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Bug#106939 TRUNCATE performance_schema.accounts causes duplicated counts in global_status
Contribution by Tencent. Problem: ======== The statement TRUNCATE performance_schema.accounts; can cause statistics reported by: SHOW GLOBAL STATUS SELECT * FROM performance_schema.global_status; to be incorrect, with session status variables counted twice. This happens only when: - show_compatibility_56 is 0 (so that status variables are aggregated by accounts, users and hosts) - some hosts are not instrumented, for example with a low performance-schema-hosts-size. Root cause: =========== Session statistics are aggregated already from each THD (THD::status_var) to the global status variable (global_status_var) This is expected. The code path for TRUNCATE performance_schema.accounts, in function PFS_account::aggregate_status(), contains an extra aggregation to global_status_var, following the design pattern of other instruments. This aggregation is not needed in case of status variables, because of the THD -> global_status_var flow already implemented in the SQL layer. Fix: ==== Simplify PFS_account::aggregate_status(), never aggregate to global_status_var. Change-Id: Id1a83621bd6c0ff998f95041cd929dc478ab7362
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Lines changed: 241 additions & 25 deletions

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‎mysql-test/suite/perfschema/r/misc_global_status.result‎

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CREATE USER user1@localhost;
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CREATE USER user2@localhost;
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CREATE USER user3@localhost;
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grant ALL on *.* to user1@localhost;
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grant ALL on *.* to user2@localhost;
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grant ALL on *.* to user3@localhost;
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SET GLOBAL show_compatibility_56=0;
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TRUNCATE TABLE performance_schema.accounts;
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FLUSH PRIVILEGES;
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CREATE TABLE test.t_range(a int, b int, PRIMARY KEY(a));
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INSERT INTO test.t_range values (1, 1), (2,2), (3, 3), (4, 4), (5, 5);
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INSERT INTO test.t_range values (6, 6), (7,7), (8, 8), (9, 9), (10, 10);
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FLUSH STATUS;
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SELECT * from test.t_range where (a >= 3) AND (a <= 5);
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a b
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3 3
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4 4
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5 5
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SELECT * from performance_schema.session_status
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WHERE VARIABLE_NAME = 'Select_range';
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VARIABLE_NAME VARIABLE_VALUE
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Select_range 1
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VARIABLE_NAME DELTA
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Select_range 1
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SELECT * from test.t_range where (a >= 3) AND (a <= 5);
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a b
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3 3
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4 4
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5 5
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SELECT * from performance_schema.session_status
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WHERE VARIABLE_NAME = 'Select_range';
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VARIABLE_NAME VARIABLE_VALUE
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Select_range 1
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VARIABLE_NAME DELTA
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Select_range 2
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SELECT * from test.t_range where (a >= 3) AND (a <= 5);
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a b
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3 3
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4 4
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5 5
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SELECT * from test.t_range where (a >= 4) AND (a <= 6);
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a b
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4 4
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5 5
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6 6
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SELECT * from performance_schema.session_status
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WHERE VARIABLE_NAME = 'Select_range';
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VARIABLE_NAME VARIABLE_VALUE
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Select_range 2
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VARIABLE_NAME DELTA
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Select_range 4
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SELECT * from test.t_range where (a >= 3) AND (a <= 5);
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a b
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3 3
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4 4
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5 5
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SELECT * from test.t_range where (a >= 4) AND (a <= 6);
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a b
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4 4
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5 5
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6 6
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SELECT * from test.t_range where (a >= 5) AND (a <= 7);
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a b
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5 5
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6 6
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7 7
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SELECT * from performance_schema.session_status
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WHERE VARIABLE_NAME = 'Select_range';
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VARIABLE_NAME VARIABLE_VALUE
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Select_range 3
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VARIABLE_NAME DELTA
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Select_range 7
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VARIABLE_NAME DELTA
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Select_range 7
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SELECT `USER`, `HOST`, VARIABLE_NAME, VARIABLE_VALUE
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FROM performance_schema.status_by_account WHERE VARIABLE_NAME = 'Select_range'
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AND `USER` LIKE 'user%'
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ORDER BY `USER`;
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USER HOST VARIABLE_NAME VARIABLE_VALUE
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user1 localhost Select_range 1
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user2 localhost Select_range 2
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user3 localhost Select_range 3
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VARIABLE_NAME DELTA
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Select_range 7
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TRUNCATE TABLE performance_schema.accounts;
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VARIABLE_NAME DELTA
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Select_range 7
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VARIABLE_NAME DELTA
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Select_range 7
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TRUNCATE TABLE performance_schema.accounts;
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VARIABLE_NAME DELTA
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Select_range 7
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DROP TABLE test.t_range;
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REVOKE ALL PRIVILEGES, GRANT OPTION FROM user1@localhost;
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REVOKE ALL PRIVILEGES, GRANT OPTION FROM user2@localhost;
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REVOKE ALL PRIVILEGES, GRANT OPTION FROM user3@localhost;
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DROP USER user1@localhost;
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DROP USER user2@localhost;
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DROP USER user3@localhost;
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SET GLOBAL show_compatibility_56=1;
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FLUSH PRIVILEGES;

