2,219 questions
Best practices
0
votes
4
replies
108
views
How to manage data state between MySQL and Clickhouse?
I have MySQL and Clickhouse running for my system. Here MySQL is the source of truth and I store analytical data such as metrics (count, avg etc..) in Clickhouse. I have aggregated tables in ...
Best practices
0
votes
8
replies
105
views
Is it a good or a bad idea to join two tables on several columns if joining on one column is enough?
Let's assume that I have two tables with columns (product_id, user_id, event_id, event_payload) AS T1 and (product_id, user_id, event_id, event_metadata) AS T2.
Then let's assume that T1 is ordered by ...
Best practices
0
votes
1
replies
56
views
ClickHouse event analytics database design
I’m designing a high-volume analytics system and I’m trying to choose the data model before the dataset becomes too large to change easily.
Current setup:
Custom app events are stored in ClickHouse
...
- 445
0
votes
1
answer
110
views
How do I preserve column structure when a clickhouse query returns no rows? [closed]
I’m working with an analytics tool in Python that queries a clickhouse database. The issue I’m running into is that when a query returns zero rows, the result sometimes also loses its column structure ...
- 19
Best practices
0
votes
2
replies
72
views
How to pass very large ID sets (500K–5M) to ClickHouse queries using clickhouse-cs (.NET)? any industry guidlines?
I am using the official **clickhouse-cs .NET driver(**https://github.com/ClickHouse/clickhouse-cs) with a ClickHouse cluster that has two nodes behind a network load balancer.
My use case requires ...
Best practices
0
votes
3
replies
84
views
How to correctly map POCO objects to InsertBinaryAsync ClickHouse
I am using the ClickHouse.Driver library in my .NET project to insert data into ClickHouse. I have a POCO class and I want to use the InsertBinaryAsync method for high-performance inserts.
I'm ...
- 45
Best practices
0
votes
2
replies
117
views
ClickHouse ORDER BY: Is it correct to put a high-cardinality column first?
In ClickHouse MergeTree tables, ORDER BY defines physical data layout and the sparse primary index is built on granule boundaries.
From an internals perspective, ORDER BY should be chosen based on ...
Tooling
0
votes
2
replies
103
views
Where to download the correct Flink ClickHouse Connector JAR for Flink 1.18
I am running Flink 1.18 (Standalone/Docker) using PyFlink and I’m trying to sink data from Pulsar to ClickHouse using the Table API.
I initially tried the standard generic JDBC connector, but I ran ...
- 1,591
0
votes
1
answer
139
views
Clickhouse conditional column selection
I am working on a dashboard in Grafana with 2 different datasources which can be selected using a dashboard variable. Both datasources contain the same table (let's call it table1 for now), however, ...
- 85
0
votes
1
answer
56
views
AggregatingMergeTree in ClickHouse. Can I transfer state of function to another table?
I wish to calculate some methrics by time granulations. So, I have a table of facts (user actions), then I calculate into AggregatingMergeTree for each day. What I want is to take state of uniqState ...
2
votes
1
answer
158
views
Why does the triggering feature not support exceptions when using Kafka engine tables
I have subscribed to a Kafka cluster A with some Kafka engine tables before, and they are working normally. I have created a new Kafka cluster now, but after subscribing to the topics of the new ...
- 31
-1
votes
1
answer
74
views
Get result from distributed table joined with local tables on every shard [closed]
I have clickhouse cluster with distributed tables sharded by Id. I need to select data from distributed table 'A_distributed' that is joined locally with 'B_local' tables on Id and then given result ...
- 1,340
0
votes
1
answer
166
views
Connection check failed: Error: Client network socket disconnected before secure TLS connection was established from Clichouse cloud service
Connection check failed: Error: Client network socket disconnected before secure TLS connection was established
Environment:
ClickHouse Cloud Service
Issue:
When trying to connect my application to ...
- 21
0
votes
0
answers
146
views
Constantly getting a connection reset error when connecting to ClickHouse from Spark
Following the Spark Native Connector in ClickHouse, I downloaded clickhouse-spark-runtime-3.5.2_0.8.0 and clickhouse-jdbc-all-0.9.2, and set the catalog configured to:
The correct username and ...
- 363
0
votes
1
answer
97
views
Normalize JSON array in Clickhouse
I have a Clickhouse table with following structure:
id
json
111
[{"productId": "718f4d00-210d-43f1-9c9c-e97733d38972", "cost": "170.00000"}, {"productId&...
- 3