commands

Commands such as ALTER USER, ALTER GROUP, ALTER ROLE, GRANT, and the
various ALTER OBJECT / OWNER TO, as well as ad-hoc clauses related to
roles such as the AUTHORIZATION clause of CREATE SCHEMA, the FOR clause
of CREATE USER MAPPING, and the FOR ROLE clause of ALTER DEFAULT
PRIVILEGES can now take the keywords CURRENT_USER and SESSION_USER as
user specifiers in place of an explicit user name.

This commit also fixes some quite ugly handling of special standards-
mandated syntax in CREATE USER MAPPING, which in particular would fail
to work in presence of a role named "current_user".

The special role specifiers PUBLIC and NONE also have more consistent
handling now.

Also take the opportunity to add location tracking to user specifiers.

Authors: Kyotaro Horiguchi.  Heavily reworked by Álvaro Herrera.
Reviewed by: Rushabh Lathia, Adam Brightwell, Marti Raudsepp.

1 files changed, 24 insertions, 21 deletions

diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index fe509b0ad1c..8186e84d339 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -973,6 +973,7 @@ _equalAlterTableCmd(const AlterTableCmd *a, const AlterTableCmd *b)
 {
 	COMPARE_SCALAR_FIELD(subtype);
 	COMPARE_STRING_FIELD(name);
+	COMPARE_NODE_FIELD(newowner);
 	COMPARE_NODE_FIELD(def);
 	COMPARE_SCALAR_FIELD(behavior);
 	COMPARE_SCALAR_FIELD(missing_ok);
@@ -1009,14 +1010,6 @@ _equalGrantStmt(const GrantStmt *a, const GrantStmt *b)
 }
 
 static bool
-_equalPrivGrantee(const PrivGrantee *a, const PrivGrantee *b)
-{
-	COMPARE_STRING_FIELD(rolname);
-
-	return true;
-}
-
-static bool
 _equalFuncWithArgs(const FuncWithArgs *a, const FuncWithArgs *b)
 {
 	COMPARE_NODE_FIELD(funcname);
@@ -1041,7 +1034,7 @@ _equalGrantRoleStmt(const GrantRoleStmt *a, const GrantRoleStmt *b)
 	COMPARE_NODE_FIELD(grantee_roles);
 	COMPARE_SCALAR_FIELD(is_grant);
 	COMPARE_SCALAR_FIELD(admin_opt);
-	COMPARE_STRING_FIELD(grantor);
+	COMPARE_NODE_FIELD(grantor);
 	COMPARE_SCALAR_FIELD(behavior);
 
 	return true;
@@ -1295,7 +1288,7 @@ _equalAlterOwnerStmt(const AlterOwnerStmt *a, const AlterOwnerStmt *b)
 	COMPARE_NODE_FIELD(relation);
 	COMPARE_NODE_FIELD(object);
 	COMPARE_NODE_FIELD(objarg);
-	COMPARE_STRING_FIELD(newowner);
+	COMPARE_NODE_FIELD(newowner);
 
 	return true;
 }
@@ -1618,7 +1611,7 @@ static bool
 _equalCreateTableSpaceStmt(const CreateTableSpaceStmt *a, const CreateTableSpaceStmt *b)
 {
 	COMPARE_STRING_FIELD(tablespacename);
-	COMPARE_STRING_FIELD(owner);
+	COMPARE_NODE_FIELD(owner);
 	COMPARE_STRING_FIELD(location);
 	COMPARE_NODE_FIELD(options);
 
@@ -1735,7 +1728,7 @@ _equalAlterForeignServerStmt(const AlterForeignServerStmt *a, const AlterForeign
 static bool
 _equalCreateUserMappingStmt(const CreateUserMappingStmt *a, const CreateUserMappingStmt *b)
 {
-	COMPARE_STRING_FIELD(username);
+	COMPARE_NODE_FIELD(user);
 	COMPARE_STRING_FIELD(servername);
 	COMPARE_NODE_FIELD(options);
 
