npm package: @joselcvarela/knex-schema-inspector
Description: Utility for extracting information about existing DB schema
Author: Rijk van Zanten
Latest version: 3.0.4

# knex-schema-inspector

Utility for extracting information about existing DB schema

This library currently supports Postgres, MySQL, MS SQL, SQLite, and OracleDB. We aim to have support for the same databases as the main knex project.

## Installation

Install the package through NPM or Yarn:

```
npm install knex-schema-inspector
```

```
yarn add knex-schema-inspector
```

## Usage

The package is initialized by passing it an instance of Knex:

```ts
import Knex from 'knex';
import schemaInspector from 'knex-schema-inspector';

const database = Knex({
  client: 'mysql',
  connection: {
    host: '127.0.0.1',
    user: 'your_database_user',
    password: 'your_database_password',
    database: 'myapp_test',
    charset: 'utf8',
  },
});

const inspector = schemaInspector(database);

export default inspector;
```

## Examples

```ts
import inspector from './inspector';

async function logTables() {
  const tables = await inspector.tables();
  console.log(tables);
}
```

## API

Note: MySQL doesn't support the `schema` parameter, as schema and database are ambiguous in MySQL.

Note 2: Some database types might return slightly more information than others. See the type files for a specific overview what to expect from driver to driver.

Note 3: MSSQL doesn't support comment for either tables or columns

### Methods

**Table**

- [`tables(): Promise<string[]>`](#tables-promisestring)
- [`tableInfo(table?: string): Promise<Table | Table[]>`](#tableinfotable-string-promisetable--table)
- [`hasTable(table: string): Promise<boolean>`](#hastabletable-string-promiseboolean)

**Columns**

- [`columns(table?: string): Promise<{ table: string, column: string }[]>`](#columnstable-string-promise-table-string-column-string-)
- [`columnInfo(table?: string, column?: string): Promise<Column[] | Column>`](#columninfotable-string-column-string-promisecolumn--column)
- [`primary(table: string): Promise<string>`](#primarytable-string-promisestring)

**Foreign Keys**

- [`foreignKeys(): Promise<ForeignKey>`](#foreign-keys)

**Misc.**

- [`withSchema(schema: string): void`](#withschemaschema-string-void)

### Tables

#### `tables(): Promise<string[]>`

Retrieve all tables in the current database.

```ts
await inspector.tables();
// => ['articles', 'images', 'reviews']
```

#### `tableInfo(table?: string): Promise<Table | Table[]>`

Retrieve the table info for the given table, or all tables if no table is specified

```ts
await inspector.tableInfo('articles');
// => {
//   name: 'articles',
//   schema: 'project',
//   comment: 'Informational blog posts'
// }

await inspector.tableInfo();
// => [
//   {
//     name: 'articles',
//     schema: 'project',
//     comment: 'Informational blog posts'
//   },
//   { ... },
//   { ... }
// ]
```

#### `hasTable(table: string): Promise<boolean>`

Check if a table exists in the current database.

```ts
await inspector.hasTable('articles');
// => true
```

### Columns

#### `columns(table?: string): Promise<{ table: string, column: string }[]>`

Retrieve all columns in a given table, or all columns if no table is specified

```ts
await inspector.columns();
// => [
//   {
//     "table": "articles",
//     "column": "id"
//   },
//   {
//     "table": "articles",
//     "column": "title"
//   },
//   {
//     "table": "images",
//     "column": "id"
//   }
// ]

await inspector.columns('articles');
// => [
//   {
//     "table": "articles",
//     "column": "id"
//   },
//   {
//     "table": "articles",
//     "column": "title"
//   }
// ]
```

#### `columnInfo(table?: string, column?: string): Promise<Column[] | Column>`

Retrieve all columns from a given table. Returns all columns if `table` parameter is undefined.

```ts
await inspector.columnInfo('articles');
// => [
//   {
//     name: "id",
//     table: "articles",
//     data_type: "VARCHAR",
//     default_value: null,
//     max_length: null,
//     numeric_precision: null,
//     numeric_scale: null,
//     is_nullable: false,
//     is_unique: false,
//     is_primary_key: true,
//     has_auto_increment: true,
//     foreign_key_column: null,
//     foreign_key_table: null,
//     comment: "Primary key for the articles collection"
//   },
//   { ... },
//   { ... }
// ]

await inspector.columnInfo('articles', 'id');
// => {
//    name: "id",
//    table: "articles",
//    data_type: "VARCHAR",
//    default_value: null,
//    max_length: null,
//    numeric_precision: null,
//    numeric_scale: null,
//    is_nullable: false,
//    is_unique: false,
//    is_primary_key: true,
//    has_auto_increment: true,
//    foreign_key_column: null,
//    foreign_key_table: null,
//    comment: "Primary key for the articles collection"
//  }
```

#### `primary(table: string): Promise<string>`

Retrieve the primary key column for a given table

```ts
await inspector.primary('articles');
// => "id"
```

### Foreign Keys

Retrieve all configured foreign key constraints.

```ts
await inspector.foreignKeys();
// => [
//   {
//     table: 'directus_files',
//     column: 'folder',
//     foreign_key_table: 'directus_folders',
//     foreign_key_column: 'id',
//     constraint_name: 'directus_files_folder_foreign',
//     on_update: 'CASCADE',
//     on_delete: 'SET NULL'
//   },
//   {
//     table: 'directus_files',
//     column: 'modified_by',
//     foreign_key_table: 'directus_users',
//     foreign_key_column: 'id',
//     constraint_name: 'directus_files_modified_by_foreign',
//     on_update: 'CASCADE',
//     on_delete: 'SET NULL'
//   }
// ]
```

### Misc.

#### `withSchema(schema: string): void`

_Not supported in MySQL_

Set the schema to use. Note: this is set on the inspector instance and only has to be done once:

```ts
inspector.withSchema('my-schema');
```

## Contributing

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.

### Tests

First start docker containers:

```shell
$ docker-compose up -d
```

Then run tests:

```shell
$ npm test
```

Standard mocha filter (grep) can be used:

```shell
$ npm test -- -g '.tableInfo'
```

## License

[MIT](https://choosealicense.com/licenses/mit/)