Query failure - may be GROUP_CONCAT not supported?

[WolfgangFahl]

https://qlever.cs.uni-freiburg.de/wikidata/0fidpY

[WolfgangFahl]

see WDscholia/scholia#1774

[joka921]

Good morning, the following variant of your query "works" on QLever:
https://qlever.cs.uni-freiburg.de/wikidata/m49coC

Issue 1:
QLever's SPARQL parser is very incomplete and needs a clean rewrite (we have already started this, but thanks for pointing this out again:

• A dot . is required between triples and filters, and after filters.
• The literal in the language filter has to be "en" rather than 'en'
• Subqueries inside OPTIONAL lead to a parse error.

Issue 2:
When "fixing" this (I removed the OPTIONAL) then the result is computed,
but the authors column is empty. The reason is, that the concatenated strings are not properly propagated.

Issue 3:
I removed some variables from the SELECT clause because our UI doesn't show all columns if there are too many.
(This is a small bug in the UI).

Thanks for reporting this.
We have a deadline upcoming this weekend, but after that this can be easily "fixed" (At least issue 2).

[hannahbast]

Moved to #615