Support for Nullable Types in Generated Structs for Expression Columns

[midsbie]

What do you want to change?

Currently, sqlc generates Go structs with non-nullable types for fields that are derived from SQL expressions, even when these fields can actually be NULL based on the SQL query logic.

Consider the following SQL query:

-- :name GetNothing :one
SELECT GREATEST(NULL)::TIMESTAMP AS updated_at

The current version of sqlc generates the following Go struct:

type GetNothing struct {
	UpdatedAt time.Time
}

Desired Output

I would like to have the ability to configure sqlc so that it generates nullable types in such scenarios. The desired Go struct would look like:

type GetNothing struct {
	UpdatedAt *time.Time // or sql.NullTime, depending on configuration
}

Proposed Solution

Ideally extend the sqlc comment syntax to enable specifying nullable types on a per query column basis. Example:

SELECT GREATEST(NULL)::TIMESTAMP AS updated_at, -- :nullable
              col1, col2,
              NULL::TEXT AS always_null, -- :nullable
              ...

What database engines need to be changed?

PostgreSQL, MySQL

What programming language backends need to be changed?

Go, Python, Kotlin