Re: [HACKERS] latest snapshot crashes backend

> > Care to give us a table:
> >  select * from pg_shadow where (usesysid is null and oid is null);
> 
> Sure, that's easy. Just negate your where clause:
> 
> tgl=> select * from pg_shadow
> tgl-> where not (usesysid is null and oid is null);
> pqReadData() -- backend closed the channel unexpectedly.
> 
> If you can reproduce this, will you have a chance to look at it? I don't
> know where the problem is, but suspect that it is farther back than the
> parser transformations. Rewrite system, optimizer, or executor??
> 

OK, here is the fix.  I am not applying it yet until 6.4 is released by
Marc, OK?  In fact, I am not sure how we are going to do patch
application after 6.4, so would someone else please apply this?

---------------------------------------------------------------------------

*** ./backend/optimizer/path/clausesel.c.orig    Wed Nov  4 16:49:35 1998
--- ./backend/optimizer/path/clausesel.c    Wed Nov  4 17:11:02 1998
***************
*** 254,259 ****
--- 254,264 ----          */         s1 = 0.1;     }
+     else if (not_clause((Node *) clause))
+     {
+         /* negate this baby */
+         return 1 - compute_selec(root, ((Expr *)clause)->args, or_selectivities);
+     }     else if (is_subplan((Node *) clause))     { 


--  Bruce Momjian                        |  http://www.op.net/~candle maillist@candle.pha.pa.us            |  (610)
853-3000+  If your life is a hard drive,     |  830 Blythe Avenue +  Christ can be your backup.        |  Drexel Hill,
Pennsylvania19026