mmtkvdb
mmtkvdb
is a crate for Rust which provides a memory-mapped key-value
database. It uses LMDB and links with an existing liblmdb
on the system.
Safety
Because of how memory-mapped I/O is being used and also because of certain
assumptions of the underlying LMDB API, opening environments and databases
requires unsafe
Rust (i.e. the programmer must ensure that certain
preconditions are met that cannot be enforced by the compiler to avoid
undefined behavior). If you aim to program in safe Rust only, this Rust
library is not suitable for you.
API Documentation
For documentation on how to use this crate, refer to the example in
src/lib.rs
.
License
See contained LICENSE
file (MIT License).
Changelog
- 2023-03-17: Version 0.15.0
- Several deprecated items have been removed:
DbOptions
Env::open_dbs
EnvRw::create_dbs
EnvRef::open_or_create_dbs
Txn::cursor_search_key_get_key
EnvRw::drop_db
requires&mut self
Env::clear_stale_readers
returnsstd::io::Result<usize>
- Improved documentation in regard to use of
unsafe
- Several deprecated items have been removed:
- 2023-03-16: Version 0.14.1
- Critical bug fixes:
- Opening the same database twice (in the same process) might have caused UB. This has been fixed.
- LMDB databases might have been closed twice if an error occurred during opening, which might have caused UB in that case. This has been fixed.
- Method
Txn::cursor_get_current_value_count
must only be called for databases withKeysDuplicate
. This is enforced by the methods signature now and could have been resulting in UB previously. - A memory leak in
EnvRw::drop_db
has been fixed and code has been cleaned up and properly documented to avoid this in the future. - Write transactions which created a cursor but never wrote any data
might have resulted in
mdb_cursor_close
being called aftermdb_dbi_close
, which is not allowed for write transaction by LMDB's API specification. This has been fixed.
- All LMDB databases get closed explicitly now before the LMDB environment is closed.
- Missing implementations for
Send
andSync
have been added forEnvRo
,EnvRw
,Db
, andCursor
. - Deprecations:
- A warning has been added to the documentation, stating that
EnvRw::drop_db
will require&mut self
in future. - Methods for opening several databases at once (with the same types) have been deprecated. The methods opening a single database should be used instead.
- A warning has been added to the documentation, stating that
- Improved "Safety" sections in public API documentation
- Code cleanup in regard to safety:
- Use
unsafe_op_in_unsafe_fn
lint and added correspondingunsafe
blocks - Added
SAFETY
comments insrc/lib.rs
- Correctly marked some private functions as
unsafe
and documented their use properly
- Use
- Critical bug fixes:
- 2023-03-10: Version 0.14.0
TxnRo
is now!Sync
(but stillSend
); users are expected to use a mutex where synchronization is required- Deprecated
Txn::cursor_search_key_get_key
- Improved documentation regarding return values of cursor methods
- Added benchmarks
For older changes, refer to the CHANGELOG.md
file.