Concurrency Control

Not Supported

There is no concurrency control protocol in LedisDB because it does not support transactions. Like Redis, LedisDB processes requests as command sequences. Each command is treated as a single atomic operation. However, LedisDB does not provide any mechanism to combine commands into transactions.

Indexes

Skip List Log-Structured Merge Tree

LedisDB uses RocksDB, LevelDB or goleveldb as storage engine and inherits their index data structure, which is the Log-Structured Merge Tree. They also use Skip List in the MemTable part.

Query Compilation

Not Supported

System Architecture

Shared-Nothing Embedded

LedisDB can be embedded in Go programs. You can also run LedisDB as an independent server. Multiple LedisDB nodes and coordinator nodes can form a cluster with partition and Master-Replica replication. Each server does not share anything with others and only communicates with each other through network connection.

Views

Not Supported

Checkpoints

Non-Blocking Consistent Blocking

LedisDB uses RocksDB, LevelDB or goleveldb as storage engine and thus inherits their checkpoint mechanisms.

Storage Model

N-ary Storage Model (Row/Record)

LedisDB uses RocksDB, LevelDB or goleveldb as storage engine and thus inherits their storage model. Data are stored in the form of ordered key-value pairs.

Joins

Not Supported

As a key/value store, no join feature is provided in LedisDB.

Storage Organization

Log-structured

LedisDB uses RocksDB, LevelDB or goleveldb as storage engine. Therefore, it inherits their Log-structured storage organization.

Query Execution

Tuple-at-a-Time Model

LedisDB uses iterators in query processing.

Storage Architecture

Disk-oriented In-Memory Hybrid

LedisDB uses RocksDB, LevelDB or goleveldb as storage engine and thus inherits their storage architecture. It also provides an option to use memory-backed storage (via goleveldb).

Logging

Logical Logging

LedisDB uses RocksDB, LevelDB or goleveldb as storage engine and thus inherits their logging mechanisms. They log all Put operations.

Stored Procedures

Not Supported

LedisDB does not support stored procedures, but like Redis, it provides the capability to evaluate scripts using the bulit-in Lua interpreter. Scripts will be cached by LedisDB and can be invoked from the cache later. However, they are just cached rather than stored.

Data Model

Key/Value

LedisDB is a key/value store, but has rich data structures. In addition to simple key/value pair, it provides Hash, List, Set, ZSet.

Compression

Dictionary Encoding Naïve (Page-Level)

LedisDB uses RocksDB, LevelDB or goleveldb as storage engine. You can enable their compression feature via configuration. Data and index blocks are compressed individually. User can choose from a list of supported compression algorithms, like LZ4 and Snappy. User can choose to use Dictionary Compression, too. Data are decompressed when LedisDB retrieves them from the underlying storage engine.

Query Interface

Custom API HTTP / REST Command-line / Shell

LedisDB can be embedded in Go programs and programs can use its API to perform queries. LedisDB also provides a query interface in redis protocol called RESP(REdis Serialization Protocol), and can be queried via redis-cli. LedisDB has HTTP API support, too.