MyBatis Batch Insert/Update For Oracle

Question

I've recently started learning to use myBatis.I am now facing such a scenario, I need to constantly fetch a new list of Objects through WebService, then for this list, I need to insert/update each object into the oracle DB table through myBatis.

The tricky part is, I cannot simply do a batch insert every time, because some of the objects might already exist in DB, for these records, I need to update the fields of them instead of a new insertion.

My current solution might be very stupid, using Java, build the list of Object from webservice, loop through each of them, do a myBatis select, if it is not a null(already exists in the db), then do a myBatis update; otherwise, do a myBatis insert for this new object.

The function is achieved. But my technical lead says it is very low-efficient, since doing a for loop using Java and insert/update one by one will consume a lot of system resource. He advised me to do batch insert using myBatis by passing a list of objects in.

Batch insertion in myBatis is straightforward, however, since I am not purely inserting(for existing records I need to do update), I don't think batch insert is appropriate here. I've googled a while for this, and realized maybe I will need to use "merge" instead of "insert" (for Oracle).

The examples I googled out for merge in myBatis is only for one object, not in a batch. Thus I want to find out whether experts could offer me some examples on how to do a batch-merge in MyBatis( The correct way to write a Mapper)?

Answer 1

The accepted answer is not the recommended way of handling batch operations. It does not show true batch statements since the batch executor mode should be used when opening a session. See this post in which a code contributor recommended that the proper way to batch update (or insert) is to open a session in batch mode and repeatedly call update (or insert) for a single record.

Here's what works for me:

public void updateRecords(final List<GisObject> objectsToUpdate) {
    final SqlSession sqlSession = MyBatisUtils.getSqlSessionFactory().openSession(ExecutorType.BATCH);
    try {
        final GisObjectMapper mapper = sqlSession.getMapper(GisObjectMapper.class);
        for (final GisObject gisObject : objectsToUpdate) {
            mapper.updateRecord(gisObject);
        }
        sqlSession.commit();
    } finally {
        sqlSession.close();
    }
}

Do not use foreach in your update/insert and ensure that it only updates/inserts a single record. I was running into unsolvable oracle errors by doing it according to the accepted answer (invalid character, statement not ended, etc.). As the linked post indicates, the update (or insert) shown in the accepted answer is actually just a giant sql statement.