heed/env.rs
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use std::any::TypeId;
use std::cmp::Ordering;
use std::collections::hash_map::{Entry, HashMap};
use std::ffi::{c_void, CString};
use std::fs::{File, Metadata};
use std::io::ErrorKind::NotFound;
#[cfg(unix)]
use std::os::unix::{
ffi::OsStrExt,
io::{AsRawFd, BorrowedFd, RawFd},
};
use std::panic::catch_unwind;
use std::path::{Path, PathBuf};
use std::process::abort;
use std::sync::{Arc, RwLock};
use std::time::Duration;
#[cfg(windows)]
use std::{
ffi::OsStr,
os::windows::io::{AsRawHandle, BorrowedHandle, RawHandle},
};
use std::{fmt, io, mem, ptr};
use heed_traits::{Comparator, LexicographicComparator};
use once_cell::sync::Lazy;
use synchronoise::event::SignalEvent;
use crate::cursor::MoveOperation;
use crate::database::DatabaseOpenOptions;
use crate::mdb::error::mdb_result;
use crate::mdb::ffi;
use crate::mdb::lmdb_flags::AllDatabaseFlags;
use crate::{Database, EnvFlags, Error, Result, RoCursor, RoTxn, RwTxn, Unspecified};
/// The list of opened environments, the value is an optional environment, it is None
/// when someone asks to close the environment, closing is a two-phase step, to make sure
/// noone tries to open the same environment between these two phases.
///
/// Trying to open a None marked environment returns an error to the user trying to open it.
static OPENED_ENV: Lazy<RwLock<HashMap<PathBuf, EnvEntry>>> = Lazy::new(RwLock::default);
struct EnvEntry {
env: Option<Env>,
signal_event: Arc<SignalEvent>,
options: EnvOpenOptions,
}
// Thanks to the mozilla/rkv project
// Workaround the UNC path on Windows, see https://github.com/rust-lang/rust/issues/42869.
// Otherwise, `Env::from_env()` will panic with error_no(123).
#[cfg(not(windows))]
fn canonicalize_path(path: &Path) -> io::Result<PathBuf> {
path.canonicalize()
}
#[cfg(windows)]
fn canonicalize_path(path: &Path) -> io::Result<PathBuf> {
let canonical = path.canonicalize()?;
let url = url::Url::from_file_path(&canonical)
.map_err(|_e| io::Error::new(io::ErrorKind::Other, "URL passing error"))?;
url.to_file_path()
.map_err(|_e| io::Error::new(io::ErrorKind::Other, "path canonicalization error"))
}
#[cfg(windows)]
/// Adding a 'missing' trait from windows OsStrExt
trait OsStrExtLmdb {
fn as_bytes(&self) -> &[u8];
}
#[cfg(windows)]
impl OsStrExtLmdb for OsStr {
fn as_bytes(&self) -> &[u8] {
&self.to_str().unwrap().as_bytes()
}
}
#[cfg(unix)]
fn get_file_fd(file: &File) -> RawFd {
file.as_raw_fd()
}
#[cfg(windows)]
fn get_file_fd(file: &File) -> RawHandle {
file.as_raw_handle()
}
#[cfg(unix)]
/// Get metadata from a file descriptor.
unsafe fn metadata_from_fd(raw_fd: RawFd) -> io::Result<Metadata> {
let fd = BorrowedFd::borrow_raw(raw_fd);
let owned = fd.try_clone_to_owned()?;
File::from(owned).metadata()
}
#[cfg(windows)]
/// Get metadata from a file descriptor.
unsafe fn metadata_from_fd(raw_fd: RawHandle) -> io::Result<Metadata> {
let fd = BorrowedHandle::borrow_raw(raw_fd);
let owned = fd.try_clone_to_owned()?;
File::from(owned).metadata()
}
/// Options and flags which can be used to configure how an environment is opened.
#[derive(Clone, Debug, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct EnvOpenOptions {
map_size: Option<usize>,
max_readers: Option<u32>,
max_dbs: Option<u32>,
flags: EnvFlags,
}
impl Default for EnvOpenOptions {
fn default() -> Self {
Self::new()
}
}
impl EnvOpenOptions {
/// Creates a blank new set of options ready for configuration.
pub fn new() -> EnvOpenOptions {
EnvOpenOptions {
map_size: None,
max_readers: None,
max_dbs: None,
flags: EnvFlags::empty(),
}
}
/// Set the size of the memory map to use for this environment.
pub fn map_size(&mut self, size: usize) -> &mut Self {
self.map_size = Some(size);
self
}
/// Set the maximum number of threads/reader slots for the environment.
pub fn max_readers(&mut self, readers: u32) -> &mut Self {
self.max_readers = Some(readers);
self
}
/// Set the maximum number of named databases for the environment.
pub fn max_dbs(&mut self, dbs: u32) -> &mut Self {
self.max_dbs = Some(dbs);
self
}
/// Set one or more [LMDB flags](http://www.lmdb.tech/doc/group__mdb__env.html).
/// ```
/// use std::fs;
/// use std::path::Path;
/// use heed::{EnvOpenOptions, Database, EnvFlags};
/// use heed::types::*;
///
/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
/// fs::create_dir_all(Path::new("target").join("database.mdb"))?;
/// let mut env_builder = EnvOpenOptions::new();
/// unsafe { env_builder.flags(EnvFlags::NO_TLS | EnvFlags::NO_META_SYNC); }
/// let dir = tempfile::tempdir().unwrap();
/// let env = unsafe { env_builder.open(dir.path())? };
///
/// // we will open the default unnamed database
/// let mut wtxn = env.write_txn()?;
/// let db: Database<Str, U32<byteorder::NativeEndian>> = env.create_database(&mut wtxn, None)?;
///
/// // opening a write transaction
/// db.put(&mut wtxn, "seven", &7)?;
/// db.put(&mut wtxn, "zero", &0)?;
/// db.put(&mut wtxn, "five", &5)?;
/// db.put(&mut wtxn, "three", &3)?;
/// wtxn.commit()?;
///
/// // force the OS to flush the buffers (see Flag::NoSync and Flag::NoMetaSync).
