Concatenate two fieds in an EntityQuery condition
I don't think it's possible this way.
I would rather split the $string in two parts, and check the two fields with each part.

$query-&gt;condition("FIELD_1)", $string_1);
$query-&gt;condition("FIELD_2)", $string_2);


You have many ways to separate the string in two.
Is this helping you ?