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Re: Distributed systems and primary keys - Mailing list pgsql-general

From Koichi Suzuki
Subject Re: Distributed systems and primary keys
Date
Msg-id CAAn2te8qBZFpZSBnwRZR=6oKYHDgkhFMe+NZaH6N_ozOVXDOiw@mail.gmail.com
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In response to Re: Distributed systems and primary keys  ("Joshua D. Drake" <jd@commandprompt.com>)
Responses Re: Distributed systems and primary keys
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In Postgres-XC, GTM assigns sequence value to all the transactions in its cluster.   XC is a kind of tightly-coupled distributed system.   In a loosely-coupled distributed system, where each database is autonomous, we may need another mechanism.

I've learned that logical replication (used to be bi-directional replication) people are doing this kind of work.

Regards;

----------
Koichi Suzuki


2013/7/12 Joshua D. Drake <jd@commandprompt.com>

On 07/12/2013 07:23 AM, Melvin Call wrote:
Hello list,

Can anyone point me to some reading material on how auto-generated
sequence primary keys are handled on distributed systems? I think the
advice used to be to use GUIDs, but I thought I read somewhere that
PostgreSQL now assigns a pool of numbers to each node when a sequence is
implemented. I have searched the PostgreSQL 9.1.5 Documentation, but
apparently my search terms are not quite what it takes, or dreamt that up.

PostgreSQL itself does not support a distributed architecture. You may be thinking of Postgres-XC?

Sequences are local to each instances and it is not a pool, it is a 64bit allocation for each sequence within the local node, generally constrained only when called from the serial (big serial being 64 bits) type to 32 bits.

Sincerely,

Joshua D. Drake




Thanks,
Melvin


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