Elasticsearch Versus RocksDB: The Old Real Time Razzle Dazzle
July 22, 2021
Something happens. The “event” is captured and written to the file. Even if you are watching the “something” happening, there is latency between the event and the sensor or the human perceiving the event. The calculus of real time is mostly avoiding too much talk about latency. But real time is hot because who wants to look at old data, not TikTok fans and not the money-fueled lovers of Robinhood.
“Rockset CEO on Mission to Bring Real-Time Analytics to the Stack” used lots of buzzwords, sidesteps inherent latency, and avoids commentary on other allegedly real-time analytics systems. Rockset is built on RockDB, an open source software. Nevertheless, there is some interesting information about Elasticsearch; for example:
- Unsupported factoids like: “Every enterprise is now generating more data than what Google had to index in [year] 2000.”
- No definition or baseline for “simple”: “The combination of the converged index along with the distributed SQL engine is what allows Rockset to be fast, scalable, and quite simple to operate.”
- Different from Elasticsearch and RocksDB: “So the biggest difference between Elastic and RocksDB comes from the fact that we support full-featured SQL including JOINs, GROUP BY, ORDER BY, window functions, and everything you might expect from a SQL database. Rockset can do this. Elasticsearch cannot.”
- Similarities with Rockset: “So Lucene and Elasticsearch have a few things in common with Rockset, such as the idea to use indexes for efficient data retrieval.”
- Jargon and unique selling proposition: “We use converged indexes, which deliver both what you might get from a database index and also what you might get from an inverted search index in the same data structure. Lucene gives you half of what a converged index would give you. A data warehouse or columnar database will give you the other half. Converged indexes are a very efficient way to build both.”
Amazon has rolled out its real time system, and there are a number of options available from vendors like Trendalyze.
Each of these vendors emphasizes real time. The problem, however, is that latency exists regardless of system. Each has use cases which make their system seem to be the solution to real time data analysis. That’s what makes horse races interesting. These unfold in real time if one is at the track. Fractional delays have big consequences for those betting their solution is the least latent.
Stephen E Arnold, July 22, 2021
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