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diff --git a/third_party/rust/rkv/src/env.rs b/third_party/rust/rkv/src/env.rs
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+++ b/third_party/rust/rkv/src/env.rs
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+// Copyright 2018-2019 Mozilla
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
+// this file except in compliance with the License. You may obtain a copy of the
+// License at http://www.apache.org/licenses/LICENSE-2.0
+// Unless required by applicable law or agreed to in writing, software distributed
+// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+// CONDITIONS OF ANY KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations under the License.
+
+use std::{
+    fs,
+    os::raw::c_uint,
+    path::{Path, PathBuf},
+};
+
+#[cfg(any(feature = "db-dup-sort", feature = "db-int-key"))]
+use crate::backend::{BackendDatabaseFlags, DatabaseFlags};
+use crate::{
+    backend::{
+        BackendEnvironment, BackendEnvironmentBuilder, BackendRoCursorTransaction,
+        BackendRwCursorTransaction, SafeModeError,
+    },
+    error::{CloseError, StoreError},
+    readwrite::{Reader, Writer},
+    store::{single::SingleStore, CloseOptions, Options as StoreOptions},
+};
+
+#[cfg(feature = "db-dup-sort")]
+use crate::store::multi::MultiStore;
+
+#[cfg(feature = "db-int-key")]
+use crate::store::integer::IntegerStore;
+#[cfg(feature = "db-int-key")]
+use crate::store::keys::PrimitiveInt;
+
+#[cfg(all(feature = "db-dup-sort", feature = "db-int-key"))]
+use crate::store::integermulti::MultiIntegerStore;
+
+pub static DEFAULT_MAX_DBS: c_uint = 5;
+
+/// Wrapper around an `Environment` (e.g. such as an `LMDB` or `SafeMode` environment).
+#[derive(Debug)]
+pub struct Rkv<E> {
+    _path: PathBuf,
+    env: E,
+}
+
+/// Static methods.
+impl<'e, E> Rkv<E>
+where
+    E: BackendEnvironment<'e>,
+{
+    pub fn environment_builder<B>() -> B
+    where
+        B: BackendEnvironmentBuilder<'e, Environment = E>,
+    {
+        B::new()
+    }
+
+    /// Return a new Rkv environment that supports up to `DEFAULT_MAX_DBS` open databases.
+    #[allow(clippy::new_ret_no_self)]
+    pub fn new<B>(path: &Path) -> Result<Rkv<E>, StoreError>
+    where
+        B: BackendEnvironmentBuilder<'e, Environment = E>,
+    {
+        Rkv::with_capacity::<B>(path, DEFAULT_MAX_DBS)
+    }
+
+    /// Return a new Rkv environment that supports the specified number of open databases.
+    pub fn with_capacity<B>(path: &Path, max_dbs: c_uint) -> Result<Rkv<E>, StoreError>
+    where
+        B: BackendEnvironmentBuilder<'e, Environment = E>,
+    {
+        let mut builder = B::new();
+        builder.set_max_dbs(max_dbs);
+
+        // Future: set flags, maximum size, etc. here if necessary.
+        Rkv::from_builder(path, builder)
+    }
+
+    /// Return a new Rkv environment from the provided builder.
+    pub fn from_builder<B>(path: &Path, builder: B) -> Result<Rkv<E>, StoreError>
+    where
+        B: BackendEnvironmentBuilder<'e, Environment = E>,
+    {
+        Ok(Rkv {
+            _path: path.into(),
+            env: builder.open(path).map_err(|e| e.into())?,
+        })
+    }
+}
+
+/// Store creation methods.
+impl<'e, E> Rkv<E>
+where
+    E: BackendEnvironment<'e>,
+{
+    /// Return all created databases.
+    pub fn get_dbs(&self) -> Result<Vec<Option<String>>, StoreError> {
+        self.env.get_dbs().map_err(|e| e.into())
+    }
+
+    /// Create or Open an existing database in (&[u8] -> Single Value) mode.
+    /// Note: that create=true cannot be called concurrently with other operations so if
+    /// you are sure that the database exists, call this with create=false.
