(Contradiction of java.sql and suggestion to it)
Intrinsically, this exception class should extend/implement a different
superclass, but since java.sql has contradiction explained below, this class
extends java.sql.SQLException currently (and hopefully temporarily).
Technically, a query for search engine does NOT have to be a subclass of SQL.
So an exception that occurs during a communication with search engine does
also not have to be a subclass of something that emulates SQL such as
SQLException done in this class.
This paradoxical design is rooted in the contradiction that java.sql package
has.