README
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Tendermint DB
Common database interface for various database backends. Primarily meant for applications built on Tendermint, such as the Cosmos SDK, but can be used independently of these as well.
Minimum Go Version
Go 1.13+
Supported Database Backends
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GoLevelDB [stable]: A pure Go implementation of LevelDB (see below). Currently the default on-disk database used in the Cosmos SDK.
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MemDB [stable]: An in-memory database using Google's B-tree package. Has very high performance both for reads, writes, and range scans, but is not durable and will lose all data on process exit. Does not support transactions. Suitable for e.g. caches, working sets, and tests. Used for IAVL working sets when the pruning strategy allows it.
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LevelDB [experimental]: A Go wrapper around LevelDB. Uses LSM-trees for on-disk storage, which have good performance for write-heavy workloads, particularly on spinning disks, but requires periodic compaction to maintain decent read performance and reclaim disk space. Does not support transactions.
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BoltDB [experimental]: A fork of BoltDB. Uses B+trees for on-disk storage, which have good performance for read-heavy workloads and range scans. Supports serializable ACID transactions.
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RocksDB [experimental]: A Go wrapper around RocksDB. Similarly to LevelDB (above) it uses LSM-trees for on-disk storage, but is optimized for fast storage media such as SSDs and memory. Supports atomic transactions, but not full ACID transactions.
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BadgerDB [experimental]: A key-value database written as a pure-Go alternative to e.g. LevelDB and RocksDB, with LSM-tree storage. Makes use of multiple goroutines for performance, and includes advanced features such as serializable ACID transactions, write batches, compression, and more.
Meta-databases
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PrefixDB [stable]: A database which wraps another database and uses a static prefix for all keys. This allows multiple logical databases to be stored in a common underlying databases by using different namespaces. Used by the Cosmos SDK to give different modules their own namespaced database in a single application database.
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RemoteDB [experimental]: A database that connects to distributed Tendermint db instances via gRPC. This can help with detaching difficult deployments such as LevelDB, and can also ease dependency management for Tendermint developers.
Tests
To test common databases, run make test. If all databases are available on the local machine, use make test-all to test them all.
Documentation
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Index ¶
- func FileExists(filePath string) bool
- func IsKeyInDomain(key, start, end []byte) bool
- type BackendType
- type Batch
- type DB
- type GoLevelDB
- func (db *GoLevelDB) Close() error
- func (db *GoLevelDB) DB() *leveldb.DB
- func (db *GoLevelDB) Delete(key []byte) error
- func (db *GoLevelDB) DeleteSync(key []byte) error
- func (db *GoLevelDB) Get(key []byte) ([]byte, error)
- func (db *GoLevelDB) Has(key []byte) (bool, error)
- func (db *GoLevelDB) Iterator(start, end []byte) (Iterator, error)
- func (db *GoLevelDB) NewBatch() Batch
- func (db *GoLevelDB) Print() error
- func (db *GoLevelDB) ReverseIterator(start, end []byte) (Iterator, error)
- func (db *GoLevelDB) Set(key []byte, value []byte) error
- func (db *GoLevelDB) SetSync(key []byte, value []byte) error
- func (db *GoLevelDB) Stats() map[string]string
- type Iterator
- type MemDB
- func (db *MemDB) Close() error
- func (db *MemDB) Delete(key []byte) error
- func (db *MemDB) DeleteSync(key []byte) error
- func (db *MemDB) Get(key []byte) ([]byte, error)
- func (db *MemDB) Has(key []byte) (bool, error)
- func (db *MemDB) Iterator(start, end []byte) (Iterator, error)
- func (db *MemDB) NewBatch() Batch
- func (db *MemDB) Print() error
- func (db *MemDB) ReverseIterator(start, end []byte) (Iterator, error)
- func (db *MemDB) Set(key []byte, value []byte) error
- func (db *MemDB) SetSync(key []byte, value []byte) error
- func (db *MemDB) Stats() map[string]string
- type PrefixDB
- func (pdb *PrefixDB) Close() error
- func (pdb *PrefixDB) Delete(key []byte) error
- func (pdb *PrefixDB) DeleteSync(key []byte) error
- func (pdb *PrefixDB) Get(key []byte) ([]byte, error)
- func (pdb *PrefixDB) Has(key []byte) (bool, error)
- func (pdb *PrefixDB) Iterator(start, end []byte) (Iterator, error)
- func (pdb *PrefixDB) NewBatch() Batch
- func (pdb *PrefixDB) Print() error
- func (pdb *PrefixDB) ReverseIterator(start, end []byte) (Iterator, error)
- func (pdb *PrefixDB) Set(key []byte, value []byte) error
- func (pdb *PrefixDB) SetSync(key []byte, value []byte) error
- func (pdb *PrefixDB) Stats() map[string]string
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func FileExists ¶
func IsKeyInDomain ¶
See DB interface documentation for more information.
