<init>

MatchAgainstExpression(
    matchColumns: List<ColumnExpression<*>>,
    searchString: String,
    searchModifier: SearchModifier? = null,
    sqlType: SqlType<Boolean> = BooleanSqlType,
    isLeafNode: Boolean = false,
    extraProperties: Map<String, Any> = emptyMap())

Match against expression, represents an match ... against ... operation in MySQL.
See https://dev.mysql.com/doc/refman/5.5/en/insert-on-duplicate.html