Database engines

AlphaDB uses one version source format for every supported database. The structure, the methods and most column attributes are the same everywhere. Only a few things depend on the database engine, mainly column types and auto-incrementing columns.

PostgreSQL MySQL

Selecting an engine

The root-level engine key tells AlphaDB which SQL dialect a version source is written for. Supported values are postgres and mysql.


{
  "engine": "postgres",
  "name": "template-name",
  "version": [ ... ]
}

The command-line interface requires engine, and verification uses it to pick the right rules. The Rust, Python and Node.js APIs select the engine in code (for example by installing alphadb-postgres or alphadb-mysql), but it’s still good practice to set engine so the version source works everywhere.

Shared syntax

These parts of a version source work the same on every engine:

Structure: the root keys (engine, name, version), versions with an _id, and default data.
Methods: createtable and altertable, including columns, primary keys, foreign keys, indexes and check constraints.
Column attributes:

Attribute	Description
`type`	The column type. Required when creating a column. The available types depend on the engine.
`length`	The column length, such as `"length": 255` for a `VARCHAR`.
`null`	Set to `true` to allow `NULL` values. Columns are `NOT NULL` unless `"null": true` is set.
`unique`	Set to `true` to add a unique constraint.
`default`	The default value for the column. See Default values.

Default values

Strings are quoted for you, so "default": "John" becomes DEFAULT 'John'. Numbers, SQL keywords and function calls are passed through as-is. Recognised keywords are CURRENT_TIMESTAMP, NOW(), CURRENT_DATE, CURRENT_TIME, LOCALTIME, LOCALTIMESTAMP and NULL; any value containing parentheses is treated as a function call.


"created_at": {
  "type": "TIMESTAMP",
  "default": "CURRENT_TIMESTAMP"
}

The engine pages list every supported column type and the rules the verifier checks: