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package sqlx
import (
"database/sql"
"database/sql/driver"
"errors"
"fmt"
"io/ioutil"
"path/filepath"
"reflect"
"strings"
"sync"
"github.com/jmoiron/sqlx/reflectx"
)
// Although the NameMapper is convenient, in practice it should not
// be relied on except for application code. If you are writing a library
// that uses sqlx, you should be aware that the name mappings you expect
// can be overridden by your user's application.
// NameMapper is used to map column names to struct field names. By default,
// it uses strings.ToLower to lowercase struct field names. It can be set
// to whatever you want, but it is encouraged to be set before sqlx is used
// as name-to-field mappings are cached after first use on a type.
var NameMapper = strings.ToLower
var origMapper = reflect.ValueOf(NameMapper)
// Rather than creating on init, this is created when necessary so that
// importers have time to customize the NameMapper.
var mpr *reflectx.Mapper
// mprMu protects mpr.
var mprMu sync.Mutex
// mapper returns a valid mapper using the configured NameMapper func.
func mapper() *reflectx.Mapper {
mprMu.Lock()
defer mprMu.Unlock()
if mpr == nil {
mpr = reflectx.NewMapperFunc("db", NameMapper)
} else if origMapper != reflect.ValueOf(NameMapper) {
// if NameMapper has changed, create a new mapper
mpr = reflectx.NewMapperFunc("db", NameMapper)
origMapper = reflect.ValueOf(NameMapper)
}
return mpr
}
// isScannable takes the reflect.Type and the actual dest value and returns
// whether or not it's Scannable. Something is scannable if:
// * it is not a struct
// * it implements sql.Scanner
// * it has no exported fields
func isScannable(t reflect.Type) bool {
if reflect.PtrTo(t).Implements(_scannerInterface) {
return true
}
if t.Kind() != reflect.Struct {
return true
}
// it's not important that we use the right mapper for this particular object,
// we're only concerned on how many exported fields this struct has
m := mapper()
if len(m.TypeMap(t).Index) == 0 {
return true
}
return false
}
// ColScanner is an interface used by MapScan and SliceScan
type ColScanner interface {
Columns() ([]string, error)
Scan(dest ...interface{}) error
Err() error
}
// Queryer is an interface used by Get and Select
type Queryer interface {
Query(query string, args ...interface{}) (*sql.Rows, error)
Queryx(query string, args ...interface{}) (*Rows, error)
QueryRowx(query string, args ...interface{}) *Row
}
// Execer is an interface used by MustExec and LoadFile
type Execer interface {
Exec(query string, args ...interface{}) (sql.Result, error)
}
// Binder is an interface for something which can bind queries (Tx, DB)
type binder interface {
DriverName() string
Rebind(string) string
BindNamed(string, interface{}) (string, []interface{}, error)
}
// Ext is a union interface which can bind, query, and exec, used by
// NamedQuery and NamedExec.
type Ext interface {
binder
Queryer
Execer
}
// Preparer is an interface used by Preparex.
type Preparer interface {
Prepare(query string) (*sql.Stmt, error)
}
// determine if any of our extensions are unsafe
func isUnsafe(i interface{}) bool {
switch v := i.(type) {
case Row:
return v.unsafe
case *Row:
return v.unsafe
case Rows:
return v.unsafe
case *Rows:
return v.unsafe
case NamedStmt:
return v.Stmt.unsafe
case *NamedStmt:
return v.Stmt.unsafe
case Stmt:
return v.unsafe
case *Stmt:
return v.unsafe
case qStmt:
return v.unsafe
case *qStmt:
return v.unsafe
case DB:
return v.unsafe
case *DB:
return v.unsafe
case Tx:
return v.unsafe
case *Tx:
return v.unsafe
case sql.Rows, *sql.Rows:
return false
default:
return false
}
}
func mapperFor(i interface{}) *reflectx.Mapper {
switch i := i.(type) {
case DB:
return i.Mapper
case *DB:
return i.Mapper
case Tx:
return i.Mapper
case *Tx:
return i.Mapper
default:
return mapper()
}
}
var _scannerInterface = reflect.TypeOf((*sql.Scanner)(nil)).Elem()
var _valuerInterface = reflect.TypeOf((*driver.Valuer)(nil)).Elem()
// Row is a reimplementation of sql.Row in order to gain access to the underlying
// sql.Rows.Columns() data, necessary for StructScan.
