[BanyanDB] Optimizing Column Encoding

[hanahmily]

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• I had searched in the issues and found no similar feature requirement.

Description

There are several optimizations we should apply to the column encoding, the column refers to tags and fields.

• Move constant values within a block to the metadata.
• Encode each column based on its data type (string, int64, or float64).
• Use low cardinality encoding when the column has a limited set of value options within a block.
• Consider encoding array types using a columnar strategy. If the array size is consistent within a block, transform the arrays into a matrix and group and encode the values within the same column.

Use case

No response

Related issues

No response

Are you willing to submit a pull request to implement this on your own?

• Yes I am willing to submit a pull request on my own!

Code of Conduct

• I agree to follow this project's Code of Conduct

[sollhui]

Please assign to me.

[wu-sheng]

Are you confident to take two in the same time? How much do you understand BanyanDB?

[sollhui]

Are you confident to take two in the same time? How much do you understand BanyanDB?

I am familiar with BanyanDB code and have contributed 10 PR, but I don't think it's an easy task. Let me discuss it with @hanahmily first

[wu-sheng]

This is on the next iteration only, unless you will finish it in time for 0.7. So, don't hurry and take your time.

@hanahmily Please note, as we are changing docs to user oriented, please make sure the file structure docs covers encoding docs with proper docs and clear examples.

[hanahmily]

@sollhui Let's discuss the details first.

@wu-sheng Sure, we will update the relevant documents according to the new structures. This change will not break the file system; therefore, we do not have to increase the file system version.

[wu-sheng]

Let's discuss details when you have the design.
I am not sure how to change the encoding doesn't affect storage structure. Changing doesn't mean breaking, such as, you have a new encoding type, which will also affect new structure in the file, but no breaking.