question: private void addReturningClause ( ) { if ( columnNames == null || columnNames . length == 0 ) { queryType = QUERY_TYPE_KEEP_UNMODIFIED ; return ; } generatesKeys = true ; StringBuilder query = new StringBuilder ( originalSQL ) ; if ( query . charAt ( query . length ( ) - 1 ) == ';' ) { query . setLength ( query . length ( ) - 1 ) ; } query . append ( '\n' ) ; query . append ( "RETURNING " ) ; for ( int i = 0 ; i < columnNames . length ; i ++ ) { query . append ( columnNames [ i ] ) ; if ( i < columnNames . length - 1 ) { query . append ( ',' ) ; } } modifiedSQL = query . toString ( ) ; }
target:  Adds the columns in columnNames to the query as generated keys.