‎mysql-test/suite/perfschema/t/misc_global_status-master.opt‎

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--loose-performance_schema_hosts_size=0

‎mysql-test/suite/perfschema/t/misc_global_status.test‎

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# Tests for PERFORMANCE_SCHEMA
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--source include/not_embedded.inc
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--source include/have_perfschema.inc
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CREATE USER user1@localhost;
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CREATE USER user2@localhost;
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CREATE USER user3@localhost;
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grant ALL on *.* to user1@localhost;
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grant ALL on *.* to user2@localhost;
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grant ALL on *.* to user3@localhost;
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# To aggregate to accounts
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SET GLOBAL show_compatibility_56=0;
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TRUNCATE TABLE performance_schema.accounts;
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FLUSH PRIVILEGES;
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CREATE TABLE test.t_range(a int, b int, PRIMARY KEY(a));
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INSERT INTO test.t_range values (1, 1), (2,2), (3, 3), (4, 4), (5, 5);
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INSERT INTO test.t_range values (6, 6), (7,7), (8, 8), (9, 9), (10, 10);
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FLUSH STATUS;
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let $initial= `SELECT VARIABLE_VALUE FROM performance_schema.global_status WHERE VARIABLE_NAME = 'Select_range'`;
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# Causes Select_range to increment (+1)
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SELECT * from test.t_range where (a >= 3) AND (a <= 5);
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SELECT * from performance_schema.session_status
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WHERE VARIABLE_NAME = 'Select_range';
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--disable_query_log
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eval SELECT VARIABLE_NAME, (VARIABLE_VALUE - $initial) AS DELTA from performance_schema.global_status WHERE VARIABLE_NAME = 'Select_range';
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--enable_query_log
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connect(con1, localhost, user1,,);
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# Causes Select_range to increment (+1)
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SELECT * from test.t_range where (a >= 3) AND (a <= 5);
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SELECT * from performance_schema.session_status
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WHERE VARIABLE_NAME = 'Select_range';
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--disable_query_log
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eval SELECT VARIABLE_NAME, (VARIABLE_VALUE - $initial) AS DELTA from performance_schema.global_status WHERE VARIABLE_NAME = 'Select_range';
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--enable_query_log
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connect(con2, localhost, user2,,);
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# Causes Select_range to increment (+2)
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SELECT * from test.t_range where (a >= 3) AND (a <= 5);
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SELECT * from test.t_range where (a >= 4) AND (a <= 6);
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SELECT * from performance_schema.session_status
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WHERE VARIABLE_NAME = 'Select_range';
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--disable_query_log
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eval SELECT VARIABLE_NAME, (VARIABLE_VALUE - $initial) AS DELTA from performance_schema.global_status WHERE VARIABLE_NAME = 'Select_range';
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--enable_query_log
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connect(con3, localhost, user3,,);
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# Causes Select_range to increment (+3)
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SELECT * from test.t_range where (a >= 3) AND (a <= 5);
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SELECT * from test.t_range where (a >= 4) AND (a <= 6);
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SELECT * from test.t_range where (a >= 5) AND (a <= 7);
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SELECT * from performance_schema.session_status
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WHERE VARIABLE_NAME = 'Select_range';
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--disable_query_log
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eval SELECT VARIABLE_NAME, (VARIABLE_VALUE - $initial) AS DELTA from performance_schema.global_status WHERE VARIABLE_NAME = 'Select_range';
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--enable_query_log
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--connection default
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--disable_query_log
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eval SELECT VARIABLE_NAME, (VARIABLE_VALUE - $initial) AS DELTA from performance_schema.global_status WHERE VARIABLE_NAME = 'Select_range';
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--enable_query_log
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SELECT `USER`, `HOST`, VARIABLE_NAME, VARIABLE_VALUE
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FROM performance_schema.status_by_account WHERE VARIABLE_NAME = 'Select_range'
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AND `USER` LIKE 'user%'
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ORDER BY `USER`;
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--disconnect con1
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--disconnect con2
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# Wait till all disconnects are completed
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let $count_sessions= 2;
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--source include/wait_until_count_sessions.inc
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--disable_query_log
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eval SELECT VARIABLE_NAME, (VARIABLE_VALUE - $initial) AS DELTA from performance_schema.global_status WHERE VARIABLE_NAME = 'Select_range';
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--enable_query_log
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TRUNCATE TABLE performance_schema.accounts;
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--disable_query_log
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eval SELECT VARIABLE_NAME, (VARIABLE_VALUE - $initial) AS DELTA from performance_schema.global_status WHERE VARIABLE_NAME = 'Select_range';
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--enable_query_log
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--disconnect con3
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# Wait till all disconnects are completed
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let $count_sessions= 1;
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--source include/wait_until_count_sessions.inc
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--disable_query_log
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eval SELECT VARIABLE_NAME, (VARIABLE_VALUE - $initial) AS DELTA from performance_schema.global_status WHERE VARIABLE_NAME = 'Select_range';
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--enable_query_log
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# Make sure TRUNCATE on accounts does not add to global_status
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TRUNCATE TABLE performance_schema.accounts;
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--disable_query_log
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eval SELECT VARIABLE_NAME, (VARIABLE_VALUE - $initial) AS DELTA from performance_schema.global_status WHERE VARIABLE_NAME = 'Select_range';
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--enable_query_log
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DROP TABLE test.t_range;
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REVOKE ALL PRIVILEGES, GRANT OPTION FROM user1@localhost;
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REVOKE ALL PRIVILEGES, GRANT OPTION FROM user2@localhost;
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REVOKE ALL PRIVILEGES, GRANT OPTION FROM user3@localhost;
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DROP USER user1@localhost;
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DROP USER user2@localhost;
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DROP USER user3@localhost;
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SET GLOBAL show_compatibility_56=1;
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FLUSH PRIVILEGES;
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‎storage/perfschema/pfs_account.cc‎

