Struct lmdb_zero::Environment
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pub struct Environment { /* fields omitted */ }
An LMDB environment which has been opened to a file.
Methods
impl Environment
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pub unsafe fn from_raw(env: *mut MDB_env) -> Self
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Wrap a raw LMDB environment handle in an Environment
.
The Environment
assumes ownership of the MDB_env
. If you do not
want this, see borrow_raw()
instead.
Unsafety
env
must point to a valid MDB_env
.
It is the caller's responsibility to ensure that nothing destroys the
MDB_env
before into_raw()
is called, and that
nothing attempts to use the MDB_env
after Environment
is dropped
normally.
It is safe for multiple Environment
s bound to the same MDB_env
to
coexist (though the others would need to be created by borrow_raw
).
However, care must be taken when using databases since by default the
Environment
will assume ownership of those as well.
pub unsafe fn borrow_raw(env: *mut MDB_env) -> Self
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Wrap a raw LMDB environment handle in an Environment
without taking
ownership.
The Environment
does not assume ownership of the MDB_env
, and will
not destroy it when it is dropped. See from_raw()
if taking ownership is desired.
Note that this does not affect assumed ownership of MDB_dbi
handles;
databases opened by Database::open
are still presumed owned.
Unsafety
env
must point to a valid MDB_env
.
It is safe for multiple Environment
s bound to the same MDB_env
to
coexist (though the others would need to be created by borrow_raw
).
However, care must be taken when using databases since by default the
Environment
will assume ownership of those as well.
pub fn as_raw(&self) -> *mut MDB_env
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Return the underlying MDB_env
handle.
Safety
While this call is in and of itself safe, the caller must ensure that
operations against the backing store do not violate Rust aliasing
rules, and must not take any action that would cause the MDB_env
to
be destroyed prematurely, or to use it after this Environment
is
destroyed.
pub fn into_raw(self) -> *mut MDB_env
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Consume this Environment
and return the underlying handle.
After this call, it is the caller's responsibility to ensure that the
MDB_env
is eventually destroyed, if it was actually owned by this
Environment
(compare from_raw
and
borrow_raw
).
Safety
While this call is in and of itself safe, the caller must ensure that operations against the backing store do not violate Rust aliasing rules.
pub fn copy(&self, path: &str, flags: Flags) -> Result<()>
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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.
Note
This call can trigger significant file size growth if run in parallel with write transactions, because it employs a read-only transaction. See long-lived transactions under Caveats.
Example
let out = tempdir::TempDir::new_in(".", "lmdbcopy").unwrap(); env.copy(out.path().to_str().unwrap(), lmdb::copy::COMPACT).unwrap(); // We could now open up an independent environment in `lmdbcopyXXXX` // or upload it somewhere, eg, while `env` could continue being // modified concurrently.
pub fn copyfd(&self, fd: Fd, flags: Flags) -> Result<()>
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Copy an LMDB environment to the specified file descriptor, 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. See
copy()
for further details.
Note
This call can trigger significant file size growth if run in parallel with write transactions, because it employs a read-only transaction. See long-lived transactions under Caveats.
pub fn stat(&self) -> Result<Stat>
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Return statistics about the LMDB environment.
pub fn info(&self) -> Result<EnvInfo>
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Return information about the LMDB environment.
pub fn sync(&self, force: bool) -> Result<()>
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Flush the data buffers to disk.
Data is always written to disk when transactions are committed, but the
operating system may keep it buffered. LMDB always flushes the OS
buffers upon commit as well, unless the environment was opened with
NOSYNC
or in part NOMETASYNC
. This call is not valid if the
environment was opened with RDONLY
.
If force
is true, force a synchronous flush. Otherwise if the
environment has the NOSYNC
flag set the flushes will be omitted, and
with MAPASYNC
they will be asynchronous.
pub unsafe fn set_flags(&self, flags: Flags, onoff: bool) -> Result<()>
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Set environment flags.
This may be used to set some flags in addition to those from
EnvBuilder::open()
, or to unset these flags. If several threads
change the flags at the same time, the result is undefined.
flags
specifies the flags to edit, not the new status of all flags.
If onoff
is true, all flags in flags
are set; otherwise, all flags
in flags
are cleared.
Unsafety
The caller must ensure that multiple threads do not call this
concurrently with itself or with get_flags()
. This could not be
accomplished by using &mut self
, since any open databases necessarily
have the environment borrowed already.
Example
unsafe { // Enable the NOMETASYNC and MAPASYNC flags env.set_flags(lmdb::open::NOMETASYNC | lmdb::open::MAPASYNC, true) .unwrap(); assert!(env.flags().unwrap().contains( lmdb::open::NOMETASYNC | lmdb::open::MAPASYNC)); // Turn MAPASYNC back off, leaving NOMETASYNC set env.set_flags(lmdb::open::MAPASYNC, false).unwrap(); assert!(env.flags().unwrap().contains(lmdb::open::NOMETASYNC)); assert!(!env.flags().unwrap().contains(lmdb::open::MAPASYNC)); }
pub fn flags(&self) -> Result<Flags>
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Get environment flags.
pub fn path(&self) -> Result<&CStr>
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Return the path that was used in EnvBuilder::open()
.
Panics
Panics if LMDB returns success but sets the path to a NULL pointer.
pub unsafe fn fd(&self) -> Result<Fd>
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Return the filedescriptor for the given environment.
Unsafety
The caller must ensure that the file descriptor is not used to subvert normal LMDB functionality, such as by writing to it or closing it.
pub unsafe fn set_mapsize(&self, size: usize) -> Result<()>
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Set the size of the memory map to use for this environment.
The size should be a multiple of the OS page size. The default is 10485760 bytes. The size of the memory map is also the maximum size of the database. The value should be chosen as large as possible, to accommodate future growth of the database.
The new size takes effect immediately for the current process but will not be persisted to any others until a write transaction has been committed by the current process. Also, only mapsize increases are persisted into the environment.
If the mapsize is increased by another process, and data has grown
beyond the range of the current mapsize, starting a transaction will
return error::MAP_RESIZED
. This function may be called with a size of
zero to adopt the new size.
Unsafety
This may only be called if no transactions are active in the current process. Note that the library does not check for this condition, the caller must ensure it explicitly.
pub fn maxreaders(&self) -> Result<u32>
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Get the maximum number of threads/reader slots for the environment.
pub fn maxkeysize(&self) -> u32
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Get the maximum size of keys and DUPSORT
data we can write.
Depends on the compile-time constant MDB_MAXKEYSIZE
in LMDB.
Default 511.
pub fn reader_check(&self) -> Result<i32>
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Check for stale entries in the reader lock table.
Returns the number of stale slots that were cleared.