BaseX-Talk

basex-talk@mailman.uni-konstanz.de

8 participants
5255 discussions

Syntax-checker
by Ben Engbers 17 Feb '22

17 Feb '22

Hi, After I had formulated the query in Basex-GUI, I tried to execute the same multi-line query in R/RbaseX. Nada ;-( In R, one can use the paste function to concatenate strings. I use this function to build a string which is passed to the RbaseX-client. Example: Stmt_1 <- "for $i in 1 to 2 return $i" => OK Stmt_2 <- paste0("for $i in 1 to 2", => ERROR "return $i") It took 2 days of debugging before I found the error. Stmt_2 is concatenated to "for $i in 1 to 2return $i" and it is clear that this can't be executed. Instead of using the "paste0"-function I should have used "paste" which introdus a space between the strings to be concatenated. This works fine. My problem is that the server/my client does not give an error-message. And this leads me to following question: It would be helpfull if the syntax for the XQuery statement was checked before sending to the server. Where in the BaseX sources can I find the code for XQuery checking? Is it possible to translate tist code into R or is that way to difficult? Ben Engbers

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Namespaces, replace, and performance
by Jonathan Robie 17 Feb '22

17 Feb '22

I wrote a query that replaced roughly 470153 text nodes with an element that had two namespaces declared on it. It ran for several hours. I didn't need or want these namespaces, they were in the original source. I rewrote the query to remove the namespaces from these nodes before replacing the text node. I don't know how quickly it ran, but I think not more than 15 minutes, the first time I checked on it, it had already finished. I made no other changes to the query. Is this surprising? Or is this a general lesson about performance and updates that add namespaces low down in the hierarchy? Or ... Jonathan

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Long-running queries: command line or BaseX Gui?
by Jonathan Robie 17 Feb '22

17 Feb '22

Do long-running queries run faster from the command line, the GUI, or about the same from either? Jonathan

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COPY DB vs. CREATE DB
by Jonathan Robie 16 Feb '22

16 Feb '22

What's the easiest way to copy a database, whether or not there is an existing copy with a given name? If I load a database with CREATE DB, it replaces any existing database with the same name. I would like to do the same with COPY DB, but it raises an error if there is a database with the same name. And DELETE DB raises an error if there isn't a database with that name. So what's the right way to do this? Jonathan

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Accessing Java constant from XQuery
by Paul L. Merchant Jr. 16 Feb '22

16 Feb '22

Hi everyone, I'm using a Java library in XQuery in BaseX and I haven't been able to determine if there's a way to access a constant string (final static String... or even just final String...) in the Java class from XQuery. For example, if the Java class is declared as package my.module; public class MyModule { public static final String TITLE ="I'm a module!"; public String hello(final String world) { return "Hello " + world; } } The XQuery to call the "hello" method is import module namespace java = 'java:my.module.MyModule'; java:hello("World!") But is there any way to access "TITLE"? I'd like to share some constants between XQuery and Java, and I could write accessor functions for these constants, but it'd be cleaner if I didn't have to. Thanks!

2 2

fn:format-date french translation
by Josselin Morvan 16 Feb '22

16 Feb '22

Hi everyone! It seems that there is no french translation for the fn:format-date() fonction with BaseX. Does anyone knows how and where I could add it to make it run with the format-date() function? Eventually, I could share the translation to make it accessible to all? Thanks a lot for your help, Best, Josselin

2 2

Best Technique for Managing Sequences of Transactions Through Web/REST App
by Eliot Kimber 15 Feb '22

15 Feb '22

My validation dashboard is coming together and I’m now at the point of moving data update orchestration into the web app itself, rather than just in the shell scripts and single-transaction XQuery scripts I have now. My question is: What is the recommended technique, or what are the available options, for orchestrating a sequence of transactions in the context of a web application? For example, I have a button, not yet implemented, that needs to trigger update or creation of one of my indexes, which involves several transactions (drop temporary work database if it exists, create new work database, do work in that database, swap work result with current production database). I know I can use a sequence of redirects to get this and of course could also orchestrate it through JavaScript running in the browser. I’m trying to avoid JavaScript in this application simply to avoid complexity and keep as much of it as possible in XQuery. I’m also trying to work out the best way to present status and feedback for long-running actions—I know how to do the javaScript programming for this but again I’m hoping I don’t have to step up to that level of sophistication, at least not yet. So curious what techniques people use or recommend for transaction orchestration and monitoring. Thanks, Eliot _____________________________________________ Eliot Kimber Sr Staff Content Engineer O: 512 554 9368 M: 512 554 9368 servicenow.com<https://www.servicenow.com> LinkedIn<https://www.linkedin.com/company/servicenow> | Twitter<https://twitter.com/servicenow> | YouTube<https://www.youtube.com/user/servicenowinc> | Facebook<https://www.facebook.com/servicenow>

