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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>12.11. Limitations</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="textsearch-psql.html" title="12.10. psql Support" /><link rel="next" href="mvcc.html" title="Chapter 13. Concurrency Control" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">12.11. Limitations</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="textsearch-psql.html" title="12.10. psql Support">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="textsearch.html" title="Chapter 12. Full Text Search">Up</a></td><th width="60%" align="center">Chapter 12. Full Text Search</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 11.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="mvcc.html" title="Chapter 13. Concurrency Control">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="TEXTSEARCH-LIMITATIONS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">12.11. Limitations</h2></div></div></div><p>
The current limitations of <span class="productname">PostgreSQL</span>'s
text search features are:
</p><div class="itemizedlist"><ul class="itemizedlist compact" style="list-style-type: bullet; "><li class="listitem" style="list-style-type: disc"><p>The length of each lexeme must be less than 2K bytes</p></li><li class="listitem" style="list-style-type: disc"><p>The length of a <code class="type">tsvector</code> (lexemes + positions) must be
less than 1 megabyte</p></li><li class="listitem" style="list-style-type: disc"><p>The number of lexemes must be less than
2<sup>64</sup></p></li><li class="listitem" style="list-style-type: disc"><p>Position values in <code class="type">tsvector</code> must be greater than 0 and
no more than 16,383</p></li><li class="listitem" style="list-style-type: disc"><p>The match distance in a <code class="literal"><<em class="replaceable"><code>N</code></em>></code>
(FOLLOWED BY) <code class="type">tsquery</code> operator cannot be more than
16,384</p></li><li class="listitem" style="list-style-type: disc"><p>No more than 256 positions per lexeme</p></li><li class="listitem" style="list-style-type: disc"><p>The number of nodes (lexemes + operators) in a <code class="type">tsquery</code>
must be less than 32,768</p></li></ul></div><p>
</p><p>
For comparison, the <span class="productname">PostgreSQL</span> 8.1 documentation
contained 10,441 unique words, a total of 335,420 words, and the most
frequent word <span class="quote">“<span class="quote">postgresql</span>”</span> was mentioned 6,127 times in 655
documents.
</p><p>
Another example — the <span class="productname">PostgreSQL</span> mailing
list archives contained 910,989 unique words with 57,491,343 lexemes in
461,020 messages.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="textsearch-psql.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="textsearch.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="mvcc.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">12.10. <span class="application">psql</span> Support </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 13. Concurrency Control</td></tr></table></div></body></html>
