Fix for bug #35732: read-only blocks SELECT statements in InnoDB
Problem: SELECTs prohibited for a transactional SE in autocommit mode if read_only is set. Fix: allow them. mysql-test/r/read_only_innodb.result: Fix for bug #35732: read-only blocks SELECT statements in InnoDB - test result. mysql-test/t/read_only_innodb.test: Fix for bug #35732: read-only blocks SELECT statements in InnoDB - test case. sql/handler.cc: Fix for bug #35732: read-only blocks SELECT statements in InnoDB - in autocommit mode thd->transaction.all list is empty thus is_real_trans set to TRUE for any SELECTs, so using it in the "read_only" check is insufficient. ha_check_and_coalesce_trx_read_only() changed to return number of engines with read-write changes. This value is used in the "read-only" check and checks for GLOBAL READ LOCK. sql/lock.cc: Fix for bug #35732: read-only blocks SELECT statements in InnoDB - added assert(protect_against_global_read_lock) before decreasing, in order to catch (uint) 0 - 1 situation due to wrong wait_if_global_read_lock()/start_waiting_global_read_lock() call sequence.
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@ -16,3 +16,33 @@ ERROR HY000: The MySQL server is running with the --read-only option so it canno
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set global read_only=0;
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drop table table_11733 ;
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drop user test@localhost;
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GRANT CREATE, SELECT, DROP ON *.* TO test@localhost;
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CREATE TABLE t1(a INT) ENGINE=INNODB;
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INSERT INTO t1 VALUES (0), (1);
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SET GLOBAL read_only=1;
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SELECT * FROM t1;
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a
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0
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1
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BEGIN;
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SELECT * FROM t1;
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a
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0
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1
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COMMIT;
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SET GLOBAL read_only=0;
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FLUSH TABLES WITH READ LOCK;
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SELECT * FROM t1;
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a
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0
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1
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BEGIN;
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SELECT * FROM t1;
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a
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0
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1
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COMMIT;
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UNLOCK TABLES;
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DROP TABLE t1;
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DROP USER test@localhost;
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echo End of 5.1 tests
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@ -41,3 +41,45 @@ set global read_only=0;
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drop table table_11733 ;
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drop user test@localhost;
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disconnect con1;
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#
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# Bug #35732: read-only blocks SELECT statements in InnoDB
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#
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# Test 1: read only mode
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GRANT CREATE, SELECT, DROP ON *.* TO test@localhost;
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connect(con1, localhost, test, , test);
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connection default;
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CREATE TABLE t1(a INT) ENGINE=INNODB;
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INSERT INTO t1 VALUES (0), (1);
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SET GLOBAL read_only=1;
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connection con1;
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SELECT * FROM t1;
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BEGIN;
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SELECT * FROM t1;
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COMMIT;
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connection default;
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SET GLOBAL read_only=0;
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#
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# Test 2: global read lock
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#
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FLUSH TABLES WITH READ LOCK;
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connection con1;
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SELECT * FROM t1;
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BEGIN;
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SELECT * FROM t1;
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COMMIT;
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connection default;
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UNLOCK TABLES;
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DROP TABLE t1;
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DROP USER test@localhost;
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disconnect con1;
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--echo echo End of 5.1 tests
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@ -952,16 +952,21 @@ int ha_prepare(THD *thd)
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A helper function to evaluate if two-phase commit is mandatory.
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As a side effect, propagates the read-only/read-write flags
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of the statement transaction to its enclosing normal transaction.
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If we have at least two engines with read-write changes we must
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run a two-phase commit. Otherwise we can run several independent
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commits as the only transactional engine has read-write changes
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and others are read-only.
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@retval TRUE we must run a two-phase commit. Returned
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if we have at least two engines with read-write changes.
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@retval FALSE Don't need two-phase commit. Even if we have two
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transactional engines, we can run two independent
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commits if changes in one of the engines are read-only.
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@retval 0 All engines are read-only.
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@retval 1 We have the only engine with read-write changes.
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@retval >1 More than one engine have read-write changes.
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Note: return value might NOT be the exact number of
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engines with read-write changes.
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*/
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static
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bool
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uint
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ha_check_and_coalesce_trx_read_only(THD *thd, Ha_trx_info *ha_list,
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bool all)
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{
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@ -998,7 +1003,7 @@ ha_check_and_coalesce_trx_read_only(THD *thd, Ha_trx_info *ha_list,
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break;
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}
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}
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return rw_ha_count > 1;
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return rw_ha_count;
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}
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@ -1061,25 +1066,8 @@ int ha_commit_trans(THD *thd, bool all)
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#ifdef USING_TRANSACTIONS
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if (ha_info)
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{
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bool must_2pc;
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if (is_real_trans && wait_if_global_read_lock(thd, 0, 0))
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{
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ha_rollback_trans(thd, all);
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DBUG_RETURN(1);
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}
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if ( is_real_trans
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&& opt_readonly
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&& ! (thd->security_ctx->master_access & SUPER_ACL)
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&& ! thd->slave_thread
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)
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{
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my_error(ER_OPTION_PREVENTS_STATEMENT, MYF(0), "--read-only");
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ha_rollback_trans(thd, all);
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error= 1;
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goto end;
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}
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uint rw_ha_count;
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bool rw_trans;
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DBUG_EXECUTE_IF("crash_commit_before", abort(););
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@ -1087,9 +1075,29 @@ int ha_commit_trans(THD *thd, bool all)
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if (is_real_trans) /* not a statement commit */
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thd->stmt_map.close_transient_cursors();
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must_2pc= ha_check_and_coalesce_trx_read_only(thd, ha_info, all);
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rw_ha_count= ha_check_and_coalesce_trx_read_only(thd, ha_info, all);
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/* rw_trans is TRUE when we in a transaction changing data */
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rw_trans= is_real_trans && (rw_ha_count > 0);
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if (!trans->no_2pc && must_2pc)
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if (rw_trans &&
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wait_if_global_read_lock(thd, 0, 0))
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{
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ha_rollback_trans(thd, all);
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DBUG_RETURN(1);
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}
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if (rw_trans &&
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opt_readonly &&
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!(thd->security_ctx->master_access & SUPER_ACL) &&
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!thd->slave_thread)
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{
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my_error(ER_OPTION_PREVENTS_STATEMENT, MYF(0), "--read-only");
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ha_rollback_trans(thd, all);
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error= 1;
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goto end;
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}
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if (!trans->no_2pc && (rw_ha_count > 1))
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{
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for (; ha_info && !error; ha_info= ha_info->next())
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{
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@ -1129,7 +1137,7 @@ int ha_commit_trans(THD *thd, bool all)
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tc_log->unlog(cookie, xid);
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DBUG_EXECUTE_IF("crash_commit_after", abort(););
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end:
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if (is_real_trans)
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if (rw_trans)
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start_waiting_global_read_lock(thd);
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}
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#endif /* USING_TRANSACTIONS */
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@ -1533,6 +1533,7 @@ void start_waiting_global_read_lock(THD *thd)
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if (unlikely(thd->global_read_lock))
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DBUG_VOID_RETURN;
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(void) pthread_mutex_lock(&LOCK_global_read_lock);
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DBUG_ASSERT(protect_against_global_read_lock);
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tmp= (!--protect_against_global_read_lock &&
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(waiting_for_read_lock || global_read_lock_blocks_commit));
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(void) pthread_mutex_unlock(&LOCK_global_read_lock);
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