Is monotonous xid8 is a right way to do?

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От Pavel Borisov
Тема Is monotonous xid8 is a right way to do?
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Msg-id CALT9ZEFkKtxqa2=53Rptc+TWD6ovMx7ACWn3tkdZ2r4j1NHKbg@mail.gmail.com
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Ответы Re: Is monotonous xid8 is a right way to do?
Re: Is monotonous xid8 is a right way to do?
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Hi hackers!

Now we have two data types xid and xid8. The first one (xid) makes a numeric ring, and xid8 are monotonous.

As per [1] "Unlike xid values, xid8 values increase strictly monotonically and cannot be reused in the lifetime of a database cluster."

As a consequence of [1] xid8 can have min/max functions (committed in [2]), which xid can not have.

When working on 64xid patch [3] we assume that even 64xid's technically can be wraparound-ed, although it's very much unlikely. I wonder what is expected to be with xid8 values at this (unlikely) 64xid wraparound? 

What do you think about this? Wouldn't it be better to change xid8 to form a numeric ring like xid? I think it is necessary for any 64-wraparound-enabled implementation of 64xids.

Please feel free to share your thoughts.

[1] https://www.postgresql.org/docs/current/datatype-oid.html
[2] https://www.postgresql.org/message-id/flat/47d77b18c44f87f8222c4c7a3e2dee6b%40oss.nttdata.com
[3] https://www.postgresql.org/message-id/flat/CACG%3DezZe1NQSCnfHOr78AtAZxJZeCvxrts0ygrxYwe%3DpyyjVWA%40mail.gmail.com

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