如何在Go中从Postgres获取NULL布尔值？

Question

Go's zero value for a bool type is false. Postgres supports an undefined BOOL type, represented as NULL. This leads to problems when trying to fetch a BOOL value from Postgres in Go:

rows,err := db.Query("SELECT UNNEST('{TRUE,FALSE,NULL}'::BOOL[])");
if err != nil {
    log.Fatal(err)
}
for rows.Next() {
    var value bool
    if err := rows.Scan(&value); err != nil {
        log.Fatal(err)
    }
    fmt.Printf("Value: %t
",value);
}

Output:

Value: true  
Value: false  
2014/11/17 09:34:26 sql: Scan error on column index 0: sql/driver: couldn't convert <nil> (<nil>) into type bool

What's the most idiomatic way around this problem? The two solutions I have imagined are neither very attractive:

1. Don't use Go's bool type. Instead I would probably use a string, and do my own conversion which accounts for nil
2. Always make sure BOOLs are either TRUE or FALSE in Postgres by using COALESCE() or some other means.

Answer 1

My preference is using a pointer:

for rows.Next() {
    var value *bool

    if err := rows.Scan(&value); err != nil {
        log.Fatal(err)
    }

    if value == nil {
        // Handle nil
    }

    fmt.Printf("Value: %t
", *value);
}