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ClickHouse® is a real-time analytics DBMS
2cfbc27f13
In case of merges/mutations, separate MemoryTracker object is used, to
track memory separately, to report this metrics.
However, the tail of those allocations hadn't been taken into account,
and in case of lots of mutations/merges it can be significant.
100% reproducible with the following example:
Start the server w/o frequent sync with RSS:
$ clickhouse-server -C /src/programs/server/config.xml -- --asynchronous_metrics_update_period_s=86400
Run the following snippet:
create table data (key Int, value Nullable(Decimal(38, 0))) engine=ReplicatedMergeTree('/ch/data', '1') order by key
insert into data values (1, -13028236692093846346337460743176821145)
alter table data modify column value UInt256
Code: 341. DB::Exception: Received from localhost:9000. DB::Exception: Exception happened during execution of mutation 'mutation_2.txt' with part 'all_1_1_0' reason: 'Code: 407. DB::Exception: Convert overflow: while executing 'FUNCTION _CAST(value :: 1, 'UInt256' :: 2) -> _CAST(value, 'UInt256') UInt256 : 3': (while reading from part ./store/dd9/dd9ef183-1270-4877-af22-8a000bdcc1b8/all_1_1_0/): While executing MergeTreeInOrder. (DECIMAL_OVERFLOW) (version 22.12.1.1)'. This error maybe retryable or not. In case of unretryable error, mutation can be killed with KILL MUTATION query. (UNFINISHED)
And track the memory:
select value/1e9 from system.metrics where metric like 'MemoryTracking'
Reported-by: @filimonov
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
- v22.11 Release Webinar Original creator, co-founder, and CTO of ClickHouse Alexey Milovidov will walk us through the highlights of the release, provide live demos, and share vision into what is coming in the roadmap.
- ClickHouse Meetup at the Deutsche Bank office in Berlin Hear from Deutsche Bank on why they chose ClickHouse for big sensitive data in a regulated environment. The ClickHouse team will then present how ClickHouse is used for real time financial data analytics, including tick data, trade analytics and risk management.
- AWS re:Invent Core members of the ClickHouse team -- including 2 of our founders -- will be at re:Invent from November 29 to December 3. We are available on the show floor, but are also determining interest in holding an event during the time there.