RE: [HACKERS] Re: possible row locking bug in 7.0.3 & 7.1

> > >> I assume this is not possible in 7.1?
> > >
> > >Just looked in heapam.c - I can fix it in two hours.
> > >The question is - should we do this now?
> > >Comments?
> >
> > It's a bug; how confident are you of the fix?

95% -:)

> I doubt if it's a bug of SELECT. Well what
> 'concurrent UPDATE then SELECT FOR UPDATE +
> SELECT' return ?

I'm going to add additional check to heapgettup and
heap_fetch:

HeapTupleSatisfies(T) is TRUE:

IF XactIsoLevel is READ_COMMITTED
and snapshot != SnapshotDirty
and !(T->t_data->t_infomask & HEAP_XMAX_INVALID)
and T->t_data->t_infomask & HEAP_XMAX_COMMITTED
and T->t_self != T->t_data->t_ctid
{
FOR ( ; ; )
{
fetch tuple->t_data->t_ctid tuple
IF t_infomask & (HEAP_XMAX_INVALID | HEAP_MARKED_FOR_UPDATE)
break; -- and return T
IF t_infomask & HEAP_XMAX_COMMITTED
{
IF t_self != ctid -- updated
continue;
break; -- deleted, return T
}
-- uncommitted update/delete
IF t_xmax != CurrentTransactionID
break; -- and return T
-- changed by current TX!
IF changed *BEFORE* this query began
{
-- DELETE + SELECT: nothing to return
-- UPDATE + SELECT: newer tuple version
-- will be/was returned by query
return NULL;
}
continue;
}
}

Vadim