[jira] Commented: (COUCHDB-227) Large Number Support Bug

["Jason Davies (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/COUCHDB-227?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12667277#action_12667277 ] 

Jason Davies commented on COUCHDB-227:
--------------------------------------

This is due to JavaScript 1.x representing all numbers as 64-bit floating point numbers, which means only 15 digits of reliability for integers (see http://www.hunlock.com/blogs/The_Complete_Javascript_Number_Reference).

JSON itself effectively allows arbitrary-precision decimals, as JSON is just a general-purpose data description language.  I am guessing that if the Python view server is used, then the view will return the correct values (as Python supports long integers).

I did some research into JavaScript and precision because I wanted to use CouchDB to do financial calculations (e.g. summation of product prices).  ECMAScript 4 (or JavaScript 2) seems to support "real decimals":

http://intertwingly.net/blog/2008/07/11/Decimal-in-ECMAScript
http://dev.opera.com/articles/view/why-i-love-ecmascript-4-real-decimals/

I'm not sure when Spidermonkey will have ECMAScript 4, but when it does it looks like we'll get all the juicy benefits of real decimals.  In the meantime, we should document this in case it gives anyone a nasty surprise...

> Large Number Support Bug
> ------------------------
>
>                 Key: COUCHDB-227
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-227
>             Project: CouchDB
>          Issue Type: Bug
>          Components: Administration Console, JavaScript View Server
>            Reporter: Adam Kocoloski
>
> It looks like SpiderMonkey rounds large integers.  To reproduce,  create a document in Futon with a field value
> 9999999999999999
> Futon will round this to 10000000000000000.  Or, create a document with that field value by some other means and then emit the field in a view.  The document will have the correct value for the field, but the value in the view will be wrong.

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