*** ./src/backend/access/heap/heapam.c.orig	2003-07-04 09:12:10.000000000 +0900
--- ./src/backend/access/heap/heapam.c	2003-07-12 13:52:43.000000000 +0900
***************
*** 479,484 ****
--- 479,517 ----
  	return r;
  }
  
+ Relation
+ conditional_relation_open(Oid relationId, LOCKMODE lockmode, bool no_wait)
+ {
+ 	Relation	r;
+ 
+ 	Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
+ 
+ 	/*
+ 	 * increment access statistics
+ 	 */
+ 	IncrHeapAccessStat(local_open);
+ 	IncrHeapAccessStat(global_open);
+ 
+ 	/* The relcache does all the real work... */
+ 	r = RelationIdGetRelation(relationId);
+ 
+ 	if (!RelationIsValid(r))
+ 		elog(ERROR, "Relation %u does not exist", relationId);
+ 
+ 	if (lockmode != NoLock)
+ 	{
+ 		if (no_wait)
+ 		{
+ 			if (!ConditionalLockRelation(r, lockmode))
+ 				elog(ERROR, "Cannot aquire relation lock");
+ 		}
+ 		else
+ 			LockRelation(r, lockmode);
+ 	}
+ 
+ 	return r;
+ }
+ 
  /* ----------------
   *		relation_openrv - open any relation specified by a RangeVar
   *
*** ./src/backend/commands/lockcmds.c.orig	2003-07-04 09:21:30.000000000 +0900
--- ./src/backend/commands/lockcmds.c	2003-07-12 13:53:30.000000000 +0900
***************
*** 58,64 ****
  		if (aclresult != ACLCHECK_OK)
  			aclcheck_error(aclresult, get_rel_name(reloid));
  
! 		rel = relation_open(reloid, lockstmt->mode);
  
  		/* Currently, we only allow plain tables to be locked */
  		if (rel->rd_rel->relkind != RELKIND_RELATION)
--- 58,64 ----
  		if (aclresult != ACLCHECK_OK)
  			aclcheck_error(aclresult, get_rel_name(reloid));
  
! 		rel = conditional_relation_open(reloid, lockstmt->mode, lockstmt->no_wait);
  
  		/* Currently, we only allow plain tables to be locked */
  		if (rel->rd_rel->relkind != RELKIND_RELATION)
*** ./src/backend/parser/gram.y.orig	2003-07-12 12:45:30.000000000 +0900
--- ./src/backend/parser/gram.y	2003-07-12 13:37:27.000000000 +0900
***************
*** 161,166 ****
--- 161,167 ----
  
  %type <ival>	opt_lock lock_type cast_context
  %type <boolean>	opt_force opt_or_replace
+ %type <boolean>	opt_no_wait
  
  %type <list>	user_list
  
***************
*** 392,397 ****
--- 393,400 ----
  	VACUUM VALID VALIDATOR VALUES VARCHAR VARYING
  	VERBOSE VERSION VIEW VOLATILE
  
+ 	WAIT
+ 
  	WHEN WHERE WITH WITHOUT WORK WRITE
  
  	YEAR_P
***************
*** 4050,4061 ****
  				}
  		;
  
! LockStmt:	LOCK_P opt_table qualified_name_list opt_lock
  				{
  					LockStmt *n = makeNode(LockStmt);
  
  					n->relations = $3;
  					n->mode = $4;
  					$$ = (Node *)n;
  				}
  		;
--- 4053,4065 ----
  				}
  		;
  
! LockStmt:	LOCK_P opt_table qualified_name_list opt_lock opt_no_wait
  				{
  					LockStmt *n = makeNode(LockStmt);
  
  					n->relations = $3;
  					n->mode = $4;
+ 					n->no_wait = $5;
  					$$ = (Node *)n;
  				}
  		;
***************
*** 4074,4079 ****
--- 4078,4087 ----
  			| ACCESS EXCLUSIVE				{ $$ = AccessExclusiveLock; }
  		;
  
+ opt_no_wait:	NO WAIT 			{ $$ = TRUE; }
+ 			| /*EMPTY*/						{ $$ = FALSE; }
+ 		;
+ 
  
  /*****************************************************************************
   *
*** ./src/backend/parser/keywords.c.orig	2003-07-12 13:39:23.000000000 +0900
--- ./src/backend/parser/keywords.c	2003-07-12 13:39:47.000000000 +0900
***************
*** 318,323 ****
--- 318,324 ----
  	{"version", VERSION},
  	{"view", VIEW},
  	{"volatile", VOLATILE},
+ 	{"wait", WAIT},
  	{"when", WHEN},
  	{"where", WHERE},
  	{"with", WITH},
*** ./src/include/nodes/parsenodes.h.orig	2003-07-12 12:48:48.000000000 +0900
--- ./src/include/nodes/parsenodes.h	2003-07-12 13:44:04.000000000 +0900
***************
*** 1593,1598 ****
--- 1593,1599 ----
  	NodeTag		type;
  	List	   *relations;		/* relations to lock */
  	int			mode;			/* lock mode */
+ 	bool		no_wait;		/* no wait mode */
  } LockStmt;
  
  /* ----------------------
*** src/include/access/heapam.h.orig	2003-07-19 14:08:22.000000000 +0900
--- src/include/access/heapam.h	2003-07-19 14:08:48.000000000 +0900
***************
*** 136,141 ****
--- 136,142 ----
  /* heapam.c */
  
  extern Relation relation_open(Oid relationId, LOCKMODE lockmode);
+ extern Relation conditional_relation_open(Oid relationId, LOCKMODE lockmode, bool no_wait);
  extern Relation relation_openrv(const RangeVar *relation, LOCKMODE lockmode);
  extern Relation relation_openr(const char *sysRelationName, LOCKMODE lockmode);
  extern void relation_close(Relation relation, LOCKMODE lockmode);