
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/ql/src/main/java/org/elasticsearch/xpack/ql/expression/AttributeMap.java
private final Set<W> set;
        UnwrappingSet(Set<W> originalSet) {
            set = unmodifiableSet(originalSet);
        }
        @Override
        public Iterator<U> iterator() {
            return new Iterator<>() {
                final Iterator<W> i = set.iterator();
                @Override
                public boolean hasNext() {
                    return i.hasNext();
                }
                @Override
                public U next() {
                    return unwrap(i.next());
                }
            };
        }
        protected abstract U unwrap(W next);
        @Override
        public Stream<U> stream() {
            return set.stream().map(this::unwrap);
        }