BaseX-Talk

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6 participants
5270 discussions

Replication, partition and the CAP theorem
by ziiro_94＠freenet.de 15 Jun '15

15 Jun '15

Hello, I consider BaseX in the context of BigData and try to compare it with other noSQL databases. Yet, there is no replication or partition mechanism implemented and BaseX is a database with a single point of failure. Am I right? Thus, my question is, how can I classify the System BaseX regarding the CAP-Theorem? Yours sincerely --- Alle Postfächer an einem Ort. Jetzt wechseln und E-Mail-Adresse mitnehmen! Rundum glücklich mit freenetMail

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XQuery - math on elements within a sequence
by Luiz Matos 15 Jun '15

15 Jun '15

Hi everyone, I'm trying to execute a XQuery sum function in a multiplication of two XML elements, but it has been difficult to avoid the iteration in a sequence of elements. For example, considering this case: sample data: <Orders> <Order> <OrderKey>1</OrderKey> <LineItem> <LineNumber>1</LineNumber> <ExtendedPrice>70848.0000</ExtendedPrice> <Discount>0.0913</Discount> <ReturnFlag>A</ReturnFlag> <LineStatus>F</LineStatus> <ShipDate>1994-09-03</ShipDate> </LineItem> <LineItem> <LineNumber>2</LineNumber> <ExtendedPrice>64372.0000</ExtendedPrice> <Discount>0.0674</Discount> <ReturnFlag>A</ReturnFlag> <LineStatus>F</LineStatus> <ShipDate>1994-08-18</ShipDate> </LineItem> <LineItem> <LineNumber>3</LineNumber> <ExtendedPrice>64247.0000</ExtendedPrice> <Discount>0.0396</Discount> <ReturnFlag>R</ReturnFlag> <LineStatus>F</LineStatus> <ShipDate>1994-10-21</ShipDate> </LineItem> </Order> . . . </Orders> XQuery: <results> { for $lineitem in collection("tpch")/Orders/Order/LineItem let $returnflag := $lineitem/ReturnFlag let $linestatus := $lineitem/LineStatus where $lineitem/ShipDate <= "1998-08-31" group by $returnflag, $linestatus order by $returnflag, $linestatus return <record> <sum_disc_price>{sum($lineitem/ExtendedPrice*(1-$lineitem/Discount))}</sum_disc_price> </record> } </results> BaseX output: [XPTY0004] Item expected, sequence found: (element ExtendedPrice {...}, ...... My question: Considering this dataset model, how can I to write this query without change its semantics? I wouldn't want to use extra functions (e.g., fn:for-each), because I need to submit the same query in an limited xquery processor. Thanks in advance! -- Luiz Matos PhD student at Federal Fluminense University

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Internal cache for often accessed node sets?
by Gioele Barabucci 15 Jun '15

15 Jun '15

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(a)svario.it>

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Re: [basex-talk] Optimization of a slow query with `//`
by Christian Grün 15 Jun '15

15 Jun '15

Hi Gioele, Queries with positional predicates such as the one that I posted in my last mail (in private, attached below) are now optimized as well. Best, Christian [1] http://files.basex.org/releases/latest/ On Mon, Jun 15, 2015 at 1:09 PM, Christian Grün <christian.gruen(a)gmail.com> wrote: > Hi Gioele, > >> I had a look at the info view but I fail to understand whether it is >> optimized or not. What should I look at? Sometimes I see a "Optimized Query" >> section, but it is not present for these two queries. > > I see. Yes, this means that the query is not rewritten. Instead, this > is one is optimized for index access, as the query info (and, > obviously, in this case the execution time) will show you: > > /descendant::tei:orth[text() = "arci"] > > I noticed that the query is not rewritten because of the positional > predicate (which are generally brain twisters in XQuery). Things look > better with the following query (but it may yield other results): > > /descendant::tei:orth > [text() = "arci"] > [ancestor-or-self::* > [@xml:lang][starts-with(@xml:lang, "san")] > ] > /parent::tei:form/parent::*[self::tei:entry or self::tei:re] > > The following query should take advantage of the index: > > for $n in /descendant::tei:orth[text() = "arci"] > where $n/ancestor-or-self::* > [@xml:lang][1][starts-with(@xml:lang, "san")] > return $n/parent::tei:form/parent::* > [self::tei:entry or self::tei:re] > > Best, > Christian

