Eli,
Example: I want to search on all the directories under 'd4' that
contain the word music.
I got several solutions, but not satisfying:
A) Loop from 'd4' to sub-dirs in first level, and use buffer list for
next iterations
when going deeper into levels. [not good: there can be many sub-dirs
with descendants,
and the loop will iter more; slow on searches].
B) Storing the directory tree structure in the form of 'root/d1/d4/d6'
and etc.
[not good: personally I can't use it (specific implementation
restriction)].
C) Descendants sub-dirs connections to sub-dirs on deeper levels, so
searching will go
over the first level sub-dirs and the descendants sub-dirs. [not good:
there can be many
sub-dirs and there would be many descendants sub-dirsl; duplicating
descendants on references].
As you say, your A and C aren't maintainable. If a node can have more
than one parent node (ie its indegree can 1), it ain't a tree, so
tree methods won't work unmodified. It's possible, though, to adapt some
tree traversal methods to a graph like yours; for an example see the
parts explosion section in
http://www.artfulsoftware.com/mysqlbook/sampler/mysqled1ch20.html.
PB
-
Eli wrote:
Hi,
I have a table of directories. Each row represents a directory, which
holds his name and desc. Another table lists sub-directories from each
directory source to its sub-directories targets.
dirs:
+--+--++
| dir_id | dir_name | dir_desc |
+--+--++
|0 | root | root dir |
| 11 | d1 | dir no. 1 |
| 12 | d2 | dir no. 2 |
| 21 | d3 | dir no. 3 |
| 22 | d4 | dir no. 4 |
| 23 | d5 | dir no. 5 |
| 31 | d6 | dir no. 6 |
| 32 | d7 | dir no. 7 |
| 41 | d8 | dir no. 8 |
| 51 | d9 | dir no. 9 |
| 52 | d10 | dir no. 10 |
| 61 | d11 | dir no. 11 |
+--+--++
12 rows in set (0.00 sec)
subdirs:
+++
| dir_source | dir_target |
+++
| 0 | 11 |
| 0 | 12 |
| 11 | 21 |
| 11 | 22 |
| 11 | 23 |
| 12 | 31 |
| 22 | 31 |
| 22 | 32 |
| 23 | 52 |
| 31 | 41 |
| 41 | 51 |
| 41 | 52 |
| 52 | 61 |
+++
13 rows in set (0.00 sec)
root (0)
+d1 (11)
| +d3 (21)
| +d4 (22)
| | +d6 (31)
| | | +d8 (41)
| | | +d9 (51)
| | | +d10 (52)
| | | +d11 (61)
| | +d7 (32)
| +d5 (23)
| +*d10* (52) -reference
+d2 (12)
+*d6* (31) -reference
Note that a directory can be contained in several parent directories
(as long as it doesn't creates circles) - references.
Example: I want to search on all the directories under 'd4' that
contain the word music.
I got several solutions, but not satisfying:
A) Loop from 'd4' to sub-dirs in first level, and use buffer list for
next iterations when going deeper into levels. [not good: there can be
many sub-dirs with descendants, and the loop will iter more; slow on
searches].
B) Storing the directory tree structure in the form of 'root/d1/d4/d6'
and etc. [not good: personally I can't use it (specific implementation
restriction)].
C) Descendants sub-dirs connections to sub-dirs on deeper levels, so
searching will go over the first level sub-dirs and the descendants
sub-dirs. [not good: there can be many sub-dirs and there would be
many descendants sub-dirsl; duplicating descendants on references].
Do you have any other suggestions? What's the better way?
-Thanks in advance... :-)
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