Types ¶
type BackendType ¶
type BackendType string
const ( // GoLevelDBBackend represents goleveldb (github.com/syndtr/goleveldb - most // popular implementation) // - pure go // - stable GoLevelDBBackend BackendType = "goleveldb" // CLevelDBBackend represents cleveldb (uses levigo wrapper) // - fast // - requires gcc // - use cleveldb build tag (go build -tags cleveldb) CLevelDBBackend BackendType = "cleveldb" // MemDBBackend represents in-memory key value store, which is mostly used // for testing. MemDBBackend BackendType = "memdb" // BoltDBBackend represents bolt (uses etcd's fork of bolt - // github.com/etcd-io/bbolt) // - EXPERIMENTAL // - may be faster is some use-cases (random reads - indexer) // - use boltdb build tag (go build -tags boltdb) BoltDBBackend BackendType = "boltdb" // RocksDBBackend represents rocksdb (uses github.com/tecbot/gorocksdb) // - EXPERIMENTAL // - requires gcc // - use rocksdb build tag (go build -tags rocksdb) RocksDBBackend BackendType = "rocksdb" BadgerDBBackend BackendType = "badgerdb" )
These are valid backend types.
type Batch ¶
type Batch interface {
// Set sets a key/value pair.
// CONTRACT: key, value readonly []byte
Set(key, value []byte) error
// Delete deletes a key/value pair.
// CONTRACT: key readonly []byte
Delete(key []byte) error
// Write writes the batch, possibly without flushing to disk. Only Close() can be called after,
// other methods will error.
Write() error
// WriteSync writes the batch and flushes it to disk. Only Close() can be called after, other
// methods will error.
WriteSync() error
// Close closes the batch. It is idempotent, but calls to other methods afterwards will error.
Close() error
}
Batch represents a group of writes. They may or may not be written atomically depending on the backend. Callers must call Close on the batch when done.
As with DB, given keys and values should be considered read-only, and must not be modified after passing them to the batch.
type DB ¶
type DB interface {
// Get fetches the value of the given key, or nil if it does not exist.
// CONTRACT: key, value readonly []byte
Get([]byte) ([]byte, error)
// Has checks if a key exists.
// CONTRACT: key, value readonly []byte
Has(key []byte) (bool, error)
// Set sets the value for the given key, replacing it if it already exists.
// CONTRACT: key, value readonly []byte
Set([]byte, []byte) error
// SetSync sets the value for the given key, and flushes it to storage before returning.
SetSync([]byte, []byte) error
// Delete deletes the key, or does nothing if the key does not exist.
// CONTRACT: key readonly []byte
Delete([]byte) error
// DeleteSync deletes the key, and flushes the delete to storage before returning.
DeleteSync([]byte) error
// Iterator returns an iterator over a domain of keys, in ascending order. The caller must call
// Close when done. End is exclusive, and start must be less than end. A nil start iterates
// from the first key, and a nil end iterates to the last key (inclusive). Empty keys are not
// valid.
// CONTRACT: No writes may happen within a domain while an iterator exists over it.
// CONTRACT: start, end readonly []byte
Iterator(start, end []byte) (Iterator, error)
// ReverseIterator returns an iterator over a domain of keys, in descending order. The caller
// must call Close when done. End is exclusive, and start must be less than end. A nil end
// iterates from the last key (inclusive), and a nil start iterates to the first key (inclusive).
