zZzzZ. — /usr/share/mysql

Editing: mysql_performance_tables.sql

--
-- PERFORMANCE SCHEMA INSTALLATION
-- Note that this script is also reused by mysql_upgrade,
-- so we have to be very careful here to not destroy any
-- existing database named 'performance_schema' if it
-- can contain user data.
-- In case of downgrade, it's ok to drop unknown tables
-- from a future version, as long as they belong to the
-- performance schema engine.
--

set @have_old_pfs= (select count(*) from information_schema.schemata where schema_name='performance_schema');

SET @cmd="SET @broken_tables = (select count(*) from information_schema.tables  where engine != 'PERFORMANCE_SCHEMA' and table_schema='performance_schema')";

-- Work around for bug#49542
SET @str = IF(@have_old_pfs = 1, @cmd, 'SET @broken_tables = 0');
PREPARE stmt FROM @str;
EXECUTE stmt;
DROP PREPARE stmt;

SET @cmd="SET @broken_views = (select count(*) from information_schema.views where table_schema='performance_schema')";

-- Work around for bug#49542
SET @str = IF(@have_old_pfs = 1, @cmd, 'SET @broken_views = 0');
PREPARE stmt FROM @str;
EXECUTE stmt;
DROP PREPARE stmt;

SET @broken_routines = (select count(*) from mysql.proc where db='performance_schema');

SET @broken_events = (select count(*) from mysql.event where db='performance_schema');

SET @broken_pfs= (select @broken_tables + @broken_views + @broken_routines + @broken_events);

--
-- The performance schema database.
-- Only drop and create the database if this is safe (no broken_pfs).
-- This database is created, even in --without-perfschema builds,
-- so that the database name is always reserved by the MySQL implementation.
--

SET @cmd= "DROP DATABASE IF EXISTS performance_schema";

SET @str = IF(@broken_pfs = 0, @cmd, 'SET @dummy = 0');
PREPARE stmt FROM @str;
EXECUTE stmt;
DROP PREPARE stmt;

SET @cmd= "CREATE DATABASE performance_schema character set utf8mb3";

SET @str = IF(@broken_pfs = 0, @cmd, 'SET @dummy = 0');
PREPARE stmt FROM @str;
EXECUTE stmt;
DROP PREPARE stmt;