BaseX-Talk

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6 participants
5250 discussions

Collations and testing for attribute equality
by James Ball 15 Nov '13

15 Nov '13

Hello, I'm doing some work matching between XML documents - one set has no characters outside the basic ASCII range while the other has a mix of of Ø and Ö and lots of others. Some are in UPPER case and some in Mixed. I need to match a "James" in one file to "JAMES" in another and so on. To do the comparisons I've been looking at BaseX's support for collations. Following the example in the documentation like this works perfectly: declare default collation 'http://basex.org/collation?strength=primary'; "Straße" = "Strasse", "Jérome" = "Jerome", "James" = "JAMES" But it doesn't work when testing attribute (or node) values in a statement like this: declare default collation 'http://basex.org/collation?strength=primary'; let $doc := doc(' <root> <test name="Straße">Straße</test> <test name="Strasse">Strasse</test> </root> ') return count($doc/root/test[@name = "Strasse"]) I would expect that to return a count of 2 but it returns a count of 1. I can get round this by calling fn:compare() like this but it feels like a hack: declare default collation 'http://basex.org/collation?strength=primary'; let $doc := doc(' <root> <test name="Straße">Straße</test> <test name="Strasse">Strasse</test> </root> ') return count($doc/root/test[0=fn:compare(@name,"Strasse")]) Is this behaviour as intended? I can see that it might make query speed and indexes much better to ignore collation for = but I couldn't find it stated in the documentation. My quick read of the specification suggested that the operation of fn:compare would drive the behaviour of eq, gt, lt etc. I think that I'm probably doing this completely the wrong way and I should be using some of the other features of Full-Text but I'm not sure. If anyone can point me in the right direction I will be very grateful. Many thanks, James

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how to get the data of a http post request?
by easy 15 Nov '13

15 Nov '13

hi,all, I can't find function in request module to get the request content. such as request:get-data(), any idea? -- 此致 easy 莫愁前路无知己，天下谁人不识君。

2 1

BaseX Scalability
by Martí Pàmies Solà 14 Nov '13

14 Nov '13

Hi, We are analysing BaseX as an option to store over 100 million xml documents, and one of our main concerns is, which scalability features it offers. We review at http://vschart.com/compare/basex/vs/exist-db that it is horizontal scalable but, on BaseX documentation portal we can not find it. Thanks, Martí.

2 1

XQUERY module for querying instance of XSD scheme ?
by jean-marc Mercier 14 Nov '13

14 Nov '13

Hi, I started to write an xquery module that performs basic operations over instances of XSD schemes. My needs are basics, I would like to list groups and abstract classes, or define automatic predicat like declare variable $XSD_scheme := doc("my_schem.xsd") declare function IsNodeOfGroup($node, $group as element(xsd:group)) as xs:boolean {..} declare function ListAbstractClassesOf($node as element()) as element(xsd:complexType)* {..} However, I guess that I am reinventing the wheel and such a module surely exists already. Has anybody heard about such a module ? Thanks, Jean-Marc

1 0

BaseX rest and PHP
by Lars Johnsen 13 Nov '13

13 Nov '13

Hi all This is a question for those with experience using PHP with BaseX and the rest interface. There is a peculiar case of lag for queries, and I wondered if it had to with how PHPdoes things, or if it is how BaseX does things (or if there is something else). This may be a long shot, but I still give it a try. The setup is fairly straight forward, with queries sent from a html-page via a PHPscript which places the call: file_get_contents(basex-rest-URL). The result is then sent back to the requesting html page. The problem is that this sometimes hangs: two or three queries then it stops or takes an awful lot of time. The peculiar thing is that the basex-rest-URL, when typed directly into browser address line, receives an immediate response, even while it is still being processed by the html-php-basex cycle. Sometimes the cycle gives an answer, sometimes not. The cycle do work when file_get_contents is directed towards an SQLite database, so it seems that there is something going on in the communication between PHP and BaseX. Any ideas? Regards Lars G Johnsen National Library of Norway

3 2

Multi threading doing slow process of Xquery Execution
by Pushpendra Singh Sengar 13 Nov '13

