add comments

pixels-cache/src/main/java/cn/edu/ruc/iir/pixels/cache/PixelsCacheReader.java

@@ -137,6 +137,7 @@ private PixelsCacheIdx search(ByteBuffer keyBuffer)
         int bytesMatchedInNodeFound = 0;
 
         // get root
+        // TODO: does root node have an edge?
         int currentNodeHeader = indexFile.getInt(currentNodeOffset);
         dramAccessCounter++;
         int currentNodeChildrenNum = currentNodeHeader & 0x000001FF;
@@ -179,10 +180,13 @@ private PixelsCacheIdx search(ByteBuffer keyBuffer)
             dramAccessCounter++;
             currentNodeChildrenNum = currentNodeHeader & 0x000001FF;
             currentNodeEdgeSize = (currentNodeHeader & 0x7FFFFE00) >>> 9;
+            // TODO: does max length of edge = 12? can we move currentNodeEdge allocation out before this loop?
             byte[] currentNodeEdge = new byte[currentNodeEdgeSize];
+            // TODO: can we get header, edge and children of a node in one memory access?
             indexFile.getBytes(currentNodeOffset + 4 + currentNodeChildrenNum * 8,
                     currentNodeEdge, 0, currentNodeEdgeSize);
             dramAccessCounter++;
+            // TODO: numEdgeBytes seems redundant.
             for (int i = 0, numEdgeBytes = currentNodeEdgeSize; i < numEdgeBytes && bytesMatched < keyLen; i++)
             {
                 if (currentNodeEdge[i] != keyBuffer.get(bytesMatched))

pixels-cache/src/main/java/cn/edu/ruc/iir/pixels/cache/PixelsRadix.java

@@ -47,30 +47,32 @@ public void putIfAbsent(long blockId, short rowGroupId, short columnId, PixelsCa
      * |root| -> |te|
      * -> |am|
      * -> |st|
+     * <p>
      * 1. If we put <test, new_value> into the original tree, it's a EXACT_MATCH with the |st| node.
      * Then we add the new_value into the node or replace the node.
-     * <p>
+     * </p><p>
      * 2. If we put <tea, new_value> into the original tree, it's a KEY_ENDS_AT_MID_EDGE with the |am| node.
      * Then we split the |am| node into two.
      * |root| -> |te|
      * -> |a|
      * -> |m|
      * -> |st|
-     * <p>
+     * </p><p>
      * 3. If we put <teak, new_value> into the original tree, it's a MATCH_END_AT_MID_EDGE with the |am| node.
      * Then we split the |am| node into three.
      * |root| -> |te|
      * -> |a|
-     * -> |m|
-     * -> |k|
+     *   -> |m|
+     *   -> |k|
      * -> |st|
-     * <p>
+     * </p><p>
      * 4. If we put <teamster, new_value> into the original tree, it's a MATCH_END_AT_END_EDGE with the |am| node.
      * Then we add a new node containing the trailing bytes from the key, and append it to the |am| node.
      * |root| -> |te|
      * -> |am|
-     * -> |ster|
+     *   -> |ster|
      * -> |st|
+     * </p>
      */
     private void putInternal(long blockId, short rowGroupId, short columnId, PixelsCacheIdx cacheIdx, boolean overwrite)
     {

pixels-hive/src/main/java/cn/edu/ruc/iir/pixels/hive/mapred/PixelsInputFormat.java

@@ -354,7 +354,7 @@ private List<Layout> getLayouts(SchemaTableName st)
     }
 
     /**
-     *
+     * TODO: reload input paths so that LOCACTION in a hive table can be empty or any path.
      * @param job
      */
     protected void init(JobConf job) throws IOException