advisedy opened a new pull request, #3562:
URL: https://github.com/apache/kvrocks/pull/3562
Fixes #2398.
### Problem
`HnswIndex` currently owns a `std::mt19937` generator directly, so every
`HnswIndex` construction also constructs the random generator.
However, the generator is only needed by `RandomizeLayer()` when inserting
vector entries. `HnswIndex` can also be constructed on query paths such as
KNN/RANGE search, where random layer generation is not used.
### Fix
- Replace the eager `std::mt19937` member with a lazily initialized
`std::unique_ptr<std::mt19937>`.
- Initialize the generator only on the first `RandomizeLayer()` call.
### Tests
new C++ gtests added (hnsw_index_test.cc):
- `RandomGeneratorIsInitializedLazily`
### AI-assisted contribution
I used an LLM to help draft the new GTest case for verifying lazy generator
initialization.
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