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ClickHouse® is a real-time analytics DBMS
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Previous patches in this series has a bottleneck in rehash(). This is the most slowest operation when insert lots of rows into the hashtable and eventually all that thread pool sometimes work as the most slowest thread since we did not have any queue of blocks. This patch adds such queue and now it scales linearly, so initialy with 1 thread I had ~4 hours for 10e9 elements (UInt64 key, UInt16 value), after this patch it works in 16 minutes with 16 threads (well actually I have to use 32 threads because of distribution of data in the source table). And now with 16 threads it works 16 times faster. Also this patch adds more optimal block splitting for the non-complex dictionaries, and usual block splitting for complex dictionaries. But anyway this moves the overhead from the loading into the hashtable threads out to the reader thread, and this is better, since reader does not uses that much CPU. v2: fix use-after-free on failed load (add missing wait in dtor) Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com> |
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ClickHouse® is an open-source column-oriented database management system that allows generating analytical data reports in real-time.
Useful Links
- Official website has a quick high-level overview of ClickHouse on the main page.
- ClickHouse Cloud ClickHouse as a service, built by the creators and maintainers.
- Tutorial shows how to set up and query a small ClickHouse cluster.
- Documentation provides more in-depth information.
- YouTube channel has a lot of content about ClickHouse in video format.
- Slack and Telegram allow chatting with ClickHouse users in real-time.
- Blog contains various ClickHouse-related articles, as well as announcements and reports about events.
- Code Browser (Woboq) with syntax highlight and navigation.
- Code Browser (github.dev) with syntax highlight, powered by github.dev.
- Contacts can help to get your questions answered if there are any.
Upcoming events
- Recording available: v22.12 Release Webinar 22.12 is the ClickHouse Christmas release. There are plenty of gifts (a new JOIN algorithm among them) and we adopted something from MongoDB. Original creator, co-founder, and CTO of ClickHouse Alexey Milovidov will walk us through the highlights of the release.
- ClickHouse Meetup at the CHEQ office in Tel Aviv - Jan 16 - We are very excited to be holding our next in-person ClickHouse meetup at the CHEQ office in Tel Aviv! Hear from CHEQ, ServiceNow and Contentsquare, as well as a deep dive presentation from ClickHouse CTO Alexey Milovidov. Join us for a fun evening of talks, food and discussion!
- ClickHouse Meetup at Microsoft Office in Seattle - Jan 18 - Keep an eye on this space as we will be announcing speakers soon!