Add optional fuzzy search using PostgreSQL pg_trgm extension

[Copilot]

Issue requested replacing LIKE with strict_word_similarity() for fuzzy search. Rather than a hard switch, this implements an opt-in approach preserving backward compatibility while enabling trigram-based fuzzy matching when desired.

Changes

• Configuration (conf/mapbender.conf-dist):

  • SEARCH_USE_TRIGRAM (default: false) — toggle fuzzy search
  • SEARCH_TRIGRAM_THRESHOLD (default: 0.3) — similarity threshold (0.0-1.0)

• Search logic (http/classes/class_metadata.php):

  • When enabled: uses word_similarity($param, searchtext) > threshold
  • When disabled: unchanged LIKE behavior
  • Threshold validated and clamped to valid range

Usage

// In mapbender.conf (requires: CREATE EXTENSION pg_trgm;)
define("SEARCH_USE_TRIGRAM", true);
define("SEARCH_TRIGRAM_THRESHOLD", 0.3);

Default behavior unchanged — existing installations unaffected.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Fuzzy search with trigram</issue_title>
<issue_description>Issue copied from:
mrmap-community#55

For the fuzzy search, there are some algorithm like levenshtein, soundex, word_similarity and so on.

https://www.postgresql.org/docs/current/fuzzystrmatch.html
https://www.postgresql.org/docs/current/pgtrgm.html

In the mapbender/http/classes/class_metadata.php in line 1284, the code could be change from:
$whereStr .= "searchtext LIKE $" . ($i + 1);
to
$whereStr .= "(strict_word_similarity($" . ($i + 1) . ", searchtext) > 0.2)";

In order to use strict_word_similarity( ) function, we need to install in the postgres first.
CREATE EXTENSION pg_trgm;

Work still need to be done: Check the performance of the search, since a new algorithm is used instead of LIKE.</issue_description>

<agent_instructions>Do you have a better way to solve the problem and it should be fast too.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@dpakprajul I think its better to close this issue as it won't go further and has no future. Okay?

• Fixes Fuzzy search with trigram #55

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