Add InnerHits functionality

[wamania]

Add the innerHits functionality as described in
https://www.elastic.co/guide/en/elasticsearch/reference/2.4/search-request-inner-hits.html
for Nested aggregation and Child/parent relations

[ruflin]

Very nice addition. Could you also update the CHANGELOG.md file with this?

[wamania]

Done !

[ruflin]

Should we require ScriptFields type here? One can just use new ScriptsFileds(...) when passing the argument. Like this we can verify the type and have less "magic".

[wamania]

I used the same structure as Elastica\Aggregation\TopHits which is very similar.

/**
     * Set script fields.
     *
     * @param array|\Elastica\Script\ScriptFields $scriptFields
     *
     * @return $this
     */
    public function setScriptFields($scriptFields)
    {
        if (is_array($scriptFields)) {
            $scriptFields = new ScriptFields($scriptFields);
        }
        return $this->setParam('script_fields', $scriptFields);
    }

I think we should keep the same prototype (we can change both).

[ruflin]

I think the scriptFields in the TopHits is probably for historical reasons as it was perhaps introduced before ScriptFields and only arrays were passed.

Unfortunately we can't remove it from TopHits directly as it would break BC. We should add a note there that it is deprecated. Even though it is not consistent I prefer not to build up more legacy and only use ScriptFields here to be supported. Otherwise there will be in more BC breaks if we remove it one day.

[wamania]

ok, i agree

[ruflin]

LGTM. Only left one minor comment. Very nice functional tests you added.

[wamania]

look good now, argument forced to type ScriptFields, test ok

[ruflin]

@wamania Merged. Thanks a lot for the addition.

[wamania]

Happy to have been usefull, tell me if i can do some thing else.

[ruflin]

Help is always welcome :-) The biggest task ahead of Elastica currently from my perspective is: #944 Already several people played around with different approaches (including me) but I think we didn't get to a final conclusion yet. More then happy to hear your thoughts on this one.