Merge pull request #1091 from ydb-platform/scan-struct

ScanStruct implementation

Author: asmyasnikov

internal/query/errors.go

@@ -7,9 +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")
-	errWrongArgumentsCount     = errors.New("wrong arguments count")
 )

internal/query/row.go

@@ -3,23 +3,24 @@ package query
 import (
 	"github.com/ydb-platform/ydb-go-genproto/protos/Ydb"
 
+	"github.com/ydb-platform/ydb-go-sdk/v3/internal/query/scanner"
 	"github.com/ydb-platform/ydb-go-sdk/v3/query"
 )
 
 var _ query.Row = (*row)(nil)
 
 type row struct {
-	scannerIndexed
-	scannerNamed
-	scannerStruct
+	scanner.IndexedScanner
+	scanner.NamedScanner
+	scanner.StructScanner
 }
 
 func newRow(columns []*Ydb.Column, v *Ydb.Value) (*row, error) {
-	data := newScannerData(columns, v.GetItems())
+	data := scanner.Data(columns, v.GetItems())
 
 	return &row{
-		newScannerIndexed(data),
-		newScannerNamed(data),
-		newScannerStruct(data),
+		scanner.Indexed(data),
+		scanner.Named(data),
+		scanner.Struct(data),
 	}, nil
 }

internal/query/scanner/data.go

@@ -0,0 +1,36 @@
+package scanner
+
+import (
+	"fmt"
+
+	"github.com/ydb-platform/ydb-go-genproto/protos/Ydb"
+
+	"github.com/ydb-platform/ydb-go-sdk/v3/internal/value"
+	"github.com/ydb-platform/ydb-go-sdk/v3/internal/xerrors"
+)
+
+type data struct {
+	columns []*Ydb.Column
+	values  []*Ydb.Value
+}
+
+func Data(columns []*Ydb.Column, values []*Ydb.Value) *data {
+	return &data{
+		columns: columns,
+		values:  values,
+	}
+}
+
+func (s data) seekByName(name string) (value.Value, error) {
+	for i := range s.columns {
+		if s.columns[i].GetName() == name {
+			return value.FromYDB(s.columns[i].GetType(), s.values[i]), nil
+		}
+	}
+
+	return nil, xerrors.WithStackTrace(fmt.Errorf("'%s': %w", name, errColumnsNotFoundInRow))
+}
+
+func (s data) seekByIndex(idx int) value.Value {
+	return value.FromYDB(s.columns[idx].GetType(), s.values[idx])
+}

internal/query/scanner/errors.go

@@ -0,0 +1,13 @@
+package scanner
+
+import (
+	"errors"
+)
+
+var (
+	errColumnsNotFoundInRow               = errors.New("some columns not found in row")
+	errFieldsNotFoundInStruct             = errors.New("some fields not found in struct")
+	errIncompatibleColumnsAndDestinations = errors.New("incompatible columns and destinations")
+	errDstTypeIsNotAPointer               = errors.New("dst type is not a pointer")
+	errDstTypeIsNotAPointerToStruct       = errors.New("dst type is not a pointer to struct")
+)

internal/query/scanner/indexed.go

@@ -0,0 +1,37 @@
+package scanner
+
+import (
+	"fmt"
+
+	"github.com/ydb-platform/ydb-go-sdk/v3/internal/value"
+	"github.com/ydb-platform/ydb-go-sdk/v3/internal/xerrors"
+)
+
+type IndexedScanner struct {
+	data *data
+}
+
+func Indexed(data *data) IndexedScanner {
+	return IndexedScanner{
+		data: data,
+	}
+}
+
+func (s IndexedScanner) Scan(dst ...interface{}) error {
+	if len(dst) != len(s.data.columns) {
+		return xerrors.WithStackTrace(
+			fmt.Errorf("%w: %d != %d",
+				errIncompatibleColumnsAndDestinations,
+				len(dst), len(s.data.columns),
+			),
+		)
+	}
+	for i := range dst {
+		v := s.data.seekByIndex(i)
+		if err := value.CastTo(v, dst[i]); err != nil {
+			return xerrors.WithStackTrace(err)
+		}
+	}
+
+	return nil
+}