@Override
  public boolean seek(ExtendedCell seekKey) throws IOException {
    return generalizedSeek(false, // This is not a lazy seek
      seekKey, false, // forward (false: this is not a reseek)
      false); // Not using Bloom filters
  }
Seeks all scanners at or below the specified seek key. If we earlied-out of a row, we may end
up skipping values that were never reached yet. Rather than iterating down, we want to give the
opportunity to re-seek.
<p>
As individual scanners may run past their ends, those scanners are automatically closed and
removed from the heap.
<p>
This function (and {@link #reseek(ExtendedCell)}) does not do multi-column Bloom filter and
lazy-seek optimizations. To enable those, call
{@link #requestSeek(ExtendedCell, boolean, boolean)}.
@param seekKey KeyValue to seek at or after
@return true if KeyValues exist at or after specified key, false if not
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/KeyValueHeap.java