Golang sqlbase.RowFetcher類代碼示例

func (td *tableDeleter) deleteAllRowsScan(ctx context.Context) error {
	tablePrefix := sqlbase.MakeIndexKeyPrefix(
		td.rd.helper.tableDesc, td.rd.helper.tableDesc.PrimaryIndex.ID)
	span := sqlbase.Span{Start: roachpb.Key(tablePrefix), End: roachpb.Key(tablePrefix).PrefixEnd()}

	valNeededForCol := make([]bool, len(td.rd.helper.tableDesc.Columns))
	for _, idx := range td.rd.fetchColIDtoRowIndex {
		valNeededForCol[idx] = true
	}

	var rf sqlbase.RowFetcher
	err := rf.Init(
		td.rd.helper.tableDesc, td.rd.fetchColIDtoRowIndex, &td.rd.helper.tableDesc.PrimaryIndex,
		false, false, td.rd.fetchCols, valNeededForCol)
	if err != nil {
		return err
	}
	if err := rf.StartScan(td.txn, sqlbase.Spans{span}, 0); err != nil {
		return err
	}

	for {
		row, err := rf.NextRow()
		if err != nil {
			return err
		}
		if row == nil {
			// Done deleting rows.
			break
		}
		_, err = td.row(ctx, row)
		if err != nil {
			return err
		}
	}
	return td.finalize(ctx)
}

func (sc *SchemaChanger) truncateAndBackfillColumnsChunk(
	added []sqlbase.ColumnDescriptor,
	dropped []sqlbase.ColumnDescriptor,
	defaultExprs []parser.TypedExpr,
	evalCtx *parser.EvalContext,
	sp sqlbase.Span,
) (roachpb.Key, bool, error) {
	var curIndexKey roachpb.Key
	done := false
	err := sc.db.Txn(func(txn *client.Txn) error {
		tableDesc, err := getTableDescFromID(txn, sc.tableID)
		if err != nil {
			return err
		}
		// Short circuit the backfill if the table has been deleted.
		if tableDesc.Deleted() {
			done = true
			return nil
		}

		updateCols := append(added, dropped...)
		fkTables := TablesNeededForFKs(*tableDesc, CheckUpdates)
		for k := range fkTables {
			if fkTables[k], err = getTableDescFromID(txn, k); err != nil {
				return err
			}
		}
		// TODO(dan): Tighten up the bound on the requestedCols parameter to
		// makeRowUpdater.
		requestedCols := make([]sqlbase.ColumnDescriptor, 0, len(tableDesc.Columns)+len(added))
		requestedCols = append(requestedCols, tableDesc.Columns...)
		requestedCols = append(requestedCols, added...)
		ru, err := makeRowUpdater(
			txn, tableDesc, fkTables, updateCols, requestedCols, rowUpdaterOnlyColumns,
		)
		if err != nil {
			return err
		}

		// TODO(dan): This check is an unfortunate bleeding of the internals of
		// rowUpdater. Extract the sql row to k/v mapping logic out into something
		// usable here.
		if !ru.isColumnOnlyUpdate() {
			panic("only column data should be modified, but the rowUpdater is configured otherwise")
		}

		// Run a scan across the table using the primary key. Running
		// the scan and applying the changes in many transactions is
		// fine because the schema change is in the correct state to
		// handle intermediate OLTP commands which delete and add
		// values during the scan.
		var rf sqlbase.RowFetcher
		colIDtoRowIndex := colIDtoRowIndexFromCols(tableDesc.Columns)
		valNeededForCol := make([]bool, len(tableDesc.Columns))
		for i := range valNeededForCol {
			_, valNeededForCol[i] = ru.fetchColIDtoRowIndex[tableDesc.Columns[i].ID]
		}
		err = rf.Init(tableDesc, colIDtoRowIndex, &tableDesc.PrimaryIndex, false, false,
			tableDesc.Columns, valNeededForCol)
		if err != nil {
			return err
		}
		// StartScan uses 0 as a sentinal for the default limit of entries scanned.
		if err := rf.StartScan(txn, sqlbase.Spans{sp}, 0); err != nil {
			return err
		}

		indexKeyPrefix := sqlbase.MakeIndexKeyPrefix(tableDesc, tableDesc.PrimaryIndex.ID)
		oldValues := make(parser.DTuple, len(ru.fetchCols))
		updateValues := make(parser.DTuple, len(updateCols))

		writeBatch := &client.Batch{}
		var i int
		for ; i < ColumnTruncateAndBackfillChunkSize; i++ {
			row, err := rf.NextRow()
			if err != nil {
				return err
			}
			if row == nil {
				break // Done
			}

			curIndexKey, _, err = sqlbase.EncodeIndexKey(
				tableDesc, &tableDesc.PrimaryIndex, colIDtoRowIndex, row, indexKeyPrefix)

			for j, col := range added {
				if defaultExprs == nil || defaultExprs[j] == nil {
					updateValues[j] = parser.DNull
				} else {
					updateValues[j], err = defaultExprs[j].Eval(evalCtx)
					if err != nil {
						return err
					}
				}
				if !col.Nullable && updateValues[j].Compare(parser.DNull) == 0 {
					return sqlbase.NewNonNullViolationError(col.Name)
				}
			}
			for j := range dropped {
				updateValues[j+len(added)] = parser.DNull
//.........這裏部分代碼省略.........