
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
private List<NamedExpression> combineProjections(List<? extends NamedExpression> upper, List<? extends NamedExpression> lower) {
            
            AttributeMap.Builder<NamedExpression> aliasesBuilder = AttributeMap.builder();
            for (NamedExpression ne : lower) {
                if ((ne instanceof Attribute) == false) {
                    aliasesBuilder.put(ne.toAttribute(), ne);
                }
            }
            AttributeMap<NamedExpression> aliases = aliasesBuilder.build();
            List<NamedExpression> replaced = new ArrayList<>();
            
            
            for (NamedExpression ne : upper) {
                NamedExpression replacedExp = (NamedExpression) ne.transformUp(Attribute.class, a -> aliases.resolve(a, a));
                replaced.add((NamedExpression) trimNonTopLevelAliases(replacedExp));
            }
            return replaced;
        }
        public static Expression trimNonTopLevelAliases(Expression e) {
            if (e instanceof Alias a) {
                return new Alias(a.source(), a.name(), a.qualifier(), trimAliases(a.child()), a.id());
            }
            return trimAliases(e);
        }
        private static Expression trimAliases(Expression e) {
            return e.transformDown(Alias.class, Alias::child);
        }
    }
    static class PushDownAndCombineLimits extends OptimizerRules.OptimizerRule<Limit> {