- BaseX-Talk - mailman.uni-konstanz.de

db:text() vs XPath
by Giuseppe Celano 19 Sep '17

19 Sep '17

I am using BaseX 8.6.4 and I am trying to do a group-by/order-by operation, and I see that two logically equivalent queries perform very differently: one cannot see the end, while the other can (and fast). I can provide further details if necessary, but these are the queries (look at the last line of both, where the difference is): (This does not work:) declare variable $p := db:open("db2")/text/line/text(); (: returns a list of values like ΠΕΡΙ#n-s---mv- :) for $u in db:open("db1")/text/s/t let $a := $u/f/text() (: returns one value like ΠΕΡΙ :) let $b := $u/(a)o/data(.) (: returns one value like n-s---mv- :) group by $k := $a || "#" || $b (: builds a value like ΠΕΡΙ#n-s---mv- :) let $n := count($u) order by $n descending return if ($p = $k) then $k || " " || $n else () (This works:) for $u in db:open("db1")/text/s/t let $a := $u/f/text() (: returns one value like ΠΕΡΙ :) let $b := $u/(a)o/data(.) (: returns one value like n-s---mv- :) group by $k := $a || "#" || $b (: builds a value like ΠΕΡΙ#n-s---mv- :) let $n := count($u) order by $n descending return if (db:text("db2", $k)) then $k || " " || $n else () The problem is with directly accessing the database with db:text() or indirectly using XPATH. I would tend to use XPATH and expect to get an underlying translation into db:text(), but this seems not to happen: why? Best, Giuseppe

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java.lang.NoClassDefFoundError: Could not initialize class java.nio.file.FileSystems$DefaultFileSystemHolder
by Liam R. E. Quin 19 Sep '17

19 Sep '17

It seems with the latest Java 1.8 - java-1.8.0-openjdk-headless-1.8.0.144-0.b01.el7_4.x86_64 on Centos 7, I can no longer drop a database, any ideas? This is with both 8.5.3 and 8.6.6, and also with the latest snapshot, BaseX867-20170824.195627.zip [[ $ bin/basexclient -p 1994 Username: admin Password: BaseX 8.6.6 [Client] Try 'help' to get more information. > open rdf Database 'rdf' was opened in 1.61 ms. > close Database 'rdf' was closed. > drop db rdf Improper use? Potential bug? Your feedback is welcome: Contact: basex-talk(a)mailman.uni-konstanz.de Version: BaseX 8.5.3 Java: Oracle Corporation, 1.8.0_131 OS: Linux, amd64 Stack Trace: java.lang.NoClassDefFoundError: Could not initialize class java.nio.file.FileSystems$DefaultFileSystemHolder at java.nio.file.FileSystems.getDefault(FileSystems.java:176) at java.nio.file.Paths.get(Paths.java:84) at org.basex.io.IOFile.toPath(IOFile.java:335) at org.basex.io.IOFile.delete(IOFile.java:243) at org.basex.io.IOFile.delete(IOFile.java:240) at org.basex.core.cmd.DropDB.drop(DropDB.java:77) at org.basex.core.cmd.DropDB.run(DropDB.java:46) at org.basex.core.Command.run(Command.java:253) at org.basex.core.Command.execute(Command.java:99) at org.basex.server.ClientListener.run(ClientListener.java:136) > open rdf Database 'rdf' was opened in 1.56 ms. > xquery count(//image) 7370 Query executed in 68.2 ms. ]] -- Liam Quin, W3C, http://www.w3.org/People/Quin/ Staff contact for Verifiable Claims WG, XQuery WG Web slave for http://www.fromoldbooks.org/

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SQL2XML
by iCloud 18 Sep '17

18 Sep '17

Hello, I wrote a small app for my own needs to convert any kind of MS-SQL tables to a XML file. Feel free to download it, use it, distribute it. FREE OF CHARGE ! Still be a BETA for the moment !! Thanks for your feedback This is the download area : https://rink.hockeyapp.net/apps/71fcf4452594429d8cf81e5f2569e8e8 Have fun Michel

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A few general questions about BaseX
by Anastasiou A. 18 Sep '17

18 Sep '17

Hello everyone I am trying to load BaseX with a large number of XML files (~500), each one a few hundreds of MBs big. BaseX fails with a message along the lines "This is too big for one database". Can I please ask: 1) Are there any logs, beyond the DB logs? If yes, where can I find them? a. The reason I am asking is because once basexgui gives the message, there is no indication about the error. Ideally, I would like to know if this is a limitation on memory amount or number of items (?). 2) The parser options include reading XML files from archives, which is very convenient, but once the file has been parsed, does BaseX require the "originals" for queries / returning results? 3) Is it possible to do federation with BaseX? In other words, let's say I split a database in two large parts (as per #1), is it possible to launch two baseX servers and then have them talk to each other so that ultimately I just query one of them and get back unified results? All the best

