Which is faster: LIMIT 1 or LIMIT 20? Presumably, fetching less rows is faster than fetching more rows. But for 16 years (since 2007) the MySQL query optimizer has had a “bug”† that not only makes LIMIT 1 slower than LIMIT 20 but can also make the former a table scan, which tends to cause problems. This happened last week where I work, and although MySQL DBAs are familiar with this bug, I’m writing this blog post for developers to more clearly illustrate and explain what’s going on and why because it’s really counterintuitive.

Which is faster: LIMIT 1 or LIMIT 20? Presumably, fetching less rows is faster than fetching more rows. But for 16 years (since 2007) the MySQL query optimizer has had a “bug”† that not only makes LIMIT 1 slower than LIMIT 20 but can also make the former a table scan, which tends to cause problems. This happened last week where I work, and although MySQL DBAs are familiar with this bug, I’m writing this blog post for developers to more clearly illustrate and explain what’s going on and why because it’s really counterintuitive.

Which is faster: LIMIT 1 or LIMIT 20? Presumably, fetching less rows is faster than fetching more rows. But for 16 years (since 2007) the MySQL query optimizer has had a “bug”† that not only makes LIMIT 1 slower than LIMIT 20 but can also make the former a table scan, which tends to cause problems. This happened last week where I work, and although MySQL DBAs are familiar with this bug, I’m writing this blog post for developers to more clearly illustrate and explain what’s going on and why because it’s really counterintuitive.