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
