*** a/src/backend/parser/analyze.c
--- b/src/backend/parser/analyze.c
***************
*** 1989,2000 **** transformUpdateStmt(ParseState *pstate, UpdateStmt *stmt)
  		attrno = attnameAttNum(pstate->p_target_relation,
  							   origTarget->name, true);
  		if (attrno == InvalidAttrNumber)
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_COLUMN),
  					 errmsg("column \"%s\" of relation \"%s\" does not exist",
  							origTarget->name,
! 						 RelationGetRelationName(pstate->p_target_relation)),
  					 parser_errposition(pstate, origTarget->location)));
  
  		updateTargetListEntry(pstate, tle, origTarget->name,
  							  attrno,
--- 1989,2020 ----
  		attrno = attnameAttNum(pstate->p_target_relation,
  							   origTarget->name, true);
  		if (attrno == InvalidAttrNumber)
+ 		{
+ 			const char *targetrefname;
+ 			const char *message_hint = NULL;
+ 
+ 			/*
+ 			 * Table-qualifying the LHS expression in SET is a common mistake;
+ 			 * provide a hint if that seems to be the problem.
+ 			 */
+ 			if (target_rte->alias)
+ 				targetrefname = target_rte->alias->aliasname;
+ 			else
+ 				targetrefname = RelationGetRelationName(pstate->p_target_relation);
+ 
+ 			if (strcmp(origTarget->name, targetrefname) == 0 &&
+ 				origTarget->indirection != NIL &&
+ 				IsA(linitial(origTarget->indirection), String))
+ 				message_hint = "Target column references in UPDATE must not be qualified";
+ 
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_COLUMN),
  					 errmsg("column \"%s\" of relation \"%s\" does not exist",
  							origTarget->name,
! 						 	RelationGetRelationName(pstate->p_target_relation)),
! 					 message_hint ? errhint("%s", message_hint) : 0,
  					 parser_errposition(pstate, origTarget->location)));
+ 		}
  
  		updateTargetListEntry(pstate, tle, origTarget->name,
  							  attrno,