When does the barrier CommandBuffer executes a Query?

I'm starting to replace my CommandBuffers for the recommended barriers, but I don't understand exactly when it executes the query. When we add to the CB or on Playback?

Example:

System 1: Add some entities to be destroyed by EndSimulationEntityCommandBufferSystem, using a query that returns 10 entities.
System 2: Create 5 entities that will fit que query to be destroyed in System 1.
EndSimulationEntityCommandBufferSystem: Will it destroy entities created in System 2?

 

I'm not sure exactly about your stated case: lots of missing information; when do the systems update?

I do believe can do something like this:

Code (CSharp):

1. public class SomeSystem : ComponentSystem
2. {
3.     private EntityQuery query;
4.     protected override void OnCreate()
5.     {
6.         query = GetEntityQuery(ComponentType.ReadOnly<CompA>(), ComponentType.ReadOnly<CompB>());
7.     }
8.     protected override void OnUpdate()
9.     {
10.         // This should succeed.
11.         PostUpdateCommands.RemoveComponent<CompA>(query);
12.         // This won't occur, I think.
13.         PostUpdateCommands.RemoveComponent<CompB>(query);
14.     }
15. }

thereby invalidating your query during the buffer playback.

P.S., obviously there's more to testing this, but I feel like I've accidentally done this to myself, before.

 

The systems update in that order, inside the Simulations group.

My question is when commands passed to an EndSimulationEntityCommandBufferSystem CommandBuffer using queries are parsed, at the moment I create the command, or when it is played back, at the end of the frame?
Because between creating the commands and playback, the query results may change.

 

I'm not sure, but I certainly believe you can invalidate your query between when you create the commands, and when they play back.

 

It plays back when the Barrier/BufferSystem you got the buffer from runs. Plays back meaning all the commands get executed & entities are created.