13 Nov '13

Hi All, I create a collection of 4.5 gb xml document. and process some Xquery in sequencial manner then it is taking adequate time to process all queries. But when I converting process to multi threading then it is taking more than 10 times of time. Please someone suggest what is the best way to process Xquey in multithreading model. MY code is following : Thread thread = new Thread(new XqueryProcessor( new Context(),"db1")); Thread thread1 = new Thread(new XqueryProcessor( new Context(),"db2")); Thread thread2 = new Thread(new XqueryProcessor( new Context(),"db3")); thread.start(); thread1.start(); thread2.start(); Xquery Processor has all queries which need to process. and db1, db2 ,db3 are basically same xml files three collection. -- Thanks & Regards , Pushpendra Singh

3 4

Xquery for noobs : the HashSet problem
by jean-marc Mercier 12 Nov '13

12 Nov '13

Hi, Following a recent discussion with BaseX team, here is a description of a problem that I don't know how to solve efficiently from within Xquery or BaseX Xquery extensions like map:module. Thus, any suggestion are welcomed ! The problem is the following : I want to write an XQUERY module called HashSet, implementing the XQUERY version of HashSet (I mean the JAVA object HashSet, or std::set in C++). An HashSet is indeed a map specialization. Thus a suggestion is to use the BaseX map:module. However, I don't know how to use it efficiently. The reasons are the following : This HashSet module 1) must expose a method "hashset:new()" to allocate memory dynamically. The map:module provides the function map:new, this point is ok, I can wrap that. 2) This module must expose a method "hashset:clear($hashset)" to de-allocate memory dynamically. The map:module provides the function map:remove, and I could remove all elements. However this point is ko for me, as, AFAIU (as far as I understand), map:remove copy an the references from a map object into a smaller map object. It does not dealllocate memory, leading to poor overall performances. 3) must expose a method "hashset:add($hashset,$element)" to add memory dynamically. Through map:module, the only possibility that I see is to wrap it as map:new($hashset, map:entry($element,$dummyboolean)). Here too, a in-memory copy is done, leading to poor overall performances. XQUERY is a very attractive langage to me. However, its very nature is to be a functional langage. The main inconvenients to working with XQUERY for me are : - first : its dynamic memory management (the in-memory printfoot of my XQUERY executables are usually tremendous). - second : it lacks powerful libraries, as complete math modules. However, I might miss something ? Do not hesitate to teach me some XQUERY basic ! Cheers JohnLeM

3 9

Replace node attribute value
by Thomas Knight 12 Nov '13

12 Nov '13

Hi everyone, I have a problem trying to replace the attribute value. For example, using factbook.xml: replace value of node attribute /mondial/country[@name='Austria']/@car_code with 'B' fails with: [XUDY0027] Replace target must not be empty. How should I be doing this? Thanks Tom

2 1

Request for information.
by yoann ponzo 12 Nov '13

12 Nov '13

3 4

Issue for JAVA Bindings for Basex 7.7
by jean-marc Mercier 11 Nov '13

11 Nov '13

Hi, To resume an exchange with BaseX members : The issue is JAVA Bindings for BAseX version <= 7.7, illustrated by the following XQUERY code import module namespace set = "java.util.HashSet";{ let $loop := for $i in 1 to 128 return set:add($i) let $loop := for $i in 1 to 128 return set:add($i) return set:size() } returning .. 129 (expected 128) Explanation : (courtesy by Christian Gruen) - The set:add function is no integer-specific function, so it allows all types of objects as argument. - This is why the XQuery item will not be explicitly cast to an integer; instead, the original Java XQuery Item object will be passed on to the Java function. - In BaseX, the first items of type xs:integer and in the range of 0-127 are cached<https://github.com/BaseXdb/basex/blob/master/basex-core/src/main/java/org/b…>. This means that if an integer like 84 is requested twice, the returned item will have the same reference in memory. - This is different for integers larger than 127: in this case, new references will be created. As XQuery items have nohashCode() function, their memory reference will be used when calculating the hash code. WorkAround : preferred : Last Stable Release 7.8 solves the issue. Other workaround : - Use the map:module to simulate HashSet (well, I do confess that I do not know how to achieve this) - wrap the JAVA Class in order to manage directly this issue (by forcing cast operation in your wrapper), then import your wrapper as a module in BAseX

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