.One() does not add a limit - resulting in unexpectedly large queries

[barneyferry]

Noticed this while investigating an increasingly large query to get the latest "version" of a resource, query.One does not seem to impose a limit at all, it simply calls

	sql, args, err := Build(ctx, q)
	if err != nil {
		return t, err
	}

	if l, ok := q.(MapperModder); ok {
		if loaders := l.GetMapperMods(); len(loaders) > 0 {
			m = scan.Mod(m, loaders...)
		}
	}

	t, err = scan.One(ctx, exec, m, sql, args...)
	if err != nil {
		return t, err
	}

meaning every .One call actually needs:

	query.Expression.Limit.SetLimit(1)

	r, err := query.One(ctx, q.db)

which is quite misleading compared to other ORMs I've used. The "One" implies it will query one row, not query all rows and only return one.

[stephenafamo]

Well........................ it isn't easy to reliably make this change.

While it is possible to change this for built queries, there are many queries that are impossible to limit. For example:

// No way to easily know if this is limited, or add a limit
psql.Raw("SELECT * FROM users")

I think not having it, is better than having it but it only applies sometimes. Being reliable and predictable is essential.

However, to prevent misunderstandings, I think the documentation of the One method should make it clear that no limit is applied, and the query is run as-is

[jacobmolby]

Or maybe the name should be changed from .One() to .First()?

[stephenafamo]

Or maybe the name should be changed from .One() to .First()?

That's a really good suggestion. The name of the method will accurately convey what it does.

This method will have to also be changed in the scan package.