@@ -1745,7 +1738,7 @@ _equalCreateUserMappingStmt(const CreateUserMappingStmt *a, const CreateUserMapp
 static bool
 _equalAlterUserMappingStmt(const AlterUserMappingStmt *a, const AlterUserMappingStmt *b)
 {
-	COMPARE_STRING_FIELD(username);
+	COMPARE_NODE_FIELD(user);
 	COMPARE_STRING_FIELD(servername);
 	COMPARE_NODE_FIELD(options);
 
@@ -1755,7 +1748,7 @@ _equalAlterUserMappingStmt(const AlterUserMappingStmt *a, const AlterUserMapping
 static bool
 _equalDropUserMappingStmt(const DropUserMappingStmt *a, const DropUserMappingStmt *b)
 {
-	COMPARE_STRING_FIELD(username);
+	COMPARE_NODE_FIELD(user);
 	COMPARE_STRING_FIELD(servername);
 	COMPARE_SCALAR_FIELD(missing_ok);
 
@@ -1853,7 +1846,7 @@ _equalCreateRoleStmt(const CreateRoleStmt *a, const CreateRoleStmt *b)
 static bool
 _equalAlterRoleStmt(const AlterRoleStmt *a, const AlterRoleStmt *b)
 {
-	COMPARE_STRING_FIELD(role);
+	COMPARE_NODE_FIELD(role);
 	COMPARE_NODE_FIELD(options);
 	COMPARE_SCALAR_FIELD(action);
 
@@ -1863,7 +1856,7 @@ _equalAlterRoleStmt(const AlterRoleStmt *a, const AlterRoleStmt *b)
 static bool
 _equalAlterRoleSetStmt(const AlterRoleSetStmt *a, const AlterRoleSetStmt *b)
 {
-	COMPARE_STRING_FIELD(role);
+	COMPARE_NODE_FIELD(role);
 	COMPARE_STRING_FIELD(database);
 	COMPARE_NODE_FIELD(setstmt);
 
@@ -1912,7 +1905,7 @@ static bool
 _equalCreateSchemaStmt(const CreateSchemaStmt *a, const CreateSchemaStmt *b)
 {
 	COMPARE_STRING_FIELD(schemaname);
-	COMPARE_STRING_FIELD(authid);
+	COMPARE_NODE_FIELD(authrole);
 	COMPARE_NODE_FIELD(schemaElts);
 	COMPARE_SCALAR_FIELD(if_not_exists);
 
@@ -1983,7 +1976,7 @@ static bool
 _equalReassignOwnedStmt(const ReassignOwnedStmt *a, const ReassignOwnedStmt *b)
 {
 	COMPARE_NODE_FIELD(roles);
-	COMPARE_STRING_FIELD(newrole);
+	COMPARE_NODE_FIELD(newrole);
 
 	return true;
 }
@@ -2455,6 +2448,16 @@ _equalXmlSerialize(const XmlSerialize *a, const XmlSerialize *b)
 	return true;
 }
 
+static bool
+_equalRoleSpec(const RoleSpec *a, const RoleSpec *b)
+{
+	COMPARE_SCALAR_FIELD(roletype);
+	COMPARE_STRING_FIELD(rolename);
+	COMPARE_LOCATION_FIELD(location);
+
+	return true;
+}
+
 /*
  * Stuff from pg_list.h
  */
@@ -3153,9 +3156,6 @@ equal(const void *a, const void *b)
 		case T_CommonTableExpr:
 			retval = _equalCommonTableExpr(a, b);
 			break;
-		case T_PrivGrantee:
-			retval = _equalPrivGrantee(a, b);
-			break;
 		case T_FuncWithArgs:
 			retval = _equalFuncWithArgs(a, b);
 			break;
@@ -3165,6 +3165,9 @@ equal(const void *a, const void *b)
 		case T_XmlSerialize:
 			retval = _equalXmlSerialize(a, b);
 			break;
+		case T_RoleSpec:
+			retval = _equalRoleSpec(a, b);
+			break;
 
 		default:
 			elog(ERROR, "unrecognized node type: %d",