These examples work differently.

So If I read this correctly, the number of results for 1. is still
identical, right? However, in the second query in 2., no results are
returned. You could report the query plan will give us some insight
into what happens here.

 

 1.
 (# db:enforceindex #) {
   for $db in db:list()[starts-with(.,'000999~')]
   return db:open($db)//*[text() contains text { 'болт' } any]
 }
 378 rows

 let $dbs := for $i in db:list()[starts-with(.,'000999~')] return $i
 for $db in $dbs
 let $ft := ft:search($db, "болт")/parent::*
 for $node in $ft
 return $node
 378 rows

 2.
 (# db:enforceindex #) {
   for $db in db:list()[starts-with(.,'000999~')]
   return db:open($db)//*[text() contains text { 'автомобиль' } any]
 }
 0 rows

 let $dbs := for $i in db:list()[starts-with(.,'000999~')] return $i
 for $db in $dbs
 let $ft := ft:search($db, "автомобиль")/parent::*
 for $node in $ft
 return $node
 2138 rows


 Why do they work differently?