forked from ent/ent
/
scan.go
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/
scan.go
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// Copyright 2019-present Facebook Inc. All rights reserved.
// This source code is licensed under the Apache 2.0 license found
// in the LICENSE file in the root directory of this source tree.
package sql
import (
"database/sql"
"database/sql/driver"
"encoding/json"
"fmt"
"reflect"
"strings"
"time"
)
// ScanOne scans one row to the given value. It fails if the rows holds more than 1 row.
func ScanOne(rows ColumnScanner, v any) error {
columns, err := rows.Columns()
if err != nil {
return fmt.Errorf("sql/scan: failed getting column names: %w", err)
}
if n := len(columns); n != 1 {
return fmt.Errorf("sql/scan: unexpected number of columns: %d", n)
}
if !rows.Next() {
if err := rows.Err(); err != nil {
return err
}
return sql.ErrNoRows
}
if err := rows.Scan(v); err != nil {
return err
}
if rows.Next() {
return fmt.Errorf("sql/scan: expect exactly one row in result set")
}
return rows.Err()
}
// ScanInt64 scans and returns an int64 from the rows.
func ScanInt64(rows ColumnScanner) (int64, error) {
var n int64
if err := ScanOne(rows, &n); err != nil {
return 0, err
}
return n, nil
}
// ScanInt scans and returns an int from the rows.
func ScanInt(rows ColumnScanner) (int, error) {
n, err := ScanInt64(rows)
if err != nil {
return 0, err
}
return int(n), nil
}
// ScanBool scans and returns a boolean from the rows.
func ScanBool(rows ColumnScanner) (bool, error) {
var b bool
if err := ScanOne(rows, &b); err != nil {
return false, err
}
return b, nil
}
// ScanString scans and returns a string from the rows.
func ScanString(rows ColumnScanner) (string, error) {
var s string
if err := ScanOne(rows, &s); err != nil {
return "", err
}
return s, nil
}
// ScanValue scans and returns a driver.Value from the rows.
func ScanValue(rows ColumnScanner) (driver.Value, error) {
var v driver.Value
if err := ScanOne(rows, &v); err != nil {
return "", err
}
return v, nil
}
// ScanSlice scans the given ColumnScanner (basically, sql.Row or sql.Rows) into the given slice.
func ScanSlice(rows ColumnScanner, v any) error {
columns, err := rows.Columns()
if err != nil {
return fmt.Errorf("sql/scan: failed getting column names: %w", err)
}
rv := reflect.ValueOf(v)
switch {
case rv.Kind() != reflect.Ptr:
if t := reflect.TypeOf(v); t != nil {
return fmt.Errorf("sql/scan: ScanSlice(non-pointer %s)", t)
}
fallthrough
case rv.IsNil():
return fmt.Errorf("sql/scan: ScanSlice(nil)")
}
rv = reflect.Indirect(rv)
if k := rv.Kind(); k != reflect.Slice {
return fmt.Errorf("sql/scan: invalid type %s. expected slice as an argument", k)
}
scan, err := scanType(rv.Type().Elem(), columns)
if err != nil {
return err
}
if n, m := len(columns), len(scan.columns); n > m {
return fmt.Errorf("sql/scan: columns do not match (%d > %d)", n, m)
}
for rows.Next() {
values := scan.values()
if err := rows.Scan(values...); err != nil {
return fmt.Errorf("sql/scan: failed scanning rows: %w", err)
}
vv, err := scan.value(values...)
if err != nil {
return err
}
rv.Set(reflect.Append(rv, vv))
}
return rows.Err()
}
// rowScan is the configuration for scanning one sql.Row.
type rowScan struct {
// column types of a row.
columns []reflect.Type
// value functions that converts the row columns (result) to a reflect.Value.
value func(v ...any) (reflect.Value, error)
}
// values returns a []any from the configured column types.
func (r *rowScan) values() []any {
values := make([]any, len(r.columns))
for i := range r.columns {
values[i] = reflect.New(r.columns[i]).Interface()
}
return values
}
// scanType returns rowScan for the given reflect.Type.
