Tracking Issue: Sparse primary key codec

[WenyXu]

What type of enhancement is this?

Performance

What does the enhancement do?

In the metrics engine scenario, when the number of primary key columns on a physical table becomes excessively large, the CPU overhead for encoding all primary keys increases dramatically. This results in significant performance bottlenecks for both write and query operations.

Proposal
Introduce a sparse primary key codec that encodes only non-null primary key columns. By skipping the encoding of null or empty columns, this change aims to:

• Reduce CPU overhead associated with primary key encoding.
• Improve overall write and query performance.

TODO

• sparse primary key codec implementation
  • support for read, write in memtable
  • backward compatibility
• pluggable codec implementation
• codec benchmark

Implementation challenges

No response