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;
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