type Row struct {
err error
unsafe bool
rows *sql.Rows
Mapper *reflectx.Mapper
}
// Scan is a fixed implementation of sql.Row.Scan, which does not discard the
// underlying error from the internal rows object if it exists.
func (r *Row) Scan(dest ...interface{}) error {
if r.err != nil {
return r.err
}
// TODO(bradfitz): for now we need to defensively clone all
// []byte that the driver returned (not permitting
// *RawBytes in Rows.Scan), since we're about to close
// the Rows in our defer, when we return from this function.
// the contract with the driver.Next(...) interface is that it
// can return slices into read-only temporary memory that's
// only valid until the next Scan/Close. But the TODO is that
// for a lot of drivers, this copy will be unnecessary. We
// should provide an optional interface for drivers to
// implement to say, "don't worry, the []bytes that I return
// from Next will not be modified again." (for instance, if
// they were obtained from the network anyway) But for now we
// don't care.
defer r.rows.Close()
for _, dp := range dest {
if _, ok := dp.(*sql.RawBytes); ok {
return errors.New("sql: RawBytes isn't allowed on Row.Scan")
}
}
if !r.rows.Next() {
if err := r.rows.Err(); err != nil {
return err
}
return sql.ErrNoRows
}
err := r.rows.Scan(dest...)
if err != nil {
return err
}
// Make sure the query can be processed to completion with no errors.
if err := r.rows.Close(); err != nil {
return err
}
return nil
}
// Columns returns the underlying sql.Rows.Columns(), or the deferred error usually
// returned by Row.Scan()
func (r *Row) Columns() ([]string, error) {
if r.err != nil {
return []string{}, r.err
}
return r.rows.Columns()
}
// ColumnTypes returns the underlying sql.Rows.ColumnTypes(), or the deferred error
func (r *Row) ColumnTypes() ([]*sql.ColumnType, error) {
if r.err != nil {
return []*sql.ColumnType{}, r.err
}
return r.rows.ColumnTypes()
}
// Err returns the error encountered while scanning.
func (r *Row) Err() error {
return r.err
}
// DB is a wrapper around sql.DB which keeps track of the driverName upon Open,
// used mostly to automatically bind named queries using the right bindvars.
type DB struct {
*sql.DB
driverName string
unsafe bool
Mapper *reflectx.Mapper
}
// NewDb returns a new sqlx DB wrapper for a pre-existing *sql.DB. The
// driverName of the original database is required for named query support.
func NewDb(db *sql.DB, driverName string) *DB {
return &DB{DB: db, driverName: driverName, Mapper: mapper()}
}
// DriverName returns the driverName passed to the Open function for this DB.
func (db *DB) DriverName() string {
return db.driverName
}
// Open is the same as sql.Open, but returns an *sqlx.DB instead.
func Open(driverName, dataSourceName string) (*DB, error) {
db, err := sql.Open(driverName, dataSourceName)
if err != nil {
return nil, err
}
return &DB{DB: db, driverName: driverName, Mapper: mapper()}, err
}
// MustOpen is the same as sql.Open, but returns an *sqlx.DB instead and panics on error.
func MustOpen(driverName, dataSourceName string) *DB {
db, err := Open(driverName, dataSourceName)
if err != nil {
panic(err)
}
return db
}
// MapperFunc sets a new mapper for this db using the default sqlx struct tag
// and the provided mapper function.
func (db *DB) MapperFunc(mf func(string) string) {
db.Mapper = reflectx.NewMapperFunc("db", mf)
}
// Rebind transforms a query from QUESTION to the DB driver's bindvar type.
func (db *DB) Rebind(query string) string {
return Rebind(BindType(db.driverName), query)
}
// Unsafe returns a version of DB which will silently succeed to scan when
// columns in the SQL result have no fields in the destination struct.