/// env.force_sync();
///
/// // opening a read transaction
/// // to check if those values are now available
/// let mut rtxn = env.read_txn()?;
///
/// let ret = db.get(&rtxn, "zero")?;
/// assert_eq!(ret, Some(0));
///
/// let ret = db.get(&rtxn, "five")?;
/// assert_eq!(ret, Some(5));
/// # Ok(()) }
/// ```
///
/// # Safety
///
/// It is unsafe to use unsafe LMDB flags such as `NO_SYNC`, `NO_META_SYNC`, or `NO_LOCK`.
pub unsafe fn flags(&mut self, flags: EnvFlags) -> &mut Self {
self.flags |= flags;
self
}
/// Open an environment that will be located at the specified path.
///
/// # Safety
/// LMDB is backed by a memory map [^1] which comes with some safety precautions.
///
/// Memory map constructors are marked `unsafe` because of the potential
/// for Undefined Behavior (UB) using the map if the underlying file is
/// subsequently modified, in or out of process.
///
/// LMDB itself has a locking system that solves this problem,
/// but it will not save you from making mistakes yourself.
///
/// These are some things to take note of:
///
/// - Avoid long-lived transactions, they will cause the database to grow quickly [^2]
/// - Avoid aborting your process with an active transaction [^3]
/// - Do not use LMDB on remote filesystems, even between processes on the same host [^4]
/// - You must manage concurrent accesses yourself if using [`EnvFlags::NO_LOCK`] [^5]
/// - Anything that causes LMDB's lock file to be broken will cause synchronization issues and may introduce UB [^6]
///
/// `heed` itself upholds some safety invariants, including but not limited to:
/// - Calling [`EnvOpenOptions::open`] twice in the same process, at the same time is OK [^7]
///
/// For more details, it is highly recommended to read LMDB's official documentation. [^8]
///
/// [^1]: <https://en.wikipedia.org/wiki/Memory_map>
///
/// [^2]: <https://github.com/LMDB/lmdb/blob/b8e54b4c31378932b69f1298972de54a565185b1/libraries/liblmdb/lmdb.h#L107-L114>
///
/// [^3]: <https://github.com/LMDB/lmdb/blob/b8e54b4c31378932b69f1298972de54a565185b1/libraries/liblmdb/lmdb.h#L118-L121>
///
/// [^4]: <https://github.com/LMDB/lmdb/blob/b8e54b4c31378932b69f1298972de54a565185b1/libraries/liblmdb/lmdb.h#L129>
///
/// [^5]: <https://github.com/LMDB/lmdb/blob/b8e54b4c31378932b69f1298972de54a565185b1/libraries/liblmdb/lmdb.h#L129>
///
/// [^6]: <https://github.com/LMDB/lmdb/blob/b8e54b4c31378932b69f1298972de54a565185b1/libraries/liblmdb/lmdb.h#L49-L52>
///
/// [^7]: <https://github.com/LMDB/lmdb/blob/b8e54b4c31378932b69f1298972de54a565185b1/libraries/liblmdb/lmdb.h#L102-L105>
///
/// [^8]: <http://www.lmdb.tech/doc/index.html>
pub unsafe fn open<P: AsRef<Path>>(&self, path: P) -> Result<Env> {
let mut lock = OPENED_ENV.write().unwrap();
let path = match canonicalize_path(path.as_ref()) {
Err(err) => {
if err.kind() == NotFound && self.flags.contains(EnvFlags::NO_SUB_DIR) {
let path = path.as_ref();
match path.parent().zip(path.file_name()) {
Some((dir, file_name)) => canonicalize_path(dir)?.join(file_name),
None => return Err(err.into()),
}
} else {
return Err(err.into());
}
}
Ok(path) => path,
};
match lock.entry(path) {
Entry::Occupied(entry) => {
let env = entry.get().env.clone().ok_or(Error::DatabaseClosing)?;
let options = entry.get().options.clone();
if &options == self {
Ok(env)
} else {
Err(Error::BadOpenOptions { env, options })
}
}
Entry::Vacant(entry) => {
let path = entry.key();
let path_str = CString::new(path.as_os_str().as_bytes()).unwrap();
unsafe {
let mut env: *mut ffi::MDB_env = ptr::null_mut();
mdb_result(ffi::mdb_env_create(&mut env))?;
if let Some(size) = self.map_size {
if size % page_size::get() != 0 {
let msg = format!(
"map size ({}) must be a multiple of the system page size ({})",
size,
page_size::get()
);
return Err(Error::Io(io::Error::new(
io::ErrorKind::InvalidInput,
msg,
)));
}
mdb_result(ffi::mdb_env_set_mapsize(env, size))?;
}
if let Some(readers) = self.max_readers {
mdb_result(ffi::mdb_env_set_maxreaders(env, readers))?;
}
if let Some(dbs) = self.max_dbs {
mdb_result(ffi::mdb_env_set_maxdbs(env, dbs))?;
}
// When the `read-txn-no-tls` feature is enabled, we must force LMDB
// to avoid using the thread local storage, this way we allow users
// to use references of RoTxn between threads safely.
