Hi there,

I am running relatively simply XQuery over a Basex database read in from about 100 MB of XML.

While performance in general is fantastic, with most queries completing in a few seconds, I am getting worryingly slow performace on certain queries using XPath axes such as preceding-sibling.

For example, the following simple (if a bit silly) query takes over 30 minutes to execute:

/tns:pois/tns:poi[not(preceding-sibling::tns:poi)]

For what it's worth, there are only about 100,000 instances of the <tns:poi> element.

So the immediate question is whether this performance is to be expected. If not, what are the obvious things to look at in terms of performance tuning?

Thanks in advance,

Constantine