MySQL 5.7 Release Notes
The users table contains a row
for each user who has connected to the MySQL server. For each
user name, the table counts the current and total number of
connections. The table size is autosized at server startup. To
set the table size explicitly, set the
performance_schema_users_size
system variable at server startup. To disable user statistics,
set this variable to 0.
The users table has the following
columns. For a description of how the Performance Schema
maintains rows in this table, including the effect of
TRUNCATE TABLE, see
Section 25.12.8, “Performance Schema Connection Tables”.
USERThe client user name for the connection. This is
NULLfor an internal thread, or for a user session that failed to authenticate.CURRENT_CONNECTIONSThe current number of connections for the user.
TOTAL_CONNECTIONSThe total number of connections for the user.