Bug#12601974 - STORED PROCEDURE SQL_MODE=NO_BACKSLASH_ESCAPES IGNORED AND BREAKS REPLICATION
Analysis: ======================== sql_mode "NO_BACKSLASH_ESCAPES": When user want to use backslash as character input, instead of escape character in a string literal then sql_mode can be set to "NO_BACKSLASH_ESCAPES". With this mode enabled, backslash becomes an ordinary character like any other. SQL_MODE set applies to the current client session. And while creating the stored procedure, MySQL stores the current sql_mode and always executes the stored procedure in sql_mode stored with the Procedure, regardless of the server SQL mode in effect when the routine is invoked. In the scenario (for which bug is reported), the routine is created with sql_mode=NO_BACKSLASH_ESCAPES. And routine is executed with the invoker sql_mode is "" (NOT SET) by executing statement "call testp('Axel\'s')". Since invoker sql_mode is "" (NOT_SET), the '\' in 'Axel\'s'(argument to function) is considered as escape character and column "a" (of table "t1") values are updated with "Axel's". The binary log generated for above update operation is as below, set sql_mode=XXXXXX (for no_backslash_escapes) update test.t1 set a= NAME_CONST('var',_latin1'Axel\'s' COLLATE 'latin1_swedish_ci'); While logging stored procedure statements, the local variables (params) used in statements are replaced with the NAME_CONST(var_name, var_value) (Internal function) (http://dev.mysql.com/doc/refman/5.6/en/miscellaneous-functions.html#function_name-const) On slave, these logs are applied. NAME_CONST is parsed to get the variable and its value. Since, stored procedure is created with sql_mode="NO_BACKSLASH_ESCAPES", the sql_mode is also logged in. So that at slave this sql_mode is set before executing the statements of routine. So at slave, sql_mode is set to "NO_BACKSLASH_ESCAPES" and then while parsing NAME_CONST of string variable, '\' is considered as NON ESCAPE character and parsing reported error for "'" (as we have only one "'" no backslash). At slave, parsing was proper with sql_mode "NO_BACKSLASH_ESCAPES". But above error reported while writing bin log, "'" (of Axel's) is escaped with "\" character. Actually, all special characters (n, r, ', ", \, 0...) are escaped while writing NAME_CONST for string variable(param, local variable) in bin log irrespective of "NO_BACKSLASH_ESCAPES" sql_mode. So, basically, the problem is that logging string parameter does not take into account sql_mode value. Fix: ======================== So when sql_mode is set to "NO_BACKSLASH_ESCAPES", escaping characters as (n, r, ', ", \, 0...) should be avoided. To do so, added a check to not to escape such characters while writing NAME_CONST for string variables in bin log. And when sql_mode is set to NO_BACKSLASH_ESCAPES, quote character "'" is represented as ''. http://dev.mysql.com/doc/refman/5.6/en/string-literals.html (There are several ways to include quote characters within a string: )
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