should be it

external/duckdb/benchmark/ldbc/queries/bi-4.sql

@@ -0,0 +1,39 @@
+/* Q4. Top posters in a country
+\set country '\'Belarus\''
+ */
+WITH top100_popular_forums AS (
+  SELECT fp_forumid AS forumid
+    FROM forum_person fp
+       , person p
+       , place ci -- city
+       , place co -- country
+   WHERE 1=1
+      -- join
+     AND fp.fp_personid = p.p_personid
+     AND p.p_placeid = ci.pl_placeid
+     AND ci.pl_containerplaceid = co.pl_placeid
+      -- filter
+     AND co.pl_name = 'Belarus'
+   GROUP BY fp_forumid
+   ORDER BY count(*) DESC, fp_forumid
+   LIMIT 100
+)
+SELECT au.p_personid AS "person.id"
+     , au.p_firstname AS "person.firstName"
+     , au.p_lastname AS "person.lastName"
+     , au.p_creationdate
+     -- a single person might be member of more than 1 of the top100 forums, so their posts should be DISTINCT counted
+     , count(DISTINCT p.m_messageid) AS postCount
+  FROM top100_popular_forums t
+       INNER JOIN forum_person fp ON (t.forumid = fp.fp_forumid)
+       -- author of the post
+       INNER JOIN person au ON (fp.fp_personid = au.p_personid)
+       LEFT JOIN message p ON (1=1
+                        AND au.p_personid = p.m_creatorid
+                        AND p.m_ps_forumid IN (SELECT forumid from top100_popular_forums)
+                        AND p.m_c_replyof IS NULL
+                           )
+ GROUP BY au.p_personid, au.p_firstname, au.p_lastname, au.p_creationdate
+ ORDER BY postCount DESC, au.p_personid
+ LIMIT 100
+;