Update CompositeAggregationBuilder.java

[FabioMNAraujo]

We want to fix this issue for a university project and we think these modifications are leading us in the right direction, but we need some help and more time to analyze more code.
This relates to: #28611

[jimczi]

We cannot accept any parent here so as explained in #28611 we should check that all parent are instances of NestedAggregatorFactory. Something like:

private boolean checkParentIsNullOrNested(AggregatorFactory<?> parent) {
        if (parent == null) {
            return true;
        } else if (parent instanceof ReverseNestedAggregatorFactory) {
            return checkParentIsNullOrNested(parent.getParent());
        } else {
            return false;
        }
    }

Then we need a test that checks that nested aggregation and composite aggregation works fine together. org.elasticsearch.search.aggregations.bucket.NestedIT would be a good place to write such tests.

[elasticmachine]

Pinging @elastic/es-analytics-geo

[FabioMNAraujo]

Pinging @elastic/es-analytics-geo

i didn't know how to call the "doBuild" function. I created in the test a CompositeBuilder and a NestedBuilder and sub-aggregated the Composite to a Nested but I don't think the test I've created actually tests the changes added to the code. If anyone could help improve the testing, I'd be grateful

[javanna]

@jimczi would you be able to help here? Thanks!

[jimczi]

@FabioMNAraujo I opened #36357 to handle nested fields in the composite aggregation. I could not use your pr directly because I didn't want to mess your master branch (you opened this pr against your master branch) so I hope you don't mind that I created a new pr for this.

[polyfractal]

I think this was closed by #37178, please feel free to re-open if that's not true or I misunderstood :)