+    pub fn open_single<'s, T>(
+        &self,
+        name: T,
+        opts: StoreOptions<E::Flags>,
+    ) -> Result<SingleStore<E::Database>, StoreError>
+    where
+        T: Into<Option<&'s str>>,
+    {
+        self.open(name, opts).map(SingleStore::new)
+    }
+
+    /// Create or Open an existing database in (Integer -> Single Value) mode.
+    /// Note: that create=true cannot be called concurrently with other operations so if
+    /// you are sure that the database exists, call this with create=false.
+    #[cfg(feature = "db-int-key")]
+    pub fn open_integer<'s, T, K>(
+        &self,
+        name: T,
+        mut opts: StoreOptions<E::Flags>,
+    ) -> Result<IntegerStore<E::Database, K>, StoreError>
+    where
+        K: PrimitiveInt,
+        T: Into<Option<&'s str>>,
+    {
+        opts.flags.set(DatabaseFlags::INTEGER_KEY, true);
+        self.open(name, opts).map(IntegerStore::new)
+    }
+
+    /// Create or Open an existing database in (&[u8] -> Multiple Values) mode.
+    /// Note: that create=true cannot be called concurrently with other operations so if
+    /// you are sure that the database exists, call this with create=false.
+    #[cfg(feature = "db-dup-sort")]
+    pub fn open_multi<'s, T>(
+        &self,
+        name: T,
+        mut opts: StoreOptions<E::Flags>,
+    ) -> Result<MultiStore<E::Database>, StoreError>
+    where
+        T: Into<Option<&'s str>>,
+    {
+        opts.flags.set(DatabaseFlags::DUP_SORT, true);
+        self.open(name, opts).map(MultiStore::new)
+    }
+
+    /// Create or Open an existing database in (Integer -> Multiple Values) mode.
+    /// Note: that create=true cannot be called concurrently with other operations so if
+    /// you are sure that the database exists, call this with create=false.
+    #[cfg(all(feature = "db-dup-sort", feature = "db-int-key"))]
+    pub fn open_multi_integer<'s, T, K>(
+        &self,
+        name: T,
+        mut opts: StoreOptions<E::Flags>,
+    ) -> Result<MultiIntegerStore<E::Database, K>, StoreError>
+    where
+        K: PrimitiveInt,
+        T: Into<Option<&'s str>>,
+    {
+        opts.flags.set(DatabaseFlags::INTEGER_KEY, true);
+        opts.flags.set(DatabaseFlags::DUP_SORT, true);
+        self.open(name, opts).map(MultiIntegerStore::new)
+    }
+
+    fn open<'s, T>(&self, name: T, opts: StoreOptions<E::Flags>) -> Result<E::Database, StoreError>
+    where
+        T: Into<Option<&'s str>>,
+    {
+        if opts.create {
+            self.env
+                .create_db(name.into(), opts.flags)
+                .map_err(|e| match e.into() {
+                    #[cfg(feature = "lmdb")]
+                    StoreError::LmdbError(lmdb::Error::BadRslot) => {
+                        StoreError::open_during_transaction()
+                    }
+                    StoreError::SafeModeError(SafeModeError::DbsIllegalOpen) => {
+                        StoreError::open_during_transaction()
+                    }
+                    e => e,
+                })
+        } else {
+            self.env.open_db(name.into()).map_err(|e| match e.into() {
+                #[cfg(feature = "lmdb")]
+                StoreError::LmdbError(lmdb::Error::BadRslot) => {
+                    StoreError::open_during_transaction()
+                }
+                StoreError::SafeModeError(SafeModeError::DbsIllegalOpen) => {
+                    StoreError::open_during_transaction()
+                }
+                e => e,
+            })
+        }
+    }
+}
+
+/// Read and write accessors.
+impl<'e, E> Rkv<E>
+where
+    E: BackendEnvironment<'e>,
+{
+    /// Create a read transaction.  There can be multiple concurrent readers for an
+    /// environment, up to the maximum specified by LMDB (default 126), and you can open
+    /// readers while a write transaction is active.
+    pub fn read<T>(&'e self) -> Result<Reader<T>, StoreError>
+    where
+        E: BackendEnvironment<'e, RoTransaction = T>,
+        T: BackendRoCursorTransaction<'e, Database = E::Database>,
+    {
+        Ok(Reader::new(self.env.begin_ro_txn().map_err(|e| e.into())?))
