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I learned how to use the Levenshtein functions in PostgreSQL

The thing is that there is a limit of 255 characters for these functions in PostgreSQL so you need to truncate the strings before comparing
Also, the trgm functions I&rsquo;ve used before are case insensitive, but Levenshtein is not, so you need to make sure to lower case both strings first


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I learned how to use the Levenshtein functions in PostgreSQL

The thing is that there is a limit of 255 characters for these functions in PostgreSQL so you need to truncate the strings before comparing
Also, the trgm functions I&rsquo;ve used before are case insensitive, but Levenshtein is not, so you need to make sure to lower case both strings first


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    <h2 class="blog-post-title" dir="auto"><a href="https://alanorth.github.io/cgspace-notes/2022-07/">July, 2022</a></h2>
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<time datetime="2022-07-02T14:07:36+03:00">Sat Jul 02, 2022</time>
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<span class="fas fa-folder" aria-hidden="true"></span>&nbsp;<a href="/categories/notes/" rel="category tag">Notes</a>


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  <h2 id="2022-07-02">2022-07-02</h2>
<ul>
<li>I learned how to use the Levenshtein functions in PostgreSQL
<ul>
<li>The thing is that there is a limit of 255 characters for these functions in PostgreSQL so you need to truncate the strings before comparing</li>
<li>Also, the trgm functions I&rsquo;ve used before are case insensitive, but Levenshtein is not, so you need to make sure to lower case both strings first</li>
</ul>
</li>
</ul>
<ul>
<li>A working query checking for duplicates in the recent AfricaRice items is:</li>
</ul>
<div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-console" data-lang="console"><span style="display:flex;"><span>localhost/dspace= ☘ SELECT text_value FROM metadatavalue WHERE  dspace_object_id IN (SELECT uuid FROM item) AND metadata_field_id=64 AND levenshtein_less_equal(LOWER(&#39;International Trade and Exotic Pests: The Risks for Biodiversity and African Economies&#39;), LEFT(LOWER(text_value), 255), 3) &lt;= 3;
</span></span><span style="display:flex;"><span>                                       text_value                                       
</span></span><span style="display:flex;"><span>────────────────────────────────────────────────────────────────────────────────────────
</span></span><span style="display:flex;"><span> International trade and exotic pests: the risks for biodiversity and African economies
</span></span><span style="display:flex;"><span>(1 row)
</span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010">
</span></span></span><span style="display:flex;"><span><span style="color:#960050;background-color:#1e0010"></span>Time: 399.751 ms
</span></span></code></pre></div><ul>
<li>There is a great <a href="https://www.crunchydata.com/blog/fuzzy-name-matching-in-postgresql">blog post discussing Soundex with Levenshtein</a> and creating indexes to make them faster</li>
<li>I want to do some proper checks of accuracy and speed against my trigram method</li>
</ul>
<h2 id="2022-07-03">2022-07-03</h2>
<ul>
<li>Start a harvest on AReS</li>
</ul>
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