sql.go

package main

import (
  "encoding/json"
  "database/sql"
)

// JSONScanner scans a column into a map.
type JSONScanner struct {
  Key string
  Map map[string]interface{}
}

func (s JSONScanner) Scan(src interface{}) error {
  s.Map[s.Key] = src
}

func QueryToJSON(db *sql.DB, query string, args ...interface{}) ([]byte, error) {
  rows, err := db.Query(query, ...args)
  if err != nil {
  	return nil, err
  }
  defer rows.Close()
  var items []interface{}

  // Fetch the column names.
  var scanners []*JSONScanner
  names, err := rows.Columns()
  if err != nil {
    return nil, err
  }
  for _, name := range(names) {
    scanners = append(scanners, &JSONScanner{Key: name})
  }

  // Now convert each row to a map.
  for rows.Next() {
    // Make a map for this row
    item := make(map[string]interface{})
    // Make each scanner update this new map.
    for _, scanner := range(scanners) {
      scanner.Map = item
    }
    // Read the row.
    if err = rows.Scan(...scanners); err != nil {
      return nil, err
    }
    // Save the map
    items = append(items, item)
  }
  if err = row.Err(); err != nil {
    return nil, err
  }
  return json.Marshal(items)
}