Release 0.50.0

[zaidoon1]

Versions

• rust-rocksdb: 0.49.1 → 0.50.0
• rust-librocksdb-sys: 0.45.1+11.1.1 → 0.46.0+11.1.1

The minor bump is justified by the MSRV change (1.89 → 1.91), which is
technically breaking for users on older Rust toolchains.

What is in this release

(Full notes in CHANGELOG.md.)

Breaking

• MSRV bumped to 1.91.0 per the rolling 6-month policy. 1.91.0 was
  released 2025-10-30, the most recent stable that satisfied the
  6-month window at the time of the bump.

Features

• librocksdb-sys: local C-API extensions for three RocksDB C++
  options that have no upstream C wrapper yet
  (optimize_multiget_for_io, uniform_cv_threshold + kAuto,
  memtable_batch_lookup_optimization). The extensions live in
  librocksdb-sys/c-api-extensions/ and compile additively alongside
  the vendored RocksDB sources; the submodule is never modified, so
  the build works on read-only source trees and needs no extra tools
  beyond the C++ compiler.
• rust-rocksdb: three matching safe-Rust setters (plus getters
  for the two bool options):
  • BlockBasedOptions::set_index_block_search_type(IndexBlockSearchType)
    • new IndexBlockSearchType enum (Binary, Interpolation,
      Auto).
  • BlockBasedOptions::set_uniform_cv_threshold(f64).
  • Options::{set,get}_memtable_batch_lookup_optimization(bool).
  • ReadOptions::{set,get}_optimize_multiget_for_io(bool).
• AsRawPtr<rocksdb_t> impl for OptimisticTransactionDB<T>
  (gated on the raw-ptr feature), by @ksurent.

Fixes

• Re-export ColumnFamilyMetaData and CSlice from the crate root
  (Expose db::ColumnFamilyMetaData (possibly other types that are accadentally private) #224, thanks to @JadedBlueEyes).

Upstream coordination

The three C-API extensions each have a matching PR open against
facebook/rocksdb. When upstream merges any of them and we bump the
submodule to a release containing it, the corresponding declaration in
c_api_extensions.h and definition in c_api_extensions.cc will be
dropped.

• optimize_multiget_for_io: facebook/rocksdb#14752
• uniform_cv_threshold + kAuto: facebook/rocksdb#14775
• memtable_batch_lookup_optimization: facebook/rocksdb#14776

Verifications run

• cargo fmt --all -- --check — clean
• cargo clippy --all-targets -- -D warnings — clean
• cargo test --doc — 10 passed
• cargo test --test test_public_api — 1 passed
• cargo check against the new version numbers — succeeds