@prestodb/presto-js-client

Presto JS Client

This is a Presto JavaScript client that connects to Presto via Presto's REST API to run queries.

Installation

npm install @prestodb/presto-js-client

Usage

Import the PrestoClient class from @prestodb/presto-js-client.

Create a new instance by passing the connection parameters.

Example

Import the Client class:

import PrestoClient from '@prestodb/presto-js-client'

Instantiate a client with connection parameters:

const client = PrestoClient({
  catalog: 'tpcs',
  host: 'localhost',
  port: 8080,
  schema: 'tiny',
  timezone: 'America/Costa_Rica',
  user: 'root',
})

Parameters

The Presto client can be configured with the following parameters:

• host: The hostname or IP address of the Presto coordinator. (Default: http://localhost)
• port: The port number of the Presto coordinator. (Default: 8080)
• user: The username to use for authentication. (Default: undefined)
• catalog: The default catalog to use for queries. (Default: undefined)
• schema: The default schema to use for queries. (Default: undefined)
• source: The name of the source you want to use for reporting purposes (Default: presto-js-client)
• timezone: The timezone to use for queries. (Default: undefined)
• authorizationToken: The value to send as-is in the Authorization header. Note: The Bearer scheme is automatically added. (Default: undefined)
• basicAuthentication: An object with a user and password inside, to be used for basic authentication. (Default: undefined)
• extraHeaders: An dictionary of key-values to send as extra headers in all requests to the API. (Default: undefined)
• interval: (DEPRECATED) The interval in milliseconds between checks for the status of a running query. (Default: 100)

Querying

The query method takes a single string parameter, which is the SQL query to be executed. The method returns a PrestoQuery object, which contains the results of the query, including the columns, data, and query ID. If the query fails, the query method will throw an error.

The string parameter to the query method must be a valid SQL query. The query can be any type of SQL query, including SELECT, INSERT, UPDATE, and DELETE statements.

Return data structure (or error state)

The query method returns a PrestoQuery object, which contains the results of the query, including the columns, data, and query ID.

If the query succeeds, the PrestoQuery object will have the following properties:

• columns: An array of objects that describe the columns in the results.
• data: An array of arrays that contain the actual data for the results.
• queryId: The ID of the query.

If the query fails, you can catch the error as a PrestoError which contains all information returned by Presto.

Example usage

The following example shows how to use the query() method to execute a SELECT statement:

const client = new PrestoClient({
  catalog: 'tpcds',
  host: 'http://localhost',
  port: 8080,
  schema: 'sf1',
  user: 'root',
})

const query = `SELECT * FROM my_table`

try {
  const prestoQuery = await client.query(query)
  const results = prestoQuery.data
} catch (error) {
  if (error instanceof PrestoError) {
    // Handle the error.
    console.error(error.errorCode)
  }
}

Additional notes

Additional notes

• The query method is asynchronous and will return a promise that resolves to a PrestoQuery object.
• The query method will automatically retry the query if it fails due to a transient error.
• The query method will cancel the query if the client is destroyed.

Get Query metadata information

Get Query Information

The getQueryInfo method retrieves comprehensive information about a specific query, based on its identifier. It returns metadata including status, execution details, statistics, and more, encapsulated within a QueryInfo object or undefined if the query does not exist.

Parameters

• queryId: The unique identifier string of the query for which information is being retrieved.

Example usage

const queryInfo = await prestoClient.getQueryInfo('your_query_id')
console.log(queryInfo)

Query catalog, schema, table and column metadata

Get Catalogs

The getCatalogs method retrieves all available database catalogs, returning them as an array of strings.

Example usage

const catalogs = await prestoClient.getCatalogs()
console.log(catalogs)

Get Schemas

The getSchemas method retrieves all schemas within a given catalog. It accepts a catalog parameter, which is a string representing the name of the catalog.

Parameters

• catalog: The name of the catalog for which to retrieve schemas.

Example usage

const schemas = await prestoClient.getSchemas('tpch')
console.log(schemas)

Get Tables

The getTables method retrieves a list of tables (of type Table) filtered by the given catalog and, optionally, the schema. It accepts an object containing catalog and optional schema parameters.

Parameters

• catalog: The catalog name.
• schema (optional): The schema name.

Example usage

const tables: Table[] = await prestoClient.getTables({ catalog: 'tpch', schema: 'sf100' })
console.log(tables)

Get Columns

The getColumns method retrieves a list of columns (of type Column) filtered for the given catalog and optional schema and table filters. It accepts an object with catalog, and optional schema and table parameters.

Parameters

• catalog: The catalog name.
• schema (optional): The schema name.
• table (optional): The table name.

Example usage

const columns: Column[] = await prestoClient.getColumns({
  catalog: 'tpch',
  schema: 'sf100',
  table: 'orders',
})
console.log(columns)

Authentication

When creating the client instance, you optionally pass one of two authentication methods.

Basic authentication

You can send a basic authorization user and password in this way:

const client = new PrestoClient({
  basicAuthentication: {
    user: 'my-user',
    password: 'my-password',
  },
  catalog: 'tpcds',
  host: 'http://localhost',
  port: 8080,
  schema: 'sf1',
  user: 'root',
})

Auth token

You can send an authorization token in the following way:

const client = new PrestoClient({
  // Do not include `Bearer` here, it is automatically added by the client
  authorizationToken: `eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c`,
  catalog: 'tpcds',
  host: 'http://localhost',
  port: 8080,
  schema: 'sf1',
  user: 'root',
})

Extra headers

You can pass any extra custom headers to the Presto client to be send on all requests performed against the host:

const client = new PrestoClient({
  catalog: 'tpcds',
  extraHeaders: {
    'X-My-Custom-Header-1': 'value',
    'X-My-Custom-Header-2': 'value',
  },
  host: 'http://localhost',
  port: 8080,
  schema: 'sf1',
  user: 'root',
})