// sqlx.Stmt and sqlx.Tx which are created from this DB will inherit its
// safety behavior.
func (db *DB) Unsafe() *DB {
return &DB{DB: db.DB, driverName: db.driverName, unsafe: true, Mapper: db.Mapper}
}
// BindNamed binds a query using the DB driver's bindvar type.
func (db *DB) BindNamed(query string, arg interface{}) (string, []interface{}, error) {
return bindNamedMapper(BindType(db.driverName), query, arg, db.Mapper)
}
// NamedQuery using this DB.
// Any named placeholder parameters are replaced with fields from arg.
func (db *DB) NamedQuery(query string, arg interface{}) (*Rows, error) {
return NamedQuery(db, query, arg)
}
// NamedExec using this DB.
// Any named placeholder parameters are replaced with fields from arg.
func (db *DB) NamedExec(query string, arg interface{}) (sql.Result, error) {
return NamedExec(db, query, arg)
}
// Select using this DB.
// Any placeholder parameters are replaced with supplied args.
func (db *DB) Select(dest interface{}, query string, args ...interface{}) error {
return Select(db, dest, query, args...)
}
// Get using this DB.
// Any placeholder parameters are replaced with supplied args.
// An error is returned if the result set is empty.
func (db *DB) Get(dest interface{}, query string, args ...interface{}) error {
return Get(db, dest, query, args...)
}
// MustBegin starts a transaction, and panics on error. Returns an *sqlx.Tx instead
// of an *sql.Tx.
func (db *DB) MustBegin() *Tx {
tx, err := db.Beginx()
if err != nil {
panic(err)
}
return tx
}
// Beginx begins a transaction and returns an *sqlx.Tx instead of an *sql.Tx.
func (db *DB) Beginx() (*Tx, error) {
tx, err := db.DB.Begin()
if err != nil {
return nil, err
}
return &Tx{Tx: tx, driverName: db.driverName, unsafe: db.unsafe, Mapper: db.Mapper}, err
}
// Queryx queries the database and returns an *sqlx.Rows.
// Any placeholder parameters are replaced with supplied args.
func (db *DB) Queryx(query string, args ...interface{}) (*Rows, error) {
r, err := db.DB.Query(query, args...)
if err != nil {
return nil, err
}
return &Rows{Rows: r, unsafe: db.unsafe, Mapper: db.Mapper}, err
}
// QueryRowx queries the database and returns an *sqlx.Row.
// Any placeholder parameters are replaced with supplied args.
func (db *DB) QueryRowx(query string, args ...interface{}) *Row {
rows, err := db.DB.Query(query, args...)
return &Row{rows: rows, err: err, unsafe: db.unsafe, Mapper: db.Mapper}
}
// MustExec (panic) runs MustExec using this database.
// Any placeholder parameters are replaced with supplied args.
func (db *DB) MustExec(query string, args ...interface{}) sql.Result {
return MustExec(db, query, args...)
}
// Preparex returns an sqlx.Stmt instead of a sql.Stmt
func (db *DB) Preparex(query string) (*Stmt, error) {
return Preparex(db, query)
}
// PrepareNamed returns an sqlx.NamedStmt
func (db *DB) PrepareNamed(query string) (*NamedStmt, error) {
return prepareNamed(db, query)
}
// Tx is an sqlx wrapper around sql.Tx with extra functionality
type Tx struct {
*sql.Tx
driverName string
unsafe bool
Mapper *reflectx.Mapper
}
// DriverName returns the driverName used by the DB which began this transaction.
func (tx *Tx) DriverName() string {
return tx.driverName
}
// Rebind a query within a transaction's bindvar type.
func (tx *Tx) Rebind(query string) string {
return Rebind(BindType(tx.driverName), query)
}
// Unsafe returns a version of Tx which will silently succeed to scan when
// columns in the SQL result have no fields in the destination struct.
func (tx *Tx) Unsafe() *Tx {
return &Tx{Tx: tx.Tx, driverName: tx.driverName, unsafe: true, Mapper: tx.Mapper}
}
// BindNamed binds a query within a transaction's bindvar type.
func (tx *Tx) BindNamed(query string, arg interface{}) (string, []interface{}, error) {
return bindNamedMapper(BindType(tx.driverName), query, arg, tx.Mapper)
}
// NamedQuery within a transaction.
