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From mark harwood <>
Subject Re: Postcode/zipcode search
Date Tue, 06 May 2008 17:19:58 GMT
Can you not convert all postcodes to coordinates and do actual distance-based matching?

You will have to pay Royal Mail or 3rd party suppliers to get hold of the PAF data required
for this geocoding (despite having funded this already as a UK tax payer- grrrr)


----- Original Message ----
From: Chris Mannion <>
Sent: Tuesday, 6 May, 2008 5:28:25 PM
Subject: Postcode/zipcode search

Hi all

I've got a bit of a niggling problem with how one of my searches is working
as opposed to how my users would like it too work.  We're indexing on UK
postcodes, which are in the format of a 3 or 4 character area code followed
by a 3 or 4 character street specific code, e.g. "NW10 7NY" or "M11 1LQ".
We originally had the values being indexed as tokenized and used a very
simple search string in the format "postcode:xxx xxx", with no grouping or
boosting or fuzzy searching, just an straight search on whatever the user
answered.  This had the benefit of finding exact matches to searches and
allowing us to search just on the area part of the code to return all
records with that area code, eg a search on "NW2" returning anything
starting NW2, like "NW2 6TB", "NW2 1ER" etc etc.

However, the downside to that was that searches could also return records
only tenuously related to what was searched for, eg. a search for "NW10 7NY"
would also return a record with a postcode "SE9 6NY" because of the slight
match of the "NY".  Obviously this was technically correct but users
complained because their searches were returning records from completely
different areas.  Our first step to put this right was to take off the
tokenization of the field, which we also weren't happy with so have
continued to fiddle.

The current status is as follows - we index the values by stripping out
spaces and tokeniing them and use a keywordAnalyzer.  In searching we also
strip spaces from the search term entered and search with a
keywordAnalyzer.  Searches for full postcodes, e.g. "NW10 7NY" find all
exact matches but also any full values that are partial matches (e.g. some
records just have "NW10" as their postcode field and the "NW10 7NY" search
pulls them back too), but searches for partial postcodes e.g. "NW10" still
only finds exact matches, e.g. it only pulls back those record that have
just "NW10" as their postcode, rather than anything *starting* with NW10 as
we'd like it to do.

Can anyone help me get this working in the way we need it too please?

Chris Mannion
iCasework and LocalAlert implementation team
0208 144 4416

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