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ClickHouse® is a real-time analytics DBMS
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Recently (#32094) test database had been overlapped, and random prefix for database had been increased from 6 to 8. But actually 6 bytes for random prefix should be enough (with existing alphabet (0-9a-z) it is 36**6=2'176'782'336), and the real reason of this overlap is that random generator by default uses shared state [1]: The functions supplied by this module are actually bound methods of a hidden instance of the random.Random class. You can instantiate your own instances of Random to get generators that don’t share state. [1]: https://docs.python.org/3/library/random.html I've played a little bit with random in python, and using default random generator it generates non-unique strings pretty fast, just in a few runs, but using SystemRandom (that uses /dev/urandom) it takes ~1 minute. Test: ```sh $ while /tmp/test.py | LANG=c sort -S5G | LANG=c uniq -d | tee /dev/stderr | wc -l | fgrep -q -x -c 0; do :; done ``` ```python #!/usr/bin/env python3 import multiprocessing import string import random def random_str(length=6): alphabet = string.ascii_lowercase + string.digits return ''.join(random.SystemRandom().choice(alphabet) for _ in range(length)) def worker(_): print(random_str()) with multiprocessing.Pool(processes=2) as pool: pool.map(worker, range(0, int(10e3))) ``` So let's switch to SystemRandom and use 6-byte prefix. |
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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.
- 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 with syntax highlight and navigation.
- Contacts can help to get your questions answered if there are any.