Map Problem: Connecting multiple keys to a single list

Question

I'm having an issue with the Map Collection. I'm trying to merge some duplicates. I have value that identifies the dupes Number__c and is appearing on multiple accounts that need to be merged.

I'm trying to create a map that has the Number__c as the key for the list of Account records that have that id. However, I end up creating a the same list for ever Key (Number__c) in the Map.

Output is currently like this.

• Key = 1, List ( Id001, Id002, Id003)
• Key = 2, List ( Id001, Id002, Id003)
• Key = 3, List ( Id001, Id002, Id003)

Here is the code so far. I completed the SOQL query earlier to get All accounts for the loop.

for(integer i=0; i < allAccts.size(); i++){    
             if (allAccts.get(i).Rating__c == 'Do Not Use' ) {
                 masterRec = allAccts.get(i);
                 allAccts.remove(i); 

            List<Id> dupes = new List<Id>(); 
            for(Account b : allAccts){  
                 if (masterRec.Number__c == b.Number__c && masterRec.Id != b.Id) {

                     dupes.add(b.Id); 

                 } 
                 mapRaccts.put(masterRec.Number__c, dupes );

Answer 1

• The problem is that you assigning every account as master account masterRec = allAccts.get(i) and adding all the accounts to the list for each key dupes.add(b.Id) and so for every key, you are getting all accounts.

Also note below points:

• This is a very low performant code because you are iteration over all accounts for each account because of inner loop. So, just for 100 accounts, you will be iteration 10,000 times.
• You should be iteration over generic for loop for (variable : list_or_set) instead of for (init_stmt; exit_condition; increment_stmt) so that you dont have to depend on size(). Check here.

Below is the code you can implement:

    List<Account> allAccts  = [SELECT Id, Name, Number__c FROM Account LIMIT 50000];
    Map<String, List<Account>> dupesMap = new Map<String, List<Account>>();

    for(Account acc : allAccts) {
        if(!dupesMap.containsKey(acc.Number__c)) {
            dupesMap.put(acc.Number__c, new List<Account>());
        }
        dupesMap.get(acc.Number__c).add(acc);
    }

    // further processing of dupesMap