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

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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...

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

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