Double-quoting column names in ON CONFLICT statement (PostgreSQL)

[steverovsky]

PostgreSQL supports uppercase in column names, but Worker class has a bug with ON CONFLICT statement.

Case: When column name in uppercase or contains uppercase letter, we get error like excluded.title does not exist (original column name is Title).

Reason: All identifiers (including column names) that are not double-quoted are folded to lower case in PostgreSQL.

Solution: Column names must to be double-quoted.

[steverovsky]

Last Job in Check failed before starting test, freeze on line:

ruby-head - #importing gemset /home/travis/.rvm/gemsets/global.gems

[mberlanda]

@steverovsky @ziggy1 Thank you very much for the time taken to write and review this PR.
The current test matrix is actually broken and it has been fixed in #51.
Once this would be merged, you may be able to rebase and get your tests working.

Would it be possible to provide an example from the psql console of the double-quoting issue on the ON CONFLICT statement?
As per today, the output of this gem is not tested yet against real datastores (that's my bad since I never finished #37 🤦‍♂ )

Thanks again for the time spent on this pr and do not hesitate to request my review

[mberlanda]

Hey @steverovsky @ziggy1 I updated the test matrix to validate any future change. Could you please rebase on the master branch and submit the PR again? Thanks