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The Since {{Version|8.6}}, the distinct values are also stored for elements and attributes of numeric type. Various queries will be evaluated much faster if an up-to-date path index is applied to rewrite descendant available (as can be observed when opening the [[GUI#Visualizations|Info View]]): * Descendant steps will be rewritten to multiple child steps. Child steps can be are evaluated faster, as fewer nodes have to be accessedtraversed:
Update Generally, update operations in BaseX are generally very fastin BaseX. By default, because the index structures will be invalidated by updates. As ; as a result, subsequent queries that benefit from index structures may be executed more slowly than before the updateslow down after updates. There are different alternatives to cope with this:
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==Name Index==
The name index contains all element and attribute references to the names of a database, all elements and the fixed-size index ids are stored attributes in the main database table. If a database is updated, new names are automatically added. Furthermore, the index It contains some basic statistical information , such as the distinct (categorical) or minimum and maximum values number of its elements and attributes. The maximum number occurrence of categories to store per a name can be changed via [[Options#MAXCATS|MAXCATS]]. The index are discarded after [[#Updates|database updates]].
The name index is e.g. applied to pre-evaluate discard location steps that will never yield results:
<pre class="brush:xquery">
The contents of the name indexes can be directly accessed with the XQuery functions [[Index Module#index:element-names|index:element-names]] and [[Index Module#index:attribute-names|index:attribute-names]].
If a database is updated, new names will be added incrementally, but the statistical information will get out-dated.
==Path Index==
The path index (which is also called ''path summary'' or ''data guide'') stores all distinct paths of the documents in the database. It contains similar additional statistical information , such as the name indexnumber of occurrence of a path, its distinct string values, and the minimum/maximum of numeric values. The index are discarded after maximum number of distinct values to store per name can be changed via [[Options#UpdatesMAXCATS|database updatesMAXCATS]].
<pre class="brush:xquery">
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* The paths statistics are e.g. used to pre-evaluate the {{Code|fn:count}} functionwill be pre-evaluated by looking up the number in the index: <pre class="brush:xquery"> count(doc('factbook')//country)</pre> * The distinct values of elements or attributes can be looked up in the index as well:
<pre class="brush:xquery">
distinct-values(db: will be rewritten and pre-evaluated by the path index :)count( docopen('factbook')//country religions)
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The contents of the path index can be directly accessed with the XQuery function [[Index Module#index:facets|index:facets]].
If a database is updated, the statistics in the path index will be invalidated.
==Document Index==
=Updates=
* After the execution of one or more update operations, the {{Command|OPTIMIZE}} command or the {{Function|Database|db:optimize}} function can be called to rebuild the index structures.
=Changelog=
;Version 8.4
* Updated: [[#Name Index|Name Index]], [[#Path Index|Path Index]]
;Version 8.4
