PrkDB

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Schema Registry ​

PrkDB includes a built-in schema registry that ensures data consistency across languages and versions. Instead of generic unstructured JSON or raw bytes, PrkDB collections are strictly typed.

Defining Collections ​

In Rust, you define collections using the #[derive(Collection)] macro. This automatically generates a Protocol Buffers (FileDescriptorSet) schema for your struct.

rust
use prkdb_macros::Collection;
use serde::{Deserialize, Serialize};

#[derive(Collection, Serialize, Deserialize, Clone, Debug)]
pub struct Product {
    #[key]
    pub sku: String,
    pub name: String,
    pub price: f64,
    pub inventory: u32,
}

Schema Registration ​

Before a client can interact with a collection, the schema must be registered with the server. You can register schemas via the prkdb CLI tool.

Registering via CLI ​

register and list require Admin, so set a credential first:

bash
export PRKDB_CREDENTIAL=change-me   # or PRKDB_ADMIN_TOKEN, deprecated
prkdb schema register --server http://127.0.0.1:8080 --collection Product --proto ./schemas/product.bin

To view all registered schemas:

bash
prkdb schema list --server http://127.0.0.1:8080

Compatibility Modes ​

When you evolve your schemas (e.g., adding or removing fields), PrkDB validates the new schema against the existing one based on the collection's compatibility mode:

  • Backward (Default): New schema can read data written by old schema. (e.g. adding an optional field)
  • Forward: Old schema can read data written by new schema.
  • Full: Schema changes must be both backward and forward compatible.
  • None: No compatibility checks are performed.

You can specify the compatibility mode during registration:

bash
prkdb schema register --server http://127.0.0.1:8080 --collection Product --proto ./schemas/product_v2.bin --compatibility backward

If a change is incompatible, the registry will reject the update unless you provide a --migration-id.

When you are using the development HTTP server (prkdb-cli serve), the schema-registry gRPC endpoint remains http://127.0.0.1:50051.