PostgreSQL unique constraint optimization guide as expected on JSONB field
Quick question that's been bugging me - I'm collaborating on a project where I'm stuck on something that should probably be simple. I'm sure I'm missing something obvious here, but I'm working with an scenario with a PostgreSQL unique constraint that doesn't seem to be enforcing uniqueness on a JSONB field... I'm using PostgreSQL 14 and trying to ensure that a particular key within a JSONB object remains unique across rows in my `users` table. Here’s how I set up the table: ```sql CREATE TABLE users ( id SERIAL PRIMARY KEY, data JSONB, CONSTRAINT unique_key UNIQUE ((data->>'username')) ); ``` When I try to insert two rows with the same `username` value in the `data` field, I expect to get a unique constraint violation. But instead, the second insert succeeds without any behavior: ```sql INSERT INTO users (data) VALUES ('{"username": "john_doe"}'); INSERT INTO users (data) VALUES ('{"username": "john_doe"}'); ``` Both inserts complete successfully, and I end up with two rows that have the same username. I checked the version compatibility and confirmed that JSONB constraints should work as expected. I also tried using an index on the JSONB field directly: ```sql CREATE UNIQUE INDEX idx_unique_username ON users ((data->>'username')); ``` However, I still run into the same scenario. When I check the index, it seems to have created successfully. Can someone guide to understand why the uniqueness constraint isn't functioning correctly on the JSONB field? Is there a limitation with the way I'm defining the constraint, or is there something else I'm missing? This is part of a larger service I'm building. Is there a better approach? The project is a microservice built with Sql.