A Day in the Life of a ClickHouse® Query — Intro to ClickHouse Internals | Tutorial on ClickHouse

Experience the unmatched power of ClickHouse® on Hetzner: https://altinity.com/altinity-cloud-on-hetzner/ ______________________ Our latest webinar, hosted by Robert Hodges (Altinity CEO), is a gentle introduction to ClickHouse internals, focusing on topics that will help your applications run faster and more efficiently. Find answers to common questions re: ClickHouse queries. 1. Why do queries run out of memory? 2. How can you make your queries even faster? 3. How should you size ClickHouse nodes for best cost-efficiency? The key to these questions and many others is knowing what happens inside ClickHouse when a query runs. We’ll discuss the basic flow of query execution, dig into how ClickHouse handles aggregation and joins, and show you how ClickHouse distributes processing within a single CPU as well as across many nodes in the network. Want the webinar slides? 👉🏼 https://www.slideshare.net/Altinity/a-day-in-the-life-of-a-clickhouse-query-webinar-slides 0:00 Introduction 5:54 Understand the engine 9:35 Processing INSERT 11:16 Improving efficiency 18:02 What happens when you INSERT? 20:07 MergeTree 27:34 Optimize INSERT 29:19 Aggregation 30:10 Process a query with Aggregates 32:33 Compute an average in parallel 33:55 ClickHouse thread doing Aggregation 35:14 Aggregation performance drivers 37:28 ClickHouse memory limits 38:47 Make aggregation queries faster 40:07 Reduce memory usage in aggregation queries 40:58 JOIN combines data between tables 42:10 Process a query with a JOIN 47:21 Example of a distributed dataset 50:22 ClickHouse pushes down JOINs by default #ClickHouseQueries #ClickHouseTraining #ClickHouseTutorial #OpenSourceDatabase #ClickHouseCommunity -------------- Join Altinity Meetups on ClickHouse: https://www.meetup.com/san-francisco-bay-area-clickhouse-meetup/ Check out more resources on ClickHouse: https://altinity.com/resources/ Visit the Altinity Documentation site: https://docs.altinity.com/ Contribute to Altinity Knowledge Base for ClickHouse: https://kb.altinity.com/ Join the Reddit community for ClickHouse: https://www.reddit.com/r/Clickhouse/ ------------- More about Altinity! 💡 Site: https://www.altinity.com​ LinkedIn: https://www.linkedin.com/company/altinity Twitter: https://twitter.com/AltinityDB Slack: https://altinity.com/slack