MySQL参数log_bin_trust_function_creators介绍
2017-10-09 17:02
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MySQL的有个参数log_bin_trust_function_creators，官方文档对这个参数的介绍、解释如下所示：
log_bin_trust_function_creators
Thisvariableapplieswhenbinaryloggingisenabled.Itcontrolswhetherstoredfunctioncreatorscanbetrustednottocreatestoredfunctionsthatwillcauseunsafeeventstobewrittentothebinarylog.Ifsetto0(thedefault),usersarenotpermittedtocreateoralterstoredfunctionsunlesstheyhavetheSUPERprivilegeinadditiontotheCREATEROUTINEorALTERROUTINEprivilege.Asettingof0alsoenforcestherestrictionthatafunctionmustbedeclaredwiththeDETERMINISTICcharacteristic,orwiththeREADSSQLDATAorNOSQLcharacteristic.Ifthevariableissetto1,MySQLdoesnotenforcetheserestrictionsonstoredfunctioncreation.Thisvariablealsoappliestotriggercreation.SeeSection23.7,“BinaryLoggingofStoredPrograms”.
简单介绍一下，当二进制日志启用后，这个变量就会启用。它控制是否可以信任存储函数创建者，不会创建写入二进制日志引起不安全事件的存储函数。如果设置为0（默认值），用户不得创建或修改存储函数，除非它们具有除CREATEROUTINE或ALTERROUTINE特权之外的SUPER权限。设置为0还强制使用DETERMINISTIC特性或READSSQLDATA或NOSQL特性声明函数的限制。如果变量设置为1，MySQL不会对创建存储函数实施这些限制。此变量也适用于触发器的创建。请参见第23.7节“BinaryLoggingofStoredPrograms”。
下面我们测试一下，当开启二进制日志后，如果变量log_bin_trust_function_creators为OFF，那么创建或修改存储函数就会报“ERROR1418(HY000):ThisfunctionhasnoneofDETERMINISTIC,NOSQL,orREADSSQLDATAinitsdeclarationandbinaryloggingisenabled(you*might*wanttousethelesssafelog_bin_trust_function_creatorsvariable)”这样的错误，如下所示：
在调用存储函数时，也会遇到这个错误,如下测试所示：
那么为什么MySQL有这样的限制呢？因为二进制日志的一个重要功能是用于主从复制，而存储函数有可能导致主从的数据不一致。所以当开启二进制日志后，参数log_bin_trust_function_creators就会生效，限制存储函数的创建、修改、调用。那么此时如何解决这个问题呢？官方文档介绍如下，具体可以参考23.7BinaryLoggingofStoredPrograms
IfyoudonotwanttorequirefunctioncreatorstohavetheSUPERprivilege(forexample,ifalluserswiththeCREATEROUTINEprivilegeonyoursystemareexperiencedapplicationdevelopers),setthegloballog_bin_trust_function_creatorssystemvariableto1.Youcanalsosetthisvariablebyusingthe--log-bin-trust-function-creators=1optionwhenstartingtheserver.Ifbinaryloggingisnotenabled,log_bin_trust_function_creatorsdoesnotapply.SUPERisnotrequiredforfunctioncreationunless,asdescribedpreviously,theDEFINERvalueinthefunctiondefinitionrequiresit.
Ifafunctionthatperformsupdatesisnondeterministic,itisnotrepeatable.Thiscanhavetwoundesirableeffects:
·Itwillmakeaslavedifferentfromthemaster.
·Restoreddatawillbedifferentfromtheoriginaldata.
Todealwiththeseproblems,MySQLenforcesthefollowingrequirement:Onamasterserver,creationandalterationofafunctionisrefusedunlessyoudeclarethefunctiontobedeterministicortonotmodifydata.Twosetsoffunctioncharacteristicsapplyhere:
·TheDETERMINISTICandNOTDETERMINISTICcharacteristicsindicatewhetherafunctionalwaysproducesthesameresultforgiveninputs.ThedefaultisNOTDETERMINISTICifneithercharacteristicisgiven.Todeclarethatafunctionisdeterministic,youmustspecifyDETERMINISTICexplicitly.
·TheCONTAINSSQL,NOSQL,READSSQLDATA,andMODIFIESSQLDATAcharacteristicsprovideinformationaboutwhetherthefunctionreadsorwritesdata.EitherNOSQLorREADSSQLDATAindicatesthatafunctiondoesnotchangedata,butyoumustspecifyoneoftheseexplicitlybecausethedefaultisCONTAINSSQLifnocharacteristicisgiven.
