Possible bug in the interaction between db:attribute(), data() and Sequences.

On Tue, Jul 4, 2023 at 10:16 AM Andreas Hengsbach | nexoma <andreas.hengsbach at nexoma.de> wrote: > > Hello all, > > > > we have probably found a bug, the cause of which is currently unclear to us. > Fortunately, the problem is reproducible in a small test case. > > > > Steps to reproduce the problem: > > > > 1. import the following XML into a BaseX database "testcase". > > > ### schnipp > > <attributes foo="bar"> > > <attribute name="test1" seq="foo"/> > > <attribute name="test2"/> > > <attribute name="test3" seq="bar"/> > > </attributes> > > ### schnapp > > 2. make sure that an attribute index has been created. > > 3. execute the following script. > > ### schnipp > let $source := db:attribute('testcase', 'bar', 'foo')/.. > > let $value := ( > > $source/attribute[@name="test1"]/@seq/data(), > > $source/attribute[@name="test2"]/@seq/data(), > > $source/attribute[@name="test3"]/@seq/data() > > ) > > return ( > > $value[2] => inspect:type() > > ) > ### schnapp > > > > Explanation: > > The example is really only meant as a test case. For our case we have already found a workaround, so we don't have a serious problem. > > > > The important thing is that the element is read from the database via db:attribute() and then the individual values are combined again into a sequence. > > In doing so, we get an untypedAtomic from attribute test1, an empty-sequence() for test2 and an untypedAtomic again for test3. > > > > Observation: > > When we read the second value of the sequence by index ($value[2]), we get back an "attribute()" instead of an untypedAtomic. > > > > Expectation: > > We would expect an untypedAtomic here again. > > > > Workaround: > > We simply used string() instead of data() to explicitly cast the value to a string. > > Versions: > > We were able to reproduce the problem with 10.4 and the current 10.6. With a very old version 7.9, however, it was not reproducible. > > > > > > Many thanks and best regards > Andreas