
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 if (child instanceof Eval eval) {
                
                var attributes = new AttributeSet(Expressions.asAttributes(eval.fields()));
                plan = maybePushDownPastUnary(filter, eval, attributes::contains);
            } else if (child instanceof RegexExtract re) {
                
                var attributes = new AttributeSet(Expressions.asAttributes(re.extractedFields()));
                plan = maybePushDownPastUnary(filter, re, attributes::contains);
            } else if (child instanceof Enrich enrich) {
                
                var attributes = new AttributeSet(Expressions.asAttributes(enrich.enrichFields()));
                plan = maybePushDownPastUnary(filter, enrich, attributes::contains);
            } else if (child instanceof Project) {
                return pushDownPastProject(filter);
            } else if (child instanceof OrderBy orderBy) {
                
                plan = orderBy.replaceChild(filter.with(orderBy.child(), condition));
            }
            
            return plan;
        }
        private static LogicalPlan maybePushDownPastUnary(Filter filter, UnaryPlan unary, Predicate<Expression> cannotPush) {
            LogicalPlan plan;
            List<Expression> pushable = new ArrayList<>();
            List<Expression> nonPushable = new ArrayList<>();
            for (Expression exp : Predicates.splitAnd(filter.condition())) {
                (exp.anyMatch(cannotPush) ? nonPushable : pushable).add(exp);
            }