On Tue, Oct 6, 2009 at 9:38 PM, Matthew Byrne <matt...@hairybrain.co.uk> wrote:
>
> The following bug has been logged online:
>
> Bug reference: 5098
> Logged by: Matthew Byrne
> Email address: matt...@hairybrain.co.uk
> PostgreSQL version: 8.4.1
> Operating system: Linux x86_64 (Ubuntu 9.04)
> Description: Levenshtein with costs is broken
> Details:
>
> The Levenshtein with costs function in the fuzzystrmatch module is coded
> incorrectly. The initial values in the distance matrix are set up as 0, 1,
> 2 etc. when they should be 0, deletion_cost, (2 * deletion_cost)... and 0,
> insertion_cost, (2 * insertion_cost) etc. respectively. This causes the
> function to return incorrect values, e.g.:
>
> SELECT LEVENSHTEIN('ABC', 'XABC', 100, 100, 100)
>
> returns 1 (the correct answer is 100).
>
> To fix this, make the following changes to fuzzystrmatch.c:
>
> Change line 244 from
> prev[i] = i;
> to
> prev[i] = i * del_c;
>
> and change line 255 from
> curr[0] = j;
> to
> curr[0] = j * ins_c;
Can you submit this as a patch file?
...Robert
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