greenplumn CSyncHashtableAccessByKey 源码
greenplumn CSyncHashtableAccessByKey 代码
文件路径：/src/backend/gporca/libgpos/include/gpos/common/CSyncHashtableAccessByKey.h
//---------------------------------------------------------------------------
// Greenplum Database
// Copyright (C) 2008 Greenplum, Inc.
//
// @filename:
// CSyncHashtableAccessByKey.h
//
// @doc:
// Accessor for allocation-less static hashtable;
// The Accessor is instantiated with a target key.
//---------------------------------------------------------------------------
#ifndef GPOS_CSyncHashtableAccessByKey_H
#define GPOS_CSyncHashtableAccessByKey_H
#include "gpos/common/CSyncHashtableAccessorBase.h"
namespace gpos
{
//---------------------------------------------------------------------------
// @class:
// CSyncHashtableAccessByKey<T, K, S>
//
// @doc:
// Accessor class to encapsulate locking of a hashtable bucket based on
// a passed key; has to know all template parameters of the hashtable
// class in order to link to the target hashtable; see file doc for more
// details on the rationale behind this class
//
//---------------------------------------------------------------------------
template <class T, class K>
class CSyncHashtableAccessByKey : public CSyncHashtableAccessorBase<T, K>
{
private:
// shorthand for accessor's base class
using Base = class CSyncHashtableAccessorBase<T, K>;
// target key
const K &m_key;
// finds the first element matching target key starting from
// the given element
T *
NextMatch(T *value) const
{
T *curr = value;
while (nullptr != curr && !Base::GetHashTable().m_eqfn(
Base::GetHashTable().Key(curr), m_key))
{
curr = Base::Next(curr);
}
return curr;
}
#ifdef GPOS_DEBUG
// returns true if current bucket matches key
BOOL
CurrentBucketMatchesKey(const K &key) const
{
ULONG bucket_idx = Base::GetHashTable().GetBucketIndex(key);
return &(Base::GetHashTable().GetBucket(bucket_idx)) ==
&(Base::GetBucket());
}
#endif // GPOS_DEBUG
public:
CSyncHashtableAccessByKey<T, K>(const CSyncHashtableAccessByKey<T, K> &) =
delete;
// ctor
CSyncHashtableAccessByKey<T, K>(CSyncHashtable<T, K> &ht, const K &key)
: Base(ht, ht.GetBucketIndex(key)), m_key(key)
{
}
// dtor
~CSyncHashtableAccessByKey() override = default;
// finds the first bucket's element with a matching key
T *
Find() const
{
return NextMatch(Base::First());
}
// finds the next element with a matching key
T *
Next(T *value) const
{
GPOS_ASSERT(nullptr != value);
return NextMatch(Base::Next(value));
}
// insert at head of target bucket's hash chain
void
Insert(T *value)
{
GPOS_ASSERT(nullptr != value);
#ifdef GPOS_DEBUG
K &key = Base::GetHashTable().Key(value);
#endif // GPOS_DEBUG
// make sure this is a valid key
GPOS_ASSERT(Base::GetHashTable().IsValid(key));
// make sure this is the right bucket
GPOS_ASSERT(CurrentBucketMatchesKey(key));
// inserting at bucket's head is required by hashtable iteration
Base::Prepend(value);
}
}; // class CSyncHashtableAccessByKey
} // namespace gpos
#endif // !GPOS_CSyncHashtableAccessByKey_H
// EOF
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