Improved element reordering performance

[simantics/platform.git] / bundles / org.simantics.db.common / src / org / simantics / db / common / utils / OrderedSetUtils.java

diff --git a/bundles/org.simantics.db.common/src/org/simantics/db/common/utils/OrderedSetUtils.java b/bundles/org.simantics.db.common/src/org/simantics/db/common/utils/OrderedSetUtils.java
index 143d3e443099f31c703503dfea77b1da7ea115f1..8e8171f85273e460bdf519df9eab706ba395b539 100644 (file)
--- a/bundles/org.simantics.db.common/src/org/simantics/db/common/utils/OrderedSetUtils.java
+++ b/bundles/org.simantics.db.common/src/org/simantics/db/common/utils/OrderedSetUtils.java
@@ -220,6 +220,27 @@ public class OrderedSetUtils {
             }
     }
 
+    /**
+     * Reorders elements with a minimum number of writes. The set of elements must remain the same. 
+     */
+    public static void reorder(WriteGraph g, Resource l, Iterable<Resource> order) throws DatabaseException {
+        Resource newPrev = l;
+        for (Resource r : order) {
+            Resource prev = OrderedSetUtils.prev(g, l, r);
+            if (!prev.equals(newPrev)) {
+                g.deny(prev, l, r);
+                g.claim(newPrev, l, r);
+            }
+            newPrev = r;
+        }
+        Resource newLast = newPrev;
+        Resource last = OrderedSetUtils.prev(g, l, l);
+        if (!last.equals(newLast)) {
+            g.deny(last, l, l);
+            g.claim(newLast, l, l);
+        }
+    }
+
     /**
      * Converts ordered set into a list.
      */