We decided to skip the support of `java.math.BigDecimal` and `java.math.BigInteger` field types in https://hibernate.atlassian.net/browse/HSEARCH-3047.
Since we need to think more about which type to use to map those fields on Elasticsearch server.
One possible solution could be extract a storing factor from Hibernate ORM field metadata, such as `@Column.length` or something like that. Then to use this value to convert the `java.math.BigDecimal` into a long, like it was done in `BigDecimalNumericFieldBridge` class of Hibernate Search 5 test code.
Note that there is a type just for that (with a static scaling factor) in Elasticsearch: scaled_float . See https://www.elastic.co/guide/en/elasticsearch/reference/current/number.html#number