// Any named placeholder parameters are replaced with fields from arg.
func (tx *Tx) NamedQuery(query string, arg interface{}) (*Rows, error) {
return NamedQuery(tx, query, arg)
}
// NamedExec a named query within a transaction.
// Any named placeholder parameters are replaced with fields from arg.
func (tx *Tx) NamedExec(query string, arg interface{}) (sql.Result, error) {
return NamedExec(tx, query, arg)
}
// Select within a transaction.
// Any placeholder parameters are replaced with supplied args.
func (tx *Tx) Select(dest interface{}, query string, args ...interface{}) error {
return Select(tx, dest, query, args...)
}
// Queryx within a transaction.
// Any placeholder parameters are replaced with supplied args.
func (tx *Tx) Queryx(query string, args ...interface{}) (*Rows, error) {
r, err := tx.Tx.Query(query, args...)
if err != nil {
return nil, err
}
return &Rows{Rows: r, unsafe: tx.unsafe, Mapper: tx.Mapper}, err
}
// QueryRowx within a transaction.
// Any placeholder parameters are replaced with supplied args.
func (tx *Tx) QueryRowx(query string, args ...interface{}) *Row {
rows, err := tx.Tx.Query(query, args...)
return &Row{rows: rows, err: err, unsafe: tx.unsafe, Mapper: tx.Mapper}
}
// Get within a transaction.
// Any placeholder parameters are replaced with supplied args.
// An error is returned if the result set is empty.
func (tx *Tx) Get(dest interface{}, query string, args ...interface{}) error {
return Get(tx, dest, query, args...)
}
// MustExec runs MustExec within a transaction.
// Any placeholder parameters are replaced with supplied args.
func (tx *Tx) MustExec(query string, args ...interface{}) sql.Result {
return MustExec(tx, query, args...)
}
// Preparex a statement within a transaction.
func (tx *Tx) Preparex(query string) (*Stmt, error) {
return Preparex(tx, query)
}
// Stmtx returns a version of the prepared statement which runs within a transaction. Provided
// stmt can be either *sql.Stmt or *sqlx.Stmt.
func (tx *Tx) Stmtx(stmt interface{}) *Stmt {
var s *sql.Stmt
switch v := stmt.(type) {
case Stmt:
s = v.Stmt
case *Stmt:
s = v.Stmt
case *sql.Stmt:
s = v
default:
panic(fmt.Sprintf("non-statement type %v passed to Stmtx", reflect.ValueOf(stmt).Type()))
}
return &Stmt{Stmt: tx.Stmt(s), Mapper: tx.Mapper}
}
// NamedStmt returns a version of the prepared statement which runs within a transaction.
func (tx *Tx) NamedStmt(stmt *NamedStmt) *NamedStmt {
return &NamedStmt{
QueryString: stmt.QueryString,
Params: stmt.Params,
Stmt: tx.Stmtx(stmt.Stmt),
}
}
// PrepareNamed returns an sqlx.NamedStmt
func (tx *Tx) PrepareNamed(query string) (*NamedStmt, error) {
return prepareNamed(tx, query)
}
// Stmt is an sqlx wrapper around sql.Stmt with extra functionality
type Stmt struct {
*sql.Stmt
unsafe bool
Mapper *reflectx.Mapper
}
// Unsafe returns a version of Stmt which will silently succeed to scan when
// columns in the SQL result have no fields in the destination struct.
func (s *Stmt) Unsafe() *Stmt {
return &Stmt{Stmt: s.Stmt, unsafe: true, Mapper: s.Mapper}
}
// Select using the prepared statement.
