unable to upsert using java datastax driver - cassandra

Question

I am unable to upsert a row using the datastax driver.
The data in the Cassandra table is stored like follows:
tag | partition_info
------------+--------------------------------------------------
sometag | {{year: 2018, month: 1}, {year: 2018, month: 2}}
tag is primary key and partition_info is a UDT
CREATE TYPE codingjedi.tag_partitions (
year bigint,
month bigint
);
I want that if a tag doesn't exist then it gets created. If tag exists then the new udt value gets appended to old one. I suppose I cannot use insert as it overrides previous value i.e. this will not work
QueryBuilder.insertInto(tableName).value("tag",model.tag)
.value("partition_info",setAsJavaSet(Set(partitionsInfo)))
I am trying to use update but it isn't working. Datastax driver gives error java.lang.IllegalArgumentException for following query
QueryBuilder.update(tableName).`with`(QueryBuilder.append("partition_info",setAsJavaSet(Set(partitionsInfo))))
.where(QueryBuilder.eq("tag", id.tag))
I tried using add and append for primary key but but got the error PRIMARY KEY part tag found in SET part
QueryBuilder.update(tableName).`with`(QueryBuilder.add("tag",id.tag))
.and(QueryBuilder.append("partition_info",setAsJavaSet(Set(partitionsInfo)))) .where(QueryBuilder.eq("tag", id.tag))

Answer 1

You're using the incorrect operation in your update statement - you're using append, but it's used to append data to columns of list types. You can use instead either add if you're adding a single value (your case, so you wont even need to wrap data into Set explicitly), or addAll if you're adding multiple values.
QueryBuilder.update(tableName)
.`with`(QueryBuilder.add("partition_info", partitionsInfo))
.where(QueryBuilder.eq("tag", id.tag))