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Optimization of a slow query with `//`
by Gioele Barabucci 15 Jun '15

15 Jun '15

Hello, I am working on an application that retrieves its data from a TEI XML file via BaseX. The following query lies at the core of this application but is too slow to be used in production: on a modern PC it requires about 600 ms to run over a 4MB file (1/10 of the complete dataset). Any suggestion on how to improve its performance (without changing the underlying TEI files) would be much appreciated. Here is the query: declare namespace tei='http://www.tei-c.org/ns/1.0'; /tei:TEI/tei:text/tei:body// *[self::tei:entry or self::tei:re] [./tei:form/tei:orth[. = "arci"] [ancestor-or-self::* [@xml:lang][1] [(starts-with(@xml:lang, "san"))] ] ] In human terms is should return all the `tei:entry` or `tei:re` that * have the word "arci" in their `/tei:form/tei:orth` element, * their nearest `xml:lang` attribute starts with 'san'. I made some tests and it turned out that the main culprit is the use of `//` in the first line. (_Main_ culprit, not the only one...) I use the `//` axis because I do not know what is the structure of the underlying TEI file. I expect BaseX to keep track of all the `tei:entry` and `tei:re` elements and their parents, so selecting the correct ones should be quite fast anyway. But the measurements disagree with my assumptions... What could I do to improve the performance of this query? Now, some remarks based on some small tests I have done: 1. Removing the [ancestor-or-self::*[....]] predicate slashes the run time in half, but the query is still way too slow. 2. Changing ./tei:form/tei:orth[. = "arci"] to ./tei:form[1]/tei:orth[1][. = "arci"] makes the query even slower. 3. changing `starts-with(@xml:lang, "san")` to `@xml:lang = 'san-xxx'` has a negligible effect. 4. Dropping the `[1]` from [@xml:lang][1] makes the whole query twice as fast. Regards, -- Gioele Barabucci <gioele(a)svario.it>

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BaseX Mac refusing to quit
by Stuart Simon 14 Jun '15

14 Jun '15

I have BaseX 8.2.1 running on Mac OS X 10.10.3 Yosemite, BaseX GUI.app, release channel. My computer has a 2.2 GHz Intel processor and 4 GB of RAM. My problem is that I have tried all the standard ways to quit BaseX, but BaseX stubbornly refuses to quit; it only closes the active windows. Is there anything I'm doing wrong, or is this a bug? -- Stuart Simon stuart.sa(a)gmail.com

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dba suggestions
by Andy Bunce 14 Jun '15

14 Jun '15

Hi Here are a couple of minor suggestions for dba enhancement/fixes (based on 8.2.1). I should get a PR together but that might be some time. 1. Login field tab order. Currently this is (1) name (2) <login bn> (3) password. Moving the login button to after the password would make sense to me as I could then tab through the fields. This could be done just be putting the button in the next row (or setting an explicit tab order if there is some reason for the current appearance.) 2. logs There is a little bug in the log sorting function. The log page is /dba/*logs*?... The field headers go to /dba/*log*?.. Also it would be nice if urls for the log display would use any supplied query parameter for initial filtering e.g going to /dba/logs?name=2015-06-09&resource=&sort=&loglist=&query=%2Fmyapp%2F would display the logs for 2015-06-09 containing /myapp/ /Andy

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Re: [basex-talk] Multiple web applications with independent xq modules
by Ioan Fericel 11 Jun '15