// Any placeholder parameters are replaced with supplied args.
func (s *Stmt) Select(dest interface{}, args ...interface{}) error {
return Select(&qStmt{s}, dest, "", args...)
}
// Get using the prepared statement.
// Any placeholder parameters are replaced with supplied args.
// An error is returned if the result set is empty.
func (s *Stmt) Get(dest interface{}, args ...interface{}) error {
return Get(&qStmt{s}, dest, "", args...)
}
// MustExec (panic) using this statement. Note that the query portion of the error
// output will be blank, as Stmt does not expose its query.
// Any placeholder parameters are replaced with supplied args.
func (s *Stmt) MustExec(args ...interface{}) sql.Result {
return MustExec(&qStmt{s}, "", args...)
}
// QueryRowx using this statement.
// Any placeholder parameters are replaced with supplied args.
func (s *Stmt) QueryRowx(args ...interface{}) *Row {
qs := &qStmt{s}
return qs.QueryRowx("", args...)
}
// Queryx using this statement.
// Any placeholder parameters are replaced with supplied args.
func (s *Stmt) Queryx(args ...interface{}) (*Rows, error) {
qs := &qStmt{s}
return qs.Queryx("", args...)
}
// qStmt is an unexposed wrapper which lets you use a Stmt as a Queryer & Execer by
// implementing those interfaces and ignoring the `query` argument.
type qStmt struct{ *Stmt }
func (q *qStmt) Query(query string, args ...interface{}) (*sql.Rows, error) {
return q.Stmt.Query(args...)
}
func (q *qStmt) Queryx(query string, args ...interface{}) (*Rows, error) {
r, err := q.Stmt.Query(args...)
if err != nil {
return nil, err
}
return &Rows{Rows: r, unsafe: q.Stmt.unsafe, Mapper: q.Stmt.Mapper}, err
}
func (q *qStmt) QueryRowx(query string, args ...interface{}) *Row {
rows, err := q.Stmt.Query(args...)
return &Row{rows: rows, err: err, unsafe: q.Stmt.unsafe, Mapper: q.Stmt.Mapper}
}
func (q *qStmt) Exec(query string, args ...interface{}) (sql.Result, error) {
return q.Stmt.Exec(args...)
}
// Rows is a wrapper around sql.Rows which caches costly reflect operations
// during a looped StructScan
type Rows struct {
*sql.Rows
unsafe bool
Mapper *reflectx.Mapper
// these fields cache memory use for a rows during iteration w/ structScan
started bool
fields [][]int
values []interface{}
}
// SliceScan using this Rows.
func (r *Rows) SliceScan() ([]interface{}, error) {
return SliceScan(r)
}
// MapScan using this Rows.
func (r *Rows) MapScan(dest map[string]interface{}) error {
return MapScan(r, dest)
}
// StructScan is like sql.Rows.Scan, but scans a single Row into a single Struct.
// Use this and iterate over Rows manually when the memory load of Select() might be
// prohibitive. *Rows.StructScan caches the reflect work of matching up column
// positions to fields to avoid that overhead per scan, which means it is not safe
// to run StructScan on the same Rows instance with different struct types.
func (r *Rows) StructScan(dest interface{}) error {
v := reflect.ValueOf(dest)
if v.Kind() != reflect.Ptr {
return errors.New("must pass a pointer, not a value, to StructScan destination")
}
v = v.Elem()
if !r.started {
columns, err := r.Columns()
if err != nil {
return err
}
m := r.Mapper
r.fields = m.TraversalsByName(v.Type(), columns)
// if we are not unsafe and are missing fields, return an error
if f, err := missingFields(r.fields); err != nil && !r.unsafe {
return fmt.Errorf("missing destination name %s in %T", columns[f], dest)
}
r.values = make([]interface{}, len(columns))
r.started = true
}
err := fieldsByTraversal(v, r.fields, r.values, true)
if err != nil {
return err
}
// scan into the struct field pointers and append to our results
err = r.Scan(r.values...)
