One of the biggest problems we have is with SOQL in Triggers, over and over again, we were using SOQL to load a list of parent/related objects, modifying their contents and then updating them.
Then one day, I realised, we didn't need to do this at all.
Here is an example of a trigger that "passed" a status field from an updated object back to it's parent:
trigger UpdateParent on Child__c (after insert, after update) { // get the list of parent object IDs ListIds = new List List(); for(Child__c thisChild : Trigger.new) { Ids.add(thisChild.ParentRef__c); } // Load up the list of parent objects and map them out for altering and updating parentList = [SELECT Id FROM Parent__c WHERE Id IN :Ids]; Map // This is our list of parents to finally update ListparentMap = new Map (); for(Parent__c thisParent : parentList) { parentMap.put(thisParent.Id, thisParent); } parentsToSave = new List for(Child__c thisChild : Trigger.new) { Parent__c par = parentMap.get(thisChild.ParentRef__c); par.Child_Status__c = thisChild.Status__c; parentsToSave.add(par); } // update the parents. update parentsToSave; }(); // Finally we're ready to go through each child in the trigger and update it's parent
That's actually pretty hefty, it's a lot of maps and lists, and the SOQL query right in the middle there, just to update one field on a related object. I think this technique is a bastardisation of the Force.com Fundamentals teachings, which has emphasis on batchification, and in it's example, probably has a lot more cause to go through this process. For me though, this could be simplified by taking advantage of a simple Force.com fact:
If you create an instance of an sObject, and assign a valid record ID to it, you can update or upsert it exactly as if it was originally loaded to memory.
This means, that as we already have our parent object IDs in a reference field, we don't need to LOAD them, we can just conjure up new ones, update the relevant field, and update them. That makes the above trigger look like this:
trigger UpdateParent on Child__c (after insert, after update) { // This is our list of parents to finally update ListparentsToSave = new List , update and, update! for(Child__c thisChild : Trigger.new) { Parent__c par = new Parent__c(); par.Id = thisChild.ParentRef__c; par.Child_Status__c = thisChild.Status__c; parentsToSave.add(par); } // update the parents. update parentsToSave; }(); // Now we can just go through each child in the trigger "instantiate" it's parent
I can literally feel my governor limits squeeling with joy already!! No SOQL, half the script statements, a quarter of the lists and maps. Fantastic.