Internal cache for often accessed node sets?
Monday, 15 June 2015 · 3 messages
GB
Gioele Barabucci15 Jun 2015 14:46 #
Hello,
thanks to the all the answers I received in the thread "Optimization of a slow query with
//" I can now make most of my queries much faster. However, while rewriting these queries I noticed that almost all the queries in my application could be rewritten in the form
/tei:TEI/tei:text/tei:body//tei:ELEM[PREDICATE]
and I wondered if it was possible to tell BaseX (or to have it understand by itself) that it can cache and reuse the results of
/tei:TEI/tei:text/tei:body//tei:ELEM
and only apply PREDICATE on the saved set of results.
Is something like this available in BaseX?
I suppose this could have a big impact on my queries, because the base query executes in about 250 ms and most of the other unoptimized queries in about 280 ms. This means that with the case in place they should complete in 30 ms (or 50 ms in more realistic terms).
I tried sending via HTTP a dummy request for
/tei:TEI/tei:text/tei:body//tei:ELEM together with a <option name='cachequery' value='true'/> to warm up the cache. Unfortunately all I got back was a "Unknown option 'CACHEQUERY'" error (with BaseX 8.2.1). Any idea why?
Regards,--
Gioele Barabucci <gioele at svario.it>
CG
Christian Grün15 Jun 2015 16:13 #
Quoted text · Gioele Barabucci · 8 lines
> I wondered if it was possible to tell BaseX (or to have it understand by > itself) that it can cache and reuse the results of > > /tei:TEI/tei:text/tei:body//tei:ELEM > > and only apply PREDICATE on the saved set of results. > > Is something like this available in BaseX?
No, I'm afraid (and I'm not sure how to easily realize this for arbitrary requests). If performance is critical, and if you believe nothing more can be done, you could still think about creating additional index structures for your data and access these instead (just as Fabrice motivated in his reply).
Quoted text · Gioele Barabucci · 3 lines
> Unfortunately all I > got back was a "Unknown option 'CACHEQUERY'" error (with BaseX 8.2.1). Any > idea why?
I now know why: Because it has recently been removed. All it did was to cache results before returning them to the client instead of streaming them. This option was only used for our GUI, but another solution has now been found there.
I have updated our documentation. Thanks for the hint,
Christian
EK
Erdal Karaca15 Jun 2015 17:32 #
Did not try this out (just a thought), but if you are using the Java API, you could hold a reference to /tei:TEI/tei:text/tei:body//tei:ELEM and execute the predicates ".[PREDICATE]" using the reference as context node.
2015-06-15 16:13 GMT+02:00 Christian Grün <christian.gruen at gmail.com>:
Quoted text · Christian Grün · 28 lines
> > I wondered if it was possible to tell BaseX (or to have it understand by > > itself) that it can cache and reuse the results of > > > > /tei:TEI/tei:text/tei:body//tei:ELEM > > > > and only apply PREDICATE on the saved set of results. > > > > Is something like this available in BaseX? > > No, I'm afraid (and I'm not sure how to easily realize this for > arbitrary requests). If performance is critical, and if you believe > nothing more can be done, you could still think about creating > additional index structures for your data and access these instead > (just as Fabrice motivated in his reply). > > > Unfortunately all I > > got back was a "Unknown option 'CACHEQUERY'" error (with BaseX 8.2.1). > Any > > idea why? > > I now know why: Because it has recently been removed. All it did was > to cache results before returning them to the client instead of > streaming them. This option was only used for our GUI, but another > solution has now been found there. > > I have updated our documentation. Thanks for the hint, > Christian >
Written for BaseX 8.2. BaseX may have changed since: please check the current documentation.
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