reducers

In many MapReduce programs, I see a reducer being used as a combiner as well. I know this is because of the specific nature of those programs. But I am wondering if they can be different. Binary Nerd Yes, a combiner can be different to the Reducer, although your Combiner will still be implementing the Reducer interface. Combiners can only be used in specific cases which are going to be job dependent. The Combiner will operate like a Reducer, but only on the subset of the Key/Values output from each Mapper. One constraint that your Combiner will have, unlike a Reducer, is that the input/output

I do not know how to access a boolean isLoading flag from reducerForm.js reducer in reducerRegister.js . I have used combineReducers() and I use isLoading to disable a button during form submit. It's initial state is false, after clicking submit, it changes to true . After the form submission is successful, isLoading is reset to false again. Below is the relevant code for this issue: actionRegister.js let _registerUserFailure = (payload) => { return { type: types.SAVE_USER_FAILURE, payload }; }; let _registerUserSuccess = (payload) => { return { type: types.SAVE_USER_SUCCESS, payload, is

Haven't been able to find anything around here regarding this error: "Store does not have a valid reducer. Make sure the argument passed to combineReducers is an object whose values are reducers." My reducer export default function FriendListReducer(state = {friends : []}, action) { switch (action.type) { case 'ADD_FRIEND': return [ { friends : action.payload.friend }, ...state.friends ] default: return state; } return state; } Combiner import { combineReducers } from 'redux'; import { FriendListReducer } from './FriendListReducer'; const rootReducer = combineReducers({ friends:

I don't understand what reduce-reducers is meant for. Should it be used in the case that I have 2 reducer functions containing the same action? function reducerA(state, action){ switch(action.type): ... case 'SAME_ACTION': {...state, field: state.field+1} } function reducerB(state, action){ switch(action.type): ... case 'SAME_ACTION': {...state, field: state.field*2} } So if I call reduceReducer on reducerA and reducerB and action 'SAME_ACTION' is invoked for {field: 0} then I would have a next state {field: 2} ? Also it seems to me that it kind of concatenates reducers (meaning merging them

Am trying to determine if there are certain hooks available in the hadoop api (hadoop 2.0.0 mrv1) to handle data skew for a reducer. Scenario : Have a custom Composite key and partitioner in place to route data to reducers. In order to deal with the odd case but very likely case of a million keys and large values ending up on the same reducer need some sort of heuristic so that this data can be further partitioned to spawn off new reducers. Am thinking of a two step process set mapred.max.reduce.failures.percent to say 10% and let the job complete rerun the job on the failed data set by

If I increase the number of mappers and decrease the number of reducers, then is there any difference in the performance (increase/decrease) of any job while execution? Also I want to ask that How to set the number of mappers and reducers? I have never played with this setting thats why I don't know about this. I know hadoop but I have code with it as I use Hive a lot. Also If I want to increase the number of mappers and reducers then how to set it and upto what value do I set it. Is it depend upon the number of instances (Lets say 10)? Please reply me I want to try this and check the

I'm currently learning React and I am trying to figure out how to use it with Redux for building a mobile app. I'm kind of confused on how the two are related/usable together. For example, I completed this tutorial in React https://www.raywenderlich.com/99473/introducing-react-native-building-apps-javascript , but now I want to play around with adding some reducers/actions to that app and I am not sure where those would tie in with what I've already done. React is a UI framework that takes care of updating the UI in response to the “source of truth” that is usually described as a state “owned”