·
1：如果数据库没有使用主从复制，那么就可以将参数log_bin_trust_function_creators设置为1。
mysql>setgloballog_bin_trust_function_creators=1;
这个动态设置的方式会在服务重启后失效，所以我们还必须在my.cnf中设置，加上log_bin_trust_function_creators=1，这样就会永久生效。
2：明确指明函数的类型，如果我们开启了二进制日志，那么我们就必须为我们的function指定一个参数。其中下面几种参数类型里面，只有DETERMINISTIC,NOSQL和READSSQLDATA被支持。这样一来相当于明确的告知MySQL服务器这个函数不会修改数据。
1DETERMINISTIC不确定的
2NOSQL没有SQl语句，当然也不会修改数据
3READSSQLDATA只是读取数据，当然也不会修改数据
4MODIFIESSQLDATA要修改数据
5CONTAINSSQL包含了SQL语句
log_bin_trust_function_creators
| Command-LineFormat | --log-bin-trust-function-creators | |
| SystemVariable | Name | log_bin_trust_function_creators |
| VariableScope | Global | |
| DynamicVariable | Yes | |
| PermittedValues | Type | boolean |
| Default | FALSE |
简单介绍一下，当二进制日志启用后，这个变量就会启用。它控制是否可以信任存储函数创建者，不会创建写入二进制日志引起不安全事件的存储函数。如果设置为0（默认值），用户不得创建或修改存储函数，除非它们具有除CREATEROUTINE或ALTERROUTINE特权之外的SUPER权限。设置为0还强制使用DETERMINISTIC特性或READSSQLDATA或NOSQL特性声明函数的限制。如果变量设置为1，MySQL不会对创建存储函数实施这些限制。此变量也适用于触发器的创建。请参见第23.7节“BinaryLoggingofStoredPrograms”。
下面我们测试一下，当开启二进制日志后，如果变量log_bin_trust_function_creators为OFF，那么创建或修改存储函数就会报“ERROR1418(HY000):ThisfunctionhasnoneofDETERMINISTIC,NOSQL,orREADSSQLDATAinitsdeclarationandbinaryloggingisenabled(you*might*wanttousethelesssafelog_bin_trust_function_creatorsvariable)”这样的错误，如下所示：
mysql>showvariableslike'log_bin';
+---------------+-------+
|Variable_name|Value|
+---------------+-------+
|log_bin|ON|
+---------------+-------+
1rowinset(0.00sec)
mysql>showvariableslike'%log_bin_trust_function_creators%';
+---------------------------------+-------+
|Variable_name|Value|
+---------------------------------+-------+
|log_bin_trust_function_creators|OFF|
+---------------------------------+-------+
1rowinset(0.00sec)
mysql>
mysql>DELIMITER//
mysql>CREATEFUNCTIONGET_UPPER_NAME(emp_idINT)
->RETURNSVARCHAR(12)
->BEGIN
->RETURN(SELECTUPPER(NAME)FROMTESTWHEREID=emp_id);
->END
->//
ERROR1418(HY000):ThisfunctionhasnoneofDETERMINISTIC,NOSQL,orREADSSQLDATAinitsdeclarationandbinaryloggingisenabled(you*might*wanttousethelesssafelog_bin_trust_function_creatorsvariable)
mysql>
在调用存储函数时，也会遇到这个错误,如下测试所示：
mysql>DELIMITER;
mysql>setgloballog_bin_trust_function_creators=1;
QueryOK,0rowsaffected(0.00sec)
mysql>DELIMITER//
mysql>CREATEFUNCTIONGET_UPPER_NAME(emp_idINT)
->RETURNSVARCHAR(12)
->BEGIN
->RETURN(SELECTUPPER(NAME)FROMTESTWHEREID=emp_id);
->END
->//
QueryOK,0rowsaffected(0.00sec)
mysql>SELECTID,
->GET_UPPER_NAME(ID)
->FROMTEST;
->//
+------+--------------------+
|ID|GET_UPPER_NAME(ID)|
+------+--------------------+
|100|KERRY|
|101|JIMMY|
+------+--------------------+
2rowsinset(0.00sec)
mysql>DELIMITER;
mysql>setgloballog_bin_trust_function_creators=0;
QueryOK,0rowsaffected(0.00sec)
mysql>SELECTID,
->GET_UPPER_NAME(ID)
->FROMTEST;
ERROR1418(HY000):ThisfunctionhasnoneofDETERMINISTIC,NOSQL,orREADSSQLDATAinitsdeclarationandbinaryloggingisenabled(you*might*wanttousethelesssafelog_bin_trust_function_creatorsvariable)
mysql>
那么为什么MySQL有这样的限制呢？因为二进制日志的一个重要功能是用于主从复制，而存储函数有可能导致主从的数据不一致。所以当开启二进制日志后，参数log_bin_trust_function_creators就会生效，限制存储函数的创建、修改、调用。那么此时如何解决这个问题呢？官方文档介绍如下，具体可以参考
IfyoudonotwanttorequirefunctioncreatorstohavetheSUPERprivilege(forexample,ifalluserswiththeCREATEROUTINEprivilegeonyoursystemareexperiencedapplicationdevelopers),setthegloballog_bin_trust_function_creatorssystemvariableto1.Youcanalsosetthisvariablebyusingthe--log-bin-trust-function-creators=1optionwhenstartingtheserver.Ifbinaryloggingisnotenabled,log_bin_trust_function_creatorsdoesnotapply.SUPERisnotrequiredforfunctioncreationunless,asdescribedpreviously,theDEFINERvalueinthefunctiondefinitionrequiresit.