func scanType(typ reflect.Type, columns []string) (*rowScan, error) {
switch k := typ.Kind(); {
case assignable(typ):
return &rowScan{
columns: []reflect.Type{typ},
value: func(v ...any) (reflect.Value, error) {
return reflect.Indirect(reflect.ValueOf(v[0])), nil
},
}, nil
case k == reflect.Ptr:
return scanPtr(typ, columns)
case k == reflect.Struct:
return scanStruct(typ, columns)
default:
return nil, fmt.Errorf("sql/scan: unsupported type ([]%s)", k)
}
}
var (
scannerType = reflect.TypeOf((*sql.Scanner)(nil)).Elem()
nullJSONType = reflect.TypeOf((*nullJSON)(nil)).Elem()
)
// nullJSON represents a json.RawMessage that may be NULL.
type nullJSON json.RawMessage
// Scan implements the sql.Scanner interface.
func (j *nullJSON) Scan(v interface{}) error {
if v == nil {
return nil
}
*j = v.([]byte)
return nil
}
// assignable reports if the given type can be assigned directly by `Rows.Scan`.
func assignable(typ reflect.Type) bool {
switch k := typ.Kind(); {
case typ.Implements(scannerType):
case k == reflect.Interface && typ.NumMethod() == 0:
case k == reflect.String || k >= reflect.Bool && k <= reflect.Float64:
case (k == reflect.Slice || k == reflect.Array) && typ.Elem().Kind() == reflect.Uint8:
default:
return false
}
return true
}
// scanStruct returns the configuration for scanning a sql.Row into a struct.
func scanStruct(typ reflect.Type, columns []string) (*rowScan, error) {
var (
scan = &rowScan{}
idxs = make([][]int, 0, typ.NumField())
names = make(map[string][]int, typ.NumField())
)
for i := 0; i < typ.NumField(); i++ {
f := typ.Field(i)
// Skip unexported fields.
if f.PkgPath != "" {
continue
}
// Support 1-level embedding to accept types as `type T struct {ent.T; V int}`.
if typ := f.Type; f.Anonymous && typ.Kind() == reflect.Struct {
for j := 0; j < typ.NumField(); j++ {
names[columnName(typ.Field(j))] = []int{i, j}
}
continue
}
names[columnName(f)] = []int{i}
}
for _, c := range columns {
var idx []int
// Normalize columns if necessary,
// for example: COUNT(*) => count.
switch name := strings.Split(c, "(")[0]; {
case names[name] != nil:
idx = names[name]
case names[strings.ToLower(name)] != nil:
idx = names[strings.ToLower(name)]
default:
return nil, fmt.Errorf("sql/scan: missing struct field for column: %s (%s)", c, name)
}
idxs = append(idxs, idx)
rtype := typ.Field(idx[0]).Type
if len(idx) > 1 {
rtype = rtype.Field(idx[1]).Type
}
switch {
// If the field is not support by the standard
// convertAssign, assume it is a JSON field.
case !supportsScan(rtype):
rtype = nullJSONType
// Create a pointer to the actual reflect
// types to accept optional struct fields.
case !nillable(rtype):
rtype = reflect.PtrTo(rtype)
}
scan.columns = append(scan.columns, rtype)
}
scan.value = func(vs ...any) (reflect.Value, error) {
st := reflect.New(typ).Elem()
for i, v := range vs {
rv := reflect.Indirect(reflect.ValueOf(v))
if rv.IsNil() {
continue
}
idx := idxs[i]
rvalue, ft := st.Field(idx[0]), st.Type().Field(idx[0])
if len(idx) > 1 {
// Embedded field.
rvalue, ft = rvalue.Field(idx[1]), ft.Type.Field(idx[1])
}
switch {
case rv.Type() == nullJSONType:
if rv = reflect.Indirect(rv); rv.IsNil() {
continue
}
if err := json.Unmarshal(rv.Bytes(), rvalue.Addr().Interface()); err != nil {
return reflect.Value{}, fmt.Errorf("unmarshal field %q: %w", ft.Name, err)
}
case !nillable(rvalue.Type()):
rv = reflect.Indirect(rv)
fallthrough
default:
rvalue.Set(rv)
}
}
return st, nil
}
return scan, nil
}
// columnName returns the column name of a struct-field.
