Re: Query Help

On Jul 23, 2010, at 11:43 AM, Liz Glasser wrote:

> I have a ton of records in my xindice database that look like:
> <MyRootElement myId=3D"...">.....</MyRootElement>
>=20
> I need the most efficient way to get a list of all values for myId. =
How can I best do this?
>=20
> Basically if this was a relational database and I had a table called =
MyRootElement, I'd do "select myId from MyRootElement". I need a xindice =
equivalent.

Hey Liz,

The query you are looking for is "/MyRootElement/@myId". Using command =
line you can query it like this (replace /db/my/collection with path to =
your collection):

  xindice xpath -c /db/my/collection -q /MyRootElement/@myId

Results should look like:

  <xq:result xmlns:xq=3D"http://xml.apache.org/xindice/Query" =
myId=3D"value" xq:col=3D"/db/my/collection" xq:key=3D"MyDocument1" />
  ...


Now, if only some % of documents in this collection contain this root =
element/attribute, then you can speed that query up by build an index on =
the element/attribute pair. Index will allow query engine to skip =
documents which do not have that element/attribute pair. Index also =
helps if you want to find a document by value of the myId attribute. =
Command to build the index looks like:

  xindice add_indexer -c /db/my/collection -n MyRootElementMyId -p =
MyRootElement@ myId


OTOH, if all documents have the same structure, then in order to extract =
all of the values, query engine will have to iterate through all of the =
documents in the collection - and index will be of no help.

Hope that helps.

Vadim