let flags = if cfg!(feature = "read-txn-no-tls") {
self.flags | EnvFlags::NO_TLS
} else {
self.flags
};
let result =
mdb_result(ffi::mdb_env_open(env, path_str.as_ptr(), flags.bits(), 0o600));
match result {
Ok(()) => {
let signal_event = Arc::new(SignalEvent::manual(false));
let inner = EnvInner { env, path: path.clone() };
let env = Env(Arc::new(inner));
let cache_entry = EnvEntry {
env: Some(env.clone()),
options: self.clone(),
signal_event,
};
entry.insert(cache_entry);
Ok(env)
}
Err(e) => {
ffi::mdb_env_close(env);
Err(e.into())
}
}
}
}
}
}
}
/// Returns a struct that allows to wait for the effective closing of an environment.
pub fn env_closing_event<P: AsRef<Path>>(path: P) -> Option<EnvClosingEvent> {
let lock = OPENED_ENV.read().unwrap();
lock.get(path.as_ref()).map(|e| EnvClosingEvent(e.signal_event.clone()))
}
/// An environment handle constructed by using [`EnvOpenOptions`].
#[derive(Clone)]
pub struct Env(Arc<EnvInner>);
impl fmt::Debug for Env {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let EnvInner { env: _, path } = self.0.as_ref();
f.debug_struct("Env").field("path", &path.display()).finish_non_exhaustive()
}
}
struct EnvInner {
env: *mut ffi::MDB_env,
path: PathBuf,
}
unsafe impl Send for EnvInner {}
unsafe impl Sync for EnvInner {}
impl Drop for EnvInner {
fn drop(&mut self) {
let mut lock = OPENED_ENV.write().unwrap();
match lock.remove(&self.path) {
None => panic!("It seems another env closed this env before"),
Some(EnvEntry { signal_event, .. }) => {
unsafe {
ffi::mdb_env_close(self.env);
}
// We signal to all the waiters that the env is closed now.
signal_event.signal();
}
}
}
}
/// A helper function that transforms the LMDB types into Rust types (`MDB_val` into slices)
/// and vice versa, the Rust types into C types (`Ordering` into an integer).
///
/// # Safety
///
/// `a` and `b` should both properly aligned, valid for reads and should point to a valid
/// [`MDB_val`][ffi::MDB_val]. An [`MDB_val`][ffi::MDB_val] (consists of a pointer and size) is
/// valid when its pointer (`mv_data`) is valid for reads of `mv_size` bytes and is not null.
unsafe extern "C" fn custom_key_cmp_wrapper<C: Comparator>(
a: *const ffi::MDB_val,
b: *const ffi::MDB_val,
) -> i32 {
let a = unsafe { ffi::from_val(*a) };
let b = unsafe { ffi::from_val(*b) };
match catch_unwind(|| C::compare(a, b)) {
Ok(Ordering::Less) => -1,
Ok(Ordering::Equal) => 0,
Ok(Ordering::Greater) => 1,
Err(_) => abort(),
}
}
/// A representation of LMDB's default comparator behavior.
///
/// This enum is used to indicate the absence of a custom comparator for an LMDB
/// database instance. When a [`Database`] is created or opened with
/// [`DefaultComparator`], it signifies that the comparator should not be explicitly
/// set via [`ffi::mdb_set_compare`]. Consequently, the database
/// instance utilizes LMDB's built-in default comparator, which inherently performs
/// lexicographic comparison of keys.
///
/// This comparator's lexicographic implementation is employed in scenarios involving
/// prefix iterators. Specifically, methods other than [`Comparator::compare`] are utilized
/// to determine the lexicographic successors and predecessors of byte sequences, which
/// is essential for these iterators' operation.
///
/// When a custom comparator is provided, the wrapper is responsible for setting
/// it with the [`ffi::mdb_set_compare`] function, which overrides the default comparison
/// behavior of LMDB with the user-defined logic.
pub enum DefaultComparator {}
impl LexicographicComparator for DefaultComparator {
#[inline]
fn compare_elem(a: u8, b: u8) -> Ordering {
a.cmp(&b)
}
#[inline]
fn successor(elem: u8) -> Option<u8> {
match elem {
u8::MAX => None,
elem => Some(elem + 1),
}
}
#[inline]
fn predecessor(elem: u8) -> Option<u8> {
match elem {
u8::MIN => None,
elem => Some(elem - 1),
}
}
#[inline]
fn max_elem() -> u8 {
u8::MAX
}
#[inline]
fn min_elem() -> u8 {
u8::MIN
}
}
/// Whether to perform compaction while copying an environment.
#[derive(Debug, Copy, Clone)]
pub enum CompactionOption {
/// Omit free pages and sequentially renumber all pages in output.
///
/// This option consumes more CPU and runs more slowly than the default.
/// Currently it fails if the environment has suffered a page leak.
Enabled,
/// Copy everything without taking any special action about free pages.
Disabled,
}
/// Whether to enable or disable flags in [`Env::set_flags`].
#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum FlagSetMode {
/// Enable the flags.
Enable,
/// Disable the flags.
Disable,
}
impl FlagSetMode {
/// Convert the enum into the `i32` required by LMDB.
/// "A non-zero value sets the flags, zero clears them."
/// <http://www.lmdb.tech/doc/group__mdb.html#ga83f66cf02bfd42119451e9468dc58445>
fn as_mdb_env_set_flags_input(self) -> i32 {
match self {
Self::Enable => 1,
Self::Disable => 0,
}
}
}
impl Env {
pub(crate) fn env_mut_ptr(&self) -> *mut ffi::MDB_env {
self.0.env
}
/// The size of the data file on disk.
