Can PostgreSQL's "COPY table FROM file" statement be used in Go? - postgresql

Question

After reading github.com/lib/pq documentation, it is still not clear for me if it is possible to copy data from a CSV file using a simple COPY <table> FROM <file> CSV HEADER command.
This is what I'm trying to do:
func CopyFromCSV(con Con, tableName, fileName string) error {
_, err := con.Exec(fmt.Sprintf("TRUNCATE %s", tableName))
if err != nil {
return err
}
stm, err := con.Prepare(fmt.Sprintf("COPY %s FROM '%s' CSV HEADER", tableName, fileName))
if err != nil {
return err
}
defer stm.Close()
_, err = stm.Exec()
return err
}
Where tableName is an existing table, and fileName the absolute path to an existing csv file.
I'm getting always the following error after the con.Prepare call: pq: unknown response for copy query: 'C'
Is it possible to do this in Go with a postgres database using the github.com/lib/pq driver?

Answer 1

The code below uses https://github.com/lib/pq
import (
"database/sql"
"fmt"
"github.com/lib/pq"
)
func bulkCopyTest() {
psqlInfo := fmt.Sprintf("host=%s port=%d user=%s password=%s dbname=%s sslmode=verify-full",
host, port, user, password, dbname)
db, err := sql.Open("postgres", psqlInfo)
if err != nil {
panic(err)
}
defer db.Close()
tx, err := db.Begin()
if err != nil {
panic(err)
}
stmt, err := tx.Prepare(pq.CopyInSchema("schemaName", "DBName", "columnName", "columnName"))
if err != nil {
panic(err)
}
//loop through an array of struct filled with data, or read from a file
for _, row := range loadCsv {
stmt.Exec(row.value1, row.value2)
if err != nil {
panic(err)
}
}
_, err = stmt.Exec()
if err != nil {
panic(err)
}
err = stmt.Close()
if err != nil {
panic(err)
}
err = tx.Commit()
if err != nil {
panic(err)
}
}

Answer 2

A rough template to execute COPY command can be found here - https://play.golang.org/p/6y5v3IW8kD
The code below should work for you.
func copyTest() {
psqlInfo := fmt.Sprintf("host=%s port=%d user=%s password=%s dbname=%s sslmode=verify-full",host, port, user, password, dbname)
db, err := sql.Open("postgres", psqlInfo)
if err != nil {
panic(err)
}
defer db.Close()
err = db.Ping()
if err != nil {
panic(err)
}
tx, err := db.Begin()
if err != nil {
panic(err)
}
_, err = tx.Exec("copy metadata.charvalues_temp from 'C:\\yourlocation\\yourfile.csv' with csv")
if err != nil {
panic(err)
}
err = tx.Commit()
if err != nil {
panic(err)
}
}