ClickHouse DBA Script Archives | Page 8 of 10

ClickHouse Troubleshooting: Avoiding Excessive Disk Swaps

Introduction Disk swapping is a technique used by operating systems to manage memory usage when the amount of available physical memory is limited. When the operating system runs out of available physical memory, it uses […]

Using TOP Command to Measure ClickHouse Server Load & Queue Length

Shiv Iyer

Introduction Measuring load and queue length of ClickHouse Server is important for troubleshooting performance bottleneck. The load is a measure of the amount of work that ClickHouse is currently doing or is capable of doing. […]

How to Monitor & Troubleshoot Log Contention in ClickHouse

Shiv Iyer

Introduction Log contention in ClickHouse occurs when multiple write operations compete for the same log file, causing performance issues and potentially leading to data corruption. Here are some steps you can take to troubleshoot and […]

Monitoring Query Latency due to Wait and Latch Events in ClickHouse

Shiv Iyer

Introduction In ClickHouse, you can monitor query latency and waits/latches using the system.query_log and system.metrics tables. Here is an example query that can be used to monitor query latency and wait/latch events: This query selects […]

How NULL Values affect ClickHouse Query Performance

ClickHouse Troubleshooting: How NULL Values affect Query Performance

Shiv Iyer

Introduction NULL values in ClickHouse can affect performance in several ways. One way is that they can increase the size of data, which can lead to slower query execution times as more data needs to […]

ClickHouse Troubleshooting: How to Identify Blocks Causing Latch Contention

Shiv Iyer

Introduction Latch contention in ClickHouse can have a significant impact on performance. A latch is a synchronization mechanism that allows multiple threads to access a shared resource, such as a data block, in a controlled […]

Streaming ClickHouse Data to Kafka

ChistaDATA Inc.

Introduction ClickHouse has an inbuilt Kafka table engine which is commonly used to read streaming messages from Apache Kafka and store it in ClickHouse. This is one of the important and widely used features of […]

Fatal Background Processes in ClickHouse

Shiv Iyer

Introduction ClickHouse is an open-source columnar database management system that is designed to handle high volumes of data and support high concurrency. However, like any complex system, it is possible for background processes to fail, […]

How to implement correlated columns in ClickHouse?

Shiv Iyer

Introduction Correlated columns are useful in many situations where you need to retrieve data from multiple tables and use data from one table to filter data in another. Some common use cases include: How are […]

ClickHouse Caches: Configuring Buffer Cache for High Performance

Shiv Iyer

Introduction The ClickHouse Buffer Cache works by caching frequently accessed data in memory. This cache reduces disk I/O operations and speeds up query performance. The buffer cache is organized as a pool of memory blocks, […]

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