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69 lines
2.0 KiB
69 lines
2.0 KiB
#include "fielddb/meta.h"
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#include "util/coding.h"
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#include <string>
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#include "leveldb/options.h"
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#include "leveldb/slice.h"
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#include "leveldb/write_batch.h"
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namespace fielddb {
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using namespace leveldb;
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// Slice MetaKV::metaKey() {
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// std::string buf;
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// PutLengthPrefixedSlice(&buf, Key);
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// PutFixed64(&buf, meta_seq);
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// PutFixed32(&buf, tag);
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// return Slice(buf);
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// }
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// Slice MetaKV::metaValue() {
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// return Slice(SerializeValue(Fields));
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// }
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//对于含有index field的put/delete的meta编码为 (KV|Key,Value)
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void MetaKV::TransPut(std::string &MetaKey,std::string &MetaValue) {
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MetaKey.clear();
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MetaValue.clear();
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//这里的改动是为了防止潜在的段错误。原来的写法中，slice(buf)对应的buf是局部的，在函数返回后，buf被销毁
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//但是slice中的指针指向的是析构的string对象的部分内存
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std::string &buf = MetaKey;
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PutFixed32(&buf, KV_Creating);
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PutLengthPrefixedSlice(&buf, Slice(name));
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// MetaKey = Slice(buf);
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// MetaValue = Slice(*value);
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}
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void MetaKV::TransDelete(std::string &MetaKey) {
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MetaKey.clear();
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std::string &buf = MetaKey;
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PutFixed32(&buf, KV_Deleting);
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PutLengthPrefixedSlice(&buf, Slice(name));
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// MetaKey = Slice(buf);
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}
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class CleanerHandler : public WriteBatch::Handler {
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public:
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WriteBatch *NeedClean;
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void Put(const Slice& key, const Slice& value) override {
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//将所有之前put的meta数据进行delete
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NeedClean->Delete(key);
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}
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void Delete(const Slice& key) override {
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//所有的传入的MetaBatch都是Put的
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assert(0);
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}
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};
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void MetaCleaner::Collect(WriteBatch &MetaBatch) {
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if(MetaBatch.ApproximateSize() <= 12) return;
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CleanerHandler Handler;
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Handler.NeedClean = &NeedClean;
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MetaBatch.Iterate(&Handler);
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}
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void MetaCleaner::CleanMetaBatch(DB *metaDB) {
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if(NeedClean.ApproximateSize() <= 12) return;
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metaDB->Write(WriteOptions(), &NeedClean);
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}
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}
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