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Re: Proposal: Commit timestamp

From: Jan Wieck <JanWieck(at)Yahoo(dot)com>
To: Jim Nasby <decibel(at)decibel(dot)org>
Cc: PostgreSQL Development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Proposal: Commit timestamp
Date: 2007-02-03 20:52:50
Message-ID: 45C4F622.8000906@Yahoo.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On 2/1/2007 11:23 PM, Jim Nasby wrote:
> On Jan 25, 2007, at 6:16 PM, Jan Wieck wrote:
>> If a per database configurable tslog_priority is given, the  
>> timestamp will be truncated to milliseconds and the increment logic  
>> is done on milliseconds. The priority is added to the timestamp.  
>> This guarantees that no two timestamps for commits will ever be  
>> exactly identical, even across different servers.
> 
> Wouldn't it be better to just store that information separately,  
> rather than mucking with the timestamp?
> 
> Though, there's anothe issue here... I don't think NTP is good for  
> any better than a few milliseconds, even on a local network.
> 
> How exact does the conflict resolution need to be, anyway? Would it  
> really be a problem if transaction B committed 0.1 seconds after  
> transaction A yet the cluster thought it was the other way around?

Since the timestamp is basically a Lamport counter which is just bumped 
be the clock as well, it doesn't need to be too precise.


Jan

-- 
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