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The Nearly all examples in this article are based on the [http://files.basex.org/xml/factbook.xml factbook.xml] document. To see how a query is rewritten, please turn on the [[GUI#Visualizations|Info View]] in the GUI or use the [[Startup_Options#BaseX_Standalone|-V flag]] on command line.
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This article is part of the [[Advanced User's Guide]] and introduces the available index structures, which are utilized by the query optimizer to rewrite expressions and speed up query evaluation.
=Structural Indexes=
==Text Index==
This index speeds up string-based equality tests and (since {{Version|7.2.1}}) range queries on text nodes. The [[Options#UPDINDEX|UPDINDEX]] option can be activated to keep this index up-to-date.
The following queries will all be rewritten for index access:
//*[text() = 'Germany'],
doc('factbook.xml')//name[. = 'Germany'],
for $c in db:open('factbook')//country[.where $c//city/name = 'Hanoi'return $c/name</pre> Since {{Version|7.2.1}}), the text index also supports range queries based on string comparisons: <pre class="brush:xquery"> db:open('Library')//Medium[Year >= '2005' and Year <= '2007'],let $min := '2011-04-16T00:00:00'let $max := '2011-04-19T23:59:59' return db:open('news')//nameentry[date-time > $min and date-time < $max]
</pre>
