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5693b1e4a4
Normally, SET SESSION SQL_LOG_BIN is used by DBAs to run a non-conflicting command locally only, ensuring it does not get replicated. Setting GLOBAL SQL_LOG_BIN would not require all sessions to disconnect. When SQL_LOG_BIN is changed globally, it does not immediately take effect for any sessions. It takes effect by becoming the session-level default inherited at the start of each new session, and this setting is kept and cached for the duration of that session. Setting it intentionally is unlikely to have a useful effect under any circumstance; setting it unintentionally, such as while intending to use SET [SESSION] is potentially disastrous. Accidentally using SET GLOBAL SQL_LOG_BIN will not show an immediate effect to the user, instead not having the desired session-level effect, and thus causing other potential problems with local-only maintenance being binlogged and executed on slaves; And transactions from new sessions (after SQL_LOG_BIN is changed globally) are not binlogged and replicated, which would result in irrecoverable or difficult data loss. This is the regular GLOBAL variables way to work, but in replication context it does not look right on a working server (with connected sessions) 'set global sql_log_bin' and none of that connections is affected. Unexperienced DBA after noticing that the command did "nothing" will change the session var and most probably won't unset the global var, causing new sessions to not be binlog. Setting GLOBAL SQL_LOG_BIN allows DBA to stop binlogging on all new sessions, which can be used to make a server "replication read-only" without restarting the server. But this has such big requirements, stop all existing connections, that it is more likely to make a mess, it is too risky to allow the GLOBAL variable. The statement 'SET GLOBAL SQL_LOG_BIN=N' will produce an error in 5.5, 5.6 and 5.7. Reading the GLOBAL SQL_LOG_BIN will produce a deprecation warning in 5.7.
210 lines
8 KiB
Text
210 lines
8 KiB
Text
set @save_binlog_format= @@global.binlog_format;
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set @save_binlog_dirct= @@global.binlog_direct_non_transactional_updates;
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create table t1 (a int) engine= myisam;
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create table t2 (a int) engine= innodb;
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SELECT @@session.binlog_format;
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@@session.binlog_format
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ROW
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SELECT @@session.binlog_direct_non_transactional_updates;
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@@session.binlog_direct_non_transactional_updates
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1
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SELECT @@session.sql_log_bin;
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@@session.sql_log_bin
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1
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SET AUTOCOMMIT=1;
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# Test that the session variable 'binlog_format',
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# 'binlog_direct_non_transactional_updates' and 'sql_log_bin'
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# are writable outside a transaction.
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# Current session values are ROW, FALSE, TRUE, respectively.
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set @@session.binlog_format= statement;
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set @@session.binlog_direct_non_transactional_updates= TRUE;
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set @@session.sql_log_bin= FALSE;
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SELECT @@session.binlog_format;
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@@session.binlog_format
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STATEMENT
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SELECT @@session.binlog_direct_non_transactional_updates;
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@@session.binlog_direct_non_transactional_updates
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1
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SELECT @@session.sql_log_bin;
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@@session.sql_log_bin
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0
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begin;
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# Test that the session variable 'binlog_format',
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# 'binlog_direct_non_transactional_updates' and 'sql_log_bin' are
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# read-only inside a transaction with no preceding updates.
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# Current session values are STATEMENT, TRUE, FALSE, respectively.
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set @@session.binlog_format= mixed;
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ERROR HY000: Cannot modify @@session.binlog_format inside a transaction
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set @@session.binlog_direct_non_transactional_updates= FALSE;
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ERROR HY000: Cannot modify @@session.binlog_direct_non_transactional_updates inside a transaction
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set @@session.sql_log_bin= FALSE;
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ERROR HY000: Cannot modify @@session.sql_log_bin inside a transaction
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insert into t2 values (1);
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# Test that the session variable 'binlog_format',
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# 'binlog_direct_non_transactional_updates' and 'sql_log_bin' are
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# read-only inside a transaction with preceding transactional updates.
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# Current session values are STATEMENT, TRUE and FALSE, respectively.
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set @@session.binlog_format= row;
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ERROR HY000: Cannot modify @@session.binlog_format inside a transaction
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set @@session.binlog_direct_non_transactional_updates= FALSE;
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ERROR HY000: Cannot modify @@session.binlog_direct_non_transactional_updates inside a transaction
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set @@session.sql_log_bin= FALSE;
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ERROR HY000: Cannot modify @@session.sql_log_bin inside a transaction
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commit;
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begin;
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insert into t1 values (2);
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# Test that the session variable 'binlog_format'
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# 'binlog_direct_non_transactional_updates' and 'sql_log_bin' are
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# read-only inside a transaction with preceding non-transactional updates.
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# Current session values are STATEMENT, TRUE, FALSE, respectively.
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set @@session.binlog_format= mixed;
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ERROR HY000: Cannot modify @@session.binlog_format inside a transaction
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set @@session.binlog_direct_non_transactional_updates= FALSE;
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ERROR HY000: Cannot modify @@session.binlog_direct_non_transactional_updates inside a transaction
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set @@session.sql_log_bin= FALSE;
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ERROR HY000: Cannot modify @@session.sql_log_bin inside a transaction
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commit;
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# Test that the session variable 'binlog_format',
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# 'binlog_direct_non_transactional_updates' and 'sql_log_bin' are
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# writable when AUTOCOMMIT=0, before a transaction has started.
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# Current session values are STATEMENT, TRUE, FALSE, respectively.
