Any query that updates the graph will run in a transaction. An updating query will always either fully succeed, or not succeed at all.
Cypher will either create a new transaction or run inside an existing one:
This can be used to have multiple queries be committed as a single transaction:
Note that a query will hold the changes in memory until the whole query has finished executing. A large query will consequently need a JVM with lots of heap space.
For using transactions over the REST API, see Section 5.1, “Transactional Cypher HTTP endpoint”.
When writing server extensions or using Neo4j embedded, remember that all iterators returned from an execution result should be either fully exhausted or closed to ensure that the resources bound to them will be properly released. Resources include transactions started by the query, so failing to do so may, for example, lead to deadlocks or other weird behavior.