Merge pull request #1083 from ydb-platform/named-scanner

added implementation of named scanner

Author: asmyasnikov

internal/query/errors.go

@@ -7,6 +7,7 @@ import (
 var (
 	ErrNotImplemented          = errors.New("not implemented yet")
 	errWrongNextResultSetIndex = errors.New("wrong result set index")
+	errColumnNotFoundByName    = errors.New("column not found by name")
 	errInterruptedStream       = errors.New("interrupted stream")
 	errClosedResult            = errors.New("result closed early")
 	errWrongResultSetIndex     = errors.New("critical violation of the logic - wrong result set index")

internal/query/scanner_named.go

@@ -1,6 +1,10 @@
 package query
 
 import (
+	"fmt"
+	"reflect"
+
+	"github.com/ydb-platform/ydb-go-sdk/v3/internal/value"
 	"github.com/ydb-platform/ydb-go-sdk/v3/internal/xerrors"
 	"github.com/ydb-platform/ydb-go-sdk/v3/query"
 )
@@ -17,6 +21,45 @@ func newScannerNamed(data *scannerData) scannerNamed {
 	}
 }
 
+func (s scannerNamed) seekByName(name string) (
+	value.Value,
+	error,
+) {
+	for i := range s.data.columns {
+		if s.data.columns[i].GetName() == name {
+			return value.FromYDB(s.data.columns[i].GetType(), s.data.values[i]), nil
+		}
+	}
+
+	return nil, xerrors.WithStackTrace(fmt.Errorf("'%s': %w", name, errColumnNotFoundByName))
+}
+
 func (s scannerNamed) ScanNamed(dst ...query.NamedDestination) error {
-	return xerrors.WithStackTrace(ErrNotImplemented)
+	if len(dst) != len(s.data.columns) {
+		return xerrors.WithStackTrace(errWrongArgumentsCount)
+	}
+
+	for i := range dst {
+		v, err := s.seekByName(dst[i].Name())
+		if err != nil {
+			return xerrors.WithStackTrace(err)
+		}
+		if err := value.CastTo(v, dst[i].Destination()); err != nil {
+			to := reflect.ValueOf(dst[i].Destination())
+			if to.Kind() != reflect.Pointer {
+				return xerrors.WithStackTrace(
+					fmt.Errorf("dst[%d].Destination() type is not a pointer ('%s')", i,
+						to.Kind().String(),
+					))
+			}
+			vv := reflect.ValueOf(v)
+			if vv.CanConvert(to.Elem().Type()) {
+				to.Elem().Set(vv.Convert(to.Elem().Type()))
+			} else {
+				return xerrors.WithStackTrace(err)
+			}
+		}
+	}
+
+	return nil
 }