== 位图（Bitmap） ==
Verbatim Bitmap 带来的空间开销，人们发明了Bitmap Compression机制。
* BBC (Byte-aligned Bitmap Compression)
* WAH (Word Aligned Hybrid)
* PLWAH (Position List Word-Aligned Hybrid)
* EWAH (Enhanced Word-Aligned Hybrid )
* CONCISE (COmpressed N Composable Integer SEt)
* PWAH (Partitioned Word-Aligned Hybrid)
* COMPAX (COMPressed Adaptive indeX )
* Roaring Bitmap [https://github.com/RoaringBitmap/RoaringBitmap Java-Roaring] [https://github.com/RoaringBitmap/CRoaring CRoaring]
* BAH (Byte Aligned Hybrid(BAH) [http://gitlab.icenter.tsinghua.edu.cn/zhenchen/BAH BAH]