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set AUTOCOMMIT=0;
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set @@session.binlog_format= row;
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set @@session.binlog_direct_non_transactional_updates= FALSE;
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set @@session.sql_log_bin= TRUE;
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SELECT @@session.binlog_format;
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@@session.binlog_format
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ROW
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SELECT @@session.binlog_direct_non_transactional_updates;
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@@session.binlog_direct_non_transactional_updates
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0
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SELECT @@session.sql_log_bin;
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@@session.sql_log_bin
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1
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insert into t1 values (3);
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# Test that the session variable 'binlog_format',
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# 'binlog_direct_non_transactional_updates' and 'sql_log_bin' are
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# read-only inside an AUTOCOMMIT=0 transaction
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# with preceding non-transactional updates.
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# Current session values are ROW, FALSE, TRUE, respectively.
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set @@session.binlog_format= statement;
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ERROR HY000: Cannot modify @@session.binlog_format inside a transaction
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set @@session.binlog_direct_non_transactional_updates= TRUE;
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ERROR HY000: Cannot modify @@session.binlog_direct_non_transactional_updates inside a transaction
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set @@session.sql_log_bin= FALSE;
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ERROR HY000: Cannot modify @@session.sql_log_bin inside a transaction
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SELECT @@session.binlog_format;
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@@session.binlog_format
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ROW
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SELECT @@session.binlog_direct_non_transactional_updates;
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@@session.binlog_direct_non_transactional_updates
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0
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SELECT @@session.sql_log_bin;
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@@session.sql_log_bin
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1
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commit;
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insert into t2 values (4);
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# Test that the session variable 'binlog_format',
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# 'binlog_direct_non_transactional_updates' and 'sql_log_bin' are
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# read-only inside an AUTOCOMMIT=0 transaction with
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# preceding transactional updates.
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# Current session values are ROW, FALSE, TRUE, respectively.
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set @@session.binlog_format= statement;
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ERROR HY000: Cannot modify @@session.binlog_format inside a transaction
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set @@session.binlog_direct_non_transactional_updates= TRUE;
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ERROR HY000: Cannot modify @@session.binlog_direct_non_transactional_updates inside a transaction
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set @@session.sql_log_bin= FALSE;
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ERROR HY000: Cannot modify @@session.sql_log_bin inside a transaction
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SELECT @@session.binlog_format;
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@@session.binlog_format
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ROW
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SELECT @@session.binlog_direct_non_transactional_updates;
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@@session.binlog_direct_non_transactional_updates
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0
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SELECT @@session.sql_log_bin;
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@@session.sql_log_bin
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1
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commit;
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begin;
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insert into t2 values (5);
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# Test that the global variable 'binlog_format' and
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# 'binlog_direct_non_transactional_updates' are
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# writable inside a transaction.
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# Current session values are ROW, FALSE, TRUE respectively.
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SELECT @@global.binlog_format;
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@@global.binlog_format
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ROW
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set @@global.binlog_format= statement;
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set @@global.binlog_direct_non_transactional_updates= TRUE;
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SELECT @@global.binlog_format;
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@@global.binlog_format
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STATEMENT
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SELECT @@global.binlog_direct_non_transactional_updates;
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@@global.binlog_direct_non_transactional_updates
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1
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commit;
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set @@global.binlog_format= @save_binlog_format;
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set @@global.binlog_direct_non_transactional_updates= @save_binlog_dirct;
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create table t3(a int, b int) engine= innodb;
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create table t4(a int) engine= innodb;
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create table t5(a int) engine= innodb;
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create trigger tr1 after insert on t3 for each row begin
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insert into t4(a) values(1);
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set @@session.binlog_format= statement;
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insert into t4(a) values(2);
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insert into t5(a) values(3);
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end |
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# Test that the session variable 'binlog_format' is read-only
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# in sub-statements.
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# Current session value is ROW.
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insert into t3(a,b) values(1,1);
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ERROR HY000: Cannot change the binary logging format inside a stored function or trigger
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SELECT @@session.binlog_format;
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@@session.binlog_format
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ROW
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create table t6(a int, b int) engine= innodb;
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create table t7(a int) engine= innodb;
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create table t8(a int) engine= innodb;
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create trigger tr2 after insert on t6 for each row begin
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insert into t7(a) values(1);
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set @@session.binlog_direct_non_transactional_updates= TRUE;
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insert into t7(a) values(2);
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insert into t8(a) values(3);
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end |
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# Test that the session variable
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# 'binlog_direct_non_transactional_updates' is
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# read-only in sub-statements.
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# Current session value is FALSE.
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insert into t6(a,b) values(1,1);
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ERROR HY000: Cannot change the binlog direct flag inside a stored function or trigger
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SELECT @@session.binlog_direct_non_transactional_updates;
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@@session.binlog_direct_non_transactional_updates
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0
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create table t9(a int, b int) engine= innodb;
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create table t10(a int) engine= innodb;
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create table t11(a int) engine= innodb;
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create trigger tr3 after insert on t9 for each row begin
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insert into t10(a) values(1);
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set @@session.sql_log_bin= TRUE;
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insert into t10(a) values(2);
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insert into t11(a) values(3);
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end |
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# Test that the session variable 'sql_log_bin' is
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# read-only in sub-statements.
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# Current session value is FALSE.
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insert into t9(a,b) values(1,1);
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ERROR HY000: Cannot change the sql_log_bin inside a stored function or trigger
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SELECT @@session.sql_log_bin;
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@@session.sql_log_bin
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1
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drop table t1;
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drop table t2;
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drop table t3;
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drop table t4;
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drop table t5;
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drop table t6;
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drop table t7;
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drop table t8;
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drop table t9;
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drop table t10;
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drop table t11;
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