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/* Copyright (c) 2010, 2021, Oracle and/or its affiliates.
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/* Copyright (c) 2010, 2022, Oracle and/or its affiliates.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License, version 2.0,
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void PFS_account::aggregate_status(PFS_user *safe_user, PFS_host *safe_host)
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{
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if (likely(safe_user != NULL && safe_host != NULL))
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{
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/*
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Aggregate STATUS_BY_ACCOUNT to:
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- STATUS_BY_USER
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- STATUS_BY_HOST
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*/
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safe_user->m_status_stats.aggregate(& m_status_stats);
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safe_host->m_status_stats.aggregate(& m_status_stats);
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m_status_stats.reset();
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return;
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}
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/*
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Never aggregate to global_status_var,
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because of the parallel THD -> global_status_var flow.
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*/
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if (safe_user != NULL)
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{
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/*
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Aggregate STATUS_BY_ACCOUNT to:
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- STATUS_BY_USER
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- GLOBAL_STATUS
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*/
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safe_user->m_status_stats.aggregate(& m_status_stats);
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m_status_stats.aggregate_to(& global_status_var);
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m_status_stats.reset();
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return;
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}
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if (safe_host != NULL)
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- STATUS_BY_HOST
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*/
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safe_host->m_status_stats.aggregate(& m_status_stats);
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m_status_stats.reset();
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return;
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}
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/*
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Aggregate STATUS_BY_ACCOUNT to:
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- GLOBAL_STATUS
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*/
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m_status_stats.aggregate_to(& global_status_var);
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m_status_stats.reset();
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return;
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}

‎storage/perfschema/table_status_by_thread.cc‎

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int table_status_by_thread::delete_all_rows(void)
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{
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/* Lock required to aggregate to global_status_vars. */
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/* Lock required to aggregate to global_status_var. */
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mysql_mutex_lock(&LOCK_status);
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reset_status_by_thread();

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