XID comparations

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От Carlos H. Reimer
Тема XID comparations
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Msg-id PEEPKDFEHHEMKBBFPOOKMELADAAA.carlosreimer@terra.com.br
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Ответы Re: XID comparations  (Tom Lane <tgl@sss.pgh.pa.us>)
Re: XID comparations  (Martijn van Oosterhout <kleptog@svana.org>)
Список pgsql-general
Hi,

I would like to understand better the logic to determine when a xid is older
than another one.

As I could understand, the XID is always incremented, never reset. If it is
true, then we can have rows with cmin ranging
from 1 to 4.294.967.295 (2^32-1).

When xid overflows (32 bits) the next one will be 3 (1 and 2 are reserved).

In this case, we could have have lines with cmin 4.294.967.295 and lines
with cmin 3. How are they compared to determine that
rows with cmin 3 are newer than rows with cmin 4.294.967.295?

Thanks in advance,

Reimer


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