[GitHub] [incubator-doris] kangpinghuang commented on a change in pull request #1577: Support Segment for BetaRowset

[GitBox <gi...@apache.org>]

kangpinghuang commented on a change in pull request #1577: Support Segment for BetaRowset
URL: https://github.com/apache/incubator-doris/pull/1577#discussion_r310489881
 
 

 ##########
 File path: be/src/olap/rowset/segment_v2/segment.h
 ##########
 @@ -0,0 +1,120 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#pragma once
+
+#include <cstdint>
+#include <string>
+#include <memory> // for unique_ptr
+#include <vector>
+
+#include "common/status.h" // Status
+#include "gen_cpp/segment_v2.pb.h"
+#include "olap/rowset/segment_v2/common.h" // rowid_t
+#include "olap/short_key_index.h"
+#include "olap/tablet_schema.h"
+#include "util/faststring.h"
+
+namespace doris {
+
+class RandomAccessFile;
+class SegmentGroup;
+class FieldInfo;
+class TabletSchema;
+class ShortKeyIndexDecoder;
+class Schema;
+
+namespace segment_v2 {
+
+class ColumnReader;
+class ColumnIterator;
+class SegmentIterator;
+
+// A Segment is used to represent a segment in memory format. When segment is
+// generated, it won't be modified, so this struct aimed to help read operation.
+// It will prepare all ColumnReader to create ColumnIterator as needed.
+// And user can create a SegmentIterator through new_iterator function.
+//
+// NOTE: This segment is used to a specified TabletSchema, when TabletSchema
+// is changed, this segemnt can not be used any more. For eample, after a schema
+// change finished, client should disalbe all cahced Segment for old TabletSchema.
+class Segment : public std::enable_shared_from_this<Segment> {
+public:
+    Segment(std::string fname, uint32_t segment_id,
+            const std::shared_ptr<TabletSchema>& tablet_schema,
+            size_t num_rows_per_block);
+    ~Segment();
+
+    Status open();
+
+    Status new_iterator(const Schema& schema, std::unique_ptr<SegmentIterator>* iter);
+
+    uint64_t id() const { return _segment_id; }
+
+    uint32_t num_rows() const { return _footer.num_rows(); }
+
+private:
+    friend class SegmentIterator;
+
+    Status new_column_iterator(uint32_t cid, ColumnIterator** iter);
 
 Review comment:
   ```suggestion
       Status _new_column_iterator(uint32_t cid, ColumnIterator** iter);
   ```

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