+    }
+
+    /// Create a write transaction.  There can be only one write transaction active at any
+    /// given time, so trying to create a second one will block until the first is
+    /// committed or aborted.
+    pub fn write<T>(&'e self) -> Result<Writer<T>, StoreError>
+    where
+        E: BackendEnvironment<'e, RwTransaction = T>,
+        T: BackendRwCursorTransaction<'e, Database = E::Database>,
+    {
+        Ok(Writer::new(self.env.begin_rw_txn().map_err(|e| e.into())?))
+    }
+}
+
+/// Other environment methods.
+impl<'e, E> Rkv<E>
+where
+    E: BackendEnvironment<'e>,
+{
+    /// Flush the data buffers to disk. This call is only useful, when the environment was
+    /// open with either `NO_SYNC`, `NO_META_SYNC` or `MAP_ASYNC` (see below). The call is
+    /// not valid if the environment was opened with `READ_ONLY`.
+    ///
+    /// Data is always written to disk when `transaction.commit()` is called, but the
+    /// operating system may keep it buffered. LMDB always flushes the OS buffers upon
+    /// commit as well, unless the environment was opened with `NO_SYNC` or in part
+    /// `NO_META_SYNC`.
+    ///
+    /// `force`: if true, force a synchronous flush. Otherwise if the environment has the
+    /// `NO_SYNC` flag set the flushes will be omitted, and with `MAP_ASYNC` they will
+    /// be asynchronous.
+    pub fn sync(&self, force: bool) -> Result<(), StoreError> {
+        self.env.sync(force).map_err(|e| e.into())
+    }
+
+    /// Retrieve statistics about this environment.
+    ///
+    /// It includes:
+    ///   * Page size in bytes
+    ///   * B-tree depth
+    ///   * Number of internal (non-leaf) pages
+    ///   * Number of leaf pages
+    ///   * Number of overflow pages
+    ///   * Number of data entries
+    pub fn stat(&self) -> Result<E::Stat, StoreError> {
+        self.env.stat().map_err(|e| e.into())
+    }
+
+    /// Retrieve information about this environment.
+    ///
+    /// It includes:
+    ///   * Map size in bytes
+    ///   * The last used page number
+    ///   * The last transaction ID
+    ///   * Max number of readers allowed
+    ///   * Number of readers in use
+    pub fn info(&self) -> Result<E::Info, StoreError> {
+        self.env.info().map_err(|e| e.into())
+    }
+
+    /// Retrieve the load ratio (# of used pages / total pages) about this environment.
+    ///
+    /// With the formular: (last_page_no - freelist_pages) / total_pages.
+    /// A value of `None` means that the backend doesn't ever need to be resized.
+    pub fn load_ratio(&self) -> Result<Option<f32>, StoreError> {
+        self.env.load_ratio().map_err(|e| e.into())
+    }
+
+    /// Sets the size of the memory map to use for the environment.
+    ///
+    /// This can be used to resize the map when the environment is already open. You can
+    /// also use `Rkv::environment_builder()` to set the map size during the `Rkv`
+    /// initialization.
+    ///
+    /// Note:
+    ///
+    /// * No active transactions allowed when performing resizing in this process. It's up
+    ///   to the consumer to enforce that.
+    ///
+    /// * The size should be a multiple of the OS page size. Any attempt to set a size
+    ///   smaller than the space already consumed by the environment will be silently
+    ///   changed to the current size of the used space.
+    ///
+    /// * In the multi-process case, once a process resizes the map, other processes need
+    ///   to either re-open the environment, or call set_map_size with size 0 to update
+    ///   the environment. Otherwise, new transaction creation will fail with
+    ///   `LmdbError::MapResized`.
+    pub fn set_map_size(&self, size: usize) -> Result<(), StoreError> {
+        self.env.set_map_size(size).map_err(Into::into)
+    }
+
+    /// Closes this environment and optionally deletes all its files from disk. Doesn't
+    /// delete the folder used when opening the environment.
+    pub fn close(self, options: CloseOptions) -> Result<(), CloseError> {
+        let files = self.env.get_files_on_disk();
+        drop(self);
+
+        if options.delete {
+            for file in files {
+                fs::remove_file(file)?;
+            }
+        }
+
+        Ok(())
+    }
+}