“Do not document”… …if not only due to that comment, it is a very interesting…
Month: January 2010
You will probably never build only one structured XMLIndex. A practical use case would be an unstructured XMLIndex, indexing the semi-structured parts of your XML, multiple structured XMLIndexes, indexing the highly structured XML islands of data and maybe even a Oracle Text Context index indexing unstructured XML data.
So the next example’s will show how to build an unstructured XMLIndex and build multiple structured XMLIndexes on top of the first one. Also it will give some examples on what to do if you have made mistakes and/or how to apply some maintenance on the XMLIndex structures. You start of by determining which sections should be addressed by the Unstructured XMLIndex and via path subsetting restrict the index to that part (also see “Oracle 11g � XMLIndex (Part 2) � XMLIndex Path Subsetting” for more info on path subsetting). There should be, I think, a good reason for indexing the same node path via multiple structured or unstructured XMLIndexes. One I can think of is to support different kind of XML Queries, but be aware that it, multiple XMLIndex structures on the same nodes, will come with an extra index maintenance overhead.
Anyway, lets say you want most part (haven’t used path subsetting here for the unstructured XMLIndex, but as said I should have done) of the XML document indexed via a unstructured XMLIndex and an extra of two structured XMLIndexes on top of the domain XMLIndex…
As said in the “rule of numb” post, test your statement before you build an XMLIndex (structured or unstructured) on you column or table XML store. The database will check on the syntax you will use but NOT on the outcome. So if you statement doesn’t have the proper result set or is even empty, than the content table(s) or path table will be indexing the wrong element values or even a null data set. Be aware that XML in Oracle is case-sensitive and critical on calling a namespace reference if one if demanded by the W3C rules.
The following example will build a single structured XMLIndex on a binary xml column.