Complete implementation of DUMP INDEX command

The DUMP INDEX command now generates a proper execution plan, and can
therefore dump indexes now.

src/main/java/edu/caltech/nanodb/commands/DumpCommand.java

 package edu.caltech.nanodb.commands;
 
 
+import java.io.FileNotFoundException;
 import java.io.PrintStream;
 
 import edu.caltech.nanodb.plannodes.PlanNode;
@@ -121,12 +122,16 @@ public abstract class DumpCommand extends Command {
 
     @Override
     public void execute(NanoDBServer server) throws ExecutionException {
-
-        try {
         // Figure out where the dumped data should go.
         PrintStream dumpOut = out;
-            if (fileName != null)
+        if (fileName != null) {
+            try {
                 dumpOut = new PrintStream(fileName);
+            }
+            catch (FileNotFoundException e) {
+                throw new ExecutionException(e);
+            }
+        }
 
         // Dump the table.
         PlanNode dumpPlan = prepareDumpPlan(server);
@@ -140,13 +145,6 @@ public abstract class DumpCommand extends Command {
         out.printf("Dumped %d rows in %f sec.%n",
             stats.getRowsProduced(), stats.getElapsedTimeSecs());
     }
-        catch (ExecutionException e) {
-            throw e;
-        }
-        catch (Exception e) {
-            throw new ExecutionException(e);
-        }
-    }
 
 
     protected abstract PlanNode prepareDumpPlan(NanoDBServer server);

src/main/java/edu/caltech/nanodb/commands/DumpIndexCommand.java

 package edu.caltech.nanodb.commands;
 
 
+import edu.caltech.nanodb.indexes.IndexInfo;
+import edu.caltech.nanodb.indexes.IndexManager;
+import edu.caltech.nanodb.plannodes.FileScanNode;
 import edu.caltech.nanodb.plannodes.PlanNode;
+import edu.caltech.nanodb.relations.TableInfo;
 import edu.caltech.nanodb.server.NanoDBServer;
+import edu.caltech.nanodb.storage.TableManager;
 
 
 /**
@@ -60,8 +65,20 @@ public class DumpIndexCommand extends DumpCommand {
 
     @Override
     protected PlanNode prepareDumpPlan(NanoDBServer server) {
-        // TODO:  Index scan!
-        return null;
+        // Open the table so we can open the index.
+        TableManager tblMgr = server.getStorageManager().getTableManager();
+        TableInfo tblInfo = tblMgr.openTable(tableName);
+
+        // Open the index.
+        IndexManager idxMgr = server.getStorageManager().getIndexManager();
+        IndexInfo idxInfo = idxMgr.openIndex(tblInfo, indexName);
+
+        // Make a file-scan plan-node over the index.
+        PlanNode plan = new FileScanNode(idxInfo, null);
+        plan.prepare();
+
+        // Done!
+        return plan;
     }