From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <46BC0A6D.9060404@proweb.co.uk> Date: Fri, 10 Aug 2007 07:49:17 +0100 From: matt User-Agent: Thunderbird 2.0.0.6 (Windows/20070728) MIME-Version: 1.0 To: Fans of the OS Plan 9 from Bell Labs <9fans@cse.psu.edu> Subject: Re: [9fans] synthetic filesystems and changing data References: <46BBC396.9040009@ec.gc.ca> In-Reply-To: <46BBC396.9040009@ec.gc.ca> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Topicbox-Message-UUID: a2dfaea8-ead2-11e9-9d60-3106f5b1d025 The coder for the file system makes the choice whether to keep a snapshot of the data to be read per FID, this way the FID reader will always get the file they asked for, which, after the first read, isn't necessarily the current version or to just return whatever each Tread asks for regardless of whether the underlying data has changed. It is akin to an SQL cursor. When I make an SQL request the rows returned are a snapshot of the data when the query was made. If I read them at one row per second there's a chance that the actual data in the datastore changes between reads. Either way there's a "tough luck" aspect, if you have a solution I'm sure everyone would be delighted to hear it :) It's a perinnial problem. When opening a file for writing some programs (acme for instance) will warn you if the file has changed since you opened it. That's a solution to the same problem. Matt