add SecondaryIndex.reload API

patch by Sam Tunnicliffe; reviewed by jbellis for CASSANDRA-4581

CHANGES.txt

@@ -1,4 +1,5 @@
 1.1.5
+ * add SecondaryIndex.reload API (CASSANDRA-4581)
  * use millis + atomicint for commitlog segment creation instead of
    nanotime, which has issues under some hypervisors (CASSANDRA-4601)
  * fix FD leak in slice queries (CASSANDRA-4571)

src/java/org/apache/cassandra/db/index/SecondaryIndex.java

@@ -65,6 +65,14 @@ public abstract class SecondaryIndex
      */
     public abstract void init();
 
+    /**
+     * Reload an existing index following a change to its configuration, 
+     * or that of the indexed column(s). Differs from init() in that we expect
+     * expect new resources (such as CFS for a KEYS index) to be created by
+     * init() but not here
+     */
+    public abstract void reload() throws IOException;
+
     /**
      * Validates the index_options passed in the ColumnDef
      * @throws ConfigurationException

src/java/org/apache/cassandra/db/index/SecondaryIndexManager.java

@@ -99,10 +99,11 @@ public class SecondaryIndexManager
             if (cdef.getIndexType() != null && !indexedColumnNames.contains(cdef.name))
                 addIndexedColumn(cdef);
 
-        for (ColumnFamilyStore cfs : getIndexesBackedByCfs())
+        Set<SecondaryIndex> reloadedIndexes = Collections.newSetFromMap(new IdentityHashMap<SecondaryIndex, Boolean>());
+        for (SecondaryIndex index : indexesByColumn.values())
         {
-            cfs.metadata.reloadSecondaryIndexMetadata(baseCfs.metadata);
-            cfs.reload();
+            if (reloadedIndexes.add(index))
+                index.reload();
         }
     }
 

src/java/org/apache/cassandra/db/index/keys/KeysIndex.java

@@ -181,4 +181,10 @@ public class KeysIndex extends PerColumnSecondaryIndex
     {
         return indexCfs.getMemtableDataSize();
     }
+
+    public void reload() throws IOException
+    {
+        indexCfs.metadata.reloadSecondaryIndexMetadata(baseCfs.metadata);
+        indexCfs.reload();
+    }
 }

test/unit/org/apache/cassandra/db/SecondaryIndexColumnSizeTest.java

@@ -137,7 +137,11 @@ public class SecondaryIndexColumnSizeTest
         public void deleteFromIndex(DecoratedKey<?> key, List<IColumn> indexedColumnsInRow)
         {  
         }
-        
+
+        @Override
+        public void reload()
+        {
+        }
     }
     
     
@@ -210,6 +214,11 @@ public class SecondaryIndexColumnSizeTest
         @Override
         public void updateColumn(DecoratedKey valueKey, ByteBuffer rowKey, IColumn col) throws IOException
         {
-        }    
+        }
+
+        @Override
+        public void reload()
+        {
+        }
     }
 }