fix: avoid early release of PostgresQueryRunner (#7109)

[alvisetrevisan]

Don't release the queryRunner too early from SelectQueryBuilder when streaming queries.

Description of change

Fixes #7109

In release 0.2.26, streaming queries for postgres were broken. The problem is that SelectQueryBuilder releases the queryRunner too early (when it might not be connected yet), and therefore prevents release at the appropriate moment (using the release callback) to happen (since it will think that it's already released, and quit).

This PR fixes this by delegating the release of the query runner to the stream callback functions, ensuring that it's called when a connection is certainly established.

To test that streaming queries now work again, I had to add pg-query-stream to the dev dependencies.

The unit test I added fails as expected without this PR's changes, but passes with the changes.

Pull-Request Checklist

• Code is up-to-date with the master branch
• npm run lint passes with this change
• npm run test passes with this change
• This pull request links relevant issues as Fixes #0000
• There are new or updated unit tests validating the change
• Documentation has been updated to reflect this change (N/A)
• The new commits follow conventions explained in CONTRIBUTING.md

[alvisetrevisan]

Tests are failing on CI, but I don't have access to the results. How can I see what goes wrong?

[nebkat]

You should have access to the CI if you log in with your GitHub account, but otherwise you can run the tests locally with the help of Docker.

Here is the error anyway:

query builder > count
    ✓ Count query should of empty table should be 0
    ✓ Count query should count database values (79ms)
    ✓ Count query should handle ambiguous values (154ms)
    ✓ counting joined query should count database values (59ms)
    ✓ counting joined queries should handle ambiguous values (171ms)
    1) "after all" hook for "counting joined queries should handle ambiguous values"


  368 passing (3m)
  8 pending
  1 failing

  1) query builder > count
       "after all" hook for "counting joined queries should handle ambiguous values":
     Error: Timeout of 60000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves. (/typeorm/build/compiled/test/functional/query-builder/count/query-builder-count.js)
      at listOnTimeout (internal/timers.js:549:17)
      at processTimers (internal/timers.js:492:7)

[alvisetrevisan]

Hi @nebkat I resolved the problems with the unit tests. This PR should be ready for review. I could not find in the CONTRIBUTING.md doc any more pointers on who I should add as reviewer, or whether anything else is needed from my side.

[starzou]

Hi @alvisetrevisan So when do we call queryRunner.release(); ?

[alvisetrevisan]

Hi @alvisetrevisan So when do we call queryRunner.release(); ?

This is done using the onEnd and onError callback (which ensures that the runner is released only after it's connectd) and is implemented already by the drivers supporting streaming queries.

[pleerock]

Looks correct. Thank you!