
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
} else {
                    throw new EsqlIllegalArgumentException("Did not expect a non-aliased aggregation {}", agg);
                }
            }
            var blocks = BlockUtils.fromListRow(result);
            return LocalSupplier.of(blocks);
        }
    }
    private static LogicalPlan skipPlan(UnaryPlan plan) {
        return new LocalRelation(plan.source(), plan.output(), LocalSupplier.EMPTY);
    }
    private static LogicalPlan skipPlan(UnaryPlan plan, LocalSupplier supplier) {
        return new LocalRelation(plan.source(), plan.output(), supplier);
    }
    protected static class PushDownAndCombineFilters extends OptimizerRules.OptimizerRule<Filter> {
        @Override
        protected LogicalPlan rule(Filter filter) {
            LogicalPlan plan = filter;
            LogicalPlan child = filter.child();
            Expression condition = filter.condition();
            if (child instanceof Filter f) {
                
                plan = f.with(Predicates.combineAnd(List.of(f.condition(), condition)));
            } else if (child instanceof Aggregate agg) { 
                
                plan = maybePushDownPastUnary(
                    filter,
                    agg,
                    e -> e instanceof Attribute && agg.output().contains(e) && agg.groupings().contains(e) == false
                        || e instanceof AggregateFunction