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From: Jens Alfke <jens@mooseyard.com>
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Subject: Detailed info on the B-tree store? Native implementations thereof?
Date: Tue, 11 Aug 2009 08:43:27 -0700

I'm interested in the underpinnings of the CouchDB server =97 the crash-=20=

proof concurrent B-tree store. There's a blog post linked to in the =20
wiki that describes the basic concepts (leaves and updated =20
intermediate nodes are appended to the file; the start of the file =20
stores two links to the root node) but is there any more detailed =20
description[1]? And is there any similar technology available that's =20
implemented in native code (C/C++)?[2]

Basically I'm interested in whether it's feasible to build a simple =20
storage system (for use in an HTML5 Web browser) that a CouchDB-=20
compatible client library could be built on top of. JChris has posted =20=

about this topic recently[3], and pointed out that the hashtable-=20
oriented key-value store currently speced in HTML5 is a poor match for =20=

CouchDB. Moreover, the SQLite database engine underneath it doesn't =20
guarantee data integrity after a hard system crash (as I know from =20
painful experience.) So: could we build a fault-tolerant B-tree based =20=

API into the browser? (This isn't just academic curiosity: I recently =20=

started work on the Chrome team at Google, and HTML5 local storage is =20=

one of my group's responsibilities.)

Thanks!

=97Jens

[1] Alas, I cannot Use The Source, Luke, as I do not have Erlang =20
skillz. :(
[2] I know of many, many B-tree libraries (Berkeley DB, =20
TokyoCabinet...) but none that are fault-tolerant.
[3] http://jchrisa.net/drl/_design/sofa/_show/post/Fixing-HTML-5-Storage=