11 Jun '15

Hi Christian, On 06/06/2015 02:39 PM, Christian Grün wrote: > Hi Ioan, > > Just recently, there has been some discussion on Tomcat and BaseX on > the mailing list. I think we managed to successully encounter various > of the problems with Tomcats in the latest snapshot [1], so I will be > interested in hearing more about your experiences with that version. Sorry for my english expressing, which unfortunately are not helped me to be well understood! I carefully watched to all recent discussions on the list, but what is of interest to us is different. I have seen that in these cases it is intended that each application to use a new instance of BaseX. And, on the same Tomcat, to use multiple separate instances of BaseX. And, in general, I have seen that BaseX is used dedicated for a single application (very suitable for embeded), and used separated instances for other applications. But in our case is exactly the opposite. We have some experience with web applications on Tomcat, made with JSP / Servlets and relational databases. The structure of the applications installed on web server looks like: -webapps -app1 -app2 -app3 Each application is developed and deployed separately, as an war archive, having everything it needs inside. We try to use BaseX in this way to access data directly in XML format. The structure should be something like: -webapps -basex -bxapp1 -xqrepo1 -bxapp2 -xqrepo2 -bxapp3 -xqrepo3 We managed to make this model functional only if all 3 repositories we have put them together: or directly under BaseX, or in a separate application and setting according to this the path in context-param/restxqpath in web.xml. But we want it so that each application to contain they repo. How? It would be possible to set in web.xml, to restxqpath, a list of several repo? Or from somewhere to be told from where to load such a list? Maybe this would be an easier solution. It implies some security problems or other constraints? We looked a bit by sources, but not have identified which part it handles this. Is welcomed any other idea. > Regarding CACHERESTXQ and .ignore: These features are already > available in that snapshot as well (but they will only be officially > announced with 8.3). Unless you don't build more complex RESTXQ > applications, you won't probably need to care about these features. > > Hope this helps, > Christian > > [1] http://files.basex.org/releases/latest/ > > We tried this last version and, indeed, for what we want does not help us. Many thanks for your understanding! Ioan

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Re: [basex-talk] Problem with xi:include - What is the correct href path?
by Kristian Kankainen 10 Jun '15

10 Jun '15

Hello! This is not the most appropriate place to ask, but I'd just like to get a hint of the overall feeling of it. Since the XInclude support is relied upon that of Java, is there any hope it will become complete some day? I'd be satisfied with answers like "I'm positive the support will be completed, but it might take some two years" or "the development seems stalled and probably nothing will happen if noone interested in it makes an effort". Thank you Kristian 08.06.2015 15:33, Christian Grün kirjutas: > Dear Asxetos, > > BaseX relies on the XInclude support of Java, which is (unfortunately) > incomplete. Your example works locally when removing the xpointer > attribute (but it will include the full bar.xml resource). > Aditionally, please note that local or relative XInclude reference > cannot be resolved with DBA, because the file to be embedded will not > be available to the database server. > > If you are interested in getting more background information, please > check out another discussion on this issue on the mailing list [1]. > > Hope this helps, > Christian > > [1] https://www.mail-archive.com/basex-talk@mailman.uni-konstanz.de/msg06197.ht… > > > On Mon, Jun 8, 2015 at 2:17 PM, Asxetos <pure.asxetos(a)gmail.com> wrote: >> Hello, >> >> I would like your help getting the following to work. >> I have document 'foo.xml' : >> >> >> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - >> <?xml version="1.0" encoding="UTF-8"?> >> <?xml-model href="http://www.tei-c.org/release/xml/tei/custom/schema/relaxng/tei_all.rng" >> type="application/xml" >> schematypens="http://relaxng.org/ns/structure/1.0" ?> >> <TEI xmlns="http://www.tei-c.org/ns/1.0"> >> <teiHeader> >> <fileDesc> >> <titleStmt> >> <title>foo</title> >> </titleStmt> >> <publicationStmt> >> <ab></ab> >> </publicationStmt> >> <sourceDesc> >> <ab></ab> >> </sourceDesc> >> </fileDesc> >> </teiHeader> >> <text> >> <body> >> <div> >> <p>I am foo!</p> >> </div> >> <include xmlns="http://www.w3.org/2001/XInclude" href="bar.xml" >> xpointer="thebar"/> >> </body> >> </text> >> </TEI> >> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - >> >> >> and document 'bar.xml' : >> >> >> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - >> <?xml version="1.0" encoding="UTF-8"?> >> <?xml-model href="http://www.tei-c.org/release/xml/tei/custom/schema/relaxng/tei_all.rng" >> type="application/xml" >> schematypens="http://relaxng.org/ns/structure/1.0" ?> >> <TEI xmlns="http://www.tei-c.org/ns/1.0"> >> <teiHeader> >> <fileDesc> >> <titleStmt> >> <title>bar</title> >> </titleStmt> >> <publicationStmt> >> <ab></ab> >> </publicationStmt> >> <sourceDesc> >> <ab></ab> >> </sourceDesc> >> </fileDesc> >> </teiHeader> >> <text> >> <body> >> <div xml:id="thebar"> >> <p>I am bar!</p> >> </div> >> </body> >> </text> >> </TEI> >> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - >> >> >> Using the administration interface (http://localhost:8984/dba) >> I create a new databse, add bar.xml and then try to add foo.xml >> This is what I get: >> >> >> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - >> HTTP ERROR 400 >> >> Problem accessing /dba/add. Reason: >> >> Stopped at /Users/Asxetos/basex/webapp/dba/databases/resources/add.xqm, >> 91/10: >> [FODC0002] "foo.xml" (Line 22): An include with href 'bar.xml'failed, >> and no fallback element was found. >> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - >> >> >> I am guessing that the href path is not correct. >> What should the value of the href attribute be? >> >> >> Thanks, >> Asxetos >> >> >> PS: notice the error message says "with href 'bar.xml'failed". It seems the >> 404 page template is missing a whitespace after the filename.

