Re: [PATCH] pageinspect function to decode infomasks

On 08/15/2017 09:55 PM, Robert Haas wrote:
> On Tue, Aug 15, 2017 at 3:42 PM, Tomas Vondra
> <tomas.vondra@2ndquadrant.com> wrote:
>> What I think we should not do is interpret the bitmasks (omitting some of
>> the information) assuming all the bits were set correctly.
> 
> I'm still confused. HEAP_XMIN_COMMITTED|HEAP_XMIN_ABORTED == 
> HEAP_XMIN_FROZEN. Nobody is proposing to omit anything; to the 
> contrary, what's being proposed is not to display the same thing
> twice (and in a misleading fashion, to boot).
> 

I understand your point. Assume you're looking at this bit of code:

     if (HeapTupleHeaderXminCommitted(enumval_tup->t_data))
         return;

which is essentially

     if (enumval_tup->t_data & HEAP_XMIN_COMMITTED)
         return;

If the function only gives you HEAP_XMIN_FROZEN, how likely is it you 
miss this actually evaluates as true?

You might say that people investigating issues in this area of code 
should be aware of how HEAP_XMIN_FROZEN is defined, and perhaps you're 
right ...

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
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