Make changes to page references atomic

h2/src/main/org/h2/mvstore/MVMap.java

@@ -154,12 +154,14 @@ public class MVMap<K, V> extends AbstractMap<K, V>
         Object k = p.getKey(at);
         Page split = p.split(at);
         Object[] keys = { k };
-        long[] children = { p.getPos(), split.getPos() };
-        Page[] childrenPages = { p, split };
+        Page.PageReference[] children = {
+                new Page.PageReference(p, p.getPos()),
+                new Page.PageReference(split, split.getPos()),
+        };
         long[] counts = { p.getTotalCount(), split.getTotalCount() };
         p = Page.create(this, writeVersion,
                 1, keys, null,
-                2, children, childrenPages, counts,
+                2, children, counts,
                 totalCount, 0, 0);
         return p;
     }

h2/src/main/org/h2/mvstore/MVStore.java

@@ -112,6 +112,9 @@ MVStore:
     a map lookup when reading old data; also, this
     old data map needs to be cleaned up somehow;
     maybe using an additional timeout
+- rollback of removeMap should restore the data -
+    which has big consequences, as the metadata map
+    would probably need references to the root nodes of all maps
 
 */
 
@@ -823,11 +826,10 @@ public class MVStore {
     /**
      * Whether the chunk at the given position is live.
      *
-     * @param pos the position of the page
+     * @param the chunk id
      * @return true if it is live
      */
-    boolean isChunkLive(long pos) {
-        int chunkId = DataUtils.getPageChunkId(pos);
+    boolean isChunkLive(int chunkId) {
         String s = meta.get(Chunk.getMetaKey(chunkId));
         return s != null;
     }
@@ -2262,9 +2264,10 @@ public class MVStore {
     }
 
     /**
-     * Remove a map.
+     * Remove a map. Please note rolling back this operation does not restore
+     * the data; if you need this ability, use Map.clear().
      * 
-     * @param map the map
+     * @param map the map to remove
      */
     public synchronized void removeMap(MVMap<?, ?> map) {
         checkOpen();
@@ -2397,7 +2400,7 @@ public class MVStore {
             return;
         }
         autoCommitDelay = millis;
-        if (fileStore == null) {
+        if (fileStore == null || fileStore.isReadOnly()) {
             return;
         }
         stopBackgroundThread();

h2/src/main/org/h2/mvstore/rtree/MVRTreeMap.java

@@ -248,13 +248,16 @@ public class MVRTreeMap<V> extends MVMap<SpatialKey, V> {
                     Object k1 = getBounds(p);
                     Object k2 = getBounds(split);
                     Object[] keys = { k1, k2 };
-                    long[] children = { p.getPos(), split.getPos(), 0 };
-                    Page[] childrenPages = { p, split, null };
+                    Page.PageReference[] children = {
+                            new Page.PageReference(p, p.getPos()),
+                            new Page.PageReference(split, split.getPos()),
+                            new Page.PageReference(null, 0)
+                    };
                     long[] counts = { p.getTotalCount(),
                             split.getTotalCount(), 0 };
                     p = Page.create(this, v,
                             2, keys, null,
-                            3, children, childrenPages, counts,
+                            3, children, counts,
                             totalCount, 0, 0);
                     // now p is a node; continues
                 }
@@ -449,12 +452,22 @@ public class MVRTreeMap<V> extends MVMap<SpatialKey, V> {
     }
 
     private Page newPage(boolean leaf, long writeVersion) {
-        Object[] values = leaf ? new Object[4] : null;
-        long[] c = leaf ? null : new long[1];
-        Page[] cp = leaf ? null : new Page[1];
+        Object[] values;
+        Page.PageReference[] refs;
+        long[] c;
+        if (leaf) {
+            values = new Object[4];
+            refs = null;
+            c = null;
+        } else {
+            values = null;
+            refs = new Page.PageReference[] {
+                    new Page.PageReference(null, 0)};
+            c = new long[1];
+        }
         return Page.create(this, writeVersion,
                 0, new Object[4], values,
-                leaf ? 0 : 1, c, cp, c, 0, 0, 0);
+                leaf ? 0 : 1, refs, c, 0, 0, 0);
     }
 
     private static void move(Page source, Page target, int sourceIndex) {