if err != nil {
return err
}
return r.Err()
}
// Connect to a database and verify with a ping.
func Connect(driverName, dataSourceName string) (*DB, error) {
db, err := Open(driverName, dataSourceName)
if err != nil {
return nil, err
}
err = db.Ping()
if err != nil {
db.Close()
return nil, err
}
return db, nil
}
// MustConnect connects to a database and panics on error.
func MustConnect(driverName, dataSourceName string) *DB {
db, err := Connect(driverName, dataSourceName)
if err != nil {
panic(err)
}
return db
}
// Preparex prepares a statement.
func Preparex(p Preparer, query string) (*Stmt, error) {
s, err := p.Prepare(query)
if err != nil {
return nil, err
}
return &Stmt{Stmt: s, unsafe: isUnsafe(p), Mapper: mapperFor(p)}, err
}
// Select executes a query using the provided Queryer, and StructScans each row
// into dest, which must be a slice. If the slice elements are scannable, then
// the result set must have only one column. Otherwise, StructScan is used.
// The *sql.Rows are closed automatically.
// Any placeholder parameters are replaced with supplied args.
func Select(q Queryer, dest interface{}, query string, args ...interface{}) error {
rows, err := q.Queryx(query, args...)
if err != nil {
return err
}
// if something happens here, we want to make sure the rows are Closed
defer rows.Close()
return scanAll(rows, dest, false)
}
// Get does a QueryRow using the provided Queryer, and scans the resulting row
// to dest. If dest is scannable, the result must only have one column. Otherwise,
// StructScan is used. Get will return sql.ErrNoRows like row.Scan would.
// Any placeholder parameters are replaced with supplied args.
// An error is returned if the result set is empty.
func Get(q Queryer, dest interface{}, query string, args ...interface{}) error {
r := q.QueryRowx(query, args...)
return r.scanAny(dest, false)
}
// LoadFile exec's every statement in a file (as a single call to Exec).
// LoadFile may return a nil *sql.Result if errors are encountered locating or
// reading the file at path. LoadFile reads the entire file into memory, so it
// is not suitable for loading large data dumps, but can be useful for initializing
// schemas or loading indexes.
//
// FIXME: this does not really work with multi-statement files for mattn/go-sqlite3
// or the go-mysql-driver/mysql drivers; pq seems to be an exception here. Detecting
// this by requiring something with DriverName() and then attempting to split the
// queries will be difficult to get right, and its current driver-specific behavior
// is deemed at least not complex in its incorrectness.
func LoadFile(e Execer, path string) (*sql.Result, error) {
realpath, err := filepath.Abs(path)
if err != nil {
return nil, err
}
contents, err := ioutil.ReadFile(realpath)
if err != nil {
return nil, err
}
res, err := e.Exec(string(contents))
return &res, err
}
// MustExec execs the query using e and panics if there was an error.
// Any placeholder parameters are replaced with supplied args.
func MustExec(e Execer, query string, args ...interface{}) sql.Result {
res, err := e.Exec(query, args...)
if err != nil {
panic(err)
}
return res
}
// SliceScan using this Rows.
func (r *Row) SliceScan() ([]interface{}, error) {
return SliceScan(r)
}
// MapScan using this Rows.
func (r *Row) MapScan(dest map[string]interface{}) error {
return MapScan(r, dest)
}
func (r *Row) scanAny(dest interface{}, structOnly bool) error {
if r.err != nil {
return r.err
}
if r.rows == nil {
r.err = sql.ErrNoRows
return r.err
}
defer r.rows.Close()
v := reflect.ValueOf(dest)
if v.Kind() != reflect.Ptr {
return errors.New("must pass a pointer, not a value, to StructScan destination")
}
if v.IsNil() {
return errors.New("nil pointer passed to StructScan destination")
}
base := reflectx.Deref(v.Type())
scannable := isScannable(base)
if structOnly && scannable {
return structOnlyError(base)
}
columns, err := r.Columns()
if err != nil {
return err
}
if scannable && len(columns) > 1 {
return fmt.Errorf("scannable dest type %s with >1 columns (%d) in result", base.Kind(), len(columns))
}
if scannable {
return r.Scan(dest)
}
m := r.Mapper
fields := m.TraversalsByName(v.Type(), columns)
// if we are not unsafe and are missing fields, return an error
if f, err := missingFields(fields); err != nil && !r.unsafe {
return fmt.Errorf("missing destination name %s in %T", columns[f], dest)
}
values := make([]interface{}, len(columns))
err = fieldsByTraversal(v, fields, values, true)
if err != nil {
return err
}
// scan into the struct field pointers and append to our results
return r.Scan(values...)
