Query Performance Introspection

How is ClickHouse executing your queries so lightning fast? Let’s take a look under the hood of the ClickHouse query engine to understand how the parallel query processing on multiple CPU cores and multiple ClickHouse nodes really works.

We will also give a hands-on demonstration of built-in features you can use to introspect and thoroughly understand the execution steps of the query pipeline in ClickHouse. This capability is vital when you want to ensure your queries are optimized for your data.

Hosted by

tom schreiber

Tom Schreiber

Consulting Architect

Agenda

0:39

Overview of query execution steps in ClickHouse

1:23

Introspecting query execution steps via EXPLAIN

2:44

The parsed query

3:12

The rewritten query

3:30

The query plan

3:42

The query pipeline

6:26

Tuning a query pipeline in ClickHouse

8:40

A 4-thread pipeline in action

12:07

A 23-thread pipeline in action

13:19

A 50-thread pipeline in action

13:51

Introspecting query execution steps via trace logs

15:33

Introspecting query ressource consumption via query logs

17:14

Summary

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