MySQL 8.0 Reference Manual
MySQL 8.0 Release Notes
The Performance Schema provides auser_variables_by_threadtable that exposes user-defined variables. These are variables defined within a specific session and include a@character preceding the name; seeUser-Defined Variables.
Theuser_variables_by_threadtable has these columns:
THREAD_IDThe thread identifier of the session in which the variable is defined.
VARIABLE_NAMEThe variable name, without the leading
@character.VARIABLE_VALUEThe variable value.
Theuser_variables_by_threadtable has these indexes:
Primary key on (
THREAD_ID,VARIABLE_NAME)
TRUNCATE TABLEis not permitted for theuser_variables_by_threadtable.