Apex中文手册

控制器执行限制确保在Force.com多租户平台上有效地使用资源。 它是由Salesforce.com指定的对代码执行有效处理的限制。

什么是调节器限制？

我们知道，Apex在多租户环境中运行; 即单个资源由所有客户和组织共享。 因此，有必要确保没有人垄断资源，因此Salesforce.com已经创建了一组管理和限制代码执行的限制。 每当任何一个调节器限制被越过，它将抛出错误，并将停止程序的执行。

从开发人员的角度来看，确保我们的代码是可扩展的并且不应该达到极限是至关重要的。所有这些限制都适用于每个交易。 单个触发器执行一个事务。

正如我们所看到的，触发器设计模式是一种避免极限误差的方法。 让我们看看一些重要的限制。

避免SOQL查询限制

每个事务只能发出100个查询，也就是说，当代码发出超过100个SOQL查询时，它会抛出错误。

例如：

以下是显示如何达到SOQL查询限制的示例：

以下触发器遍历客户列表，并使用字符串“Ok to Pay”更新子记录（发票）描述。

//Heper class:Below code needs o be checked.
public class CustomerTriggerHelper {
	
	public static void isAfterUpdateCall(Trigger.new) {
		createInvoiceRecords(trigger.new);//Method call
		updateCustomerDescription(trigger.new);
	}

	//Method To Create Invoice Records
	public static void createInvoiceRecords (List<apex_customer__c> customerList) {
		for (APEX_Customer__c objCustomer: customerList) {
			if (objCustomer.APEX_Customer_Status__c == 'Active' && trigger.oldMap.get(objCustomer.id).APEX_Customer_Status__c == 'Inactive') {//condition to check the old value and new value
				APEX_Invoice__c objInvoice = new APEX_Invoice__c();
				objInvoice.APEX_Status__c = 'Pending';
				InvoiceList.add(objInvoice);
			}
		}
		insert InvoiceList;//DML to insert the Invoice List in SFDC
	}

	//Method to update the invoice records
	public static updateCustomerDescription (List<apex_customer__c> customerList) {
		for (APEX_Customer__c objCust: customerList) {
			List<apex_invoice__c> invList = [SELECT Id, Name, APEX_Description__c FROM APEX_Invoice__c WHERE APEX_Customer__c = :objCust.id];//This query will fire for the number of records customer list has and will hit the governor limit when records are more than 100 
			for (APEX_Invoice__c objInv: invList) {
				objInv.APEX_Description__c = 'OK To Pay';
				update objInv;//Update invoice, this will also hit the governor limit for DML if large number(150) of records are there
			}
		}
	} 
}

当方法'updateCustomerDescription'被调用，并且客户记录的数量大于100时，它将达到SOQL限制。

为了避免这种情况，不要在For循环中写入SOQL查询。 在这种情况下，SOQL查询已经写入for循环。

下面是我们可以避免DML以及SOQL限制的示例。 我们使用嵌套关系查询来获取发票记录，并使用上下文变量trigger.newMap来获取id和Customer记录的映射。

//SOQL-Good Way to Write Query and avoid limit exception
//Helper Class
public class CustomerTriggerHelper {
	
	public static void isAfterUpdateCall(Trigger.new) {
		createInvoiceRecords(trigger.new);//Method call
		updateCustomerDescription(trigger.new, trigger.newMap);
	}

	//Method To Create Invoice Records
	public static void createInvoiceRecords (List<apex_customer__c> customerList) {
		for (APEX_Customer__c objCustomer: customerList) {
			if (objCustomer.APEX_Customer_Status__c == 'Active' && trigger.oldMap.get(objCustomer.id).APEX_Customer_Status__c == 'Inactive') {//condition to check the old value and new value
				APEX_Invoice__c objInvoice = new APEX_Invoice__c();
				objInvoice.APEX_Status__c = 'Pending';
				InvoiceList.add(objInvoice);
			}
		}
		insert InvoiceList;//DML to insert the Invoice List in SFDC
	}

	//Method to update the invoice records
	public static updateCustomerDescription (List<apex_customer__c> customerList, Map<id, apex_customer__c> newMapVariable) {
		List<apex_customer__c> customerListWithInvoice = [SELECT id, Name,(SELECT Id, Name, APEX_Description__c FROM APEX_Invoice__r) FROM APEX_Customer__c WHERE Id IN :newMapVariable.keySet()];//Query will be for only one time and fetches all the records
		List<apex_invoice__c> invoiceToUpdate = new List<apex_invoice__c>();
		for (APEX_Customer__c objCust: customerList) {
			for (APEX_Invoice__c objInv: invList) {
				objInv.APEX_Description__c = 'OK To Pay';
				invoiceToUpdate.add(objInv);//Add the modified records to List
			}
		}
		update invoiceToUpdate;
	} 
}

