Allow custom queries in painless scripting language

[scottbuckel]

This allows the user to write a custom query in the painless scripting language https://www.elastic.co/guide/en/elasticsearch/painless/current/index.html.

For example, to search for a post by meta.birthday for all people born in March, you can use the following code:

$args['custom_query'][] = "doc['meta.birthday'].value.getMonthValue() == 3";

[tlovett1]

@sebumd this is interesting. Assuming it works and @tott and @brandwaffle, are okay with it. I think we can add this. However, first please run your PR through PHPCS as there are some issues.

[scottbuckel]

@tlovett1 thanks! I fixed the PHPCS issue.

@tott @brandwaffle what's the process to get this tested, approved and released for ElasticPress? Right now I'm using a hacked version of the module in production and would like to be able to include this feature and update to the latest when it comes out.

[Rahmon]

Hi @sebumd.

I would like to review this PR. Could you provide more information to test it? I've tried but looks like the filter is not applied.

[scottbuckel]

@Rahmon This is how I'm using it myself:

 if (isset($_GET['birthDateYear']) && !empty($_GET['birthDateYear'])) {
    $birthDateYear = esc_html($_GET['birthDateYear']);
    $args['custom_query'][] = "doc['meta.birthdate.date'].value.getYear() == " . $birthDateYear;
}