Changes

This article is part of the [[Advanced User's Guide]] and introduces the available index structures, which are utilized by the . The query optimizer compiler tries to rewrite expressions optimize and speed up query evaluationqueries by applying the index whenever it is possible and seems promising.

Nearly all Most 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, and if an index is used, please turn on the [[GUI#Visualizations|Info View]] in the GUI or use the [[Command-Line Options#BaseX_Standalone|-V flag]] on the command line. The message following message…:

* A message like <code>- applying attribute Applying text index for "item0Japan"</code> …indicates indicates that the full-text index is applied to speed up the search of the shown string. The following message… * <code>- removing Removing path with no index results</code> …indicates indicates that a specified string in a path expression will never yield results. Because of that, the path does not need to be evaluated at all.* If you cannot find any index optimization hints in the info output, it often helps if you rewrite and index processing can be skippedsimplify your query.