// Empty keys are not valid.
// CONTRACT: No writes may happen within a domain while an iterator exists over it.
// CONTRACT: start, end readonly []byte
ReverseIterator(start, end []byte) (Iterator, error)
// Close closes the database connection.
Close() error
// NewBatch creates a batch for atomic updates. The caller must call Batch.Close.
NewBatch() Batch
// Print is used for debugging.
Print() error
// Stats returns a map of property values for all keys and the size of the cache.
Stats() map[string]string
}
DB is the main interface for all database backends. DBs are concurrency-safe. Callers must call Close on the database when done.
Keys cannot be nil or empty, while values cannot be nil. Keys and values should be considered read-only, both when returned and when given, and must be copied before they are modified.
type GoLevelDB ¶
type GoLevelDB struct {
// contains filtered or unexported fields
}
func NewGoLevelDBWithOpts ¶
func (*GoLevelDB) DeleteSync ¶
DeleteSync implements DB.
func (*GoLevelDB) ReverseIterator ¶
ReverseIterator implements DB.
type Iterator ¶
type Iterator interface {
// Domain returns the start (inclusive) and end (exclusive) limits of the iterator.
// CONTRACT: start, end readonly []byte
Domain() (start []byte, end []byte)
// Valid returns whether the current iterator is valid. Once invalid, the Iterator remains
// invalid forever.
Valid() bool
// Next moves the iterator to the next key in the database, as defined by order of iteration.
// If Valid returns false, this method will panic.
Next()
// Key returns the key at the current position. Panics if the iterator is invalid.
// CONTRACT: key readonly []byte
Key() (key []byte)
// Value returns the value at the current position. Panics if the iterator is invalid.
// CONTRACT: value readonly []byte
Value() (value []byte)
// Error returns the last error encountered by the iterator, if any.
Error() error
// Close closes the iterator, relasing any allocated resources.
Close() error
}
Iterator represents an iterator over a domain of keys. Callers must call Close when done. No writes can happen to a domain while there exists an iterator over it, some backends may take out database locks to ensure this will not happen.
Callers must make sure the iterator is valid before calling any methods on it, otherwise these methods will panic. This is in part caused by most backend databases using this convention.
As with DB, keys and values should be considered read-only, and must be copied before they are modified.
Typical usage:
var itr Iterator = ... defer itr.Close()
for ; itr.Valid(); itr.Next() {
k, v := itr.Key(); itr.Value()
...
}
if err := itr.Error(); err != nil {
...
}
type MemDB ¶
type MemDB struct {
// contains filtered or unexported fields
}
MemDB is an in-memory database backend using a B-tree for storage.
For performance reasons, all given and returned keys and values are pointers to the in-memory database, so modifying them will cause the stored values to be modified as well. All DB methods already specify that keys and values should be considered read-only, but this is especially important with MemDB.
func (*MemDB) Iterator ¶
Iterator implements DB. Takes out a read-lock on the database until the iterator is closed.
func (*MemDB) ReverseIterator ¶
ReverseIterator implements DB. Takes out a read-lock on the database until the iterator is closed.
type PrefixDB ¶
type PrefixDB struct {
// contains filtered or unexported fields
}
PrefixDB wraps a namespace of another database as a logical database.
func NewPrefixDB ¶
NewPrefixDB lets you namespace multiple DBs within a single DB.
func (*PrefixDB) DeleteSync ¶
DeleteSync implements DB.
func (*PrefixDB) ReverseIterator ¶
ReverseIterator implements DB.
Source Files
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Directories
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| Path | Synopsis |
|---|---|
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remotedb is a package for connecting to distributed Tendermint db.DB instances.
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remotedb is a package for connecting to distributed Tendermint db.DB instances. |
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grpcdb
grpcdb is the distribution of Tendermint's db.DB instances using the gRPC transport to decouple local db.DB usages from applications, to using them over a network in a highly performant manner.
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grpcdb is the distribution of Tendermint's db.DB instances using the gRPC transport to decouple local db.DB usages from applications, to using them over a network in a highly performant manner. |