How to Measure Query Processing Time Without Returning Rows

Question

My query is returning many rows but I’m only interested in the query processing time. How do I omit the query output and check for query processing time?

Answer

Append FORMAT Null to your query to configure the output format to Null. This prevents data from being transmitted to the client. For example:

SELECT
    customer_id,
    count() AS total,
    any(review_headline)
FROM amazon_reviews
GROUP BY customer_id
ORDER BY total DESC
FORMAT Null

The response will return the number of rows processed and the elapsed time, but 0 rows will be returned:

0 rows in set. Elapsed: 25.288 sec. Processed 222.04 million rows, 13.50 GB (8.78 million rows/s., 533.77 MB/s.)

Last modified on July 2, 2026

How to identify the most expensive queries in ClickHouseLearn how to use the `query_log` table in ClickHouse to identify the most memory and CPU-intensive queries across distributed nodes.

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