When Join_buffer_space_limit is set to the minimum value, the query speed is increased dozens of times, which is unreasonable.

Steps to reproduce:
1. Use the mariadb:11.0 container image to create a container, and create a database for the test
2. Use the SQL statement in init_tables.sql to build a table
3. Use select_query.sql to query, the query time on my machine is about 9s

But when performing the same steps 1 and 2, and before performing step 3, SET Session join_buffer_space_limit = 2048;
The query time will drop to about 0.8s

Theoretically, `join_buffer_space_limit` is merely an upper limit, and a larger value should result in faster query speeds.