I'm trying to figure out which is more efficient (xpath or xquery select), so if someone has knowledge on this I'd appreciate any input. This may or may not be specific to the implementation of BaseX.
For example, the following queries return the same thing, but which one is faster? Does basex treat them the same way? 1 uses xquery select, 2 uses xpath 1. for $x in doc('test')/* where $x/node="value" return $x OR 2. for $x in doc('test')/*[node="value"] return $x
Thanks. -tjw
Dear Travis,
it always depends on the XQuery implementation, and its optimizer, which query variant will be evaluated more efficiently. In BaseX, your two example queries...
for $x in doc('test')/* where $x/node="value" return $x for $x in doc('test')/*[node="value"] return $x
...will both be simplified/rewritten to this query:
doc('test')/*[node="value"]
The "Query Info" panel in BaseX will give you more insight on how your queries are compiled and optimized.
Hope this helps, Christian
On Sun, Jan 31, 2010 at 10:57 PM, Travis Webb tjwebb@vt.edu wrote:
I'm trying to figure out which is more efficient (xpath or xquery select), so if someone has knowledge on this I'd appreciate any input. This may or may not be specific to the implementation of BaseX. For example, the following queries return the same thing, but which one is faster? Does basex treat them the same way? 1 uses xquery select, 2 uses xpath
- for $x in doc('test')/* where $x/node="value" return $x
OR 2. for $x in doc('test')/*[node="value"] return $x Thanks. -tjw
___________________________
Christian Gruen Universitaet Konstanz Department of Computer & Information Science D-78457 Konstanz, Germany Tel: +49 (0)7531/88-4449, Fax: +49 (0)7531/88-3577 http://www.inf.uni-konstanz.de/~gruen
Thanks for the response. In the API, It looks like I can make use of precompiled queries; is this so? If so, and I precompile the query, will it still be optimized at runtime, or will it be executed exactly as it is written?
-tjw
On Sun, Jan 31, 2010 at 5:16 PM, Christian Grün christian.gruen@gmail.comwrote:
Dear Travis,
it always depends on the XQuery implementation, and its optimizer, which query variant will be evaluated more efficiently. In BaseX, your two example queries...
for $x in doc('test')/* where $x/node="value" return $x for $x in doc('test')/*[node="value"] return $x
...will both be simplified/rewritten to this query:
doc('test')/*[node="value"]
The "Query Info" panel in BaseX will give you more insight on how your queries are compiled and optimized.
Hope this helps, Christian
On Sun, Jan 31, 2010 at 10:57 PM, Travis Webb tjwebb@vt.edu wrote:
I'm trying to figure out which is more efficient (xpath or xquery
select),
so if someone has knowledge on this I'd appreciate any input. This may or may not be specific to the implementation of BaseX. For example, the following queries return the same thing, but which one
is
faster? Does basex treat them the same way? 1 uses xquery select, 2 uses xpath
- for $x in doc('test')/* where $x/node="value" return $x
OR 2. for $x in doc('test')/*[node="value"] return $x Thanks. -tjw
Christian Gruen Universitaet Konstanz Department of Computer & Information Science D-78457 Konstanz, Germany Tel: +49 (0)7531/88-4449, Fax: +49 (0)7531/88-3577 http://www.inf.uni-konstanz.de/~gruen
Thanks for the response. In the API, It looks like I can make use of precompiled queries; is this so? If so, and I precompile the query, will it still be optimized at runtime, or will it be executed exactly as it is written? -tjw
You probably refer to prepared queries? This processing mode basically allows to bind different variable values to the same query and execute it several times. The actual query compilation is very fast, so there was no real need of precompiling it yet. – Christian
On Sun, Jan 31, 2010 at 5:16 PM, Christian Grün christian.gruen@gmail.com wrote:
Dear Travis,
it always depends on the XQuery implementation, and its optimizer, which query variant will be evaluated more efficiently. In BaseX, your two example queries...
for $x in doc('test')/* where $x/node="value" return $x for $x in doc('test')/*[node="value"] return $x
...will both be simplified/rewritten to this query:
doc('test')/*[node="value"]
The "Query Info" panel in BaseX will give you more insight on how your queries are compiled and optimized.
Hope this helps, Christian
On Sun, Jan 31, 2010 at 10:57 PM, Travis Webb tjwebb@vt.edu wrote:
I'm trying to figure out which is more efficient (xpath or xquery select), so if someone has knowledge on this I'd appreciate any input. This may or may not be specific to the implementation of BaseX. For example, the following queries return the same thing, but which one is faster? Does basex treat them the same way? 1 uses xquery select, 2 uses xpath
- for $x in doc('test')/* where $x/node="value" return $x
OR 2. for $x in doc('test')/*[node="value"] return $x Thanks. -tjw
Christian Gruen Universitaet Konstanz Department of Computer & Information Science D-78457 Konstanz, Germany Tel: +49 (0)7531/88-4449, Fax: +49 (0)7531/88-3577 http://www.inf.uni-konstanz.de/~gruen
basex-talk@mailman.uni-konstanz.de
-
Christian Grün -
Travis Webb