Hello Gioele, I have a souvenir that the use of namespaces was slowing down (or maybe invalidating) the structure index. Someone @BaseX will certainly correct me if I am wrong, but if your data is single namespaced, what about reloading data with the "skip namespaces" option enabled and test if performance improves ?
Another solution could be to create an index collection, where key would be your search terms, and values the node-pre or node-id of your (sub-)documents. Best regards, Fabrice -----Message d'origine----- De : basex-talk-boun...@mailman.uni-konstanz.de [mailto:basex-talk-boun...@mailman.uni-konstanz.de] De la part de Gioele Barabucci Envoyé : vendredi 12 juin 2015 10:42 À : basex-talk@mailman.uni-konstanz.de Objet : [basex-talk] Optimization of a slow query with `//` Hello, I am working on an application that retrieves its data from a TEI XML file via BaseX. The following query lies at the core of this application but is too slow to be used in production: on a modern PC it requires about 600 ms to run over a 4MB file (1/10 of the complete dataset). Any suggestion on how to improve its performance (without changing the underlying TEI files) would be much appreciated. Here is the query: declare namespace tei='http://www.tei-c.org/ns/1.0'; /tei:TEI/tei:text/tei:body// *[self::tei:entry or self::tei:re] [./tei:form/tei:orth[. = "arci"] [ancestor-or-self::* [@xml:lang][1] [(starts-with(@xml:lang, "san"))] ] ] In human terms is should return all the `tei:entry` or `tei:re` that * have the word "arci" in their `/tei:form/tei:orth` element, * their nearest `xml:lang` attribute starts with 'san'. I made some tests and it turned out that the main culprit is the use of `//` in the first line. (_Main_ culprit, not the only one...) I use the `//` axis because I do not know what is the structure of the underlying TEI file. I expect BaseX to keep track of all the `tei:entry` and `tei:re` elements and their parents, so selecting the correct ones should be quite fast anyway. But the measurements disagree with my assumptions... What could I do to improve the performance of this query? Now, some remarks based on some small tests I have done: 1. Removing the [ancestor-or-self::*[....]] predicate slashes the run time in half, but the query is still way too slow. 2. Changing ./tei:form/tei:orth[. = "arci"] to ./tei:form[1]/tei:orth[1][. = "arci"] makes the query even slower. 3. changing `starts-with(@xml:lang, "san")` to `@xml:lang = 'san-xxx'` has a negligible effect. 4. Dropping the `[1]` from [@xml:lang][1] makes the whole query twice as fast. Regards, -- Gioele Barabucci <gio...@svario.it>
