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, 32 insertions, 18 deletions

diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index ac133023b4f..497559df588 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -285,6 +285,25 @@ typedef struct CollateClause
 } CollateClause;
 
 /*
+ * RoleSpec - a role name or one of a few special values.
+ */
+typedef enum RoleSpecType
+{
+	ROLESPEC_CSTRING,		/* role name is stored as a C string */
+	ROLESPEC_CURRENT_USER,	/* role spec is CURRENT_USER */
+	ROLESPEC_SESSION_USER,	/* role spec is SESSION_USER */
+	ROLESPEC_PUBLIC			/* role name is "public" */
+} RoleSpecType;
+
+typedef struct RoleSpec
+{
+	NodeTag		type;
+	RoleSpecType roletype;	/* Type of this rolespec */
+	char	   *rolename;	/* filled only for ROLESPEC_CSTRING */
+	int			location;	/* token location, or -1 if unknown */
+} RoleSpec;
+
+/*
  * FuncCall - a function or aggregate invocation
  *
  * agg_order (if not NIL) indicates we saw 'foo(... ORDER BY ...)', or if
@@ -1263,7 +1282,7 @@ typedef struct CreateSchemaStmt
 {
 	NodeTag		type;
 	char	   *schemaname;		/* the name of the schema to create */
-	char	   *authid;			/* the owner of the created schema */
+	Node	   *authrole;		/* the owner of the created schema */
 	List	   *schemaElts;		/* schema components (list of parsenodes) */
 	bool		if_not_exists;	/* just do nothing if schema already exists? */
 } CreateSchemaStmt;
@@ -1362,7 +1381,8 @@ typedef struct AlterTableCmd	/* one subcommand of an ALTER TABLE */
 	NodeTag		type;
 	AlterTableType subtype;		/* Type of table alteration to apply */
 	char	   *name;			/* column, constraint, or trigger to act on,
-								 * or new owner or tablespace */
+								 * or tablespace */
+	Node	   *newowner;		/* RoleSpec */
 	Node	   *def;			/* definition of new column, index,
 								 * constraint, or parent table */
 	DropBehavior behavior;		/* RESTRICT or CASCADE for DROP cases */
@@ -1434,17 +1454,11 @@ typedef struct GrantStmt
 								 * or plain names (as Value strings) */
 	List	   *privileges;		/* list of AccessPriv nodes */
 	/* privileges == NIL denotes ALL PRIVILEGES */
-	List	   *grantees;		/* list of PrivGrantee nodes */
+	List	   *grantees;		/* list of RoleSpec nodes */
 	bool		grant_option;	/* grant or revoke grant option */
 	DropBehavior behavior;		/* drop behavior (for REVOKE) */
 } GrantStmt;
 
-typedef struct PrivGrantee
-{
-	NodeTag		type;
-	char	   *rolname;		/* if NULL then PUBLIC */
-} PrivGrantee;
-
 /*
  * Note: FuncWithArgs carries only the types of the input parameters of the
  * function.  So it is sufficient to identify an existing function, but it
@@ -1487,7 +1501,7 @@ typedef struct GrantRoleStmt
 	List	   *grantee_roles;	/* list of member roles to add/delete */
 	bool		is_grant;		/* true = GRANT, false = REVOKE */
 	bool		admin_opt;		/* with admin option */
-	char	   *grantor;		/* set grantor to other than current role */
+	Node	   *grantor;		/* set grantor to other than current role */
 	DropBehavior behavior;		/* drop behavior (for REVOKE) */
 } GrantRoleStmt;
 
@@ -1699,7 +1713,7 @@ typedef struct CreateTableSpaceStmt
 {
 	NodeTag		type;
 	char	   *tablespacename;
-	char	   *owner;
+	Node	   *owner;
 	char	   *location;
 	List	   *options;
 } CreateTableSpaceStmt;
@@ -1825,7 +1839,7 @@ typedef struct CreateForeignTableStmt
 typedef struct CreateUserMappingStmt
 {
 	NodeTag		type;
-	char	   *username;		/* username or PUBLIC/CURRENT_USER */
+	Node	   *user;			/* user role */
 	char	   *servername;		/* server name */
 	List	   *options;		/* generic options to server */
 } CreateUserMappingStmt;
@@ -1833,7 +1847,7 @@ typedef struct CreateUserMappingStmt
 typedef struct AlterUserMappingStmt
 {
 	NodeTag		type;
-	char	   *username;		/* username or PUBLIC/CURRENT_USER */
+	Node	   *user;			/* user role */
 	char	   *servername;		/* server name */
 	List	   *options;		/* generic options to server */
 } AlterUserMappingStmt;
@@ -1841,7 +1855,7 @@ typedef struct AlterUserMappingStmt
 typedef struct DropUserMappingStmt
 {
 	NodeTag		type;
-	char	   *username;		/* username or PUBLIC/CURRENT_USER */
+	Node	   *user;			/* user role */
 	char	   *servername;		/* server name */
 	bool		missing_ok;		/* ignore missing mappings */
 } DropUserMappingStmt;
@@ -1991,7 +2005,7 @@ typedef struct CreateRoleStmt
 typedef struct AlterRoleStmt
 {
 	NodeTag		type;
-	char	   *role;			/* role name */
+	Node	   *role;			/* role */
 	List	   *options;		/* List of DefElem nodes */
 	int			action;			/* +1 = add members, -1 = drop members */
 } AlterRoleStmt;
@@ -1999,7 +2013,7 @@ typedef struct AlterRoleStmt
 typedef struct AlterRoleSetStmt
 {
 	NodeTag		type;
-	char	   *role;			/* role name */
+	Node	   *role;			/* role */
 	char	   *database;		/* database name, or NULL */
 	VariableSetStmt *setstmt;	/* SET or RESET subcommand */
 } AlterRoleSetStmt;
@@ -2375,7 +2389,7 @@ typedef struct AlterOwnerStmt
 	RangeVar   *relation;		/* in case it's a table */
 	List	   *object;			/* in case it's some other object */
 	List	   *objarg;			/* argument types, if applicable */
-	char	   *newowner;		/* the new owner */
+	Node	   *newowner;		/* the new owner */
 } AlterOwnerStmt;
 
 
@@ -2831,7 +2845,7 @@ typedef struct ReassignOwnedStmt
 {
 	NodeTag		type;
 	List	   *roles;
-	char	   *newrole;
+	Node	   *newrole;
 } ReassignOwnedStmt;
 
 /*