Ifafunctionthatperformsupdatesisnondeterministic,itisnotrepeatable.Thiscanhavetwoundesirableeffects:
·Itwillmakeaslavedifferentfromthemaster.
·Restoreddatawillbedifferentfromtheoriginaldata.
Todealwiththeseproblems,MySQLenforcesthefollowingrequirement:Onamasterserver,creationandalterationofafunctionisrefusedunlessyoudeclarethefunctiontobedeterministicortonotmodifydata.Twosetsoffunctioncharacteristicsapplyhere:
·TheDETERMINISTICandNOTDETERMINISTICcharacteristicsindicatewhetherafunctionalwaysproducesthesameresultforgiveninputs.ThedefaultisNOTDETERMINISTICifneithercharacteristicisgiven.Todeclarethatafunctionisdeterministic,youmustspecifyDETERMINISTICexplicitly.
·TheCONTAINSSQL,NOSQL,READSSQLDATA,andMODIFIESSQLDATAcharacteristicsprovideinformationaboutwhetherthefunctionreadsorwritesdata.EitherNOSQLorREADSSQLDATAindicatesthatafunctiondoesnotchangedata,butyoumustspecifyoneoftheseexplicitlybecausethedefaultisCONTAINSSQLifnocharacteristicisgiven.
·
1：如果数据库没有使用主从复制，那么就可以将参数log_bin_trust_function_creators设置为1。
mysql>setgloballog_bin_trust_function_creators=1;
这个动态设置的方式会在服务重启后失效，所以我们还必须在my.cnf中设置，加上log_bin_trust_function_creators=1，这样就会永久生效。
2：明确指明函数的类型，如果我们开启了二进制日志，那么我们就必须为我们的function指定一个参数。其中下面几种参数类型里面，只有DETERMINISTIC,NOSQL和READSSQLDATA被支持。这样一来相当于明确的告知MySQL服务器这个函数不会修改数据。
1DETERMINISTIC不确定的
2NOSQL没有SQl语句，当然也不会修改数据
3READSSQLDATA只是读取数据，当然也不会修改数据
4MODIFIESSQLDATA要修改数据
5CONTAINSSQL包含了SQL语句
mysql>showvariableslike'log_bin_trust_function_creators';
+---------------------------------+-------+
|Variable_name|Value|
+---------------------------------+-------+
|log_bin_trust_function_creators|OFF|
+---------------------------------+-------+
1rowinset(0.00sec)
mysql>DROPFUNCTIONGET_UPPER_NAME;
QueryOK,0rowsaffected(0.00sec)
mysql>DELIMITER//
mysql>CREATEFUNCTIONGET_UPPER_NAME(emp_idINT)
->RETURNSVARCHAR(12)
->READSSQLDATA
->BEGIN
->RETURN(SELECTUPPER(NAME)FROMTESTWHEREID=emp_id);
->END
->//
QueryOK,0rowsaffected(0.01sec)
mysql>DELIMITER;
mysql>SELECTID,
->GET_UPPER_NAME(ID)
->FROMTEST;
+------+--------------------+
|ID|GET_UPPER_NAME(ID)|
+------+--------------------+
|100|KERRY|
|101|JIMMY|
+------+--------------------+
2rowsinset(0.00sec)
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