RocksDB VS MariaDB

RocksDB: A high-performance embedded database optimized for multi-core CPUs and fast storage like SSDs. Its use of a log-structured merge-tree (LSM tree) makes it suitable for applications requiring high throughput and efficient storage, such as streaming data processing.

[RocksDB](https://rocksdb.org/) isn’t a distributed storage system, fwiw. It’s an embedded KV engine similar to LevelDB, LMDB, or really sqlite (though that’s full SQL, not just KV)

To output the top 3 rocks, our engine has to first store all the rocks in some sorted way. To do this, we of course picked RocksDB, an embedded lexicographically sorted key-value store, which acts as the sorting operation's persistent state. In our RocksDB state, the diffs are keyed by the value of weight, and since RocksDB is sorted, our stored diffs are automatically sorted by their weight.

The in-memory version of Memgraph uses Delta storage to support multi-version concurrency control (MVCC). However, for larger-than-memory storage, we decided to use the Optimistic Concurrency Control Protocol (OCC) since we assumed conflicts would rarely happen, and we could make use of RocksDB’s transactions without dealing with the custom layer of complexity like in the case of Delta storage.

I was looking at https://github.com/facebook/rocksdb/ but it seems to not allow queries by value, as my last requirmenet.

Tuning RocksDB well is a very very hard challenge, and one that I am happy to not do day to day anymore. RocksDB is very powerful but it comes with other very sharp edges. Compaction is one of those, and all answers are likely workload dependent.

If you are worried about write amplification then leveled compactions are sub-optimal. I would try the universal compaction.

- https://github.com/facebook/rocksdb/wiki/Universal-Compactio...

It's fairly challenging to write a KV database, and takes several years of development to get the balance right between performance and reliability and avoiding data loss. Maybe read through the documentation for RocksDB https://github.com/facebook/rocksdb/wiki/RocksDB-Overview and watch the video on why it was developed and that may give you an impression of what is involved.

LMDB is much more sain in the sense that it supports real ACID transactions instead of savepoints for RocksDB. The latter is heavy and consumes a lot more memory for a lot less read throughput. However, RocksDB has a much better parallel and concurrent write story, where you can merge entries with merge functions and therefore write from multiple CPUs.

https://github.com/facebook/rocksdb/issues?q=is%3Aissue+clic...

Here are some bugs in JeMalloc:

MariaDB [1] is a community developed fork of MySQL, so you can feel free to use that in place of MySQL.

Another alternative would be Percona [2] which is a drop-in replacement for Oracle MySQL.

About PostgreSQL I haven't had that much of personal experience with it, but for sure I plan to learn it, because it has been battle-tested for years with lots of well-known projects, such as Django framework, for instance.

[1] https://github.com/MariaDB/server

[2] https://github.com/percona/percona-server

aka mariadb-dumpslow (aka mysqldumpslow) or pt-query-digest

My recollection is that it was created when Oracle took over MySQL in order to continue to have a community-driven GPLv2 "mysql compatible" server; I was expecting them to be more different than they are, but for comparison one is a "clean" GPLv2" and the other has more words and a link to oracle.com: https://github.com/mysql/mysql-server/blob/mysql-8.0.31/LICE... https://github.com/MariaDB/server/blob/mariadb-10.11.1/COPYI...

git clone --recursive --depth 1 --branch 10.5 https://github.com/MariaDB/server.git cmake . # needs cmake3 make make install

RUN git clone \ --branch mariadb-10.5.15 \ --depth 1 \ --recurse-submodules \ https://github.com/mariadb/server.git \ ~/server

Hi everyone! Our team just released EdgelessDB, an open-source database built on MariaDB that runs completely inside Intel SGX enclaves. As storage engine, it uses RocksDB with a custom encryption engine. The engine uses AES-GCM and is optimized for RocksDB’s specific SST file layout and the enclave environment. It has some nice properties like global confidentiality and verifiability and it considers strong attackers like malicious admins or rootkits. It also delivers rather low overheads (<10% for the TPC-C benchmark on Azure). In short: all data is only ever decrypted inside the enclave. This is different from other databases, where data and corresponding keys are processed in the clear in memory. We believe this is useful because (1) it’s very secure and (2) it enables some interesting use cases, like secure data pooling between parties. If you’re interested in trying it out: here’s a quickstart guide. In essence, you can run the Docker image with a single command on any recent Intel Xeon with SGX. Code and more info can be found on GitHub. Would be great to get your feedback on this :-)

MariaDB has 268 contributors vs 83 contributors to MySQL *