在Golang中重用或复制* sql.Rows

Question

Is it possible to reuse the same *sql.Rows after the *sql.Rows.Next() was called so I could pass it to another function?

rows, err := db.Query(...)
for rows.Next() {
    // rows.Scan()
}
anotherFunction(rows) // NOT WORKING: This rows became empty.

I tried to make another copy of the *sql.Rows but it didn't work.

rows, err := db.Query(...)
anotherRows := *rows
// PANIC: call of load copies lock value: database/sql.Rows contains sync.RWMutex

Answer 1

The database/sql package does not provide any means to rewind the Rows, after you have read them, i.e. it is a "forward only" result set.

Moreover, it will maintain a link to the underlying (physical) database connection, inside it, making it a bad idea to copy it or pass it around.

If you need to apply multiple functions to your data, just Scan all the rows, to get a slice of data objects, and then pass this around.

Scan will make a copy of the data you read:

Scan copies the columns from the matched row into the values pointed at by dest.

so you can then safely Close your Rows object (releasing any associated database resources).

You should watch out for errors too, after executing the Query (err) and after reading the rows, via rows.Err().