Databases

One of the most powerful and unique features of SlashDB is the ability to automatically discover tables, views and relations in databases.

In this section we're going to connect SlashDB to a sample database and make it usable to user admin. The procedure is fairly simple and will take just a moment.

Database Definitions list

The Database Definitions page provides a list of all data sources available for viewing and interaction. It can be searched using search field above the list or sorted by clicking on headers of the columns.

The list is accessible from the main Menu Configure > Databass or direct URL /dbdef. It is available only admin and users with Administrative privilege to view list of Databases.

The list can be searched using search field above the list or sorted by clicking on headers of the columns.

On the list you can find button to edit database details, Database ID, Type, Description, Connection status, button that toggles the state of the selected database and link to JSON representation.

Adding a new database

1. Click on Configure > Databases in menu to show list of database definitions

2. Next click the in top right corner. The button is visible for admin and users with Administrative Privilege to create new database.

3. The modal of empty Database Confguration will appear.

3. In the Database ID field give the database a unique name and optionally put a short description in the Description field.

4. Select appropriate database type from the Type drop-down menu and fill out the remaining fields on the screen. Hover your mouse cursor over the icon to learn more about the purpose of the field and configuration tips.

Note that depending on the database type selected the list of fields may be different than pictured.

5. When finished click the Save button. If Use Credentials for Current User is selected then on saving another modal will popup showing updated user configuration with mapping to the database defined using Database User and Database Password. Save and close and then Close the configuration of the database.

Now the newly added database will appear in the Database Definitions table.

Connect to database

Use on Data Discovery /db or Database Definitions /dbdef page to change the Connection status of the database.

Failed Connection

When something goes wrong while connecting to a datbase, SlashDB will change the Connection status to Failed. If necessary, it will also display a notification bellow the databases list, with more information about the problem.

A failed connection usually occurs because of the following two reasons:

• an error in the database configuration - please check the database definition for typos/errors,
• network errors due to a firewall blocking access to the database or network down time - check the firewall and grant access from the SlashDB host to the host and port on which the database server is running.

You may need to ask your database and/or network administrator for help.

Configuration File

Database configurations are stored in YAML file /etc/slashdb/databases.cfg.

A simple configuration for single SQLite database called Chinook looks like below

Chinook:
  alternate_key: {}
  autoload: true
  autoload_user: {dbpass: '', dbuser: ''}
  connection: /var/lib/slashdb/sqlite/chinook.sqlite
  creator: admin
  db_encoding: utf-8
  db_id: Chinook
  db_schema: null
  db_type: sqlite
  desc: Example SQLite database
  excluded_columns: {}
  execute: []
  foreign_keys: {}
  autoconnect: true
  read: []
  write: []

It's easier to modify database configuration using Configuration GUI. Some features are hidden and require modifying databases.cfg manually.

Database Configuration Attributes

The file stores all database configurations in dictionary like structure. The keys of the highest level are unique database ids. Each database configuration has several attributes. Below you can find all attributes explained and some examples.

alternate_key

Data Discovery reflects only tables with primary keys. When a primary key is not defined it may be manually added to config under in alternate_key dictionary.

Since database views typically don't have primary key, this feature allows to them to SlashDB.

The alternate_key is a dictionary. The keys in the dictionary are names of tables, values are lists of column names that can be treated as artificial primary key.

Example:

Chinook:
  alternate_key:
    Table1: [col1, col2]
    ViewCustomer: [CustomerId]

autoload

When true tells SlashDB to make a full reflect on database. This will discover tables, columns, primary and foreign keys and automatically add them to the API.

When false SlashDB will be looking for the model installed as plugin with the same name. This feature is used for advanced use cases with custom built ORM model.

Example:

SlashDB will automatically discover database model

Chinook:
  autoload: true

SlashDB will be looking for a custom model installed as a plugin.

Chinook:
  autoload: false

autoload_user

It's a dictionary that stores login and password to the database to be used for reflect purposes. It must be used together with autoload = true

Example:

Chinook:
  autoload: true
  autoload_user: {dbuser: 'john', dbpass: 'secretpasssowrd'}

connection

Connection stores location of the database.

For SQLite it's path to file e.g. /home/john/database.sqlite.

For MS SQL, DB2, MySQL, MariDB, PostgreSQL it's host, port and database e.g. 192.168.1.1:1433/Chinook.

For Oracle it's host, port and SID e.g. 192.168.1.1:1521/xe

Example

Chinook:
  connection: database.my-domain:1433/Chinook

creator

Creator options is used for administrative purposes. User which adds a new database config is assigned as a creator and is automatically granted permissions to read, modify and connect the database.

Example

User admin has added the database to SlashDB.

Chinook:
  creator: admin

db_encoding

This option tells SlashDB what is the charset encoding in the database. This information in required to correctly process diacritic characters. Allowed values are:

Example:

The character set used by database is UTF-8.

Chinook:
  db_encoding: 'utf-8'

db_id

Unique database id that is used in other configuration files: users.cfg and querydefs.cfg. Also the id becomes an API endpoint in Data Discovery e.g. /db/Chinook.

Example:

Chinook:
  db_id: Chinook

db_schema

This option is used if SlashDB should connect to certain schema in the database. That's applicable for databases that support use schema like MS SQL, PostgreSQL, Oracle, DB2. If not provided a default user schema is used.

Example:

Use database schema dbo when reflecting model.

Chinook:
  db_schema: dbo

db_type

Defines what sort of a database server SlashDB is connecting.

Allowed values are:

• sqlite for SQLite
• mssql for MS SQL Server
• oracle for Oracle
• db2 for IBM DB2
• mysql for MySQL or MariaDB
• postgresql for PostgreSQL

Example:

The database Chinook is SQLite

Chinook:
  db_type: sqlite

desc

Non-obligatory additional description of the purpose of the API or any other useful notes.

Example:

Chinook:
  desc: A sample music store database

excluded_columns

This option allows to exclude certain columns from the API but columns cannot be part on relationship constraint.

When primary key column is excluded the table won't be added to the API. This can be used as a feature to hide some tables.

Option excluded_columns expects a dictionary object where key is table name and value is list of column names to be excluded form API.

Example: To exclude a regular columns Company, Address and City from table Customer and BillingAddress from table Invoice

Chinook:
  excluded_columns:
    Customer: [Company, Address, City]
    Invoice: [BillingAddress]

To exclude a table from API exclude the primary key.

Chinook:
  excluded_columns:
    InvoiceLine: [InvoiceLineId]

foreign_keys

Deprecated. Should be empty dictionary or null.

Chinook:
  foreign_keys: null

autoconnect

This option accept true or false value that define if the API should connect automatically to the server when SlashDB starts.

Example:

To load (reflect) Chinook database automatically on start of the service.

Chinook:
  autoconnect: true

read

List of users allow to view the database config. Account admin is always privileged and doesn't have to listed.

Example:

Only john, mike and admin will be able view the config details.

Chinook:
  read: [john, mike]

write

List of users allowed to modify the database config.Account admin is always privileged and doesn't have to listed.

Example:

Only john, mike and admin will be able view the config details.

Chinook:
  read: [john, mike]

execute

It's a list of SlashDB users allowed to control state of that particular API - connect or disconnect. Account admin is always privileged and doesn't have to listed.

Example:

Only john, mike and admin will be able change the state of the connection.

Chinook:
  execute: [john, mike]