DAZ wrote:
> On Dec 28, 8:07�pm, Mark Reginald James <m...@bigpond.net.au> wrote:
>
>> One alternative is to make the ancestor array a string key
>> to each record ("abe|homer|bart"), allowing instant retrieval.
>
> This seems like a relatively good idea, could have a string-key called
> family_tree or something and just do find_by_family_tree("abe|homer|
> bart")
> This doesn't quite feel right - it seems like the only info you should
> need to keep is a person's parent (from which you can then find their
> parent and so forth). It might also lead to some very long strings
> eventually!
I tend to like this idea as well, and is probably what I would do. The
caching of the ancestry would seem to be the most efficient. However,
there is one change I would make. I would reverse the ancestry so it
would be ("bart|homer|abe"). Doing this would make string comparisons
more efficient because you are looking for "bart" so having "bart" at
the beginning of the string may slightly increase the string comparison
efficiency.
> This doesn't quite feel right - it seems like the only info you should
> need to keep is a person's parent (from which you can then find their
> parent and so forth). It might also lead to some very long strings
> eventually!
This, however, I don't agree with. You need the full ancestry to
whatever the "root" objects is. The idea is to make one comparison with
no joins. The only way to do that I can think of is to have all the
information available at the row level.
If you end up with a very deep hierarchy, which would result in very
long strings, you could consider hashing the strings. This way you would
have a consistent length string to compare.
Example MD5 Hash:
bart|homer|abe = a92b11363ef020716f1ce3104e0cb0d8 (32 chars)
bart|homer|abe|john|william|ted|sam|joeseph|adam|bart|bill|jack =
ff2f4ad181a029935b89a36c7cd1dfbe (32 chars)
Obviously in some cases your losing rather than gaining, but at least
the string is consistent in length no matter how long the input string
becomes.
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