To be fair, absorbing the architecture and indexing behavior of a modern
RDBMS isn't trivial either. XML content adds another dimension, but I
hope you find the performance guide at
http://developer.marklogic.com/pubs/4.0/ helpful. There are also useful
bits of server architecture discussion in the dev and admin guides.
In the general case I wouldn't expect adding a range index to greatly
improve value query performance. The list cache is pretty efficient at
keeping frequently-used terms in memory.
Usually the range indexes are created for applications that need
particular features: fast sorting on a node value, fast range queries,
fast access to distinct values, etc.
-- Mike
Whitby, Rob, CMG wrote:
Wow, I didn't realise that. It will improve performance though right? On
a large database I assume the index of all XML elements and attributes
can't be held in memory.
Understanding how the functions relate to the indexes is probably one of
areas I've found hardest with MarkLogic.
Thanks
Rob
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Michael
Blakeley
Sent: 12 November 2008 16:55
To: General Mark Logic Developer Discussion
Cc: [EMAIL PROTECTED]
Subject: Re: [MarkLogic Dev General] Improving XPathPerformance
onSearchResults
Actually that query does *not* require any special indexes. The server
always indexes all XML element values and element-attribute values.
You would only need an attribute range index for a fast "order by" on
keyword/@value, or for a cts:attribute-value-range-query term, or for
cts:element-attribute-values() and its associated functions.
-- Mike
Whitby, Rob, CMG wrote:
If you put an attribute range index on keyword/@value you can do
something like this:
cts:search(
/doc/classifications/classification,
cts:element-attribute-value-query(xs:Qname("keyword",
xs:Qname("value"), "something")
)
(untested!)
Rob
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Steve
Sent: 12 November 2008 14:41
To: James Clippinger
Cc: General Mark Logic Developer Discussion
Subject: Re: [MarkLogic Dev General] Improving XPath Performance
onSearchResults
I should probably add that I'm trying to extract all classification
values for the documents that have a specific keyword value.
On Wed, Nov 12, 2008 at 2:40 PM, Steve <[EMAIL PROTECTED]>
wrote:
Thanks for your response.
I've tried your suggestion and it doesn't really help. Looking at the
profiling document, I can see that it's clearly the XPath on the
document results that is slowing the who thing down. Is there any
other ways that I can improve this. I've included a sample document
(small), so you can see what I'm trying to achieve.
<doc>
<classifications>
<classification value="123" />
<classification value="324" />
</classifications>
<keywords>
<keyword value="word1" />
<keyword value="word2" />
</keywords>
</doc>
On Wed, Nov 12, 2008 at 2:24 PM, James Clippinger
<[EMAIL PROTECTED]> wrote:
Steve, your query is doing some heavyweight filtering for the XPath
because it is doing two steps:
1) Execute the cts:search(): generate a list of all documents
matching the query in relevance order.
2) Execute the XPath: reorder the documents into document order and
find only those with /doc/classifications/classification elements,
returning those classification elements.
Since you are using XPath and thus returning results in document
order, you probably want to use cts:contains() in an XPath predicate
rather than cts:search(). cts:contains() in a rooted XPath
expression will use the search indexes when appropriate, so it's as
fast as the equivalent
cts:search() expression. Try this:
let $search := cts:element-attribute-word-query(fn:QName("",
"keyword"), fn:QName("", "value"), "something") return
fn:collection()/doc[cts:contains(.,
$search)/classifications/classification
James
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Steve
Sent: Wednesday, November 12, 2008 8:54 AM
To: [email protected]
Subject: [MarkLogic Dev General] Improving XPath Performance on
SearchResults
I've written a query which I use to search my data set and I am
able
to get the results back very quickly. However the results that I
get
back show the complete document that the search matched, where as I
want a particular node returned.
At the moment I'm doing this:
let $search := cts:element-attribute-word-query(fn:QName("",
"keyword"), fn:QName("", "value"), "something") let $results :=
cts:search(fn:collection(),
$search)/doc/classifications/classification
return $results
I've tried profiling this query and I've found that there is a big
lag filtering the $results of the search using XPath.
Is there any way, either through using a different query or search
notation, or by indexes etc that I can speed this up.
Thanks in advance...
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