Building a version source from a directory

Instead of maintaining one large JSON file, you can split a version source across many small files in a directory and let AlphaDB combine them into a single version source at runtime. This lives in the alphadb::version_source module, which is gated behind the version-source crate feature.

[dependencies]
alphadb = { version = "...", features = ["version-source"] }

Directory layout

A version source directory contains one config file and one file per version.

my-version-source/
├── adb-config.json
├── 1.0.0-create-users.json
├── 1.1.0-add-index.json
└── 1.2.0-add-email.json

The config file must be named adb-config.json or _adb-config.json (exactly one must be present). It defines the root-level name and engine:

{
  "name": "example-db",
  "engine": "mysql"
}

Every other file is a version file. Its name must start with a valid version number followed by a hyphen (<version>-<description>.json); the leading version number becomes the version’s _id. The file itself is a JSON object of methods, without an _id key:

{
  "createtable": {
    "users": {
      "primary_key": "id",
      "id": { "type": "INT", "auto_increment": true },
      "name": { "type": "VARCHAR", "length": 100 }
    }
  }
}

Usage

build_version_source_from_dir reads the directory and returns the combined version source as a serde_json::Value, ready to pass to update.

use std::path::PathBuf;
use alphadb::version_source::build_version_source_from_dir;
 
let version_source = build_version_source_from_dir(&PathBuf::from("path/to/my-version-source"))
    .expect("Failed to build version source");
 
// Hand it to the database as a string
let version_source_string = serde_json::to_string(&version_source).unwrap();

The result is a normal version source with the name and engine taken from the config file, and one entry in version per version file:

{
  "name": "example-db",
  "engine": "mysql",
  "version": [
    { "_id": "1.0.0", "createtable": { "users": { /* ... */ } } },
    { "_id": "1.1.0", "altertable": { "users": { /* ... */ } } },
    { "_id": "1.2.0", "altertable": { "users": { /* ... */ } } }
  ]
}