From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: [PATCH] pageinspect function to decode infomasks |
Date: | 2017-10-14 17:58:01 |
Message-ID: | CA+Tgmoau_pmZzs7c50xg7rmvtExdRLnNtX7sSYW7y1iMBUapAA@mail.gmail.com |
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On Fri, Oct 13, 2017 at 4:36 PM, Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> No, I'm arguing that they're just bits. Show the bits, rather than
> interpreting what is displayed. Document that there are other logical
> states that are represented as composites of contradictory/mutually
> exclusive states.
/me shrugs.
I think it's perfectly sensible to view those 2 bits as making up a
2-bit field with 4 states rather than displaying each bit
individually, but you obviously disagree. Fair enough.
>> I guess it ends wherever we decide to stop.
>
> You can take what you're saying much further. What about
> HEAP_XMAX_SHR_LOCK, and HEAP_MOVED? Code like HEAP_LOCKED_UPGRADED()
> pretty strongly undermines the idea that these composite values are
> abstractions.
HEAP_MOVED is obviously a different kind of thing. The combination of
both bits has no meaning distinct from the meaning of the individual
bits; in fact, I think it's a shouldn't-happen state. Not sure about
HEAP_XMAX_SHR_LOCK.
> pg_filedump doesn't display HEAP_XMIN_FROZEN, either. (Nor does it
> ever display any of the other composite t_infomask/t_infomask2
> values.)
I can think of two possible explanations for that. Number one, the
tool was written before HEAP_XMIN_FROZEN was invented and hasn't been
updated for those changes. Number two, the author of the tool agrees
with your position rather than mine.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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