• Implement std::error::Error for SetDurabilityError
• Fix compilation error on various non-tier-1 platforms, such as wasm32-unknown

• Fix performance issue where a transaction with a large number of writes would cause
  WriteTransaction::abort() and committing non-durable transactions to become slow

• Fix correctness issue with range(), extract_from_if(), and retain_in(). If a RangeBounds
  with start > end was passed as an argument and start and end keys were stored in different
  internal pages in the database (i.e. a sufficient condition is that more than 4KiB of key-value
  pairs were between the two keys) then these methods would perform as if the argument had been
  start..
• Fix performance regression, from redb 2.x, where Durability::None commits could become linearly
  slower during a series of transactions.

• Fix correctness issue with range(), extract_from_if(), and retain_in(). If a RangeBounds
  with start > end was passed as an argument and start and end keys were stored in different
  internal pages in the database (i.e. a sufficient condition is that more than 4KiB of key-value
  pairs were between the two keys) then these methods would perform as if the argument had been
  start..

• Fix correctness issue with range(), drain(), and drain_filter(). If a RangeBounds
  with start > end was passed as an argument and start and end keys were stored in different
  internal pages in the database (i.e. a sufficient condition is that more than 4KiB of key-value
  pairs were between the two keys) then these methods would perform as if the argument had been
  start..

3.0.0 - 2025-08-09

Removes support for file format v2.

Use Database::upgrade(), in redb 2.6, to migrate to the v3 file format.

General storage optimizations

The v3 file format has been further optimized to reduce the size of the database. Databases with only
a few small keys will see the largest benefit, and the minimum size of a database file has decreased
from ~2.5MiB to ~50KiB. To achieve the smallest file size call Database::compact() before
dropping the Database.

Additionally, performance is ~15% better in bulk load benchmarks. This was achieved by implementing
a custom hash function for various in-memory HashSets and HashMaps, and by optimizing the usage
of buffers held in Arcs to reduce the number of atomic instructions executed.

Optimize storage of tuple types

Storage of variable width tuple types with arity greater than 1 is more efficient. The new format
elides the length of any fixed width fields and uses varint encoding for the lengths of all variable
width fields.

Note that this encoding is not compatible with the serialization of variable width tuples used in prior versions.
To load tuple data created prior to version 3.0, wrap them in the Legacy type.
For example, TableDefinition<u64, (&str, u32)> becomes TableDefinition<u64, Legacy<(&str, u32)>>.
Fixed width tuples, such as (u32, u64) are backwards compatible.

Derive for Key and Value traits

Key and Value can be derived using the redb-derive crate. Note that it does not support
schema migration. The recommended pattern to migrate schema is to create a new table, and then
perform a migration from the old table to the new table.

Read-only multi-process support

Multiple processes may open the same database file for reading by using the new ReadOnlyDatabase
type. On platforms which support file locks, this acquires a shared lock on the database file.

Enable garbage collection in Durability::None transactions

Non-durable transactions will now free pages when possible (pages allocated in a preceding
non-durable transaction which are no longer referenced).
This resolves an issue where a long sequence of non-durable transactions led to significant growth
in the size of the database file.
This change increases the RAM required for a sequence of non-durable transactions, such that RAM
proportional to the net change in the database is now used. However, it will never use more than
about 0.2% of the database file size.

Other changes

• Add ReadOnlyDatabase
• Add Builder::open_read_only()
• Add StorageBackend::close()
• Add Table::get_mut()
• Add chrono_v0_4 feature flag which enables serialization of the NaiveDate, NaiveTime,
  NaiveDatetime, DateTime<FixedOffset>, and FixedOffset types in the chrono crate
• Add uuid feature flag which enables serialization of the Uuid type in the uuid crate
• Change StorageBackend::read() to accept a &mut [u8] output argument instead of returning
  a Vec<u8>
• Change Table::insert_reserve() to take usize instead of u32 as the argument type
• Change TypeName::name() to be public
• Change ReadTransactionStillInUse to contain a Box
• Change set_durability() to return a Result
• Move Database::cache_stats() and Database::begin_read() to ReadableDatabase trait
• Rename AccessGuardMut to AccessGuardMutInPlace. Note that a new AccessGuardMut struct has
  been added; it serves a different purpose
• Remove Durability::Paranoid
• Fix a rare case where check_integrity() returned Ok(false) even though no repair was required,
  when called on a database that was not shutdown cleanly and was automatically repaired when opened
• Disallow access to the database from read transactions after the Database as been
  dropped. Access will now return DatabaseClosed

• Forward compatibility improvement which makes the file format more flexible to support a potential
  future optimization

• Fix a forward compatibility issue which caused a crash when opening databases created with redb
  3.x. Note that opening 3.x databases with redb 2.x is not generally supported and only works
  in certain situations.

Add support for the v3 file format.

This file format improves savepoints.
Savepoints in the v3 format have constant, and small, overhead. Creating
and restoring them is also much faster. The v3 file format also supports
savepoints on large databases (v2 has a limit around 32TB). This release
creates v2 databases by default. Use Builder::create_with_file_format_v3()
and Database::upgrade(), respectively, to enable and migrate to v3.

The upcoming 3.0 release will only support the v3 file format.

• Add Builder::create_with_file_format_v3()
• Add Database::upgrade()

• Add rename_table() and rename_multimap_table()
• Add Key and Value implementations for the unary tuple type (i.e. (T,))
• Fix an issue which could cause a panic when concurrently performing read and write transactions,
  when debug_assertions were enabled
• Optimize retain() and retain_in() to use less space in the database file
• Improve handling of some internal errors to return LockPoisoned instead of panicking