fdb-record-layer

The Record Layer doesn't currently support foreign key constraints, so foreign keys are more of an “design pattern” than a first-class feature. For example, in a sample schema in the repository, an “Order” message has have a field called “item_id” that points to the primary key of an “Item” message: https://github.com/FoundationDB/fdb-record-layer/blob/792c95... There isn't an automatic check to make sure the item exists, though, nor are there cascading deletes. That being said, I don't think the architecture is incompatible with that feature, so it would be a reasonable feature request. There are some guidelines regarding field type changes in the schema evolution guide: https://foundationdb.github.io/fdb-record-layer/SchemaEvolut... Most data type changes are incompatible with either Protobuf's serialization format or the FDB Tuple laye

You're right the Record Layer doesn't yet have join support, but note PR #306 [1]. We support aggregate indexes but can't run aggregate “reports” that aren't backed by indexes. The rationale for this is covered in the paper (see [2]), but note that doesn't preclude such support being added into or on top of Record Layer (also discussed in the paper). The Record Layer does a whole bunch of work to deal with index maintenance (see our docs [3])). Our “index maintainer” abstraction (discussed in the paper) makes maintaining our indexes (including those that are basically materialized views) completely seamless from the user's perspective, even for updates and deletes. We also have a lot of tooling for making efficient schema migrations. For example, schema migrations are performed lazily (when the data is accessed), so they aren't limited by