ReductStore is a personal project started by Alexey Timin in 2021 with no publicly stated derivations or inspirations from other existing database systems. It has since received monthly releases and bug fixes. Alexey Timin remains the sole major contributor to this project. The project is currently undergoing a major rewrite with Rust and is actively seeking new collaborators to join.
ReductStore currently does not support checkpoints.
ReductStore directly writes blobs to disk using MessageLite::SerializeToOstream(std::ostream * output) function from Protocol Buffers (Google), which by default does not do any compression.
ReductStore maintains three Data abstractions: Entry (logical), Block (logical, physical), and Bucket (logical). Each Entry is a blob associated with a key and a timestamp. Each logical Block contains one or multiple Entries of the same timestamp. Logical Blocks with the same microsecond level begin time are grouped and stored as a single physical Block backed by a single file on disk. Entries that are within the same bucket and smaller than the file system's minimum file size are grouped and stored together into a single Block (backed by one file) to reduce the storage overhead of small files. A Bucket logically contains one or multiple physical blocks and is typically used to separate time series data by topic or user.
Buckets enforce storage limits (the total blob size and the total number of entries within the Bucket) and write behavior (reject write or delete earliest) when the storage limit is reached.
Deleting a single Entry or a Block is not supported. The minimum deletion level is a Bucket.
ReductStore does not support foreign keys.
Index is not supported. A BRIN-like storage hack is implemented.
Block begin time is defined as the creation time of the block, with microsecond precision. Multiple logical blocks with the same begin time are grouped and stored as a single file on disk. Block start timestamp is embedded in the filename for range queries to perform binary search to locate the first relevant block.
ReductStore is not a transactional database. No isolation control mechanism is implemented.
ReductStore does not support logging currently.
ReductStore does not support and does not benefit from query compilation currently. Only range queries and continuous queries are supported, which always performs binary search and/or linear search to locate the starting/ending files for read/write.
ReductStore adopts Entry-at-a-Time model.
Provides HTTP methods for Entry level read, write, and range query. Provides HTTP methods for Bucket level metadata read, metadata update, create, and remove. Provides HTTP methods for Server level statistics read, bucket statistics read, and engine health check. Provides HTTP methods for token-based access control.
ReductStore is a shared-everything disk-oriented time-series database that directly persists/retrieves Entries to/from disk and does not cache any intermediate results in memory during query execution.
ReductStore adopts a hybrid storage model. Within a single Block, all metadata fields (timestamps, user-defined labels, file offsets) of all Entries are stored together in a row-oriented fashion as a file header, while blobs of all Entries are stored consecutively in the remaining part of the file.
Entries within each logical Block are sorted by timestamp. Logical Blocks are sorted by earliest entry timestamp, grouped by microsecond-level granularity into a single physical Block, and stored as a single file on disk.