2 1

'Flatten' a collection
by Ben Engbers 14 Feb '22

14 Feb '22

Hi, I have a collection of 740 XML-documents which I want to flatten. The files all have the same structure: <handeling id="h_1"> <datum date="d_1"/> <spreekbeurt><spreker>spreker_1</spreker></spreekbeurt> <spreekbeurt><spreker>spreker_3</spreker></spreekbeurt> </handeling> <handeling id="h_2"> <datum date="d_2"/> <spreekbeurt> <spreker>spreker_2</spreker></spreekbeurt><spreekbeurt> <spreker>spreker_1</spreker><spreekbeurt> <spreker>spreker_4</spreker></spreekbeurt> </handeling> <handeling id="h_3"> <datum date="d_3"/> <spreekbeurt><spreker>spreker_2</spreker></spreekbeurt> <spreekbeurt><spreker>spreker_3</spreker></spreekbeurt> <spreekbeurt><spreker>spreker_2</spreker></spreekbeurt> <spreekbeurt><spreker>spreker_1</spreker></spreekbeurt> </handeling> The following query gives this result: import module namespace functx = "http://www.functx.com"; let $Blogs := collection("Blog") let $Turns := collection("Blog") for $Blog in collection("Blog"), $Turn in collection("Blog") where $Turn//datum/@date = $Blog//datum/@date order by $Blog//datum/@date count $Count let $Id := $Blog/handeling/@id let $Datum := $Blog//datum/@date let $Speaker := $Turn//spreker/text() return($Id, $Datum, $Speaker, $Count) id="h_1" date="d_1" spreker_1 spreker_3 1 id="h_2" date="d_2" spreker_2 spreker_1 spreker_4 2 id="h_3" date="d_3" spreker_2 spreker_3 spreker_2 spreker_1 3 But what I eventually need is this (for clarity shown as a table): 1, id="h_1", date="d_1", 1, spreker_1 1, id="h_1", date="d_1", 2, spreker_3 2, id="h_2", date="d_2", 1, spreker_2 2, id="h_2", date="d_2", 2, spreker_1 2, id="h_2", date="d_2", 3, spreker_4 3, id="h_3", date="d_3", 1, spreker_2 3, id="h_3", date="d_3", 2, spreker_3 3, id="h_3", date="d_3", 3, spreker_2 3, id="h_3", date="d_3", 4, spreker_1 The first counter indicates the position in $Blog. and the second counter indicates the position in $Turn I expected that the following query would return what I was looking for: for $Blog in collection("Blog") order by $Blog//datum/@date let $Id := $Blog/handeling/@id let $Datum := $Blog//datum/@date count $countOuter return ( for $Turn in collection("Blog") where $Turn//datum/@date = $Blog//datum/@date let $Speaker := $Turn//spreker/text() return ($countOuter, $Id, $Datum, $Speaker)) Instead it returns 1, id="h_1", date="d_1", 1, spreker_1, spreker_3 2, id="h_2", date="d_2", 1, spreker_2, spreker_1, spreker_4 3, id="h_3", date="d_3", 1, spreker_2, spreker_3, spreker_2, spreker_1 I have 2 questions: 1: Is it possible to use separate counters for the inner and the outer loop? (How should I define the $countInner?) 2: How can I formulate the query for getting the correct output? Ben Engbers

4 3

combining queries from mutiple sources
by Eric Levy 14 Feb '22

14 Feb '22

I am completely new to BaseX, and trying to conceive of a way to use it to process a compound query that combines an external query with a static one. The core idea is a very simple application, expressed as an XQuery file, that results in the following sequence of actions: 1. Extraction of data from a database, by some query. 2. Modification of the results of (1), by some query. 3. Persistence of the results from (2), back into the database from which the data was originally extracted. The modifications given in (2) would be expressed external to the application, supplied as input per invocation, in a separate file or in a command-line parameter. Thus, the overall operation would entail static components, the fixed parts of the application, represented by (1) and (3), and dynamic components, passed by the invocation, represented by (2). I realize such a processing pipeline may be achieved through queries supplied in a full application accessing the database by one of the language-specific APIs, but I am trying to consider an approach that requires use only of XQuery statements, without involving a separate programming language or formal build process. Does the design of BaseX accommodate an application having the structure as described?

4 4

Feature request - file listing
by Hans-Juergen Rennau 12 Feb '22

12 Feb '22

Dear BaseX people, I have a feature request: a function which does the same as file:list, but returns the full paths. (In the explanation, I call it "file:list2") Rationale: (a) It is the full paths what we need in order to parse the files (doc(), json:doc(), csv:doc(), html:doc()). (b) The combination of file listing and parsing in a single expression is of matchless elegance and expressivenessJust think about how we can extend this into a single list+parse+navigate+report expression, like: file:list2($folder, true(), $fname) ! doc(.) ! //returnCode[. ne 0]/concat(base-uri(.), ': ', .) (Wow! Is there any language or tool competing with this compactness and readability?) Currently, if I don't overlook something, I have to do this: file:list($dir, false(), $fname) ! concat($dir, '/', .) ! doc(.) => count() I emphasize the psychological aspect. Every time I have the pleasure to give a workshop about XQuery, I show off how elegant it is to parse a whole file system tree into a forest of nodes in a single expression. And I am always embarrassed about this clumsy fumbling montage of a path. It's as if Mozart had fallen asleep while writing his xquery sonata, knocked over the inkwell and now there is this splash smeared out on the score. You would be my heroes if you can spare us that. Kind regards,Hans-Jürgen

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