Re: MultiXactId error after upgrade to 9.3.4

Stephen Frost wrote:

> Further review leads me to notice that both HEAP_XMAX_IS_MULTI and
> HEAP_XMAX_INVALID are set:
> 
> t_infomask  | 6528
> 
> 6528 decimal -> 0x1980
> 
> 0001 1001 1000 0000
> 
> Which gives us:
> 
> 0000 0000 1000 0000 - HEAP_XMAX_LOCK_ONLY
> 0000 0001 0000 0000 - HEAP_XMIN_COMMITTED
> 0000 1000 0000 0000 - HEAP_XMAX_INVALID
> 0001 0000 0000 0000 - HEAP_XMAX_IS_MULTI
> 
> Which shows that both HEAP_XMAX_INVALID and HEAP_XMAX_IS_MULTI are set.
> Of some interest is that HEAP_XMAX_LOCK_ONLY is also set..

This combination seems reasonable.  This tuple had two FOR SHARE
lockers, so it was marked HEAP_XMAX_SHARED_LOCK|HEAP_XMAX_IS_MULTI
(0x1080).  Then those lockers finished, and somebody else checked the
tuple with a tqual.c routine (say HeapTupleSatisfiesUpdate), which saw
the lockers were gone and marked it as HEAP_XMAX_INVALID (0x800),
without removing the Xmax value and without removing the other bits.

This is all per spec, so we must cope.

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services