Integrating SQL Commenter with Postgrex for Enhanced Query Tracing

The article details how to use sqlcommenter, a tool designed to append trace context to SQL queries, making database interactions clearer in PostgreSQL logs. Initially, the author struggled to implement this in Elixir with Ecto but later revisited the idea after gaining a deeper understanding of Ecto's internals. A pull request was created to enable addition of comments in Postgrex queries, which is now available in version 0.19.3. By utilizing Ecto.Repo's callback functions, comments can be automatically appended to queries. The article explains the implementation of the prepare_query callback and highlights important considerations about PostgreSQL prepared statements and query string variations. The sqlcommenter format is also discussed, ensuring comments are properly encoded to maintain SQL validity. The author provides examples and invites feedback on the value of this content for the community.