Performance issue: stripComments blocks event loop for 12s

[swarmiakimmo]

We did a CPU profiling for our node app and noticed that the query normalization blocks event loop for quite a while:

stripComments function was taking 12 seconds in one long SQL query we were using.

Wanted to report this for others possibly investigating the same, feel free to close. Unfortunately I don't have a reproducible query example.

[swarmiakimmo]

Our workaround was to simply disable query normalisation.

[gajus]

Can you share a query that was causing this?

[mvakula]

@gajus here's example test which reproduces the issue

test('parse long query', (t) => {
  const params = [...Array(30_000).keys()].map(i => `$${i}`).join(', ')
  const query = `
  SELECT 1
  FROM foo
  WHERE id IN (
    ${params}
  )
  `
  console.time('parse')
  const subject = stripComments(query)
  console.timeEnd('parse')
  t.true(true);
})

npm test will output

> [email protected] test
> NODE_ENV=test nyc ava --verbose --serial


  ✔ factories › createQueryNormalisationInterceptor › strips comments from the query

  ✖ Timed out while running tests

parse: 24.216s
  ─

  1 test passed

Ava test runner default timeout is 10s. I ran tests with macbook i9.