Java: Manual rewrite of the ExternalLibraryUsage query to limit the number of returned results.

Author: michaelnebel

java/ql/src/Telemetry/ExternalLibraryUsage.ql

@@ -9,13 +9,28 @@
 import java
 import ExternalApi
 
-from int usages, string jarname
-where
+private predicate getRelevantUsages(string jarname, int usages) {
   usages =
     strictcount(Call c, ExternalApi a |
       c.getCallee().getSourceDeclaration() = a and
       not c.getFile() instanceof GeneratedFile and
       a.jarContainer() = jarname and
       not a.isUninteresting()
     )
+}
+
+private int getOrder(string jarname) {
+  jarname =
+    rank[result](string jar, int usages |
+      exists(ExternalApi api | jar = api.jarContainer()) and getRelevantUsages(jar, usages)
+    |
+      jar order by usages desc, jar
+    )
+}
+
+from ExternalApi api, string jarname, int usages
+where
+  jarname = api.jarContainer() and
+  getRelevantUsages(jarname, usages) and
+  getOrder(jarname) <= resultLimit()
 select jarname, usages order by usages desc