I have heard multiple times that its rather slow, but haven’t seen any benchmarks. Would make sense, as a dynamically typed, garbage collected language Clojure is not the greatest fit to implement a database in.
The question is, are the things you gain worth it?
I would be surprised if Datomic's core code was written in Clojure rather than Java (and these days Java's performance can get you pretty far in implementing a database, see e.g. Cassandra).
Most highly performance-sensitive code in the Clojure ecosystem is a Clojure wrapper around a Java core.
But yes as I said elsewhere, it would be great if Cognitect allowed people to post benchmark results.
I‘ve used Cassandra, its not that impressive. Much slower than the C++ rewrite (ScyllaDB?), latency issues due to GC, can’t hold a candle to Clickhouse. And they’ve been optimizing it for a long time now.
Cassandra and ClickHouse are designed to do different things. To flip things around, have you compared the latency of a single-row update or delete in Cassandra vs ClickHouse?
If you care about the latency of a single row update or delete, Clickhouse is definitely the wrong tool for the job. First, it doesn’t really have deletes(afaik). Second, you need to batch updates aggressively to get good throughput.
But you’re right C* and CH are designed to do different things. I just found the difference in general performance across everything (startup, schema changes, throughput, query performance, optimization opportunities) to be quite pronounced. One feels like a race car, the other not so much.
Idiomatic Clojure is slower than JS, but you can make Clojure somewhat close to Java by writing Java with parenthesis(lots of interop from Clojure). One of the devs of Datomic brag about how it was only 200KLOC of Clojure, but if you extract the datomic tar, the lib dir has probably more that 2Million LOC of open source Java libs.
