I have a large set of data (that will be stored in MySQL) that I wish to
match to and am wondering what the best method is.
Assume the following data in table LCATIN_MATCH:
LCATIN_ID LCATIN_PATTERN PARENT_ID
10 6
11 4 10
13 2 11
12 9 11
14 1 13
15 2 13
The string 6438 should return 11, 6421 14, 6422 15 and 6499 12.
I've read a bit about btrees on the zope wiki and wonder if that's the best
way. However I am struggling with the basics:
1. How do I get the data from MySQL into a btree in Zope? Something like:
from BTrees.IIBTree import *
t = IIBTree()
t.update() # errr, no
2. How do I find the matching node i.e. when I want to know that 6422
relates to location_id 15?
Any help or pointers to further documentation would be appreciated.
Regards
Cameron
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5. Dezember 2005 16:57:03 +1300 Cameron Beattie <kjcsb (AT) orcon (DOT) net.nz
wrI've read a bit about btrees on the zope wiki and wonder if that's the
best way. However I am struggling with the basics:
1. How do I get the data from MySQL into a btree in Zope? Something like:
from BTrees.IIBTree import *
t = IIBTree()
t.update() # errr, no

Reading helps:

<>

2. How do I find the matching node i.e. when I want to know that 6422
relates to location_id 15?

I still have no idea what your example should tell me. A BTree basically
implements the same API as a Python dictionary. If you can implement your
solution in pure Python then you can just switch to BTrees. But I have no
idea about your example especially BTrees implement a 1:1
relationship (when using an IIBTree).
-aj

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Thanks for the many replies. I apologise for the original message which was
obviously very unclear - I will try to correct that.

Basically I want to match a telephone number to a rate table. Assume the
following rate table:
Telephone code Rate
649 1
6421 2
6422 2.5
64 1.5

The following table sets out the appropriate rate to return for a given
telephone number
Dialled number Returned rate
649123 1
643123 1.5
6421111 2
64221 2.5

Things to note:
If there is no match the right-most digit is removed until there is a match
e.g. 643123 matches to 64
The length of the "dialled number" is not consistent e.g. 649123 vs 64221
The length of the "telephone code" is not consistent e.g. 64 vs 6422

I want to do this frequently and at low cost i.e. ideally in memory. Perhaps
the best way is to write a procedure in MySQL however I am interested in any
python-based alternatives.

Regards

Cameron

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6. Dezember 2005 14:55:08 +1300 Cameron Beattie <kjcsb (AT) orcon (DOT) net.nz
wrote:
I want to do this frequently and at low cost i.e. ideally in memory.
Perhaps the best way is to write a procedure in MySQL however I am
interested in any python-based alternatives.

I pointed you already to the BTrees documentation.
-aj

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6. Dezember 2005 14:55:08 +1300 Cameron Beattie <kjcsb (AT) orcon (DOT) net.nz
wrote:

I want to do this frequently and at low cost i.e. ideally in memory.
Perhaps the best way is to write a procedure in MySQL however I am
interested in any python-based alternatives.

Your problem is more an algorithmic problem than q question of the data
representation. Store the mapping as some BTree (possibly IIBTree using
normalized integers for the values). Then you have to iterate over all
prefixes of the dialed number starting with the longest prefix to the
smallest prefix. Then perform a lookup of the prefix in your BTree
this is should not take more than five lines of code and requires a maximum
of #(length_of_dialed_number) comparisons. If you want it more complicated
construct a tree and you'll have a logarithmic number of comparisons. I
doubt that it is worth the effort since the first solution should be fast
enough unless your dialed number is hundreds of digits long :-)
-aj

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Am Dienstag, den 06.12.2005, 14:55 +1300 schrieb Cameron Beattie:
Thanks for the many replies. I apologise for the original message which was
obviously very unclear - I will try to correct that.

I want to do this frequently and at low cost i.e. ideally in memory. Perhaps
the best way is to write a procedure in MySQL however I am interested in any
python-based alternatives.

*hint* use postgres instead where you can write stored functions in
python too :-)
(With some little modifications on the zope database adaptor you
could even return a dictionary or btree object as result
of your query then :-)

SCNR
Tino

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