BIT(N) columns don't include the N size in their types.

[alarbada]

Setup:

CREATE TABLE bit_columns (
    bit1_col BIT(1),
    bit8_col BIT(8),
    bit16_col BIT(16),
    bit64_col BIT(64)
);

Example:

package main

import (
	"database/sql"
	"fmt"
	"log"

	_ "github.com/go-sql-driver/mysql"
)

func main() {
	db, err := sql.Open("mysql", "user:pass@tcp(127.0.0.1:3306)/dbname")
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	rows, err := db.Query("SELECT * FROM bit_columns LIMIT 1")
	if err != nil {
		log.Fatal(err)
	}
	defer rows.Close()

	colTypes, err := rows.ColumnTypes()
	if err != nil {
		log.Fatal(err)
	}

	for _, colType := range colTypes {
		fmt.Println(colType.Name())
		fmt.Println(colType.DecimalSize())
		fmt.Println(colType.DatabaseTypeName())
		fmt.Println(colType.Length())
	}
}

Output:

bit1_col
0 0 false
BIT
0 false // <- why 0?
bit8_col
0 0 false
BIT
0 false // <- why 0?
bit16_col
0 0 false
BIT
0 false // <- why 0?
bit64_col
0 0 false
BIT
0 false // <- why 0?

I would expect that the Length() method would return the mysql specified bit size, or at least have some way to get that piece of information from *sql.ColumnType.

I'm using github.com/go-sql-driver/mysql v1.8.1.

[methane]

Note that it returns false too. It means we can not get the value.

MySQL returns length in their resultset header. But its meaning is differ from database/sql's.
So we do not support ColumnType.Length(). It returns false always.

[alarbada]

Oh, what a shame, thanks for the quick answer anyways.
So the only way to get that N would be to obtain it via a separate query then?