Updating the database

A initialized database is ready to be updated. Before updating, a version source must be created.

Version source

For this example we’ll use a very simple version source. It’s a JSON file.


{
  "name": "example-db",
  "version": [{
    "_id": "1.0.0",
    "createtable": {
      "customers": {
        "primary_key": "customer_id",
        "customer_id": {
          "type": "INT",
          "a_i": true
        },
        "name": {
          "type": "VARCHAR",
          "length": 100,
          "unique": true
        },
        "created": {
          "type": "DATETIME"  
        }
      }
    },
    "default_data": {
     "customers": [
        {
          "customer_id": 1,
          "name": "John",
          "created": "2023-10-31 02:12:52.000000"
        },
        {
          "customer_id": 2,
          "name": "Brian",
          "created": "2022-02-21 11:42:19.000000"
        },
        {
          "customer_id": 3,
          "name": "Anouk",
          "created": "2021-06-12 08:13:48.000000"
        }
      ]
    }
  }]
}

This will create the following table in your database:

customer_id 🔑	name	created
1	John	2023-10-31 02:12:52.000000
2	Brian	2022-02-21 11:42:19.000000
3	Anouk	2021-06-12 08:13:48.000000

Read from file

AlphaDB expects a String for the version source, so we can simple read the contents of the JSON file and supply it to the update method.


use std::fs;
use alphadb::utils::types::ToleratedVerificationIssueLevel;
 
let version_source = match fs::read_to_string("path/to/version-source.json") {
	Ok(f) => f,
	Err(_) => panic!("An error occured while opening the version source file!")
};

The update method takes a couple more arguments. Let’s take a look at the function definition:


fn update(
	&mut self,
	version_source: String,
	update_to_version: Option<&str>, // Optionally set the max version to update to
	no_data: bool, // Whether the default data should be inserted or not
	verify: bool, // Wheter the version source should be checked for errors before updating
	allowed_error_priority: ToleratedVerificationIssueLevel,
) -> Result<(), UpdateError>

Tolerated verification issue level

When verify is set to true, the version source will be verified before running the update. The verification process separates errors in different priorities. With allowed_error_priority you specify the level at which the verification will fail.

ℹ️ For a full explanation of what is checked during verification, see the global version source verification documentation.

Run updates


db.update(version_source, None, false, true, ToleratedVerificationIssueLevel::Low);

The update will now include default data, first be verified and fail whenever there is an issue with a higher priority than ToleratedVerificationIssueLevel::Low.