/
query-columns.go
82 lines (68 loc) · 2.07 KB
/
query-columns.go
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package dbutil
import (
"reflect"
"github.com/juju/errors"
)
// QueryCol fetches a single column from the query result.
// dest must be a pointer to slice of column type.
func QueryCol(db Querier, dest interface{}, query string, args ...interface{}) error {
destType := reflect.TypeOf(dest)
if destType.Kind() != reflect.Ptr || destType.Elem().Kind() != reflect.Slice {
return errors.Errorf("Invalid type of dest: %T (slice pointer required)", dest)
}
aArgs := make(Args, len(args))
for i, a := range args {
aArgs[i] = a
}
destValue := reflect.ValueOf(dest)
destSlice := reflect.Indirect(destValue)
elemType := destType.Elem().Elem()
err := QueryRows(db, query, aArgs, func(s RowScanner) error {
el := reflect.New(elemType)
if err := s.Scan(el.Interface()); err != nil {
return err
}
destSlice = reflect.Append(destSlice, reflect.Indirect(el))
return nil
})
if err != nil {
return err
}
reflect.Indirect(destValue).Set(destSlice)
return nil
}
// QueryCols fetches all columns from the query result.
// dest must be a pointer to slice of structs with fields
// ordered and typed as columns.
func QueryCols(db Querier, dest interface{}, query string, args ...interface{}) error {
destType := reflect.TypeOf(dest)
if destType.Kind() != reflect.Ptr ||
destType.Elem().Kind() != reflect.Slice ||
destType.Elem().Elem().Kind() != reflect.Struct {
return errors.Errorf("Invalid type of dest: %T (slice of structs pointer required)", dest)
}
aArgs := make(Args, len(args))
for i, a := range args {
aArgs[i] = a
}
destValue := reflect.ValueOf(dest)
destSlice := reflect.Indirect(destValue)
elemType := destType.Elem().Elem()
err := QueryRows(db, query, aArgs, func(s RowScanner) error {
el := reflect.New(elemType)
as := make(Args, elemType.NumField())
for i := range as {
as[i] = reflect.Indirect(el).Field(i).Addr().Interface()
}
if err := s.Scan(as...); err != nil {
return err
}
destSlice = reflect.Append(destSlice, el.Elem())
return nil
})
if err != nil {
return err
}
reflect.Indirect(destValue).Set(destSlice)
return nil
}