Fix the error returned when class already exists

[kulshekhar]

Currently the createClass method of PosgresStorageAdapter throws a Parse.Error.INVALID_CLASS_NAME exception on an attempt to insert a class that already exists.

This PR changes this exception to Parse.Error.DUPLICATE_VALUE (which is also what the MongoDB adapter throws in a similar case)

[kulshekhar]

@flovilmart there's another change I've made in the same method that this PR touches. However, the reason for that change is different. Should I update this PR with the new change or should I open another PR?

[flovilmart]

Yeah update ahead :)

[facebook-github-bot]

@kulshekhar updated the pull request - view changes

[kulshekhar]

The new change wraps the class creation in a transaction. This should fix a race condition (largely observable only during testing)

[flovilmart]

@kulshekhar awesome!
There is that PR that introduced extracting all the SQL commands outside: #2600

[kulshekhar]

@flovilmart Thanks. I wasn't aware of that PR.

Do you want this PR to be changed in some way?

[flovilmart]

it's outdated, not mergeable, I was thinking you could pick it up as you're nailing that area :)

[kulshekhar]

Sure, I'll make a note of it. The priority is to make Postgres a first class, well tested option for Parse first :)

[kulshekhar]

Looks like this fixed the bug that was causing Postgres tests to fail. Although these tests are now failing due to another issue. Progress!! 🤘

[flovilmart]

Awesome man! Merging then. there is that PR: #2907 that fixes the tests too.