kangpinghuang commented on a change in pull request #1633: add zone map 
page(#1390)
URL: https://github.com/apache/incubator-doris/pull/1633#discussion_r316629485
 
 

 ##########
 File path: be/src/olap/rowset/segment_v2/column_zone_map.h
 ##########
 @@ -0,0 +1,166 @@
+// 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 <vector>
+#include <memory>
+
+#include "common/status.h"
+#include "util/coding.h"
+#include "util/slice.h"
+#include "util/faststring.h"
+#include "olap/olap_cond.h"
+#include "olap/olap_define.h"
+#include "olap/rowset/segment_v2/binary_plain_page.h"
+#include "gen_cpp/segment_v2.pb.h"
+
+namespace doris {
+
+namespace segment_v2 {
+
+// This class encode column pages' zone map.
+// The binary is encoded by BinaryPlainPageBuilder
+class ColumnZoneMapBuilder {
+public:
+    ColumnZoneMapBuilder(const TypeInfo* type_info) : _type_info(type_info),
+            _min_value(nullptr), _max_value(nullptr),
+            _null_flag(false), _non_null_flag(false) {
+        PageBuilderOptions options;
+        options.data_page_size = 0;
+        _page_builder.reset(new BinaryPlainPageBuilder(options));
+        _field.reset(Field::create_by_type(_type_info->type()));
+        _max_string_value = _arena.Allocate(OLAP_STRING_MAX_LENGTH);
+        _min_value = _arena.Allocate(_type_info->size());
+        // we should allocate max varchar length and set to max for min value
+        Slice* min_slice = (Slice*)_min_value;
+        min_slice->data = _max_string_value;
+        min_slice->size = OLAP_STRING_MAX_LENGTH;
+        _field->set_to_max(_min_value);
+        _max_value = _arena.Allocate(_type_info->size());
+        _field->set_to_min(_max_value);
+    }
+
+    Status add(const uint8_t* vals, size_t count) {
+        if (vals != nullptr) {
+            for (int i = 0; i < count; ++i) {
+                if (_field->compare(_min_value, (char*)vals) > 0) {
+                    _field->deep_copy_content(_min_value, (const char*)vals, 
&_arena);
+                }
+                if (_field->compare(_max_value, (char*)vals) < 0) {
+                    _field->deep_copy_content(_max_value, (const char*)vals, 
&_arena);
+                }
+                vals += _type_info->size();
+                if (!_non_null_flag) {
+                    _non_null_flag = true;
+                }
+            }
+        } else {
+            if (!_null_flag) {
+                _null_flag = true;
+            }
+        }
+        return Status::OK();
+    }
+
+    Status flush() {
+        ZoneMapPB page_zone_map;
+        page_zone_map.set_min(_field->to_string(_min_value));
+        page_zone_map.set_max(_field->to_string(_max_value));
+        page_zone_map.set_null_flag(_null_flag);
+        page_zone_map.set_non_null_flag(_non_null_flag);
+        std::string serialized_zone_map;
+        bool ret = page_zone_map.SerializeToString(&serialized_zone_map);
+        if (!ret) {
+            return Status::InternalError("serialize zone map failed");
+        }
+        Slice data(serialized_zone_map.data(), serialized_zone_map.size());
+        size_t num = 1;
+        RETURN_IF_ERROR(_page_builder->add((const uint8_t*)&data, &num));
+        // reset the variables
+        // we should allocate max varchar length and set to max for min value
+        Slice* min_slice = (Slice*)_min_value;
+        min_slice->data = _max_string_value;
+        min_slice->size = OLAP_STRING_MAX_LENGTH;
+        _field->set_to_max(_min_value);
+        _field->set_to_min(_max_value);
+        _null_flag = false;
+        _non_null_flag = false;
+        return Status::OK();
+    }
+
+    Slice finish() {
+        return _page_builder->finish();
+    }
+
+private:
+    const TypeInfo* _type_info;
+    std::unique_ptr<BinaryPlainPageBuilder> _page_builder;
+    std::unique_ptr<Field> _field;
+    // memory will be managed by arena
+    char* _min_value;
 
 Review comment:
   I will add struct ZoneMap

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