///
/// # Example
///
/// ```
/// use heed::EnvOpenOptions;
///
/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
/// let dir = tempfile::tempdir()?;
/// let size_in_bytes = 1024 * 1024;
/// let env = unsafe { EnvOpenOptions::new().map_size(size_in_bytes).open(dir.path())? };
///
/// let actual_size = env.real_disk_size()? as usize;
/// assert!(actual_size < size_in_bytes);
/// # Ok(()) }
/// ```
pub fn real_disk_size(&self) -> Result<u64> {
let mut fd = mem::MaybeUninit::uninit();
unsafe { mdb_result(ffi::mdb_env_get_fd(self.env_mut_ptr(), fd.as_mut_ptr()))? };
let fd = unsafe { fd.assume_init() };
let metadata = unsafe { metadata_from_fd(fd)? };
Ok(metadata.len())
}
/// Return the raw flags the environment was opened with.
///
/// Returns `None` if the environment flags are different from the [`EnvFlags`] set.
pub fn flags(&self) -> Result<Option<EnvFlags>> {
self.get_flags().map(EnvFlags::from_bits)
}
/// Enable or disable the environment's currently active [`EnvFlags`].
///
/// ```
/// use std::fs;
/// use std::path::Path;
/// use heed::{EnvOpenOptions, Database, EnvFlags, FlagSetMode};
/// use heed::types::*;
///
/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
/// fs::create_dir_all(Path::new("target").join("database.mdb"))?;
/// let mut env_builder = EnvOpenOptions::new();
/// let dir = tempfile::tempdir().unwrap();
/// let env = unsafe { env_builder.open(dir.path())? };
///
/// // Env was opened without flags.
/// assert_eq!(env.get_flags().unwrap(), EnvFlags::empty().bits());
///
/// // Enable a flag after opening.
/// unsafe { env.set_flags(EnvFlags::NO_SYNC, FlagSetMode::Enable).unwrap(); }
/// assert_eq!(env.get_flags().unwrap(), EnvFlags::NO_SYNC.bits());
///
/// // Disable a flag after opening.
/// unsafe { env.set_flags(EnvFlags::NO_SYNC, FlagSetMode::Disable).unwrap(); }
/// assert_eq!(env.get_flags().unwrap(), EnvFlags::empty().bits());
/// # Ok(()) }
/// ```
///
/// # Safety
///
/// It is unsafe to use unsafe LMDB flags such as `NO_SYNC`, `NO_META_SYNC`, or `NO_LOCK`.
///
/// LMDB also requires that only 1 thread calls this function at any given moment.
/// Neither `heed` or LMDB check for this condition, so the caller must ensure it explicitly.
pub unsafe fn set_flags(&self, flags: EnvFlags, mode: FlagSetMode) -> Result<()> {
// safety: caller must ensure no other thread is calling this function.
// <http://www.lmdb.tech/doc/group__mdb.html#ga83f66cf02bfd42119451e9468dc58445>
mdb_result(unsafe {
ffi::mdb_env_set_flags(
self.env_mut_ptr(),
flags.bits(),
mode.as_mdb_env_set_flags_input(),
)
})
.map_err(Into::into)
}
/// Return the raw flags the environment is currently set with.
pub fn get_flags(&self) -> Result<u32> {
let mut flags = mem::MaybeUninit::uninit();
unsafe { mdb_result(ffi::mdb_env_get_flags(self.env_mut_ptr(), flags.as_mut_ptr()))? };
let flags = unsafe { flags.assume_init() };
Ok(flags)
}
/// Returns some basic informations about this environment.
pub fn info(&self) -> EnvInfo {
let mut raw_info = mem::MaybeUninit::uninit();
unsafe { ffi::mdb_env_info(self.0.env, raw_info.as_mut_ptr()) };
let raw_info = unsafe { raw_info.assume_init() };
EnvInfo {
map_addr: raw_info.me_mapaddr,
map_size: raw_info.me_mapsize,
last_page_number: raw_info.me_last_pgno,
last_txn_id: raw_info.me_last_txnid,
maximum_number_of_readers: raw_info.me_maxreaders,
number_of_readers: raw_info.me_numreaders,
}
}
/// Returns the size used by all the databases in the environment without the free pages.
///
/// It is crucial to configure [`EnvOpenOptions::max_dbs`] with a sufficiently large value
/// before invoking this function. All databases within the environment will be opened
/// and remain so.
pub fn non_free_pages_size(&self) -> Result<u64> {
let compute_size = |stat: ffi::MDB_stat| {
(stat.ms_leaf_pages + stat.ms_branch_pages + stat.ms_overflow_pages) as u64
* stat.ms_psize as u64
};
let mut size = 0;
let mut stat = mem::MaybeUninit::uninit();
unsafe { mdb_result(ffi::mdb_env_stat(self.env_mut_ptr(), stat.as_mut_ptr()))? };
let stat = unsafe { stat.assume_init() };
size += compute_size(stat);
let rtxn = self.read_txn()?;
// Open the main database
let dbi = self.raw_open_dbi::<DefaultComparator>(rtxn.txn, None, 0)?;
// We're going to iterate on the unnamed database
let mut cursor = RoCursor::new(&rtxn, dbi)?;
while let Some((key, _value)) = cursor.move_on_next(MoveOperation::NoDup)? {
if key.contains(&0) {
continue;
}
let key = String::from_utf8(key.to_vec()).unwrap();
// Calling `ffi::db_stat` on a database instance does not involve key comparison
// in LMDB, so it's safe to specify a noop key compare function for it.
if let Ok(dbi) = self.raw_open_dbi::<DefaultComparator>(rtxn.txn, Some(&key), 0) {
let mut stat = mem::MaybeUninit::uninit();
unsafe { mdb_result(ffi::mdb_stat(rtxn.txn, dbi, stat.as_mut_ptr()))? };
let stat = unsafe { stat.assume_init() };
size += compute_size(stat);
}
}
Ok(size)
}
/// Options and flags which can be used to configure how a [`Database`] is opened.
pub fn database_options(&self) -> DatabaseOpenOptions<Unspecified, Unspecified> {
DatabaseOpenOptions::new(self)
}
/// Opens a typed database that already exists in this environment.
