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236 lines
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236 lines
10 KiB
// Copyright 2018-2019 Mozilla
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
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// this file except in compliance with the License. You may obtain a copy of the
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// License at http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software distributed
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// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
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// CONDITIONS OF ANY KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations under the License.
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#![allow(clippy::from_over_into)] // TODO: `Into` implementations in [safe/lmdb]/flags.rs
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//! A simple, humane, typed key-value storage solution. It supports multiple backend
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//! engines with varying guarantees, such as [LMDB](http://www.lmdb.tech/doc/) for
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//! performance, or "SafeMode" for reliability.
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//!
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//! It aims to achieve the following:
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//!
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//! - Avoid sharp edges (e.g., obscure error codes for common situations).
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//! - Correctly restrict access to one handle per process via a
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//! [Manager](struct.Manager.html).
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//! - Use Rust's type system to make single-typed key stores safe and ergonomic.
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//! - Encode and decode values via [bincode](https://docs.rs/bincode/)/[serde](https://docs.rs/serde/)
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//! and type tags, achieving platform-independent storage and input/output flexibility.
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//!
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//! It exposes these primary abstractions:
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//!
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//! - [Manager](struct.Manager.html): a singleton that controls access to environments
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//! - [Rkv](struct.Rkv.html): an environment contains a set of key/value databases
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//! - [SingleStore](store/single/struct.SingleStore.html): a database contains a set of
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//! key/value pairs
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//!
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//! Keys can be anything that implements `AsRef<[u8]>` or integers
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//! (when accessing an [IntegerStore](store/integer/struct.IntegerStore.html)).
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//!
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//! Values can be any of the types defined by the [Value](value/enum.Value.html) enum,
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//! including:
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//!
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//! - booleans (`Value::Bool`)
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//! - integers (`Value::I64`, `Value::U64`)
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//! - floats (`Value::F64`)
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//! - strings (`Value::Str`)
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//! - blobs (`Value::Blob`)
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//!
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//! See [Value](value/enum.Value.html) for the complete list of supported types.
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//!
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//! ## Basic Usage
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//! ```
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//! use rkv::{Manager, Rkv, SingleStore, Value, StoreOptions};
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//! use rkv::backend::{SafeMode, SafeModeEnvironment};
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//! use std::fs;
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//! use tempfile::Builder;
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//!
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//! // First determine the path to the environment, which is represented on disk as a
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//! // directory containing two files:
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//! //
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//! // * a data file containing the key/value stores
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//! // * a lock file containing metadata about current transactions
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//! //
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//! // In this example, we use the `tempfile` crate to create the directory.
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//! //
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//! let root = Builder::new().prefix("simple-db").tempdir().unwrap();
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//! fs::create_dir_all(root.path()).unwrap();
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//! let path = root.path();
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//!
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//! // The `Manager` enforces that each process opens the same environment at most once by
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//! // caching a handle to each environment that it opens. Use it to retrieve the handle
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//! // to an opened environment—or create one if it hasn't already been opened:
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//! let mut manager = Manager::<SafeModeEnvironment>::singleton().write().unwrap();
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//! let created_arc = manager.get_or_create(path, Rkv::new::<SafeMode>).unwrap();
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//! let env = created_arc.read().unwrap();
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//!
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//! // Then you can use the environment handle to get a handle to a datastore:
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//! let store = env.open_single("mydb", StoreOptions::create()).unwrap();
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//!
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//! {
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//! // Use a write transaction to mutate the store via a `Writer`. There can be only
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//! // one writer for a given environment, so opening a second one will block until
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//! // the first completes.
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//! let mut writer = env.write().unwrap();
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//!
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//! // Keys are `AsRef<[u8]>`, while values are `Value` enum instances. Use the `Blob`
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//! // variant to store arbitrary collections of bytes. Putting data returns a
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//! // `Result<(), StoreError>`, where StoreError is an enum identifying the reason
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//! // for a failure.
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//! store.put(&mut writer, "int", &Value::I64(1234)).unwrap();
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//! store.put(&mut writer, "uint", &Value::U64(1234_u64)).unwrap();
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//! store.put(&mut writer, "float", &Value::F64(1234.0.into())).unwrap();
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//! store.put(&mut writer, "instant", &Value::Instant(1528318073700)).unwrap();
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//! store.put(&mut writer, "boolean", &Value::Bool(true)).unwrap();
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//! store.put(&mut writer, "string", &Value::Str("Héllo, wörld!")).unwrap();
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//! store.put(&mut writer, "json", &Value::Json(r#"{"foo":"bar", "number": 1}"#)).unwrap();
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//! store.put(&mut writer, "blob", &Value::Blob(b"blob")).unwrap();
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//!
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//! // You must commit a write transaction before the writer goes out of scope, or the
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//! // transaction will abort and the data won't persist.
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//! writer.commit().unwrap();
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//! }
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//!
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//! {
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//! // Use a read transaction to query the store via a `Reader`. There can be multiple
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//! // concurrent readers for a store, and readers never block on a writer nor other
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//! // readers.
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//! let reader = env.read().expect("reader");
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//!
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//! // Keys are `AsRef<u8>`, and the return value is `Result<Option<Value>, StoreError>`.
