BaseX-Talk

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12 participants
5242 discussions

Pretty-print the -V optimized query? See what indexes are used?
by Jonathan Robie 12 Aug '21

12 Aug '21

Is there a way to pretty-print the optimized query from the -V option? What is the best way to see which indexes are being used? Jonathan

2 1

XProc?
by Jonathan Robie 12 Aug '21

12 Aug '21

What hooks does BaseX provide for XProc? Where can I find examples of BaseX use in an XProc pipeline? Jonathan

3 2

PR for DBA issue
by Marco Lettere 03 Aug '21

03 Aug '21

Dear Christian, I've just submitted a PR [1] that fixes an issue occurring with some combination of browser/proxy and that we stumbled upon in 9.5.3 beta. I attach a picture that shows how it looks like in DBA. To make error disappear it's sufficient to put a . in the query input. We propose to make query parameter optional in signature of RestXQ handling that call. Let us know if any further info is required. Regards, Marco. [1] https://github.com/BaseXdb/basex/pull/2030

1 0

Sequence of operations in a .bxs file?
by Jonathan Robie 29 Jul '21

29 Jul '21

What order dependencies are there for operations in a bxs file? I am setting up an environment that populates two databases from upstream sources. It runs queries to modify the structure somewhat, they adds an index, then calls optimize. After that it exports to a directory for comparison. Does order matter? What is a good order? CREATE DB wlc-trees ./trees RUN ./xquery/add-wlc-verses-words.xq CREATE INDEX ATTRIBUTE OPTIMIZE EXPORT ./out/wlc SET CHOP false SET EXPORTER indent=no,omit-xml-declaration=no CREATE DB oshb-morphology ./morphhb/wlc RUN ./xquery/oshb-pure-qere-reading.xq RUN ./xquery/merge-proper-nouns-oshb.xq CREATE INDEX ATTRIBUTE OPTIMIZE EXPORT ./out/oshb Thanks! Jonathan

2 1

Create a database and populate it with the result of a query
by Jonathan Robie 29 Jul '21

29 Jul '21

I would like to be able to create a database and populate it with the result of a query done on multiple databases. How do I do that? Jonathan

3 3

java.lang.RuntimeException: Data Access out of bounds
by Jonathan Robie 29 Jul '21

29 Jul '21

Any ideas what this might mean? What should I do? Jonathan

4 6

Merge/combine databases in memory constrained environment
by Matthew Dziuban 27 Jul '21

27 Jul '21

Hi all, I have two databases in BaseX, source_db and target_db, and would like to merge them by matching on the id attribute of each element and upserting the element with a `replace` or an `insert` depending on whether the element was found in the `target_db`. `source_db` has about 100,000 elements, and `target_db` has about 1,000,000 elements. The databases look like this:  <root> <element id="1"> <element id="2"> </root>  <root> <element id="1"> </root> And my query to merge the two looks like this: for $e in (db:open("source_db")/root/element) return ( if (exists(db:open("target_db")/root/element[@id = data($e/@id)])) then replace node db:open("target_db")/root/element[@id = data($e/@id)] with $e else insert node $e into db:open("target_db")/root ) When running the query, however, I keep getting memory constraint errors. Using a POST request to BaseX's REST interface I get "Out of Main Memory" and using the BaseX java client ( https://github.com/BaseXdb/basex/blob/master/basex-examples/src/main/java/o…) I get "java.io.IOException: GC overhead limit exceeded". Ideally I would like to just process one element from source_db at a time to avoid memory issues, but it seems like my query isn't doing this. I've tried using the `db:copynode false` pragma but it did not make a difference. Is there any way to accomplish this? Thanks in advance! Matt

3 7

Converting a Java Set to a BaseX sequence
by Reece Dunn 23 Jul '21

23 Jul '21

Hi, I'm making use of the Java bindings in BaseX, with some of the functions returning List<String> and Set<String> types. For List<String> I can adapt that to a sequence using: declare namespace List = "java:java.util.List"; declare function util:list-to-sequence($list) { for $n in 0 to List:size($list) - 1 return List:get($list, $n cast as xs:int) }; however, I'm not sure how to do the equivalent for Set<String> (or more generally, any Iterator<T>) without converting it to a list or array first, as Set only has size() and iterator() methods. Has anyone done this before? The best I can come up with is the following, which relies on the size of the set and the number of next calls in the iterator to be the same (where it should be checking hasNext): declare namespace Set = "java:java.util.Set"; declare namespace Iterator = "java:java.util.Iterator"; declare function util:set-to-sequence($set) { let $iterator := Set:iterator($set) for $n in 0 to Set:size($set) - 1 return Iterator:next($iterator) }; More generally, it would be helpful for BaseX to have adapters for Java arrays, Lists, Sets, Maps, and Iterables/Iterators to XQuery (XDM) types and functions to construct them in XQuery (like my util:list-to-sequence function above). Kind regards, Reece

2 12

Dropping namespaces on import, serialization
by Jonathan Robie 23 Jul '21

23 Jul '21

I am playing with datasets in which namespaces are unhelpful because they make output harder to read. For production use, though, I want the namespaces to be there. Ideally, I would like to tell BaseX to drop namespaces while serializing. Sometimes. Ideally, I would like to be able to set this as an option in a .bxs file. Is that possible? Thanks! Jonathan

3 2

Different result sets using positional predicates in path expression and where clause
by Kristian Kankainen 23 Jul '21

23 Jul '21

Hello, I noticed I get different result sets with the following queries and I can't understand how they differ from each other. 1) Correct behaviour, returns 3 records let $file := db:list("Snomed")[matches(.,"MRCM")][3] return for $record in (db:open("Snomed", $file)/csv/record) [position() = (1 to 3)] return $record 2) Unexpected behaviour, returns 21 records let $file := db:list("Snomed")[matches(.,"MRCM")][3] return for $record in (db:open("Snomed", $file)/csv/record) where position() = (1 to 3) return $record I have highlighted the one line that differs between them, e.g the first uses the positional predicate in a path expression and the second uses it in a where clause. Best regards, Kristian Kankainen

3 2

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