do not serialize dropped columns to sstable header

Author: smiklosovic

src/java/org/apache/cassandra/db/SerializationHeader.java

@@ -112,13 +112,21 @@ public static SerializationHeader make(TableMetadata metadata, Collection<SSTabl
         EncodingStats.Collector stats = new EncodingStats.Collector();
         RegularAndStaticColumns.Builder columns = RegularAndStaticColumns.builder();
         // We need to order the SSTables by descending generation to be sure that we use latest column metadata.
-        for (SSTableReader sstable : orderByDescendingGeneration(sstables))
+
+        Collection<SSTableReader> ssTableReaders = orderByDescendingGeneration(sstables);
+
+        for (SSTableReader sstable : ssTableReaders)
         {
             stats.updateTimestamp(sstable.getMinTimestamp());
             stats.updateLocalDeletionTime(sstable.getMinLocalDeletionTime());
             stats.updateTTL(sstable.getMinTTL());
-            columns.addAll(sstable.header.columns());
+            for (ColumnMetadata column : sstable.header.columns())
+            {
+                if (metadata.getDroppedColumn(column.name.bytes) == null)
+                    columns.add(column);
+            }
         }
+
         return new SerializationHeader(true, metadata, columns.build(), stats.get());
     }
 

src/java/org/apache/cassandra/db/compaction/CursorCompactor.java

@@ -636,6 +636,16 @@ private boolean mergeCells(int cellMergeLimit, DeletionTime activeDeletion, Live
         ReusableLivenessInfo cellLiveness = cellCursor.cellLiveness;
         DataOutputBuffer tempCellBuffer = null;
 
+        if (metadata().getDroppedColumn(cellCursor.cellColumn.name.bytes) != null)
+        {
+            for (int i = 0; i < cellMergeLimit; i++)
+            {
+                if (sstableCursors[i].state() == CELL_VALUE_START)
+                    sstableCursors[i].skipCellValue();
+            }
+            return isRowDropped;
+        }
+
         if (cellCursor.cellColumn.isComplex())
             throw new UnsupportedOperationException("TODO: Not ready for complex cells.");
         if (cellCursor.cellColumn.isCounterColumn())