}
// StructScan a single Row into dest.
func (r *Row) StructScan(dest interface{}) error {
return r.scanAny(dest, true)
}
// SliceScan a row, returning a []interface{} with values similar to MapScan.
// This function is primarily intended for use where the number of columns
// is not known. Because you can pass an []interface{} directly to Scan,
// it's recommended that you do that as it will not have to allocate new
// slices per row.
func SliceScan(r ColScanner) ([]interface{}, error) {
// ignore r.started, since we needn't use reflect for anything.
columns, err := r.Columns()
if err != nil {
return []interface{}{}, err
}
values := make([]interface{}, len(columns))
for i := range values {
values[i] = new(interface{})
}
err = r.Scan(values...)
if err != nil {
return values, err
}
for i := range columns {
values[i] = *(values[i].(*interface{}))
}
return values, r.Err()
}
// MapScan scans a single Row into the dest map[string]interface{}.
// Use this to get results for SQL that might not be under your control
// (for instance, if you're building an interface for an SQL server that
// executes SQL from input). Please do not use this as a primary interface!
// This will modify the map sent to it in place, so reuse the same map with
// care. Columns which occur more than once in the result will overwrite
// each other!
func MapScan(r ColScanner, dest map[string]interface{}) error {
// ignore r.started, since we needn't use reflect for anything.
columns, err := r.Columns()
if err != nil {
return err
}
values := make([]interface{}, len(columns))
for i := range values {
values[i] = new(interface{})
}
err = r.Scan(values...)
if err != nil {
return err
}
for i, column := range columns {
dest[column] = *(values[i].(*interface{}))
}
return r.Err()
}
type rowsi interface {
Close() error
Columns() ([]string, error)
Err() error
Next() bool
Scan(...interface{}) error
}
// structOnlyError returns an error appropriate for type when a non-scannable
// struct is expected but something else is given
func structOnlyError(t reflect.Type) error {
isStruct := t.Kind() == reflect.Struct
isScanner := reflect.PtrTo(t).Implements(_scannerInterface)
if !isStruct {
return fmt.Errorf("expected %s but got %s", reflect.Struct, t.Kind())
}
if isScanner {
return fmt.Errorf("structscan expects a struct dest but the provided struct type %s implements scanner", t.Name())
}
return fmt.Errorf("expected a struct, but struct %s has no exported fields", t.Name())
}
// scanAll scans all rows into a destination, which must be a slice of any
// type. If the destination slice type is a Struct, then StructScan will be
// used on each row. If the destination is some other kind of base type, then
// each row must only have one column which can scan into that type. This
// allows you to do something like:
//
// rows, _ := db.Query("select id from people;")
// var ids []int
// scanAll(rows, &ids, false)
//
// and ids will be a list of the id results. I realize that this is a desirable
// interface to expose to users, but for now it will only be exposed via changes
// to `Get` and `Select`. The reason that this has been implemented like this is
// this is the only way to not duplicate reflect work in the new API while
// maintaining backwards compatibility.