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retrieving the name of the archive?
by Graydon Saunders 18 Sep '17

18 Sep '17

Hello -- BaseX will happily consume zip archives; this is just splendid for loading up a bunch of docx files. Now I find myself wanting the name of the docx file -- the original name of the archive -- and I don't know how to retrieve that. (or if it can be!) But I think it must be there somewhere because db:path repeats the standard OOXML file paths: [Content_Types].xml word/document.xml word/footnotes.xml word/footer1.xml word/endnotes.xml word/theme/theme1.xml word/settings.xml docProps/custom.xml customXml/itemProps2.xml docProps/app.xml customXml/item2.xml customXml/itemProps1.xml word/fontTable.xml customXml/item1.xml customXml/item3.xml customXml/itemProps3.xml customXml/item4.xml customXml/itemProps4.xml word/numbering.xml word/styles.xml word/webSettings.xml docProps/core.xml word/people.xml over and over; if they were all going to exactly that there'd be one copy, and all several hundred docx files are there by content. (db:list-details tells me about > 4000 individual xml files.) If I can get the name of the original archive, how do I do that? Thanks! Graydon

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Basex Inner Workings
by Anastasiou A. 18 Sep '17

18 Sep '17

Hello everyone Quick question: Is there any document / URL where I could find out more about how does Basex access the disk during its operation? For example, are there any reads to be expected during executing a query? Through iotop, I can see 3-4 processes reading during startup, then another 2, very briefly firing when opening the database and then during querying there are periodic writes (?) but of very brief duration. I was wondering if there is anything that could be done from the point of view of the hardware to speed up queries (?) (except a more powerful machine at the moment) All the best Athanasios Anastasiou

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Is there any documentation on the narrow limits of XQuery index optimization in BaseX?
by Omar Siam 18 Sep '17

18 Sep '17

Hi list! Recently I started to wonder why functions in my XQuery modules make no use of indexes unless I force them to by using the respective function like db:text(). Now I just did some I think minimal changes to the example for text index at: http://docs.basex.org/wiki/Indexes#Text_Index. If I just change it like below I loose almost all index optimization. The only optimizations left are: * Using db:open or collection with a string but not one in a variable of a for FLOWR expression or the simple map operator. * Using xquery:eval and passing a context with db:open or collection Is there any chance that this will change any time soon? Is this a fundamental restriction? Best regards Omar xquery version "3.1"; declare namespace _ = "urn:local:namespace:_"; import module namespace functx = "http://www.functx.com"; declare function _:_1st_example($ctx as document-node()) { $ctx//*[text() = 'Germany'] }; declare function _:_2nd_example($file as xs:string) { doc($file)//name[. = 'Germany'] }; declare function _:_3rd_example($dbname as xs:string+) { ( for $c in ($dbname!collection(.))//country where $c//city/name = 'Hanoi' return $c/name, $dbname!xquery:eval("//*[text() = 'Vietnam']", map {'': db:open(.)})) }; ( (: 1st example :) _:_1st_example(.), (: 2nd example :) _:_2nd_example('factbook.xml'), (: 3rd example :) _:_3rd_example(('factbook', 'factbook')), xs:string(_:_1st_example) ) Optimized Query: (let $ctx_314 := . return $ctx_314/descendant::*[(text() = "Germany")], db:open-pre("factbook",0)/descendant::name[(. = "Germany")], (for $c_317 in (("factbook", "factbook") ! collection(.))/descendant::country[(descendant::city/name = "Hanoi")] return $c_317/name, (("factbook", "factbook") ! xquery:eval("//*[text() = 'Vietnam']", map { "":db:open(.) }))), _:_1st_example cast as xs:string?) Compiling: [...] - RUNTIME: pre-evaluate root() to document-node() - RUNTIME: rewrite descendant-or-self step(s) - RUNTIME: apply text index for "Vietnam" - RUNTIME: pre-evaluate root() to document-node() - RUNTIME: rewrite descendant-or-self step(s) - RUNTIME: apply text index for "Vietnam"

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Re: [basex-talk] Simple Map Operator in oXygen XML (XQJ)
by Omar Siam 18 Sep '17

