Is saveAll() of MongoRepository inserting data in one bulk?

Question

I want to make the save operation efficient, so I'd like to write a bulk of objects to Mongo once in a while (i.e. when exceeding some capacity)

Would saveAll() do that for me? Should I use BulkOperations instead?

Answer 1

Short answer, yes, but only if all documents are new. If not, it will insert or update one by one.

Take a look at SimpleMongoRepository (MongoRepository's default implementation):

public <S extends T> List<S> saveAll(Iterable<S> entities) {
        Assert.notNull(entities, "The given Iterable of entities not be null!");
        Streamable<S> source = Streamable.of(entities);
        boolean allNew = source.stream().allMatch((it) -> {
            return this.entityInformation.isNew(it);
        });
        if (allNew) {
            List<S> result = (List)source.stream().collect(Collectors.toList());
            return new ArrayList(this.mongoOperations.insert(result, this.entityInformation.getCollectionName()));
        } else {
            return (List)source.stream().map(this::save).collect(Collectors.toList());
        }
    }

Notice that when all documents are new, the repository will use MongoOperations.insert method (MongoTemplate is the implementation), Then, if you look at that method's code you'll realize it does a batch insert:

public <T> Collection<T> insert(Collection<? extends T> batchToSave, String collectionName) {
        Assert.notNull(batchToSave, "BatchToSave must not be null!");
        Assert.notNull(collectionName, "CollectionName must not be null!");
        return this.doInsertBatch(collectionName, batchToSave, this.mongoConverter);
    }

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UPDATE 2021:

As of spring-data-mongodb 1.9.0.RELEASE (current 3.2.2), BulkOperations comes with a lot of extra features.

If more advanced tasks are needed other than just saving a bunch of documents, then BulkOperations class is the way to go.

It covers bulk inserts, updates, and deletes:

• insert(List<? extends Object> documents)
• remove(List removes)
• updateMulti(List<Pair<Query,Update>> updates)