Re: Object like pg_class.relkind = 's' or 'c' have on-disk

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От Katsuhiko Okano
Тема Re: Object like pg_class.relkind = 's' or 'c' have on-disk
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Msg-id 42394FC5.3030103@po.ntts.co.jp
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Ответ на Re: Object like pg_class.relkind = 's' or 'c' have on-disk file?  (Tom Lane <tgl@sss.pgh.pa.us>)
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OK.understand.
I'll exclude  relkind IN( 's' , 'c' )  file in backup set.
THANKS Qingqing Zhou & tom lane!

Tom Lane wrote:
> "Qingqing Zhou" <zhouqq@cs.toronto.edu> writes:
>
>>Pg_xactlock is always there as a special relation.
>
>
> pg_xactlock isn't really a relation.  The way I think about it is that
> it's a dummy entry in pg_class that exists to reserve a relation OID
> for a specific purpose --- namely, we can lock transaction IDs by
> locking what would otherwise be a page of that relation.
>
> There was some talk recently about reorganizing the locktag design
> so that transaction lock tags would be clearly distinguishable from
> any lock associated with a relation.  If we got that done, there'd
> be no need for the pg_xactlock entry at all.
>
>
>>I am not sure about 'c'.
>
>
> 'c' entries in pg_class are for composite types.  They don't have
> any associated disk storage either.
>
>             regards, tom lane
>
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Don't 'kill -9' the postmaster
>

--
----------------------------------------
Katsuhiko Okano
k_okano@po.ntts.co.jp
NTT Software Corp. (division "NBRO-PT6")


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