How can I include a new column in a Golang Apache Beam PCollection?

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To add a new column to a Golang Apache Beam PCollection, you can use the ParDo transform. You can create a new struct that includes the new column as a field, and then write a ParDo function that takes each element in the PCollection, adds the new column value to the struct, and emits the updated struct as output.

Here's an example code snippet that demonstrates how to add a new column "age_group" to a PCollection of Person structs:

type Person struct {
    Name      string
    Age       int
}

type PersonWithAgeGroup struct {
    Name      string
    Age       int
    AgeGroup  string
}

func AddAgeGroup(person Person) PersonWithAgeGroup {
    var ageGroup string

    if person.Age <= 18 {
        ageGroup = "Child"
    } else if person.Age <= 65 {
        ageGroup = "Adult"
    } else {
        ageGroup = "Senior"
    }

    return PersonWithAgeGroup{
        Name:      person.Name,
        Age:       person.Age,
        AgeGroup:  ageGroup,
    }
}

func main() {
    // Create a PCollection of Person structs
    pcoll := beam.CreateList(ctx, []Person{
        {"Alice", 25},
        {"Bob", 45},
        {"Charlie", 70},
        {"David", 7},
    })

    // Apply the ParDo transform to add the age_group column
    pcollWithAgeGroup := beam.ParDo(ctx, AddAgeGroup, pcoll)

    // Print the output PCollection
    beam.ParDo(ctx, func(p PersonWithAgeGroup) {
        fmt.Printf("%v, %v, %v\n", p.Name, p.Age, p.AgeGroup)
    }, pcollWithAgeGroup)
}

This code defines a function AddAgeGroup that takes a Person struct, calculates the age group based on the age of the person, and returns a new PersonWithAgeGroup struct that includes the new age_group field. The ParDo transform is then applied to the input PCollection to call the AddAgeGroup function for each element, producing a new PCollection of PersonWithAgeGroup structs. Finally, a second ParDo transform is applied to print out the elements of the output PCollection.