imay commented on a change in pull request #1341: Add plain page
URL: https://github.com/apache/incubator-doris/pull/1341#discussion_r295756183
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File path: be/src/olap/rowset/segment_v2/plain_page.h
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@@ -0,0 +1,170 @@
+#pragma once
+
+#include "util/coding.h"
+#include "util/faststring.h"
+#include "olap/olap_common.h"
+#include "olap/types.h"
+#include "olap/rowset/segment_v2/page_builder.h"
+#include "olap/rowset/segment_v2/page_decoder.h"
+#include "olap/rowset/segment_v2/options.h"
+
+namespace doris {
+
+namespace segment_v2 {
+
+static const size_t plainPageHeaderSize = sizeof(uint32_t) * 2;
+
+template<FieldType Type>
+class PlainPageBuilder : public PageBuilder {
+public:
+ PlainPageBuilder(const PageBuilderOptions *options) :
+ _options(options) {
+ // Reserve enough space for the block, plus a bit of slop since
+ // we often overrun the block by a few values.
+ _buffer.reserve(plainPageHeaderSize + _options->data_page_size + 1024);
+ reset();
+ }
+
+ bool is_page_full() override {
+ return _buffer.size() > _options->data_page_size;
+ }
+
+ Status add(const uint8_t *vals, size_t *count) override {
+ size_t old_size = _buffer.size();
+ _buffer.resize(old_size + *count * SIZE_OF_TYPE);
+ memcpy(&_buffer[old_size], vals, *count * SIZE_OF_TYPE);
+ _count += *count;
+ return Status::OK();
+ }
+
+ Status get_dictionary_page(Slice *dictionary_page) override {
+ return Status::NotSupported("get_dictionary_page not supported in
plain page builder");
+ }
+
+ Slice finish(const rowid_t page_first_rowid) override {
+ encode_fixed32_le((uint8_t *) &_buffer[0], _count);
+ encode_fixed32_le((uint8_t *) &_buffer[4], page_first_rowid);
+ return Slice(_buffer.data(), plainPageHeaderSize + _count *
SIZE_OF_TYPE);
+ }
+
+ void reset() override {
+ _count = 0;
+ _buffer.clear();
+ _buffer.resize(plainPageHeaderSize);
Review comment:
you should reserve enough space for data to avoid needless data copy
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