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/
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