On Sun, Jul 10, 2011 at 10:52 AM, Christopher Melen
<relativef...@hotmail.co.uk> wrote:
>
> Hi,
>
>
> I am developing an application which analyses audio data, and I have recently
> been looking into Sqlite as a possible file format. The result of an analysis
> in my application is a hierarchical data set, where each level in the
> hierarchy represents a summary of the level below, taking the max of each
> pair in the sub-level, in the following way:
>
>
> 251 214
>
>
> 251 54 201 214
>
>
> 251 91 17 54 31 201
> 214 66
>
>
> 251 18 5 91 11 17 54 16 9 31 201 148 173 214 43 66
>
>
> Such a structure essentially represents the same data set at different levels
> of resolution ('zoom levels', if you like). My first experiments involved a
> btree-like structure (actually something closer to an enfilade* or counted
> btree**), where the data stored in each node is simply a summary of its child
> nodes. Edits to any node at the leaf level propagate up the tree, whilst
> large edits simply entail unlinking pointers to subtrees, thus making edits
> on any scale generally log-like in nature. This works fine as an in-memory
> structure, but since my data sets might potentially grow fairly large (a few
> hundred MB at least) I need a disk-based solution. I naively assumed that I
> might be able to utilize Sqlite's btree layer in order to implement this more
> effectively; this doesn't seem possible, however, given that the btree layer
> isn't directly exposed, and in any case it doesn't map onto the user
> interface in any way that seems helpful for this task.
>
I developed an option tree that is heirarchal and is basically like a
registry. I only store the parent_id, since order isn't entirely
important.
node_id | parent_node_id | content | sequence
maybe adding a sequence if which is to the left or right is
important.... but this isn't really binary treeing either....
if you want what's under a thing just select who has that node_id as a
parent_node_id
>
> I am aware of some of the ways in which hierarchical or tree-like structures
> can be represented in a database (adjacency lists, nested sets, materialized
> paths, etc.), but none of these seems to offer a good solution. What I'm
> experimenting with at present is the idea of entering each node of the
> hierarchy into the database as a blob (of say, 1024 bytes), while maintaining
> a separate in-memory tree which then maps on to this flat database of nodes
> (each node in the tree maintains a pointer to a node in the database).
>
>
> I would be very interested in
> thoughts/observations
> on this problem - or even better a solution!
>
>
>
> Many thanks in advance,
> Christopher
>
>
> * http://en.wikipedia.org/wiki/Enfilade_(Xanadu)
> ** http://www.chiark.greenend.org.uk/~sgtatham/algorithms/cbtree.html
>
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