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From: Jens Alfke <jens@couchbase.com>
To: "user@couchdb.apache.org" <user@couchdb.apache.org>
Date: Mon, 5 Nov 2012 10:47:06 -0800
Subject: Re: Exist test?
Thread-Topic: Exist test?
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On Nov 5, 2012, at 10:22 AM, Kevin Burton <rkevinburton@charter.net> wrote:

> I am calling CreateDocument<Document>() but I suspect that testing if the=
 document exists first may perform better in the long run. I am using Dream=
Seat for my driver but I suspect other drivers have a similar "test". My pr=
oblem is that I don't know what to test for and I am unfamiliar with the av=
ailable methods. Any one successfully use such a pattern (preferably with D=
reamSeat) that tests for existence then creates if the document doesn't exi=
st? Keep in mind I don't initially have an id. Thank you.

I don=92t know anything about that particular API, but in general, check-th=
en-create doesn=92t work well in a concurrent environment. It=92s prone to =
race conditions where something else creates the resource in between your c=
heck call and your create call. (The canonical example is checking whether =
a file exists, then creating the file, which is a classic old security hole=
 in privileged Unix tools.)

=97Jens=