DML批量调用

正如我们在许多示例中看到的，我们一直在列表中添加修改的记录，然后对该列表执行DML操作，而不是对单个记录执行DML。 下面是同样的例子。 这是批量触发器以及触发器帮助器类模式的示例。 您必须先保存帮助程序类，然后保存触发器。

注意：将以下代码粘贴到我们之前创建的“CustomerTriggerHelper”类中。

//Helper Class
public class CustomerTriggerHelper {
    
    public static void isAfterUpdateCall(List<apex_customer__c> customerList, Map<id, apex_customer__c> mapIdToCustomers, Map<id, apex_customer__c> mapOldItToCustomers) {
        createInvoiceRecords(customerList, mapOldItToCustomers);//Method call
        updateCustomerDescription(customerList,mapIdToCustomers, mapOldItToCustomers);
    }

    //Method To Create Invoice Records
    public static void createInvoiceRecords (List<apex_customer__c> customerList, Map<id, apex_customer__c> mapOldItToCustomers) {
        List<apex_invoice__c> InvoiceList = new List<apex_invoice__c>();
        List<apex_customer__c> customerToInvoice = [SELECT id, Name FROM APEX_Customer__c LIMIT 1];
        for (APEX_Customer__c objCustomer: customerList) {
            if (objCustomer.APEX_Customer_Status__c == 'Active' && mapOldItToCustomers.get(objCustomer.id).APEX_Customer_Status__c == 'Inactive') {//condition to check the old value and new value
                APEX_Invoice__c objInvoice = new APEX_Invoice__c();
                objInvoice.APEX_Status__c = 'Pending';
                objInvoice.APEX_Customer__c = objCustomer.id;
                InvoiceList.add(objInvoice);
            }
        }
        system.debug('InvoiceList&&&'+InvoiceList);
        insert InvoiceList;//DML to insert the Invoice List in SFDC. This also follows the Bulk pattern
    }

    //Method to update the invoice records
    public static void updateCustomerDescription (List<apex_customer__c> customerList, Map<id, apex_customer__c> newMapVariable, Map<id, apex_customer__c> oldCustomerMap) {
        List<apex_customer__c> customerListWithInvoice = [SELECT id, Name,(SELECT Id, Name, APEX_Description__c FROM Invoices__r) FROM APEX_Customer__c WHERE Id IN :newMapVariable.keySet()];//Query will be for only one time and fetches all the records
        List<apex_invoice__c> invoiceToUpdate = new List<apex_invoice__c>();
		List<apex_invoice__c> invoiceFetched = new List<apex_invoice__c>();
		invoiceFetched = customerListWithInvoice[0].Invoices__r;
		system.debug('invoiceFetched'+invoiceFetched);
        system.debug('customerListWithInvoice****'+customerListWithInvoice);
		for (APEX_Customer__c objCust: customerList) {
			system.debug('objCust.Invoices__r'+objCust.Invoices__r);
            if (objCust.APEX_Active__c == true && oldCustomerMap.get(objCust.id).APEX_Active__c == false) {
				for (APEX_Invoice__c objInv: invoiceFetched) {
					system.debug('I am in For Loop'+objInv);
					objInv.APEX_Description__c = 'OK To Pay';
					invoiceToUpdate.add(objInv);//Add the modified records to List
				}
			}
        }
		system.debug('Value of List ***'+invoiceToUpdate);
        update invoiceToUpdate;//This statement is Bulk DML which performs the DML on List and avoids the DML Governor limit
    } 
}

//Trigger Code for this class: Paste this code in 'Customer_After_Insert' trigger on Customer Object
trigger Customer_After_Insert on APEX_Customer__c (after update) {
    CustomerTriggerHelper.isAfterUpdateCall(Trigger.new, trigger.newMap, trigger.oldMap);//Trigger calls the helper class and does not have any code in Trigger
}

其他Salesforce Governor限制

以下是一些重要的Salesforce Governor限制，我们需要记住。 你可以检查其他Salesforce Governor限制以及使用Salesdorce.com Apex开发人员指南。