# bitcoinleveldb-meta crate description
This crate provides functionality related to the
metadata management in the LevelDB key-value
store.
Notice: "This crate is part of a direct
translation from C++ to Rust of the bitcoin
core. As such, some of the function bodies may
still be in the process of translation. Please
note that this system will become testable once
the translation process is complete."
Tokens:
- Saver
- SaverState
- after_file
- before_file
- expanded_compaction_byte_size_limit
- find_file
- find_smallest_boundary_file
- get_file_iterator
- max_bytes_for_level
- max_file_size_for_level
- max_grand_parent_overlap_bytes
- save_value
- some_file_overlaps_range
- total_file_size
- AddBoundaryInputsTest
- FindFileTest
- add
- create_file_meta_data
- dbversion_set_test_main
- default
- drop
- find
- find_file_test_empty
- find_file_test_multiple
- find_file_test_multiple_null_boundaries
- find_file_test_overlap_sequence_checks
- find_file_test_overlapping_files
- find_file_test_single
- overlaps
- Tag
- get_internal_key
- get_level
The metadata management in LevelDB handles various
properties of the underlying database files such
as their size, location, and range of keys they
cover. This crate provides functions to locate
files in the database, calculate their size, and
detect overlapping files. It also provides tools
to set limits on the size of files in different
levels of the database, as well as limits on the
total size of the database.
The crate implements a Saver interface for
iterating over database files, and a SaverState
structure that tracks the progress of the
iteration. The crate also provides functions to
create file metadata and determine their level
based on their size.
In addition, the crate includes test functions for
finding database files and detecting overlapping
files.
Note that this crate is still in the process of
being translated from C++ to Rust, so some
functions may not yet be available. Once the
translation process is complete, this crate will
become fully testable.
59> which metadata do we track in leveldb?
In LevelDB, metadata is tracked for each file that
stores key-value pairs. This metadata includes the
file number, file size, file creation time, file
modification time, the smallest and largest key
stored in the file, the largest sequence number of
the entries in the file, and a flag indicating
whether the file has been marked for compaction.
LevelDB also tracks metadata about the entire
database, such as the current database version,
the maximum file size, the number of levels in the
database, the size ratio between levels, and the
target file size for each level. This metadata is
stored in the "MANIFEST" file, which is
a log-structured file that records changes to the
database metadata over time.
60> thanks -- how else do we use metadata in this
system?
Metadata plays an important role in LevelDB for
various purposes such as:
1. Version management: LevelDB maintains a version
set that stores metadata for all versions of
the database. This metadata includes the
current version, the previous version, and
a list of all versions. The version set helps
to track changes to the database over time and
facilitates compaction and garbage collection.
2. File management: LevelDB uses metadata to
manage files in the database. For example, it
tracks the file number, file size, and creation
time of each file. This information is used to
perform operations such as file deletion, file
opening, and file iteration.
3. Indexing: LevelDB uses metadata to index keys
in the database. The metadata includes
information about the location of keys and the
mapping of keys to their associated
values. This information is used to perform
operations such as key lookups, range scans,
and compaction.
4. Compression: LevelDB uses metadata to track
compression information for files in the
database. The metadata includes information
such as the compression algorithm used and the
compression ratio achieved. This information is
used to optimize compression and decompression
performance and to ensure data integrity.
Overall, metadata is a crucial component of the
LevelDB system that enables efficient and
effective management of data and resources.