func columnName(f reflect.StructField) string {
name := strings.ToLower(f.Name)
if tag, ok := f.Tag.Lookup("sql"); ok {
name = tag
} else if tag, ok := f.Tag.Lookup("json"); ok {
name = strings.Split(tag, ",")[0]
}
return name
}
// nillable reports if the reflect-type can have nil value.
func nillable(t reflect.Type) bool {
switch t.Kind() {
case reflect.Interface, reflect.Slice, reflect.Map, reflect.Ptr, reflect.UnsafePointer:
return true
}
return false
}
// scanPtr wraps the underlying type with rowScan.
func scanPtr(typ reflect.Type, columns []string) (*rowScan, error) {
typ = typ.Elem()
scan, err := scanType(typ, columns)
if err != nil {
return nil, err
}
wrap := scan.value
scan.value = func(vs ...any) (reflect.Value, error) {
v, err := wrap(vs...)
if err != nil {
return reflect.Value{}, err
}
pt := reflect.PtrTo(v.Type())
pv := reflect.New(pt.Elem())
pv.Elem().Set(v)
return pv, nil
}
return scan, nil
}
func supportsScan(t reflect.Type) bool {
if t.Implements(scannerType) || reflect.PtrTo(t).Implements(scannerType) {
return true
}
if t.Kind() == reflect.Ptr {
t = t.Elem()
}
switch t.Kind() {
case reflect.Bool, reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
reflect.Float32, reflect.Float64, reflect.Pointer, reflect.String:
return true
case reflect.Slice:
return t == reflect.TypeOf(sql.RawBytes(nil)) || t == reflect.TypeOf([]byte(nil))
case reflect.Interface:
return t == reflect.TypeOf((*any)(nil)).Elem()
default:
return t == reflect.TypeOf(time.Time{}) || t.Implements(scannerType)
}
}
// UnknownType is a named type to any indicates the info
// needs to be extracted from the underlying rows.
type UnknownType any
// ScanTypeOf returns the type used for scanning column i from the database.
func ScanTypeOf(rows *Rows, i int) any {
unknown := new(any)
ct, err := rows.ColumnTypes()
if err != nil || len(ct) <= i {
return unknown
}
rt := ct[i].ScanType()
if rt.Kind() == reflect.Pointer {
rt = rt.Elem()
}
// Handle NULL values.
switch rt.Kind() {
case reflect.Bool:
rt = reflect.TypeOf(sql.NullBool{})
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
rt = reflect.TypeOf(sql.NullInt64{})
case reflect.Float32, reflect.Float64:
rt = reflect.TypeOf(sql.NullFloat64{})
case reflect.String:
rt = reflect.TypeOf(sql.NullString{})
}
return reflect.New(rt).Interface()
}
// SelectValues maps a selected column to its value.
// Used by the generated code for storing runtime selected columns/expressions.
type SelectValues map[string]any
// Set sets the value of the given column.
func (s *SelectValues) Set(name string, v any) {
if *s == nil {
*s = make(SelectValues)
}
if pv, ok := v.(*any); ok && pv != nil {
v = *pv
}
(*s)[name] = v
}
// Get returns the value of the given column.
func (s SelectValues) Get(name string) (any, error) {
v, ok := s[name]
if !ok {
return nil, fmt.Errorf("%s value was not selected", name)
}
if v == nil {
return nil, nil
}
switch rv := reflect.Indirect(reflect.ValueOf(v)).Interface().(type) {
case NullString:
if rv.Valid {
return rv.String, nil
}
case NullInt64:
if rv.Valid {
return rv.Int64, nil
}
case NullFloat64:
if rv.Valid {
return rv.Float64, nil
}
case NullBool:
if rv.Valid {
return rv.Bool, nil
}
case NullTime:
if rv.Valid {
return rv.Time, nil
}
case sql.RawBytes:
return []byte(rv), nil
default:
return rv, nil
}
return nil, nil
}