
Filing this issue to track a question/comment that was raised by @ywangd  here https://github.com/elastic/elasticsearch/pull/98309#discussion_r1294115440

One question I do have is why we chose to [execute the LookupRequest with the enrich origin](https://github.com/elastic/elasticsearch/blob/2e4440ff1c0decf79f8a40688566411f7d518aa7/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/enrich/EnrichLookupService.java#L141C2-L141C2). It means the following query works when the user has access to only the playlist index without access to either the songs enrich policy or its associated index.

```
FROM playlist | ENRICH songs ON song_id
```

It feels a bit weird to me that we have no control on who can use what enrich process. That said, we don't have a good story around enrich and ingest pipeline either, i.e. we have no control over who can use what pipeline where a pipeline can contain an enrich processor. There have been quite a few complaints from users and we have an https://github.com/elastic/elasticsearch/issues/57586 for it. I wonder whether we should not repeat the problem here with ES|QL. On the surface, it might be easier to tackle compared to ingest pipelines since ES|QL is read-only and has no "bulk" operations. What do you think?
x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/LogicalPlanOptimizer.java
transientEval.add(aliased);
                    }
                    
                    else {
                        newAggs.add((NamedExpression) agg.replaceChildren(Collections.singletonList(s)));
                    }
                } else {
                    newAggs.add(agg);
                }
            }
            LogicalPlan plan = aggregate;
            if (changed) {
                var source = aggregate.source();
                plan = new Aggregate(aggregate.source(), aggregate.child(), aggregate.groupings(), newAggs);
                
                if (transientEval.size() > 0) {
                    plan = new Eval(source, plan, transientEval);
                    
                    
                    
                    plan = new EsqlProject(source, plan, Expressions.asAttributes(aggs));
                }
            }
            return plan;
        }
        private static String temporaryName(NamedExpression agg, AggregateFunction af) {
            return "__" + agg.name() + "_" + af.functionName() + "@" + Integer.toHexString(af.hashCode());
        }
    }
    static class ConvertStringToByteRef extends OptimizerRules.OptimizerExpressionRule<Literal> {