Bazaar, OLPC, and the "no-packs" repository format.

Aaron Bentley aaron.bentley at utoronto.ca
Thu Dec 20 13:09:48 GMT 2007


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John Arbash Meinel wrote:

> I think this is a good analysis, and certainly something we could do. I
> actually think we could do it with existing packs, and just turn off the
> autopack functionality (or just set it to run much less often).
> 
> We would still need a form of index that could handle this sort of thing,
> though. At the moment packs start to perform poorly when you have too many of
> them. Because it is bisecting each index looking for the key you requested.

I guess I should have expanded on this.  The reason I was suggesting not
doing it with packs is because packs require indices.  And indices get
slow when you have too many.

I was planning on using the filesystem as the index.  I'm assuming it
already has  O(log n) access to named content, and we can easily
determine the names we're looking for.  The graph data could be
1. stored with the content
2. stored as a separate set of little files.
3. stored as extended file attributes ?

> Robert has at least conceptualized a hash-based index, so lookups become more
> of an O(1) operation. Which makes it O(N) for N packs, but that is better than
> O(N log(M)) for our current indexes. I wonder if you could even combine the
> hash maps to make it O(1) across all indexes that you have read...
> 
> Alternatively, we could just insert the data into the SQLite DB.

I discussed it with Mike, and apparently the OLPC environment does not
provide direct access to the database.  Perhaps that could change, but I
was designing assuming it wouldn't.

> I know I
> looked into it in the past.  SQLite ended up taking a bit longer to start up,

Startup time should not be an issue, since it would already be in memory.

Aaron
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