lib/Query/Common/CriterionVisitor/ContentIdIn.php
public function visit(Criterion $criterion, CriterionVisitor $subVisitor = null)
    {
        return '(' .
            implode(
                ' OR ',
                array_map(
                    function ($value) {
                        return 'content_id_id:"' . $value . '"';
                    },
                    $criterion->value
                )
            ) .
            ')';
    }
public function visit(Criterion $criterion, CriterionVisitor $subVisitor = null)
    {
        return '(' .
            implode(
                ' OR ',
                array_map(
                    function ($value) {
                        return 'content_id_id:"' . $value . '"';
                    },
                    $criterion->value
                )
            ) .
            ')';
    }
Map field value to a proper Solr representation.

@param \eZ\Publish\API\Repository\Values\Content\Query\Criterion $criterion
@param \EzSystems\EzPlatformSolrSearchEngine\Query\CriterionVisitor $subVisitor

@return string