memoizedConnectReduxForm.js

import { connect } from 'react-redux';
import { createSelectorCreator } from 'reselect';
import { reduxForm } from 'redux-form';

function memoize(func, equalityCheck = (a, b) =>  a === b) {
  const lastArgsCache = {};
  const lastResultCache = {};
  return (...args) => {
    const memoizeKey = args.pop();
    const lastArgs = lastArgsCache[memoizeKey];
    const lastResult = lastResultCache[memoizeKey];
    if (lastArgs !== undefined &&
        args.every((value, index) => equalityCheck(value, lastArgs[index]))) {
        return lastResult;
    }

    const result = func(...args);
    lastArgsCache[memoizeKey] = args;
    lastResultCache[memoizeKey] = result;
    return result;
  };
}

function createSelector(...args) {
  return createSelectorCreator(memoize)(...args);
}

export function connectReduxForm(...args) {
  const formName = args[0].form;

  const selector = createSelector(
    ({ form }, { formKey }) => form && form[formName] && (formKey ? form[formName][formKey] : form[formName]),
    ( state, { formKey } ) => formKey,
    ( state, { formKey } ) => formKey || '_default_memoize_key',
    ( form, formKey ) => formKey ? { form: { [formName]: { [formKey]: form } } } : { form: { [formName]: form } }
  );

  return DecoratedComponent => connect(selector)(reduxForm(...args)(DecoratedComponent));
}

Improve performance issue of multiple records of form with redux-form.
Especially when there are more than 30-40 records, focusing one single form element forces all redux-form-connected component to rerender. It's possible to implement shouldComponentUpdate function, but still there is a waste of processing.