I am using BaseX 8.6.4 and I am trying to do a group-by/order-by operation, and I see that two logically equivalent queries perform very differently: one cannot see the end, while the other can (and fast). I can provide further details if necessary, but these are the queries (look at the last line of both, where the difference is):
(This does not work:)
declare variable $p := db:open("db2")/text/line/text(); (: returns a list of values like ΠΕΡΙ#n-s---mv- :)
for $u in db:open("db1")/text/s/t let $a := $u/f/text() (: returns one value like ΠΕΡΙ :) let $b := $u/@o/data(.) (: returns one value like n-s---mv- :) group by $k := $a || "#" || $b (: builds a value like ΠΕΡΙ#n-s---mv- :) let $n := count($u) order by $n descending return if ($p = $k) then $k || " " || $n else ()
(This works:)
for $u in db:open("db1")/text/s/t let $a := $u/f/text() (: returns one value like ΠΕΡΙ :) let $b := $u/@o/data(.) (: returns one value like n-s---mv- :) group by $k := $a || "#" || $b (: builds a value like ΠΕΡΙ#n-s---mv- :) let $n := count($u) order by $n descending return if (db:text("db2", $k)) then $k || " " || $n else ()
The problem is with directly accessing the database with db:text() or indirectly using XPATH. I would tend to use XPATH and expect to get an underlying translation into db:text(), but this seems not to happen: why?
Best, Giuseppe