///
/// If the database was previously opened in this program run, types will be checked.
///
/// ## Important Information
///
/// LMDB has an important restriction on the unnamed database when named ones are opened.
/// The names of the named databases are stored as keys in the unnamed one and are immutable,
/// and these keys can only be read and not written.
///
/// ## LMDB read-only access of existing database
///
/// In the case of accessing a database in a read-only manner from another process
/// where you wrote, you might need to manually call [`RoTxn::commit`] to get metadata
/// and the database handles opened and shared with the global [`Env`] handle.
///
/// If not done, you might raise `Io(Os { code: 22, kind: InvalidInput, message: "Invalid argument" })`
/// known as `EINVAL`.
pub fn open_database<KC, DC>(
&self,
rtxn: &RoTxn,
name: Option<&str>,
) -> Result<Option<Database<KC, DC>>>
where
KC: 'static,
DC: 'static,
{
let mut options = self.database_options().types::<KC, DC>();
if let Some(name) = name {
options.name(name);
}
options.open(rtxn)
}
/// Creates a typed database that can already exist in this environment.
///
/// If the database was previously opened during this program run, types will be checked.
///
/// ## Important Information
///
/// LMDB has an important restriction on the unnamed database when named ones are opened.
/// The names of the named databases are stored as keys in the unnamed one and are immutable,
/// and these keys can only be read and not written.
pub fn create_database<KC, DC>(
&self,
wtxn: &mut RwTxn,
name: Option<&str>,
) -> Result<Database<KC, DC>>
where
KC: 'static,
DC: 'static,
{
let mut options = self.database_options().types::<KC, DC>();
if let Some(name) = name {
options.name(name);
}
options.create(wtxn)
}
pub(crate) fn raw_init_database<C: Comparator + 'static>(
&self,
raw_txn: *mut ffi::MDB_txn,
name: Option<&str>,
flags: AllDatabaseFlags,
) -> Result<u32> {
match self.raw_open_dbi::<C>(raw_txn, name, flags.bits()) {
Ok(dbi) => Ok(dbi),
Err(e) => Err(e.into()),
}
}
fn raw_open_dbi<C: Comparator + 'static>(
&self,
raw_txn: *mut ffi::MDB_txn,
name: Option<&str>,
flags: u32,
) -> std::result::Result<u32, crate::mdb::lmdb_error::Error> {
let mut dbi = 0;
let name = name.map(|n| CString::new(n).unwrap());
let name_ptr = match name {
Some(ref name) => name.as_bytes_with_nul().as_ptr() as *const _,
None => ptr::null(),
};
// safety: The name cstring is cloned by LMDB, we can drop it after.
// If a read-only is used with the MDB_CREATE flag, LMDB will throw an error.
unsafe {
mdb_result(ffi::mdb_dbi_open(raw_txn, name_ptr, flags, &mut dbi))?;
if TypeId::of::<C>() != TypeId::of::<DefaultComparator>() {
mdb_result(ffi::mdb_set_compare(raw_txn, dbi, Some(custom_key_cmp_wrapper::<C>)))?;
}
};
Ok(dbi)
}
/// Create a transaction with read and write access for use with the environment.
///
/// ## LMDB Limitations
///
/// Only one [`RwTxn`] may exist simultaneously in the current environment.
/// If another write transaction is initiated, while another write transaction exists
/// the thread initiating the new one will wait on a mutex upon completion of the previous
/// transaction.
pub fn write_txn(&self) -> Result<RwTxn> {
RwTxn::new(self)
}
/// Create a nested transaction with read and write access for use with the environment.
///
/// The new transaction will be a nested transaction, with the transaction indicated by parent
/// as its parent. Transactions may be nested to any level.
///
/// A parent transaction and its cursors may not issue any other operations than _commit_ and
/// _abort_ while it has active child transactions.
pub fn nested_write_txn<'p>(&'p self, parent: &'p mut RwTxn) -> Result<RwTxn<'p>> {
RwTxn::nested(self, parent)
}
/// Create a transaction with read-only access for use with the environment.
///
/// You can make this transaction `Send`able between threads by
/// using the `read-txn-no-tls` crate feature.
/// See [`Self::static_read_txn`] if you want the txn to own the environment.
///
/// ## LMDB Limitations
///
/// It's possible to have multiple read transactions in the same environment
/// while there is a write transaction ongoing.
///
/// But read transactions prevent reuse of pages freed by newer write transactions,
/// thus the database can grow quickly. Write transactions prevent other write transactions,
/// since writes are serialized.
///
/// So avoid long-lived read transactions.
///
/// ## Errors
///
/// * [`crate::MdbError::Panic`]: A fatal error occurred earlier, and the environment must be shut down
/// * [`crate::MdbError::MapResized`]: Another process wrote data beyond this [`Env`] mapsize and this env
/// map must be resized
/// * [`crate::MdbError::ReadersFull`]: a read-only transaction was requested, and the reader lock table is
/// full
pub fn read_txn(&self) -> Result<RoTxn> {
RoTxn::new(self)
}
/// Create a transaction with read-only access for use with the environment.
