Re: [BUGS] Breakage with VACUUM ANALYSE + partitions

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От Fabien COELHO
Тема Re: [BUGS] Breakage with VACUUM ANALYSE + partitions
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Msg-id alpine.DEB.2.10.1605030712070.927@sto
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Ответ на Re: [BUGS] Breakage with VACUUM ANALYSE + partitions  (Andres Freund <andres@anarazel.de>)
Ответы Re: [BUGS] Breakage with VACUUM ANALYSE + partitions  (Andres Freund <andres@anarazel.de>)
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Hello,

>> I'm unsure about switching enum to #define, could be an enum still with
>> explicit values set, something like:
>
> An enum doesn't have a benefit for a bitmask imo - you can't "legally"
> use it as a type for functions accepting the bitmask.

I do not understand. I suggested to use enum to enumerate the bitmask 
constants, ISTM that it does not preclude to use it as a bitmask as you 
do, it is just a replacement of the #define? The type constraint on the 
enum does not disallow bitmasking values, I checked with both gcc & clang.

>> I'm fuzzy about the _OPEN_DELETED part because it is an oxymoron. Is it
>> RECREATE really?
>
> No. The relevant explanation is at the top of the file:

[...]

> *        -- Optionally, any number of inactive segments of size 0 blocks.
> *    Inactive segments are those that once contained data but are currently
> *    not needed because of an mdtruncate() operation.  The reason for leaving
> *    them present at size zero, rather than unlinking them, is that other
> *    backends and/or the checkpointer might be holding open file references to
> *    such segments.  If the relation expands again after mdtruncate(), such
> *    that a deactivated segment becomes active again, it is important that
> *    such file references still be valid --- else data might get written
> *    out to an unlinked old copy of a segment file that will eventually
> *    disappear.

Ok.

Then should it be _OPEN_INACTIVE[TED] or _OPEN_TRUNCATED rather than 
_OPEN_DELETED, which is contradictory?

-- 
Fabien.



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