While we've worked hard to make updates to newer versions of Neo4j as pleasant as possible, these are a few things to be aware of, particularly when switching to a major revision.
Neo4j 3.5 Upgrade FAQ
Upgrade FAQs for Neo4j 3.4 and earlier
What is in 3.5?
It’s all in the blog post, which you can read here: Neo4j Graph Database 3.5: Everything You Need to Know.
Where are the Release Notes?
Release notes for all Neo4j releases can be found here.
Is 3.5 an API-Breaking Release?
No. Minor releases are a place to deprecate features and functionality, which includes public APIs. However, we will not remove deprecated functionality until a major release. Note: Upgrading from a version prior to Neo4j 3.0 means that the 3.0 Upgrade FAQs apply, and this would then be a breaking release. If you are upgrading from a 2.x release, see the Upgrade FAQ Archive.
Migrate configuration from a pre-3.0 version
When migrating to Neo4j 3.5 from a release prior to 3.0 please note that most configuration settings have been renamed to support a more consistent naming scheme. Also note that neo4j.properties and neo4j-server.properties have been merged into a single neo4j.conf file. Since many settings have been changed between Neo4j 2.x and Neo4j 3.x, it is advisable to use the config-migrator utility to migrate the config files and settings for you. The config-migrator can be found in the bin/tools directory of Neo4j 3.x, and can be invoked with a command like:
java -jar config-migrator.jar path/to/neo4j2.3 path/to/neo4j3.5. Take note of any warnings printed, and manually review the edited config files produced. The warnings will alert you to deprecated settings, or settings it did not know about (spelling mistakes, etc) that require manual intervention.
Manually Migrate Native Indexes
Beginning with 3.2, native indexes were introduced to replace Lucene indexes for specific data types for performance gain reasons. 3.5 completes the transition to native for remaining data types plus composite indexes. It is important to note that the current index implementation is not migrated automatically and to benefit from native indexes, existing indexes must be manually dropped and re-created post-upgrade. The choice of index provider is controlled by the setting:
dbms.index.default_schema_provider. For more information on native indexes, please refer to here.
Where in the Documentation Can I Learn More about Upgrades?
The Upgrade section of the Neo4j Operations Manual can be found here, and also covers upgrades specific to 3.4. The store upgrade happens by starting your Neo4j data store (after making the backup) with Neo4j 3.4 and the configuration
dbms.allow_upgrade=true enabled in the configuration file conf/neo4j.conf
Are there any Backwards-Compatibility Options?
Yes. Cypher lets you specify what version of the Cypher compiler you would like to use. See the Operations Manual for details. Also of note is the new Causal Clustering architecture introduced in 3.1 and further improved in 3.5. Note that 3.5 will be the last version to support the previous Master/Slave clustering architecture available in prior versions. You can upgrade an HA system to 3.5, and save the cluster changes for a later date to simplify the process. However, you will need to remain on 3.5 until you migrate to Causal Clustering.
Is the Store Upgrade Reversible?
No, once your data store is upgraded, it cannot be rolled back. For this reason, Neo4j makes a backup of each store file as part of the upgrade to 3.4. Make sure you have at least double the size of your Neo4j store available as free space on your disk, before you upgrade. After the upgrade is successful, those backup files will be removed automatically.
How Long Will the Upgrade Take?
This will depend largely on what version you are upgrading from, and the size of your database. We recommend you try this out in a test environment first, to get an idea of the timing, and help you plan your upgrade. Upgrading from 3.x to 3.5 should be quite fast, while upgrading from pre-3.0 to 3.x will take longer due to the Lucene upgrade. Don’t forget though that you will first need to test your application to make sure it works! Chances are that that you may have to make some changes.
When Should I Upgrade?
Upgrading to Neo4j 3.5 from a 3.x version will be very straightforward and will yield immediate performance and governance benefits. You will also have the opportunity to take advantage of new features. If you are in the development and planning phase, then upgrade straight away! If you are already in production with Neo4j, or have a lot of dependencies, test it first and make sure that you have the upgrade steps and dependencies sorted out before upgrading production.
Are Rolling Upgrades Supported?
Yes, from 3.4 onward. Rolling upgrades let you upgrade a cluster while it is running.
What Version Can I Upgrade From?
Neo4j 3.5 supports direct upgrades from 2.3 and newer. It is generally recommended to upgrade from the most recent patch of your current Neo4j release, as that is the tested upgrade path from pre-3.5 releases to 3.5. Previous versions, such as 2.2, have to be upgraded to 2.3.latest first.
How Long Can I Continue Using 3.4?
3.4 will continue to be supported for at least 18 months following its release, until November 17, 2019, per the terms of your Support Agreement. Any fixes deemed applicable to the 3.4 release will be released in a 3.4.x release. As of the time of this writing, the latest stable 3.4.x release is 3.4.10. Commercial customers can view currently Supported Versions here.