kandi X-RAY | ClickHouse Summary
kandi X-RAY | ClickHouse Summary
ClickHouse is an open-source column-oriented database management system that allows generating analytical data reports in real-time.
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ClickHouse Key Features
ClickHouse Examples and Code Snippets
Trending Discussions on ClickHouse
I'd like to know if there is an approach or projection pattern to be able to choose SQL driver at runtime in Golang when both of these drivers have the same name. I want to switch between HTTP ClickHouse driver (https://github.com/mailru/go-clickhouse) and native TCP ClickHouse driver (https://github.com/ClickHouse/clickhouse-go) using an environment variable....
ANSWERAnswered 2022-Mar-28 at 14:53
Since version 2 of mailru/go-clickhouse it is possible to use both of them, authors have changed driver name to
I'm playing with Kafka engine on ClickHouse cluster. At the moment ClickHouse 22.1 cluster and Kafka are run in Docker. Here are configurations: https://github.com/apanasevich/clickhouse-etl-cluster
Here are DDL for Kafka integration:...
ANSWERAnswered 2022-Mar-13 at 12:04
The problem was that DDL for view was incorrect. Unfortunately, it somehow warked for
MergeTree engine but didn't work for
This is the corrected script:
I've a python script that outputs the input:...
ANSWERAnswered 2022-Mar-01 at 14:00
tag in function config (
I want to use Clickhouse as an OLAP and PostgreSQL as an OLTP database.
The problem is that queries to Clickhouse run slower than on Postgres. The query is as below:...
ANSWERAnswered 2022-Feb-20 at 21:45
There are ways to shoot your feet with Clickhouse
I have a table like:
create table test (id String, timestamp DateTime, somestring String) ENGINE = MergeTree ORDER BY (id, timestamp)
i inserted 100 records then inserted another 100 records and i run select query
select * from test clickhouse returning with 2 parts their lengths are 100 and they are ordered in themselves. Then i run the query
optimize table test and it started to return with 1 part and its length is 200 and ordered. So should i run optimize query after all insert and does it increase select query performance like
select count(*) from test where id = 'foo' ?
ANSWERAnswered 2022-Jan-27 at 17:13
Usually not, you can rely on Clickhouse background merges.
Also, Clickhouse has no intention to merge all the data from the partition into one part file, because "over-optimization" can affect performance too
I'm setting up clickhouse-backup utility locally. I go through the installation steps and now I'm stuck on the step with changing settings for '.config.yml' file.
sudo ./clickhouse-backup create from the folder where I decompressed the utility and could found created backup in
When I execute:...
ANSWERAnswered 2022-Jan-25 at 14:31
./clickhouse-backup default-config this command generates a template for the config with default settings.
In clickhouse, how can I separate number by comma?...
ANSWERAnswered 2022-Jan-25 at 14:19
Such formatting to strings from numbers is not implemented.
I'm running ClickHouse Docker image on MacBook M1 and getting the following error....
ANSWERAnswered 2021-Nov-03 at 13:47
Have you tried adding
--platform linux/amd64 in the run command?
I have a table with products names in PostgreSql database. Total rows is ~30M. And I have history of prices in ClickHouse. I want to join names to prices. DDL to create dictionary:...
ANSWERAnswered 2022-Jan-17 at 14:54
Such optimization is not implemented, yet.
Initially supposed that dictionaries to be used with only
Table representation were introduced much later.
Internally Dictionaries are the set of hash tables -- if your dictionary has 50 attributes then it will be 50 hash tables. These hash tables are very fast if you do seek by key, but very slow if you need to find the next element.
Right now the query
SELECT name FROM products_dict WHERE product_id IN ('97646239') is executed in very straightforward way, though it could be converted into
dictGet under the hood.
From the documentation, you have to put a NOT NULL modifier in the column definition to mark it as such, just like for other SQL databases.
Consider this table:...
ANSWERAnswered 2022-Jan-05 at 14:55
Clickhouse behaviour with
Not Null constraints is not compatible with other databases.
You can overcome it using check constraints https://clickhouse.com/docs/en/sql-reference/statements/create/table/#constraints
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