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-- name: ListAuthorsByAgentIDs :many
SELECT authors.* FROM authors, agents
WHERE authors.agent_id = agents.id AND agents.id = ANY($1::bigint[]);

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type Loaders struct {
	AgentByAuthorID  *AgentLoader
	AuthorsByAgentID *AuthorSliceLoader
}

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package dataloaders

// ...
//go:generate dataloaden AuthorSliceLoader int64 []github.com/[username]/gqlgen-sqlc-example/pg.Author

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func (r *authorResolver) Agent(ctx context.Context, obj *pg.Author) (*pg.Agent, error) {
	return r.DataLoaders.Retrieve(ctx).AgentByAuthorID.Load(obj.ID)
}

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func newLoaders(ctx context.Context, repo pg.Repository) *Loaders {
	return &Loaders{
		// individual loaders will be initialized here
		AgentByAuthorID: newAgentByAuthorID(ctx, repo),
	}
}

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// order
result := make([]*pg.Agent, len(authorIDs))
for i, authorID := range authorIDs {
	result[i] = groupByAuthorID[authorID]
}
return result, nil

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// group
groupByAuthorID := make(map[int64]*pg.Agent, len(authorIDs))
for _, r := range res {
	groupByAuthorID[r.AuthorID] = &pg.Agent{
		ID:    r.ID,
		Name:  r.Name,
		Email: r.Email,
	}
}

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type Repository interface {
	// agent queries
	// ...
	ListAgentsByAuthorIDs(ctx context.Context, authorIDs []int64) ([]ListAgentsByAuthorIDsRow, error)
}

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-- name: ListAgentsByAuthorIDs :many
SELECT agents.*, authors.id AS author_id FROM agents, authors
WHERE agents.id = authors.agent_id AND authors.id  = ANY($1::bigint[]);

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// db query
res, err := repo.ListAgentsByAuthorIDs(ctx, authorIDs)
if err != nil {
	return nil, []error{err}
}