Implement Bit-sliced index for CRoaring

[Smallhi]

There are implements for bit slice index in java and go. Do we need in C/C++?

I think implementing Bit-sliced index for CRoaring include these tasks:

• support mutable Bit-sliced index in C
• support RangeBitmap in C
• A range Index demo for postgres using RangeBitmap in C
• A mutable bit-sliced index demo for postgres using bit-sliced index in C
• A range index demo for Apache Parequet file-format in C/C++
• A mutable bit-sliced index demo for Apache Parequet file-format using Bit-sliced index in C

@lemire we've implemented mutable Bit-sliced index in C and using it for postgres. Due to there are two implements for bit-sliced index, (BSI and RangeBitmap), one is mutable but the performance is poor, the other is immutable ,but the performance is great. Could we make a decision or re-design it ?

cc @ richardstartin

refer to :

1. https://richardstartin.github.io/posts/range-bitmap-index
2. https://richardstartin.github.io/posts/range-predicates
3. https://github.com/RoaringBitmap/RoaringBitmap/tree/master/bsi
4. could you merge this lib to RoraringBtimap? lemire/BitSliceIndex#1

[lemire]

Yes, a pull request to provide this functionality in C is invited.

[patelprateek]

@Smallhi : I alos have this use case , any idea when would we be able to merge this implementation.
Also i have a noob question : Why is bit sliced index dependent on Rangebitmap implementation ? What exactly is the difference between range index and bit slice index ?