/// Contrary to [`Self::read_txn`], this version **owns** the environment, which
/// means you won't be able to close the environment while this transaction is alive.
///
/// You can make this transaction `Send`able between threads by
/// using the `read-txn-no-tls` crate feature.
///
/// ## LMDB Limitations
///
/// It's possible to have multiple read transactions in the same environment
/// while there is a write transaction ongoing.
///
/// But read transactions prevent reuse of pages freed by newer write transactions,
/// thus the database can grow quickly. Write transactions prevent other write transactions,
/// since writes are serialized.
///
/// So avoid long-lived read transactions.
///
/// ## Errors
///
/// * [`crate::MdbError::Panic`]: A fatal error occurred earlier, and the environment must be shut down
/// * [`crate::MdbError::MapResized`]: Another process wrote data beyond this [`Env`] mapsize and this env
/// map must be resized
/// * [`crate::MdbError::ReadersFull`]: a read-only transaction was requested, and the reader lock table is
/// full
pub fn static_read_txn(self) -> Result<RoTxn<'static>> {
RoTxn::static_read_txn(self)
}
/// Copy an LMDB environment to the specified path, with options.
///
/// This function may be used to make a backup of an existing environment.
/// No lockfile is created, since it gets recreated at need.
pub fn copy_to_file<P: AsRef<Path>>(&self, path: P, option: CompactionOption) -> Result<File> {
let file = File::options().create_new(true).write(true).open(&path)?;
let fd = get_file_fd(&file);
unsafe { self.copy_to_fd(fd, option)? };
// We reopen the file to make sure the cursor is at the start,
// even a seek to start doesn't work properly.
let file = File::open(path)?;
Ok(file)
}
/// Copy an LMDB environment to the specified file descriptor, with compaction option.
///
/// This function may be used to make a backup of an existing environment.
/// No lockfile is created, since it gets recreated at need.
///
/// # Safety
///
/// The [`ffi::mdb_filehandle_t`] must have already been opened for Write access.
pub unsafe fn copy_to_fd(
&self,
fd: ffi::mdb_filehandle_t,
option: CompactionOption,
) -> Result<()> {
let flags = if let CompactionOption::Enabled = option { ffi::MDB_CP_COMPACT } else { 0 };
mdb_result(ffi::mdb_env_copyfd2(self.0.env, fd, flags))?;
Ok(())
}
/// Flush the data buffers to disk.
pub fn force_sync(&self) -> Result<()> {
unsafe { mdb_result(ffi::mdb_env_sync(self.0.env, 1))? }
Ok(())
}
/// Returns the canonicalized path where this env lives.
pub fn path(&self) -> &Path {
&self.0.path
}
/// Returns an `EnvClosingEvent` that can be used to wait for the closing event,
/// multiple threads can wait on this event.
///
/// Make sure that you drop all the copies of `Env`s you have, env closing are triggered
/// when all references are dropped, the last one will eventually close the environment.
pub fn prepare_for_closing(self) -> EnvClosingEvent {
let mut lock = OPENED_ENV.write().unwrap();
match lock.get_mut(self.path()) {
None => panic!("cannot find the env that we are trying to close"),
Some(EnvEntry { env, signal_event, .. }) => {
// We remove the env from the global list and replace it with a None.
let _env = env.take();
let signal_event = signal_event.clone();
// we must make sure we release the lock before we drop the env
// as the drop of the EnvInner also tries to lock the OPENED_ENV
// global and we don't want to trigger a dead-lock.
drop(lock);
EnvClosingEvent(signal_event)
}
}
}
/// Check for stale entries in the reader lock table and clear them.
///
/// Returns the number of stale readers cleared.
pub fn clear_stale_readers(&self) -> Result<usize> {
let mut dead: i32 = 0;
unsafe { mdb_result(ffi::mdb_reader_check(self.0.env, &mut dead))? }
// safety: The reader_check function asks for an i32, initialize it to zero
// and never decrements it. It is safe to use either an u32 or u64 (usize).
Ok(dead as usize)
}
/// Resize the memory map to a new size.
///
/// # Safety
///
/// According to the [LMDB documentation](http://www.lmdb.tech/doc/group__mdb.html#gaa2506ec8dab3d969b0e609cd82e619e5),
/// it is okay to call `mdb_env_set_mapsize` for an open environment as long as no transactions are active,
/// but the library does not check for this condition, so the caller must ensure it explicitly.
pub unsafe fn resize(&self, new_size: usize) -> Result<()> {
if new_size % page_size::get() != 0 {
let msg = format!(
"map size ({}) must be a multiple of the system page size ({})",
new_size,
page_size::get()
);
return Err(Error::Io(io::Error::new(io::ErrorKind::InvalidInput, msg)));
}
mdb_result(unsafe { ffi::mdb_env_set_mapsize(self.env_mut_ptr(), new_size) })
.map_err(Into::into)
}
/// Get the maximum size of keys and MDB_DUPSORT data we can write.
///
/// Depends on the compile-time constant MDB_MAXKEYSIZE. Default 511
pub fn max_key_size(&self) -> usize {
let maxsize: i32 = unsafe { ffi::mdb_env_get_maxkeysize(self.env_mut_ptr()) };
maxsize as usize
}
}
/// Contains information about the environment.
