hadoop中combiner是什么
Combiner（合并器）在Hadoop中，Combiner（合并器）是一个可选的阶段，用于优化MapReduce任务的性能。它是在Map阶段输出之后、规约（reduction）之前执行的。Combiner的作用是在Map任务的本地节点上对Map阶段的输出进行局部聚合。它接收Map任务输出的键值对，并将具有相同键的键值...
Reachability(判断网络是否连接)
类似于一个网络状况的探针。 [[NSNotificationCenterdefaultCenter]addObserver:selfselector:@selector(reachabilityChanged:)name:kReachabilityChangedNotificationobject:nil];&nbs...
ORA-24940: invalid combination of string namespace, string presentation and string receive protocol
文档解释ORA-24940:invalidcombinationofstringnamespace,stringpresentationandstringreceiveprotocolCause:Aninvalidcombinationofnamespace,presentationandreceiveprotocol...
ORA-39172: Cannot remap transportable tablespace names with compatibility of string.
文档解释ORA-39172:Cannotremaptransportabletablespacenameswithcompatibilityofstring.Cause:Theuserattemptedtoremapatablespacenameinatransportabletablespacejobwhenthec...
ORA-14701: partition-extended name or bind variable must be used for DMLs on tables partitioned by the System method
文档解释ORA-14701:partition-extendednameorbindvariablemustbeusedforDMLsontablespartitionedbytheSystemmethodCause:Userattemptednottousepartition-extendedsyntaxforata...
ORA-24369: required callbacks not registered for one or more bind handles
文档解释ORA-24369:requiredcallbacksnotregisteredforoneormorebindhandlesCause:NocallbackshavebeenregisteredforoneormoreofthebindhandleswhicharepartoftheRETURNINGclau...
ORA-09802: Conversion of binary label to string failed.
文档解释ORA-09802:Conversionofbinarylabeltostringfailed.Cause:ORACLEwasunabletoconvertabinarylabeltoastring.Action:ChecktheUNIXerrornumberforapossibleoperatingsyste...
ORA-15239: allocation unit size higher than string requires RDBMS compatibility string
文档解释ORA-15239:allocationunitsizehigherthanstringrequiresRDBMScompatibilitystringCause:TheallocationunitsizerequestedexceededthelimitimposedbytheRDBMScompatibili...