ClickHouse is a very powerful database for analytics. Microsoft Excel is one of the world’s most popular business applications. There are several ways to bring ClickHouse data to Excel spreadsheets. In this article we will explain how to connect Excel to ClickHouse using the Mondrian OLAP server. This approach has been pioneered in Sergei Semenkov’s[…]
This final article completes our tour of array capabilities. We’ll survey functions for array map and reduce operations, demonstrating behavior and commenting on performance. This is an opportunity to dig further into lambdas, which are critical for using arrays effectively.
ClickHouse arrays combine neatly with GROUP BY aggregation. We show how arrays track sequences and offer a couple of ways to do funnel analysis.
ClickHouse is a polyglot database that can talk to many external systems using dedicated engines or table functions. In modern cloud systems, the most important external system is object storage. It can hold raw data to import from or export to other systems (aka a data lake) and offer cheap and highly durable storage for table data. ClickHouse now supports both of these uses for S3 compatible object storage.
ClickHouse contributors regularly add analytic features that go beyond standard SQL. This design approach is common in successful open source projects and reflects a bias toward solving real-world problems creatively. Arrays are a great example.
Data backups are an inglorious but vital part of IT operations. They are most challenging in “big data” deployments, such as analytics databases. This article will explore the plumbing involved in backing up ClickHouse and introduce the clickhouse-backup tool for automating the process.
Our colleague Mikhail Filimonov just published an excellent ClickHouse Kafka Engine FAQ. It provides users with answers to common questions about using stable versions, configuration parameters, standard SQL definitions, and many other topics. Even experienced users are likely to learn something new.
But what if you are getting started and need help setting up Kafka and ClickHouse for the first time? Good news! This article is for you.
Kafka is a popular way to stream data into ClickHouse. ClickHouse has a built-in connector for this purpose — the Kafka engine. This article collects typical questions that we get in our support cases regarding the Kafka engine usage. We hope that our recommendations will help to avoid common problems.
Mutable data is generally unwelcome in OLAP databases. ClickHouse is no exception to the rule. Like some other OLAP products, ClickHouse did not even support updates originally. Later on, updates were added, but like many other things they were added in a “ClickHouse way.”
Even now, ClickHouse updates are asynchronous, which makes them difficult to use in interactive applications. Still, in many use cases users need to apply modifications to existing data and expect to see the effect immediately. Can ClickHouse do that? Sure it can.
A common use case in time series applications is to get the measurement value at a given point of time. For example, if there is a stream of measurements, one often needs to query the measurement as of current time or as of the same day yesterday and so on. Financial market data analysis and all sorts of monitoring applications are typical examples.
Databases have different ways to achieve this task and ClickHouse is not an exception here. In fact, ClickHouse offers at least 5 different approaches. In this article, we will review and compare them.
Multi-volume storage is crucial in many use cases. It helps to reduce storage costs as well as improves query performance by allowing placement of the most critical application data on the fastest storage devices. Monitoring data is a classic use case. The value of data degrades rapidly over time. The last day, last week, last month, and previous year data have very different access patterns, which in turn correspond to various storage needs.
Dec 28, 2019
Grafana is a popular tool to create dashboards of time series data. It features outstanding graphics, interactive displays that zoom in on data, and support for a wide range of data sources. It turns out that one of those data sources is ClickHouse, and Grafana is a great way to visualize ClickHouse data.