#[derive(Debug, Clone, Copy)]
pub struct EnvInfo {
/// Address of the map, if fixed.
pub map_addr: *mut c_void,
/// Size of the data memory map.
pub map_size: usize,
/// ID of the last used page.
pub last_page_number: usize,
/// ID of the last committed transaction.
pub last_txn_id: usize,
/// Maximum number of reader slots in the environment.
pub maximum_number_of_readers: u32,
/// Number of reader slots used in the environment.
pub number_of_readers: u32,
}
/// A structure that can be used to wait for the closing event.
/// Multiple threads can wait on this event.
#[derive(Clone)]
pub struct EnvClosingEvent(Arc<SignalEvent>);
impl EnvClosingEvent {
/// Blocks this thread until the environment is effectively closed.
///
/// # Safety
///
/// Make sure that you don't have any copy of the environment in the thread
/// that is waiting for a close event. If you do, you will have a deadlock.
pub fn wait(&self) {
self.0.wait()
}
/// Blocks this thread until either the environment has been closed
/// or until the timeout elapses. Returns `true` if the environment
/// has been effectively closed.
pub fn wait_timeout(&self, timeout: Duration) -> bool {
self.0.wait_timeout(timeout)
}
}
impl fmt::Debug for EnvClosingEvent {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("EnvClosingEvent").finish()
}
}
#[cfg(test)]
mod tests {
use std::io::ErrorKind;
use std::time::Duration;
use std::{fs, thread};
use crate::types::*;
use crate::{env_closing_event, EnvOpenOptions, Error};
#[test]
fn close_env() {
let dir = tempfile::tempdir().unwrap();
let env = unsafe {
EnvOpenOptions::new()
.map_size(10 * 1024 * 1024) // 10MB
.max_dbs(30)
.open(dir.path())
.unwrap()
};
// Force a thread to keep the env for 1 second.
let env_cloned = env.clone();
thread::spawn(move || {
let _env = env_cloned;
thread::sleep(Duration::from_secs(1));
});
let mut wtxn = env.write_txn().unwrap();
let db = env.create_database::<Str, Str>(&mut wtxn, None).unwrap();
wtxn.commit().unwrap();
// Create an ordered list of keys...
let mut wtxn = env.write_txn().unwrap();
db.put(&mut wtxn, "hello", "hello").unwrap();
db.put(&mut wtxn, "world", "world").unwrap();
let mut iter = db.iter(&wtxn).unwrap();
assert_eq!(iter.next().transpose().unwrap(), Some(("hello", "hello")));
assert_eq!(iter.next().transpose().unwrap(), Some(("world", "world")));
assert_eq!(iter.next().transpose().unwrap(), None);
drop(iter);
wtxn.commit().unwrap();
let signal_event = env.prepare_for_closing();
eprintln!("waiting for the env to be closed");
signal_event.wait();
eprintln!("env closed successfully");
// Make sure we don't have a reference to the env
assert!(env_closing_event(dir.path()).is_none());
}
#[test]
fn reopen_env_with_different_options_is_err() {
let dir = tempfile::tempdir().unwrap();
let _env = unsafe {
EnvOpenOptions::new()
.map_size(10 * 1024 * 1024) // 10MB
.open(dir.path())
.unwrap()
};
let result = unsafe {
EnvOpenOptions::new()
.map_size(12 * 1024 * 1024) // 12MB
.open(dir.path())
};
assert!(matches!(result, Err(Error::BadOpenOptions { .. })));
}
#[test]
fn open_env_with_named_path() {
let dir = tempfile::tempdir().unwrap();
fs::create_dir_all(dir.path().join("babar.mdb")).unwrap();
let _env = unsafe {
EnvOpenOptions::new()
.map_size(10 * 1024 * 1024) // 10MB
.open(dir.path().join("babar.mdb"))
.unwrap()
};
let _env = unsafe {
EnvOpenOptions::new()
.map_size(10 * 1024 * 1024) // 10MB
.open(dir.path().join("babar.mdb"))
.unwrap()
};
}
#[test]
#[cfg(not(windows))]
fn open_database_with_writemap_flag() {
let dir = tempfile::tempdir().unwrap();
let mut envbuilder = EnvOpenOptions::new();
envbuilder.map_size(10 * 1024 * 1024); // 10MB
envbuilder.max_dbs(10);
unsafe { envbuilder.flags(crate::EnvFlags::WRITE_MAP) };
let env = unsafe { envbuilder.open(dir.path()).unwrap() };
let mut wtxn = env.write_txn().unwrap();
let _db = env.create_database::<Str, Str>(&mut wtxn, Some("my-super-db")).unwrap();
wtxn.commit().unwrap();
}
#[test]
fn open_database_with_nosubdir() {
let dir = tempfile::tempdir().unwrap();
let mut envbuilder = EnvOpenOptions::new();
unsafe { envbuilder.flags(crate::EnvFlags::NO_SUB_DIR) };
let _env = unsafe { envbuilder.open(dir.path().join("data.mdb")).unwrap() };
}
#[test]
fn create_database_without_commit() {
let dir = tempfile::tempdir().unwrap();
let env = unsafe {
EnvOpenOptions::new()
.map_size(10 * 1024 * 1024) // 10MB
.max_dbs(10)
.open(dir.path())
.unwrap()
};
let mut wtxn = env.write_txn().unwrap();
let _db = env.create_database::<Str, Str>(&mut wtxn, Some("my-super-db")).unwrap();
wtxn.abort();
let rtxn = env.read_txn().unwrap();
let option = env.open_database::<Str, Str>(&rtxn, Some("my-super-db")).unwrap();
assert!(option.is_none());
}
#[test]
fn open_already_existing_database() {
let dir = tempfile::tempdir().unwrap();
let env = unsafe {
EnvOpenOptions::new()
.map_size(10 * 1024 * 1024) // 10MB
.max_dbs(10)
.open(dir.path())
.unwrap()
};
// we first create a database
let mut wtxn = env.write_txn().unwrap();
let _db = env.create_database::<Str, Str>(&mut wtxn, Some("my-super-db")).unwrap();
wtxn.commit().unwrap();
// Close the environement and reopen it, databases must not be loaded in memory.