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//! println!("Get int {:?}", store.get(&reader, "int").unwrap());
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//! println!("Get uint {:?}", store.get(&reader, "uint").unwrap());
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//! println!("Get float {:?}", store.get(&reader, "float").unwrap());
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//! println!("Get instant {:?}", store.get(&reader, "instant").unwrap());
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//! println!("Get boolean {:?}", store.get(&reader, "boolean").unwrap());
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//! println!("Get string {:?}", store.get(&reader, "string").unwrap());
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//! println!("Get json {:?}", store.get(&reader, "json").unwrap());
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//! println!("Get blob {:?}", store.get(&reader, "blob").unwrap());
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//!
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//! // Retrieving a non-existent value returns `Ok(None)`.
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//! println!("Get non-existent value {:?}", store.get(&reader, "non-existent").unwrap());
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//!
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//! // A read transaction will automatically close once the reader goes out of scope,
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//! // so isn't necessary to close it explicitly, although you can do so by calling
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//! // `Reader.abort()`.
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//! }
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//!
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//! {
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//! // Aborting a write transaction rolls back the change(s).
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//! let mut writer = env.write().unwrap();
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//! store.put(&mut writer, "foo", &Value::Str("bar")).unwrap();
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//! writer.abort();
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//! let reader = env.read().expect("reader");
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//! println!("It should be None! ({:?})", store.get(&reader, "foo").unwrap());
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//! }
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//!
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//! {
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//! // Explicitly aborting a transaction is not required unless an early abort is
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//! // desired, since both read and write transactions will implicitly be aborted once
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//! // they go out of scope.
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//! {
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//! let mut writer = env.write().unwrap();
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//! store.put(&mut writer, "foo", &Value::Str("bar")).unwrap();
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//! }
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//! let reader = env.read().expect("reader");
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//! println!("It should be None! ({:?})", store.get(&reader, "foo").unwrap());
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//! }
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//!
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//! {
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//! // Deleting a key/value pair also requires a write transaction.
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//! let mut writer = env.write().unwrap();
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//! store.put(&mut writer, "foo", &Value::Str("bar")).unwrap();
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//! store.put(&mut writer, "bar", &Value::Str("baz")).unwrap();
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//! store.delete(&mut writer, "foo").unwrap();
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//!
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//! // A write transaction also supports reading, and the version of the store that it
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//! // reads includes the changes it has made regardless of the commit state of that
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//! // transaction.
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//! // In the code above, "foo" and "bar" were put into the store, then "foo" was
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//! // deleted so only "bar" will return a result when the database is queried via the
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//! // writer.
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//! println!("It should be None! ({:?})", store.get(&writer, "foo").unwrap());
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//! println!("Get bar ({:?})", store.get(&writer, "bar").unwrap());
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//!
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//! // But a reader won't see that change until the write transaction is committed.
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//! {
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//! let reader = env.read().expect("reader");
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//! println!("Get foo {:?}", store.get(&reader, "foo").unwrap());
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//! println!("Get bar {:?}", store.get(&reader, "bar").unwrap());
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//! }
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//! writer.commit().unwrap();
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//! {
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//! let reader = env.read().expect("reader");
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//! println!("It should be None! ({:?})", store.get(&reader, "foo").unwrap());
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//! println!("Get bar {:?}", store.get(&reader, "bar").unwrap());
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//! }
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//!
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//! // Committing a transaction consumes the writer, preventing you from reusing it by
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//! // failing at compile time with an error. This line would report "error[E0382]:
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//! // borrow of moved value: `writer`".
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//! // store.put(&mut writer, "baz", &Value::Str("buz")).unwrap();
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//! }
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//!
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//! {
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//! // Clearing all the entries in the store with a write transaction.
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//! {
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//! let mut writer = env.write().unwrap();
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//! store.put(&mut writer, "foo", &Value::Str("bar")).unwrap();
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//! store.put(&mut writer, "bar", &Value::Str("baz")).unwrap();
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//! writer.commit().unwrap();
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//! }
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//!
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//! {
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//! let mut writer = env.write().unwrap();
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//! store.clear(&mut writer).unwrap();
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//! writer.commit().unwrap();
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//! }
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//!
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//! {
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//! let reader = env.read().expect("reader");
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//! println!("It should be None! ({:?})", store.get(&reader, "foo").unwrap());
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//! println!("It should be None! ({:?})", store.get(&reader, "bar").unwrap());
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//! }
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//!
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//! }
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//!
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//! ```
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mod env;
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mod error;
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mod helpers;
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mod manager;
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mod readwrite;
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pub mod backend;
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#[cfg(feature = "lmdb")]
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pub mod migrator;
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pub mod store;
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pub mod value;
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pub use backend::{DatabaseFlags, EnvironmentFlags, WriteFlags};
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pub use env::Rkv;
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pub use error::{DataError, MigrateError, StoreError};
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pub use manager::Manager;
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#[cfg(feature = "lmdb")]
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pub use migrator::Migrator;
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pub use readwrite::{Readable, Reader, Writer};
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pub use store::{keys::EncodableKey, single::SingleStore, CloseOptions, Options as StoreOptions};
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pub use value::{OwnedValue, Value};
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#[cfg(feature = "db-dup-sort")]
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pub use store::multi::MultiStore;
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#[cfg(feature = "db-int-key")]
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pub use store::integer::IntegerStore;
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#[cfg(feature = "db-int-key")]
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pub use store::keys::PrimitiveInt;
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#[cfg(all(feature = "db-dup-sort", feature = "db-int-key"))]
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pub use store::integermulti::MultiIntegerStore;
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