65 lines
2.1 KiB
C
65 lines
2.1 KiB
C
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#ifndef MERGE_HELPER_H
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#define MERGE_HELPER_H
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#include "db/dbformat.h"
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#include "leveldb/slice.h"
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#include <string>
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namespace leveldb {
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class Comparator;
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class Iterator;
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class Logger;
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class MergeOperator;
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class MergeHelper {
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public:
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MergeHelper(const Comparator* user_comparator,
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const MergeOperator* user_merge_operator,
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Logger* logger,
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bool assert_valid_internal_key)
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: user_comparator_(user_comparator),
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user_merge_operator_(user_merge_operator),
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logger_(logger),
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assert_valid_internal_key_(assert_valid_internal_key) {}
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// Merge entries until we hit
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// - a corrupted key
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// - a Put/Delete,
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// - a different user key,
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// - a specific sequence number (snapshot boundary),
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// or - the end of iteration
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// iter: (IN) points to the first merge type entry
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// (OUT) points to the first entry not included in the merge process
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// stop_before: (IN) a sequence number that merge should not cross.
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// 0 means no restriction
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// at_bottom: (IN) true if the iterator covers the bottem level, which means
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// we could reach the start of the history of this user key.
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void MergeUntil(Iterator* iter, SequenceNumber stop_before = 0,
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bool at_bottom = false);
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// Query the merge result
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// These are valid until the next MergeUtil call
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// IMPORTANT: the key type could change after the MergeUntil call.
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// Put/Delete + Merge + ... + Merge => Put
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// Merge + ... + Merge => Merge
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Slice key() { return Slice(key_); }
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Slice value() { return Slice(value_); }
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private:
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const Comparator* user_comparator_;
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const MergeOperator* user_merge_operator_;
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Logger* logger_;
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Iterator* iter_; // in: the internal iterator, positioned at the first merge entry
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bool assert_valid_internal_key_; // enforce no internal key corruption?
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// the scratch area that holds the result of MergeUntil
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// valid up to the next MergeUntil call
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std::string key_;
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std::string value_;
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};
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} // namespace leveldb
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#endif
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