CouchDB如何计算修订号 [英] How does CouchDB calculate the Revision number

问题描述

我试图了解CouchDB如何计算文档的修订ID。我从源头注意到，它是通过以下这段代码计算的：

I'm trying to understand how CouchDB calculates the revision id for a document. I notice from the source that it's calculated by this bit of code here:

couch_util:md5(term_to_binary([Deleted, OldStart, OldRev, Body, Atts2]))

我知道，如果我创建一个没有附件中，CouchDB始终对其进行修订-1-967a00dff5e02add41819138abb3284d，十进制为<<< 150,122,0,223,245,224,42,221,65,129,145,56,171,179,40,77 >>。

And I know that if I create a new empty document with no attachments, CouchDB always gives it a revision of 1-967a00dff5e02add41819138abb3284d which, in decimal is <<150,122,0,223,245,224,42,221,65,129,145,56,171,179,40,77>>.

但是，如果我在erlang提示符下输入以下内容（对于false，则为false；对于OldStart，0为OldRev，为空正文，没有附件）：

However, if I type the following into the erlang prompt (false for deleted, 0 for OldStart, 0 for OldRev, an empty body and no attachments):

erlang:md5(term_to_binary([false, 0, 0, [], []])).                   

我总是得到

<<26,196,244,40,211,149,193,185,214,6,230,61,54,138,62,132>>

回来。

那我是什么

推荐答案

在阅读从CouchDB中的Erlang视图中发出元组我意识到我做错的不是包装元组中空的属性列表。我不知道为什么沙发会这样做，但这就是问题所在。

After reading the answer to Emit Tuples From Erlang Views In CouchDB I realised that what I was doing wrong was not wrapping the empty proplist for body in a tuple. I'm not sure why couch does that, but that's what the problem was.

erlang:md5(term_to_binary([false, 0, 0, {[]}, []])).

给出正确的答案

< < 150,122,0,223,245,224,42,221,65,129,145,56,171,179,40,77 >>

<<150,122,0,223,245,224,42,221,65,129,145,56,171,179,40,77>>

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