sqlpad/lib/presto.js

Web app for writing and running SQL queries and visualizing the results. Supports Postgres, MySQL, SQL Server, Crate and Vertica.

const fetch = require('node-fetch')
const NEXT_URI_TIMEOUT = 100

module.exports = { send }

// Util - setTimeout as a promise
function wait(ms) {
  return new Promise(resolve => setTimeout(resolve, ms))
}

// Get Presto headers from config
function getHeaders(config) {
  const headers = { 'X-Presto-User': config.user }
  if (config.catalog) {
    headers['X-Presto-Catalog'] = config.catalog
  }
  if (config.schema) {
    headers['X-Presto-Schema'] = config.schema
  }
  return headers
}

// Given config and query, returns promise with the results
function send(config, query) {
  if (!config.url) {
    return Promise.reject(new Error('config.url is required'))
  }
  const results = {
    data: []
  }
  return fetch(`${config.url}/v1/statement`, {
    method: 'POST',
    body: query,
    headers: getHeaders(config)
  })
    .then(response => response.json())
    .then(statement => handleStatementAndGetMore(results, statement, config))
}

function updateResults(results, statement) {
  if (statement.data && statement.data.length) {
    results.data = results.data.concat(statement.data)
  }
  if (statement.columns) {
    results.columns = statement.columns
  }
  return results
}

function handleStatementAndGetMore(results, statement, config) {
  if (statement.error) {
    console.error(statement.error) // has .errorName and .message
    results.error = statement.error
    return Promise.resolve(results)
  }
  results = updateResults(results, statement)
  if (!statement.nextUri) {
    return Promise.resolve(results)
  }
  return wait(NEXT_URI_TIMEOUT)
    .then(() => fetch(statement.nextUri, { headers: getHeaders(config) }))
    .then(response => response.json())
    .then(statement => handleStatementAndGetMore(results, statement, config))
}