Apex - Governer Limits

州长执行限制确保在Force.com多租户平台上有效使用资源。它是Salesforce.com在代码执行时指定的有效处理限制。

什么是Governer Limits？

众所周知，Apex在多租户环境中运行，即所有客户和组织共享一个资源。因此，有必要确保没有人垄断资源，因此Salesforce.com创建了一组限制代码执行的限制。每当超过任何一个调控器限制时，它将抛出错误并停止执行程序。

从开发人员的角度来看，确保我们的代码应该是可扩展的并且不应该达到极限是很重要的。

所有这些限制都适用于每笔交易。单个触发器执行是一个事务。

正如我们所看到的，触发器设计模式有助于避免限制错误。我们现在将看到其他重要的限制。

避免SOQL查询限制

每个事务只能发出100个查询，也就是说，当您的代码发出超过100个SOQL查询时，它将抛出错误。

例子 (Example)

此示例显示如何达到SOQL查询限制 -

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

// Helper 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_customer__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
         }
      }
   }
}

当调用'updateCustomerDescription'方法并且客户记录数超过100时，它将达到SOQL限制。为避免这种情况，请勿在For循环中编写SOQL查询。在这种情况下，SOQL查询已在For循环中编写。

以下示例将说明如何避免DML以及SOQL限制。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批量电话

此示例显示批量触发器以及触发器助手类模式。您必须先保存辅助类，然后保存触发器。

Note - 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

下表列出了重要的Governer Limits。

描述	限制
总堆大小	6 MB/12 MB
发布的DML语句总数	150
单个SOSL查询检索的记录总数	2000
发出的SOSL查询总数	20
Database.getQueryLocator检索的记录总数	10000
SOQL查询检索的记录总数	50000

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