@heroku-cli/plugin-pg-v5/commands/outliers.js

Heroku CLI plugin to manage Postgres.

'use strict'

const cli = require('heroku-cli-util')
const psql = require('../lib/psql')

async function ensurePGStatStatement(db) {
  let query = `
SELECT exists(
  SELECT 1 FROM pg_extension e LEFT JOIN pg_namespace n ON n.oid = e.extnamespace
  WHERE e.extname='pg_stat_statements' AND n.nspname IN ('public', 'heroku_ext')
) AS available`
  let output = await psql.exec(db, query)

  if (!output.includes('t')) {
    throw new Error(`pg_stat_statements extension need to be installed first.
You can install it by running: CREATE EXTENSION pg_stat_statements WITH SCHEMA heroku_ext;`)
  }
}

function outliersQuery(version, limit, truncate) {
  let truncatedQueryString = truncate ?
    'CASE WHEN length(query) <= 40 THEN query ELSE substr(query, 0, 39) || \'…\' END' :
    'query'

  if (version >= 13) {
    return `
SELECT
  interval '1 millisecond' * total_exec_time AS total_exec_time,
  to_char((total_exec_time/sum(total_exec_time) OVER()) * 100, 'FM90D0') || '%'  AS prop_exec_time,
  to_char(calls, 'FM999G999G999G990') AS ncalls,
  interval '1 millisecond' * (blk_read_time + blk_write_time) AS sync_io_time,
  ${truncatedQueryString} AS query
FROM pg_stat_statements
WHERE userid = (SELECT usesysid FROM pg_user WHERE usename = current_user LIMIT 1)
ORDER BY total_exec_time DESC
LIMIT ${limit}
`
  }

  return `
SELECT
  interval '1 millisecond' * total_time AS total_exec_time,
  to_char((total_time/sum(total_time) OVER()) * 100, 'FM90D0') || '%'  AS prop_exec_time,
  to_char(calls, 'FM999G999G999G990') AS ncalls,
  interval '1 millisecond' * (blk_read_time + blk_write_time) AS sync_io_time,
  ${truncatedQueryString} AS query
FROM pg_stat_statements
WHERE userid = (SELECT usesysid FROM pg_user WHERE usename = current_user LIMIT 1)
ORDER BY total_time DESC
LIMIT ${limit}
`
}

async function run(context, heroku) {
  const fetcher = require('../lib/fetcher')

  const {app, args, flags} = context
  const {database} = args

  let db = await fetcher(heroku).database(app, database)
  let version = await psql.fetchVersion(db)

  await ensurePGStatStatement(db)

  if (flags.reset) {
    await psql.exec(db, 'SELECT pg_stat_statements_reset()')
    return
  }

  let limit = 10
  if (flags.num) {
    if (/^(\d+)$/.exec(flags.num)) {
      limit = Number.parseInt(flags.num)
    } else {
      throw new Error(`Cannot parse num param value "${flags.num}" to a number`)
    }
  }

  let query = outliersQuery(version, limit, flags.truncate)
  let output = await psql.exec(db, query)
  process.stdout.write(output)
}

module.exports = {
  topic: 'pg',
  command: 'outliers',
  description: 'show 10 queries that have longest execution time in aggregate',
  needsApp: true,
  needsAuth: true,
  args: [{name: 'database', optional: true}],
  flags: [
    {name: 'reset', description: 'resets statistics gathered by pg_stat_statements'},
    {name: 'truncate', char: 't', description: 'truncate queries to 40 characters'},
    {name: 'num', char: 'n', description: 'the number of queries to display (default: 10)', hasValue: true},
  ],
  run: cli.command({preauth: true}, run),
}