Subject: Re: [xsl] Using memory addressing to retrieve a value vice using a software string library to retrieve a value From: "Michael Kay mike@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> Date: Fri, 20 Nov 2015 18:00:21 -0000 |
> I am aware of at least two very efficient algorithms: > > 1. Using *suffix-trees* -- all possible suffixes of the given > string are organized as a trie. The search (same as the contains() > function) is very fast. > > But whether we are talking about searching for elements, or searching for substrings, the designer of an XPath engine has to make choices about the trade-off between tree-building time, tree-searchiing time, space occupied by the tree, and size of the XPath engine itself. For documents stored in a database, the developers generally delegate some of these decisions to the database designer, asking them to choose what index structures to build. For documents held transiently in memory, building indexes like a suffix-tree is very unlikely to be cost-effective unless you know that the same data will be processed in this kind of way very frequently. Whatever engineering choices are made, they are likely to vary significantly from one XPath engine to another, which makes Roger's question completely meaningless. Michael Kay Saxonica
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