THthe-alchemist·Mar 2, 2021
Also wanted to share my overall positive experience with Clickhouse.
UPSIDES
* started a 3-node cluster using the official Docker images super quickly
* ingested billions of rows super fast
* great compression (of course, depends on your data's characteristics)
* features like https://clickhouse.tech/docs/en/engines/table-engines/merget... are amazing to see
* ODBC support. I initially said "Who uses that??", but we used it to connect PostgreSQL and so we can keep the non-timeseries data in PostgreSQL but still access PostgreSQL tables in Clickhouse (!)
* you can go the other way too: read Clickhouse from PostgreSQL (see https://github.com/Percona-Lab/clickhousedb_fdw, although we didn't try this)
* PRs welcome, and quickly reviewed. (We improved the ODBC UUID support)
* code quality is pretty high.
DOWNSIDES
* limited JOIN capabilities,
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which is expected from a timeseries-oriented database like Clickhouse. It's almost impossible to implement JOINs at this kind of scale. The philosophy is "If it won't be fast as scale, we don't support it"
* not-quite-standard SQL syntax, but they've been improving it
* limited DELETE support, which is also expected from this kind of database, but rarely used in the kinds of environments that CH usually runs in (how often do people delete data from ElasticSearch?)
It's really an impressive piece of engineering. Hats off to the Yandex crew.