func scanAll(rows rowsi, dest interface{}, structOnly bool) error {
var v, vp reflect.Value
value := reflect.ValueOf(dest)
// json.Unmarshal returns errors for these
if value.Kind() != reflect.Ptr {
return errors.New("must pass a pointer, not a value, to StructScan destination")
}
if value.IsNil() {
return errors.New("nil pointer passed to StructScan destination")
}
direct := reflect.Indirect(value)
slice, err := baseType(value.Type(), reflect.Slice)
if err != nil {
return err
}
isPtr := slice.Elem().Kind() == reflect.Ptr
base := reflectx.Deref(slice.Elem())
scannable := isScannable(base)
if structOnly && scannable {
return structOnlyError(base)
}
columns, err := rows.Columns()
if err != nil {
return err
}
// if it's a base type make sure it only has 1 column; if not return an error
if scannable && len(columns) > 1 {
return fmt.Errorf("non-struct dest type %s with >1 columns (%d)", base.Kind(), len(columns))
}
if !scannable {
var values []interface{}
var m *reflectx.Mapper
switch rows.(type) {
case *Rows:
m = rows.(*Rows).Mapper
default:
m = mapper()
}
fields := m.TraversalsByName(base, columns)
// if we are not unsafe and are missing fields, return an error
if f, err := missingFields(fields); err != nil && !isUnsafe(rows) {
return fmt.Errorf("missing destination name %s in %T", columns[f], dest)
}
values = make([]interface{}, len(columns))
for rows.Next() {
// create a new struct type (which returns PtrTo) and indirect it
vp = reflect.New(base)
v = reflect.Indirect(vp)
err = fieldsByTraversal(v, fields, values, true)
if err != nil {
return err
}
// scan into the struct field pointers and append to our results
err = rows.Scan(values...)
if err != nil {
return err
}
if isPtr {
direct.Set(reflect.Append(direct, vp))
} else {
direct.Set(reflect.Append(direct, v))
}
}
} else {
for rows.Next() {
vp = reflect.New(base)
err = rows.Scan(vp.Interface())
if err != nil {
return err
}
// append
if isPtr {
direct.Set(reflect.Append(direct, vp))
} else {
direct.Set(reflect.Append(direct, reflect.Indirect(vp)))
}
}
}
return rows.Err()
}
// FIXME: StructScan was the very first bit of API in sqlx, and now unfortunately
// it doesn't really feel like it's named properly. There is an incongruency
// between this and the way that StructScan (which might better be ScanStruct
// anyway) works on a rows object.
// StructScan all rows from an sql.Rows or an sqlx.Rows into the dest slice.
// StructScan will scan in the entire rows result, so if you do not want to
// allocate structs for the entire result, use Queryx and see sqlx.Rows.StructScan.
// If rows is sqlx.Rows, it will use its mapper, otherwise it will use the default.
func StructScan(rows rowsi, dest interface{}) error {
return scanAll(rows, dest, true)
}
// reflect helpers
func baseType(t reflect.Type, expected reflect.Kind) (reflect.Type, error) {
t = reflectx.Deref(t)
if t.Kind() != expected {
return nil, fmt.Errorf("expected %s but got %s", expected, t.Kind())
}
return t, nil
}
// fieldsByName fills a values interface with fields from the passed value based
// on the traversals in int. If ptrs is true, return addresses instead of values.
// We write this instead of using FieldsByName to save allocations and map lookups
// when iterating over many rows. Empty traversals will get an interface pointer.
// Because of the necessity of requesting ptrs or values, it's considered a bit too
// specialized for inclusion in reflectx itself.
func fieldsByTraversal(v reflect.Value, traversals [][]int, values []interface{}, ptrs bool) error {
v = reflect.Indirect(v)
if v.Kind() != reflect.Struct {
return errors.New("argument not a struct")
}
for i, traversal := range traversals {
if len(traversal) == 0 {
values[i] = new(interface{})
continue
}
f := reflectx.FieldByIndexes(v, traversal)
if ptrs {
values[i] = f.Addr().Interface()
} else {
values[i] = f.Interface()
}
}
return nil
}
func missingFields(transversals [][]int) (field int, err error) {
for i, t := range transversals {
if len(t) == 0 {
return i, errors.New("missing field")
}
}
return 0, nil
}
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