Hi Martin, Thanks for the analysis. As you’ve already indicated, the combination of documents with and without namespaces triggered an optimization that should only take effect if all documents of a database have the same default namespace The bug has been fixed; a new snapshot is online [1,2]. Best, Christian [1] https://github.com/BaseXdb/basex/issues/1831 [2] http://files.basex.org/releases/latest/ On Mon, Mar 30, 2020 at 11:26 AM Martin Honnen <martin.honnen@gmx.de> wrote:

Am 29.03.2020 um 16:26 schrieb Martin Honnen:

...

Using BaseX 9.3.2, why does a query

collection('/test-db-1/bib')//Q{}libro

return 6 items while

collection('/test-db-1/bib')//libro

gives 0 items?

If I run

collection('/test-db-1/bib')//Q{}libro, collection('/test-db-1/bib')//libro

the info window shows

Compiling: - rewrite fn:collection([uri]) to document-node() item: collection("/test-db-1/bib") -> db:open-pre("test-db-1", 12000002) - merge steps: descendant::element(libro) - rewrite fn:collection([uri]) to document-node() item: collection("/test-db-1/bib") -> db:open-pre("test-db-1", 12000002) - remove step without results: element(libro) - rewrite iter step to empty sequence: element(libro) -> () - rewrite cached path to empty sequence: db:open-pre("test-db-1", 12000002)/descendant-or-self::node()/() -> () - rewrite expression list to iter path: (db:open-pre("test-db-1", 12000002)/descendant::element(libro), ()) -> db:open-pre("test-db-1", 12000002)/descendant::element(libro) Optimized Query: db:open-pre("test-db-1", 12000002)/descendant::element(libro) Query: collection('/test-db-1/bib')//Q{}libro, collection('/test-db-1/bib')//libro Result: - Hit(s): 6 Items - Updated: 0 Items - Printed: 1455 b - Read Locking: test-db-1 - Write Locking: (none)

It seems the problems occurs if I have one document in the db that has elements in a namespace and one with elements in no namespace.

So if there is only one document with no namespaces then both collection('/test-db-3/ex2')//foo and collection('/test-db-3/ex2')//Q{}foo select the `foo` elements in no namespace but if there is a document using a namespace as well in the db then collection('/test-db-3/ex2')//foo does not select the `foo` elements in no namespace.

Are there any db/namespace related settings in BaseX that cause that behaviour?