Implement Theta Sketch

[Xuanwo]

The iceberg side requires:

A serialized form of a "compact" Theta sketch generated by the Apache DataSketches library.

From https://iceberg.apache.org/puffin-spec/?h=datas#apache-datasketches-theta-v1-blob-type

We use Theta to store values such as ndv.

I'm interested in implementing this feature. However, my current bandwidth is limited, so it might be better not to include it in the v0.1 release.

[ZENOTME]

I'm interested in this and willing to send a PR for this later. I try to split it into 3 steps:

1. sketch and hash table
2. serialization/deserialization
3. set op

[tisonkun]

@ZENOTME @Xuanwo Is ThetaSketch supported now? I can see we finished part 1 and 2 but perhaps the set op part is still missing?

[ZENOTME]

@ZENOTME @Xuanwo Is ThetaSketch supported now? I can see we finished part 1 and 2 but perhaps the set op part is still missing?

Yes, I will send a PR for this part recently .