public StoreFileScanner getPreadScanner(boolean cacheBlocks, long readPt, long scannerOrder,
    boolean canOptimizeForNonNullColumn) {
    return getReader().getStoreFileScanner(cacheBlocks, true, false, readPt, scannerOrder,
      canOptimizeForNonNullColumn);
  }
Get a scanner which uses pread.
<p>
Must be called after initReader.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HStoreFile.java