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17 docs tagged with "performance"

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Filter with PREWHERE

Wondering when to use PREWHERE in ClickHouse? Here's how to optimize filtering with PREWHERE and minimize scan size in ClickHouse.

Optimize memory usage for joins

ClickHouse has different algorithms for join operations. Here's how to choose which join algorithm to use to reduce memory usage.

Optimize queries with Sum and Count

Sum() and Count() are the most common ClickHouse aggregations. Here's how to speed up queries in ClickHouse that use a sum and count aggregation.

Optimize single row joins

Wondering how to optimize single row joins in ClickHouse? Use a CROSS JOIN to improve join efficiency in ClickHouse.

Speed up ARGMIN and ARGMAX aggregations

ClickHouse currently is not able to use the knowledge of the sort key from a table to speed up aggregations. This means that to get the ARGMIN() or ARGMAX() values from a table it will read all values even if it's sorted by that column:

Use LowCardinality

ClickHouse LowCardinality types can improve the speed of your queries. Here is how and when to use LowCardinality to optimize column storage for faster queries.