Use topological sorting to sort tables by dependency

src/main/scala/gitbucket/core/util/JDBCUtil.scala

@@ -6,6 +6,7 @@ import java.text.SimpleDateFormat
 import javax.xml.stream.{XMLStreamConstants, XMLInputFactory, XMLOutputFactory}
 import ControlUtil._
 import scala.StringBuilder
+import scala.annotation.tailrec
 import scala.collection.mutable
 import scala.collection.mutable.ListBuffer
 
@@ -144,6 +145,8 @@ object JDBCUtil {
         writer.writeStartDocument("UTF-8", "1.0")
         writer.writeStartElement("tables")
 
+        println(allTablesInDatabase.mkString(", "))
+
         allTablesInDatabase.reverse.foreach { tableName =>
           if (targetTables.contains(tableName)) {
             writer.writeStartElement("delete")
@@ -292,12 +295,34 @@ object JDBCUtil {
         val result = TableDependency(tableName, childTables(meta, tableName))
         result
       }
-      tables.sortWith { (a, b) =>
-        a.children.contains(b.tableName)
-      }.map(_.tableName)
+
+      val edges = tables.flatMap { table =>
+        table.children.map { child => (table.tableName, child) }
+      }
+
+      tsort(edges).toSeq
     }
 
     case class TableDependency(tableName: String, children: Seq[String])
+
+
+    def tsort[A](edges: Traversable[(A, A)]): Iterable[A] = {
+      @tailrec
+      def tsort(toPreds: Map[A, Set[A]], done: Iterable[A]): Iterable[A] = {
+        val (noPreds, hasPreds) = toPreds.partition { _._2.isEmpty }
+        if (noPreds.isEmpty) {
+          if (hasPreds.isEmpty) done else sys.error(hasPreds.toString)
+        } else {
+          val found = noPreds.map { _._1 }
+          tsort(hasPreds.mapValues { _ -- found }, done ++ found)
+        }
+      }
+
+      val toPred = edges.foldLeft(Map[A, Set[A]]()) { (acc, e) =>
+        acc + (e._1 -> acc.getOrElse(e._1, Set())) + (e._2 -> (acc.getOrElse(e._2, Set()) + e._1))
+      }
+      tsort(toPred, Seq())
+    }
   }
 
 }