SQLAlchemy: Emulate composite unique constraints

[amotl]

About

On the SQLAlchemy support subsystem, improve the UNIQUE constraints polyfill to accept multiple column names, for emulating unique composite keys.

References

• SQLAlchemy: Improve uniqueness polyfill to accept multiple columns (composite unique constraint / unique composite key) #69
• Fix uniqueness constraint with .auth.db.models.SqlUser.username mlflow-cratedb#52 (review)

[matriv]

Does this issues a select query on every insert/update to check that the uniqueness is respected?

[amotl]

Does this issues a select query on every insert/update to check that the uniqueness is respected?

There is no other chance to do it differently, right?

[matriv]

Does this issues a select query on every insert/update to check that the uniqueness is respected?

There is no other chance to do it differently, right?

No, but I'm wondering if we should document it as it will impact performance.

[amotl]

I'm wondering if we should document it as it will impact performance.

It is just a polyfill for making a few humble applications "compatible". We don't actively advertise this as a feature, it is just code sitting in a repository to be reused where applicable.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files	Coverage Δ
cratedb_toolkit/sqlalchemy/polyfill.py	100.00% <100.00%> (ø)

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