| | |
| | from pathlib import Path |
| | from typing import Union |
| |
|
| | from .base import BaseStorageBackend |
| |
|
| |
|
| | class LmdbBackend(BaseStorageBackend): |
| | """Lmdb storage backend. |
| | |
| | Args: |
| | db_path (str): Lmdb database path. |
| | readonly (bool): Lmdb environment parameter. If True, disallow any |
| | write operations. Defaults to True. |
| | lock (bool): Lmdb environment parameter. If False, when concurrent |
| | access occurs, do not lock the database. Defaults to False. |
| | readahead (bool): Lmdb environment parameter. If False, disable the OS |
| | filesystem readahead mechanism, which may improve random read |
| | performance when a database is larger than RAM. Defaults to False. |
| | **kwargs: Keyword arguments passed to `lmdb.open`. |
| | |
| | Attributes: |
| | db_path (str): Lmdb database path. |
| | """ |
| |
|
| | def __init__(self, |
| | db_path, |
| | readonly=True, |
| | lock=False, |
| | readahead=False, |
| | **kwargs): |
| | try: |
| | import lmdb |
| | except ImportError: |
| | raise ImportError( |
| | 'Please run "pip install lmdb" to enable LmdbBackend.') |
| |
|
| | self.db_path = str(db_path) |
| | self.readonly = readonly |
| | self.lock = lock |
| | self.readahead = readahead |
| | self.kwargs = kwargs |
| | self._client = None |
| |
|
| | def get(self, filepath: Union[str, Path]) -> bytes: |
| | """Get values according to the filepath. |
| | |
| | Args: |
| | filepath (str or Path): Here, filepath is the lmdb key. |
| | |
| | Returns: |
| | bytes: Expected bytes object. |
| | |
| | Examples: |
| | >>> backend = LmdbBackend('path/to/lmdb') |
| | >>> backend.get('key') |
| | b'hello world' |
| | """ |
| | if self._client is None: |
| | self._client = self._get_client() |
| |
|
| | filepath = str(filepath) |
| | with self._client.begin(write=False) as txn: |
| | value_buf = txn.get(filepath.encode('ascii')) |
| | return value_buf |
| |
|
| | def get_text(self, filepath, encoding=None): |
| | raise NotImplementedError |
| |
|
| | def _get_client(self): |
| | import lmdb |
| |
|
| | return lmdb.open( |
| | self.db_path, |
| | readonly=self.readonly, |
| | lock=self.lock, |
| | readahead=self.readahead, |
| | **self.kwargs) |
| |
|
| | def __del__(self): |
| | if self._client is not None: |
| | self._client.close() |
| |
|
