[GitHub] [incubator-doris] gaodayue commented on a change in pull request #1572: Add new format short key index

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

gaodayue commented on a change in pull request #1572: Add new format short key index
URL: https://github.com/apache/incubator-doris/pull/1572#discussion_r309664107
 
 

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 File path: be/src/olap/short_key_index.h
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+// 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 <iterator>
+#include <string>
+#include <vector>
+
+#include "common/status.h"
+#include "gen_cpp/segment_v2.pb.h"
+#include "util/faststring.h"
+#include "util/slice.h"
+
+namespace doris {
+
+// Used to encode a segment short key indices to binary format. This version
+// only accepts binary key, client should assure that input key is sorted,
+// otherwise error could happens. This builder would arrange data in following
+// format.
+//      index = encoded_keys + encoded_offsets + footer + footer_size + checksum
+//      encoded_keys = binary_key + [, ...]
+//      encoded_offsets = encoded_offset + [, ...]
+//      encoded_offset = variant32
+//      footer = ShortKeyFooterPB
+//      footer_size = fixed32
+//      checksum = fixed32
+// Usage:
+//      ShortKeyIndexBuilder builder(segment_id, num_rows_per_block);
+//      builder.add_item(key1);
+//      ...
+//      builder.add_item(keyN);
+//      builder.finalize(segment_size, num_rows, &slices);
+// TODO(zc):
+// 1. If this can leverage binary page to save key and offset data
+// 2. Extending this to save in a BTree like struct, which can index full key
+//    more than short key
+class ShortKeyIndexBuilder {
+public:
+    ShortKeyIndexBuilder(uint32_t segment_id,
+                         uint32_t num_rows_per_block) {
+        _footer.set_segment_id(segment_id);
+        _footer.set_num_rows_per_block(num_rows_per_block);
+    }
+    
+    Status add_item(const Slice& key);
+
+    Status finalize(uint32_t segment_size, uint32_t num_rows, std::vector<Slice>* slices);
+
+private:
+    segment_v2::ShortKeyFooterPB _footer;
+
+    faststring _key_buf;
+    faststring _offset_buf;
+    std::string _footer_buf;
+    std::vector<uint32_t> _offsets;
 
 Review comment:
   it's not used

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