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Add SizeEstimate to CDBBatch

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This allows estimating the in-memory size of a LevelDB batch.
This commit is contained in:
Pieter Wuille 2017-04-25 11:29:04 -07:00
parent b4b057a3e0
commit e66dbde6d1
1 changed files with 25 additions and 1 deletions
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26
src/dbwrapper.h
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@ -55,11 +55,19 @@ private:
CDataStream ssKey;
CDataStream ssValue;
size_t size_estimate;
public:
/**
* @param[in] _parent CDBWrapper that this batch is to be submitted to
*/
CDBBatch(const CDBWrapper &_parent) : parent(_parent), ssKey(SER_DISK, CLIENT_VERSION), ssValue(SER_DISK, CLIENT_VERSION) { };
CDBBatch(const CDBWrapper &_parent) : parent(_parent), ssKey(SER_DISK, CLIENT_VERSION), ssValue(SER_DISK, CLIENT_VERSION), size_estimate(0) { };
void Clear()
{
batch.Clear();
size_estimate = 0;
}
template <typename K, typename V>
void Write(const K& key, const V& value)
@ -74,6 +82,14 @@ public:
leveldb::Slice slValue(ssValue.data(), ssValue.size());
batch.Put(slKey, slValue);
// LevelDB serializes writes as:
// - byte: header
// - varint: key length (1 byte up to 127B, 2 bytes up to 16383B, ...)
// - byte[]: key
// - varint: value length
// - byte[]: value
// The formula below assumes the key and value are both less than 16k.
size_estimate += 3 + (slKey.size() > 127) + slKey.size() + (slValue.size() > 127) + slValue.size();
ssKey.clear();
ssValue.clear();
}
@ -86,8 +102,16 @@ public:
leveldb::Slice slKey(ssKey.data(), ssKey.size());
batch.Delete(slKey);
// LevelDB serializes erases as:
// - byte: header
// - varint: key length
// - byte[]: key
// The formula below assumes the key is less than 16kB.
size_estimate += 2 + (slKey.size() > 127) + slKey.size();
ssKey.clear();
}
size_t SizeEstimate() const { return size_estimate; }
};
class CDBIterator