18 Sep '17

Ok. Interesting. Please someone note this in the Wiki so there are no surprises. For the ! syntax I can just stick with for in return but missing map {} is a reason to switch to dba. Best regards Omar Am 04.09.2017 um 17:14 schrieb Charles Foster: > Hi Michael, > > BaseX XQJ supports XQuery 3.0 syntax I believe, but not XQuery 3.1 > specific syntax. > > It would be possible to update the XQJ driver to support XQuery 3.1 > syntax, but it would mean upgrading the internal XQuery parser and > re-writer. > > Omar, as a work around you could potentially use equivalent functions > in the standard F&O library (fn). > > Kind Regards, > > Charles > > >> On 4 Sep 2017, at 22:02, Michael Seiferle <ms(a)basex.org >> <mailto:ms@basex.org>> wrote: >> >> Hi Omar, >> /cc Hi @Charles, >> >> you are right, this has nothing to with oXygen in particular! >> Yet: I am not even sure if XQJ is meant to support anything but >> XQuery 1.0. >> Charles might correct me if I am wrong, but I don’t think there’s an >> easy way to add 3.1 features to the current XQJ implementation. >> >> Best from Konstanz >> >> Michael >> >> >> >> >> >>> Am 04.09.2017 um 16:42 schrieb Omar Siam <Omar.Siam(a)oeaw.ac.at >>> <mailto:Omar.Siam@oeaw.ac.at>>: >>> >>> Good idea but I was pretty sure that this comes from within BaseX >>> not oXygen. You can configure the parser and the executor of your >>> XQuery in oXygen und I used BaseX for both. >>> >>> So I found in basex-examples a XQJ tutorial. And just by changing >>> Part1.java a little and filling in the example query from the Wiki I >>> also get >>> >>> XQJQS001 - Invalid XQuery syntax, syntax does not pass static >>> validation. >>> Root Cause: >>> net.xqj.basex.bin.bB: Lexical error at line 1, column 12. >>> Encountered: " " (32), after : "!" >>> at >>> org.basex.examples.xqj.tutorial.simplemaptest.main(simplemaptest.java:34) >>> at >>> org.basex.examples.xqj.tutorial.simplemaptest.main(simplemaptest.java:34) >>> >>> So most probably BaseX'es XQJ parser does not understand the simple >>> map operator. >>> >>> XQSequence xqjs = xqje.executeQuery("xquery version \"3.1\"; (1 to 10) ! element node { . }"); >>> >>> Am 04.09.2017 um 15:37 schrieb Michael Seiferle: >>>> Hi Omar, >>>> >>>> Looks like that error message is generated by oXygen; you might want to crosspost to their list. >>>> >>>> Best >>>> Michael >>>> >>>>> Am 04.09.2017 um 14:31 schrieb Omar Siam<Omar.Siam(a)oeaw.ac.at>: >>>>> >>>>> Hi! >>>>> >>>>> I just tried to use ther Simple Map Operator while writing an XQuery in oXygen XML and executing the query using a client/server BaseX 8.6.6 data source. I configured it as described here:http://docs.basex.org/wiki/Integrating_oXygen >>>>> >>>>> When I use the Simple Map Operator (!) I only get "Invalid XQuery syntax, syntax does not pass static validation.". For example using "(1 to 10) ! element node { . }" >>>>> >>>>> If I run that XQuery in DBA for example it works. >>>>> >>>>> Any ideas? >>>>> >>>>> Best regards >>>>> >>>>> Omar Siam >>>>> >>> >> >

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json-to-xml and xpath
by Günter Dunz-Wolff 18 Sep '17

18 Sep '17

Dear all, I’m trying to get data out of json via xquery. This is my scenario: 1. Fetching data with fetch:text() calling a REST-API 2. Transforming the data with json-to-xml, so I’ll get something like <array xmlns="http://www.w3.org/2005/xpath-functions“> <map> <string key=„word1“>gehen</string> ... </map> ... </array> 3. In my xqm-file I have: let $json_xml := json-to-xml(my_fetched_json) 4. I try to get „gehen“ with $json_xml//string[@key='word1‘], but it yields nothing, also $json_xml//string yields nothing. Only $json_xml//text() yields all string-values into a long string. What am I doing wrong? Or is there another way, to work with JSON-Data to get values of a given key? Thanks in advance, Günter

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Startup hooks or persisting jobs
by Kendall Shaw 18 Sep '17

18 Sep '17

Am I missing an existing way to run xquery at startup (basex web service running under tomcat)? I have jobs that I schedule, but I have to schedule them again if basex is shutdown. I can test for basex being started outside of basex and then execute queries, but if there is already a way to do this within basex, I would rather do that. Kendall

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