mysql> show global variables like 'binlog_format'; +---------------+-------+ | Variable_name | Value | +---------------+-------+ | binlog_format | MIXED | +---------------+-------+ 1 row in set (0.08 sec) Part3:知識儲備
When running in MIXED logging format, the server automatically switches from statement-based to row-based logging under the following conditions: When a DML statement updates an NDBCLUSTER table. When a function contains UUID(). When one or more tables with AUTO_INCREMENT columns are updated and a trigger or stored function is invoked. Like all other unsafe statements, this generates a warning if binlog_format = STATEMENT. When any INSERT DELAYED is executed. When a call to a UDF is involved. If a statement is logged by row and the session that executed the statement has any temporary tables, logging by row is used for all subsequent statements (except for those accessing temporary tables) until all temporary tables in use by that session are dropped. This is true whether or not any temporary tables are actually logged. Temporary tables cannot be logged using row-based format; thus, once row-based logging is used, all subsequent statements using that table are unsafe. The server approximates this condition by treating all statements executed during the session as unsafe until the session no longer holds any temporary tables. When FOUND_ROWS() or ROW_COUNT() is used. (Bug #12092, Bug #30244) When USER(), CURRENT_USER(), or CURRENT_USER is used. (Bug #28086) When a statement refers to one or more system variables. (Bug #31168) 可以看出，在官方文檔中，何時(shí)MIXED格式會轉(zhuǎn)換為ROW格式中，并未提到limit語句會將MIXED格式轉(zhuǎn)換為ROW，國內(nèi)不少書籍和博客上也未有提及，本文記錄這個(gè)案例，希望對遇到這個(gè)問題和未來可能遇到這個(gè)問題的讀者能夠節(jié)省處理時(shí)間，盡快定位到根源。
Statement-based replication of LIMIT clauses in DELETE, UPDATE, and INSERT ... SELECT statements is unsafe since the order of the rows affected is not defined. (Such statements can be replicated correctly with statement-based replication only if they also contain an ORDER BY clause.) When such a statement is encountered:
When using STATEMENT mode, a warning that the statement is not safe for statement-based replication is now issued.When using STATEMENT mode, warnings are issued for DML statements containing LIMIT even when they also have an ORDER BY clause (and so are made deterministic). This is a known issue. (Bug #42851) When using MIXED mode, the statement is now automatically replicated using row-based mode. ——總結(jié)——
