I have the following scenario occuring in my code:

Custom Object A has 100 records.

Custom Object B also has 100 records (every record of B will have a corresponding record with A).

for (Custom_Object_A a : A_Collection) {
    for (Custom_Object_B b : B_Collection) {
        if (b.id == a.id) {
            b.field1 = a.field1;
update B_Collection;

So the above code will execute 100 * 100 = 10000 computations.

Will this be memory intensive on Salesforce ?


Just use a map. By the way, two records of different SObjectType will never have the same Id, because they will have a different key prefix (the first three characters). You can see this for yourself:

system.assertNotEquals(SObjectType.A__c.getKeyPrefix(), SObjectType.B__c.getKeyPrefix());

I will assume there is some sort of lookup relationship. It does not really matter which direction. I will take your word that the relationship is 1-to-1.

Map<Id, A__c> aMap = new Map<Id, A__c>([SELECT Id FROM A__c]);
for (B__c b : [SELECT A__c FROM B__c])
    A__c correspondingRecord = aMap.get(b.A__c);
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  • Hmm...I was doing Map before. also..i just wanted to which one would be less strainful on Salesforce servers..I am gonna keep the processing with the @future notation as such i will have like 60 sec of CPU time when compared to synchronous which is 10 sec... – Rainmaker Mar 10 '16 at 3:25
  • Um. So does this answer your question? I'm not sure I follow. – Adrian Larson Mar 10 '16 at 3:26
  • Tx for your response....I did try out the functionality via Map and its working fine. I just wanted to know which among these two ("M x N" vs Map) is less strainful on Salesforce servers ?..Hope I am clear – Rainmaker Mar 10 '16 at 3:30
  • It is definitely more efficient to use a map and a single loop. Apex generates Map<Id, SObject> very efficiently. – Adrian Larson Mar 10 '16 at 3:31

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