env.prepare_for_closing().wait();
let env = unsafe {
EnvOpenOptions::new()
.map_size(10 * 1024 * 1024) // 10MB
.max_dbs(10)
.open(dir.path())
.unwrap()
};
let rtxn = env.read_txn().unwrap();
let option = env.open_database::<Str, Str>(&rtxn, Some("my-super-db")).unwrap();
assert!(option.is_some());
}
#[test]
fn resize_database() {
let dir = tempfile::tempdir().unwrap();
let page_size = page_size::get();
let env = unsafe {
EnvOpenOptions::new().map_size(9 * page_size).max_dbs(1).open(dir.path()).unwrap()
};
let mut wtxn = env.write_txn().unwrap();
let db = env.create_database::<Str, Str>(&mut wtxn, Some("my-super-db")).unwrap();
wtxn.commit().unwrap();
let mut wtxn = env.write_txn().unwrap();
for i in 0..64 {
db.put(&mut wtxn, &i.to_string(), "world").unwrap();
}
wtxn.commit().unwrap();
let mut wtxn = env.write_txn().unwrap();
for i in 64..128 {
db.put(&mut wtxn, &i.to_string(), "world").unwrap();
}
wtxn.commit().expect_err("cannot commit a transaction that would reach the map size limit");
unsafe {
env.resize(10 * page_size).unwrap();
}
let mut wtxn = env.write_txn().unwrap();
for i in 64..128 {
db.put(&mut wtxn, &i.to_string(), "world").unwrap();
}
wtxn.commit().expect("transaction should commit after resizing the map size");
assert_eq!(10 * page_size, env.info().map_size);
}
/// Non-regression test for
/// <https://github.com/meilisearch/heed/issues/183>
///
/// We should be able to open database Read-Only Env with
/// no prior Read-Write Env opening. And query data.
#[test]
fn open_read_only_without_no_env_opened_before() {
let expected_data0 = "Data Expected db0";
let dir = tempfile::tempdir().unwrap();
{
// We really need this env to be dropped before the read-only access.
let env = unsafe {
EnvOpenOptions::new()
.map_size(16 * 1024 * 1024 * 1024) // 10MB
.max_dbs(32)
.open(dir.path())
.unwrap()
};
let mut wtxn = env.write_txn().unwrap();
let database0 = env.create_database::<Str, Str>(&mut wtxn, Some("shared0")).unwrap();
wtxn.commit().unwrap();
let mut wtxn = env.write_txn().unwrap();
database0.put(&mut wtxn, "shared0", expected_data0).unwrap();
wtxn.commit().unwrap();
// We also really need that no other env reside in memory in other thread doing tests.
env.prepare_for_closing().wait();
}
{
// Open now we do a read-only opening
let env = unsafe {
EnvOpenOptions::new()
.map_size(16 * 1024 * 1024 * 1024) // 10MB
.max_dbs(32)
.open(dir.path())
.unwrap()
};
let database0 = {
let rtxn = env.read_txn().unwrap();
let database0 =
env.open_database::<Str, Str>(&rtxn, Some("shared0")).unwrap().unwrap();
// This commit is mandatory if not committed you might get
// Io(Os { code: 22, kind: InvalidInput, message: "Invalid argument" })
rtxn.commit().unwrap();
database0
};
{
// If we didn't committed the opening it might fail with EINVAL.
let rtxn = env.read_txn().unwrap();
let value = database0.get(&rtxn, "shared0").unwrap().unwrap();
assert_eq!(value, expected_data0);
}
env.prepare_for_closing().wait();
}
// To avoid reintroducing the bug let's try to open again but without the commit
{
// Open now we do a read-only opening
let env = unsafe {
EnvOpenOptions::new()
.map_size(16 * 1024 * 1024 * 1024) // 10MB
.max_dbs(32)
.open(dir.path())
.unwrap()
};
let database0 = {
let rtxn = env.read_txn().unwrap();
let database0 =
env.open_database::<Str, Str>(&rtxn, Some("shared0")).unwrap().unwrap();
// No commit it's important, dropping explicitly
drop(rtxn);
database0
};
{
// We didn't committed the opening we will get EINVAL.
let rtxn = env.read_txn().unwrap();
// The dbg!() is intentional in case of a change in rust-std or in lmdb related
// to the windows error.
let err = dbg!(database0.get(&rtxn, "shared0"));
// The error kind is still ErrorKind Uncategorized on windows.
// Behind it's a ERROR_BAD_COMMAND code 22 like EINVAL.
if cfg!(windows) {
assert!(err.is_err());
} else {
assert!(
matches!(err, Err(Error::Io(ref e)) if e.kind() == ErrorKind::InvalidInput)
);
}
}
env.prepare_for_closing().wait();
}
}
#[test]
fn max_key_size() {
let dir = tempfile::tempdir().unwrap();
let env = unsafe { EnvOpenOptions::new().open(dir.path().join(dir.path())).unwrap() };
let maxkeysize = env.max_key_size();
eprintln!("maxkeysize: {}", maxkeysize);
if cfg!(feature = "longer-keys") {
// Should be larger than the default of 511
assert!(maxkeysize > 511);
} else {
// Should be the default of 511
assert_eq!(maxkeysize, 511);
}
}
}