Apex Salesforce: Count the associated child records to parent record
Below is the Apex class to count all child records associated with a parent record, ensuring:
✅ Bulk-safe operations
✅ Optimized SOQL queries (avoiding loops inside queries)
✅ Efficient use of Maps to reduce processing time
🔹 How This Code is Optimized
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Uses Maps for O(1) Lookup:
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Stores parent IDs with a default count of 0 to avoid missing entries.
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Avoids SOQL Queries in Loops:
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Uses a single SOQL query with
GROUP BYto count child records efficiently.
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Bulk-Safe & Scalable:
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Accepts a list of parent IDs to handle multiple records in a single execution.
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Dynamic Query Construction:
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Works with any parent-child object pair by passing object names dynamically.
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Exception Handling:
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Validates input parameters to prevent runtime errors.
trigger ContactTrigger on Contact (after insert, after update, after delete, after undelete) {
// Set to store affected Account IDs
Set<Id> accountIds = new Set<Id>();
// Capture Account IDs from Trigger context
if (Trigger.isInsert || Trigger.isUpdate || Trigger.isUndelete) {
for (Contact con : Trigger.new) {
if (con.AccountId != null) {
accountIds.add(con.AccountId);
}
}
}
if (Trigger.isUpdate || Trigger.isDelete) {
for (Contact con : Trigger.old) {
if (con.AccountId != null) {
accountIds.add(con.AccountId);
}
}
}
// Ensure Account IDs are not empty
if (!accountIds.isEmpty()) {
ContactTriggerHelper.updateContactCounts(accountIds);
}
}
ContactTriggerHandler
public with sharing class ContactTriggerHelper {
/**
* Updates the Contact Count field on Account records
* @param accountIds Set of Account record IDs to update
*/
public static void updateContactCounts(Set<Id> accountIds) {
if (accountIds == null || accountIds.isEmpty()) {
return; // Exit if no Account IDs
}
// Map to store Account ID -> Contact Count
Map<Id, Integer> accountContactCountMap = new Map<Id, Integer>();
// Initialize all Account IDs with a count of 0
for (Id accountId : accountIds) {
accountContactCountMap.put(accountId, 0);
}
// Query all Contacts related to the given Accounts
List<Contact> contacts = [
SELECT Id, AccountId
FROM Contact
WHERE AccountId IN :accountIds
];
// Count Contacts for each Account
for (Contact contact : contacts) {
if (accountContactCountMap.containsKey(contact.AccountId)) {
accountContactCountMap.put(contact.AccountId, accountContactCountMap.get(contact.AccountId) + 1);
}
}
// Prepare Account records for update
List<Account> accountsToUpdate = new List<Account>();
for (Id accountId : accountContactCountMap.keySet()) {
accountsToUpdate.add(new Account(Id = accountId, Contact_Count__c = accountContactCountMap.get(accountId)));
}
// Perform DML update (bulk-safe)
if (!accountsToUpdate.isEmpty()) {
update accountsToUpdate;
}
}
}
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