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java.io.IOException: Stream Closed
by Ketill Fenne 10 Jun '15

10 Jun '15

Hi! >From time to time I see the following error: java.io.IOException: Stream Closed at java.io.RandomAccessFile.seek0(Native Method) at java.io.RandomAccessFile.seek(RandomAccessFile.java:557) at org.basex.io.random.TableDiskAccess.readBlock(TableDiskAccess.java:520) at org.basex.io.random.TableDiskAccess.readPage(TableDiskAccess.java:485) at org.basex.io.random.TableDiskAccess.cursor(TableDiskAccess.java:464) at org.basex.io.random.TableDiskAccess.read1(TableDiskAccess.java:148) at org.basex.data.Data.kind(Data.java:307) at org.basex.query.value.node.DBNode$4.next(DBNode.java:349) at org.basex.query.expr.path.IterStep$1.next(IterStep.java:38) at org.basex.query.expr.path.IterStep$1.next(IterStep.java:32) at org.basex.query.expr.path.IterPath$1.next(IterPath.java:58) at org.basex.query.expr.path.IterPath$1.next(IterPath.java:36) at org.basex.query.expr.gflwor.For$1.next(For.java:79) at org.basex.query.expr.gflwor.GFLWOR$1.next(GFLWOR.java:95) at org.basex.query.MainModule$1.next(MainModule.java:114) at org.basex.server.ServerQuery.execute(ServerQuery.java:130) at org.basex.api.client.LocalQuery.cache(LocalQuery.java:48) at org.basex.api.client.Query.more(Query.java:76) An example of how I query and iterate: DBResult dbResult = null; LocalQuery results = null; try { xPath = xPath.indexOf("/") == -1 ? "/" + xPath : xPath; String myQuery = "for $doc in (" + getContentCollectionQuery(PPSCONTENT_DATABASE_NAME) + " ) " + xPath + createNameCondition(name, PPSCONTENT_DATABASE_NAME) + createDateCondition(version) + " " + " return (data($doc/topic/@id))"; dbResult = runQuery(myQuery); results = dbResult.getXmlResults(); String topic = null; if (results.more()) { topic = results.next(); } return topic; } catch (QueryException e) { PPLogger.getInstance().error("Error in getTopicForDocWithName: " + e.getMessage()); return null; } catch (IOException e) { PPLogger.getInstance().error("Error in getTopicForDocWithName: " + e.getMessage()); return null; } finally { if (results != null) results.close(); if (dbResult != null) dbResult.close(); } The error occurs randomly, but is always "triggered" by "results.more()" and I am not able to reproduce it at will. Is there something wrong or missing in how I iterate the results? I am using BaseX8.2.1 on windows 7. Kind regards Ketill Fenne

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