core/sql/refresh/RuMultiTxnContext.h

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// Licensed to the Apache Software Foundation (ASF) under one
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#ifndef _RU_MULTI_TXN_CONTEXT_H_
#define _RU_MULTI_TXN_CONTEXT_H_

/* -
*-C++-*-
******************************************************************************
*
* File:         RuMultiTxnContext.h
* Description:  Definition of class CRUMultiTxnContext.
*
* Created:      08/17/2000
* Language:     C++
*
*
******************************************************************************
*/

//--------------------------------------------------------------------------//
// The purpose of this class is to create a stack abstract to the rows in the 
// context log.
//
// Prior to any use of this class the user must call the ReadRowsFromContextUMD() 
// function.
//
//--------------------------------------------------------------------------//

#include "RuSQLStaticStatementContainer.h"

class REFRESH_LIB_CLASS CRUMultiTxnContext {
public:
	
	//----------------------------------//
	//	Public Members
	//----------------------------------//	
public:

	virtual ~CRUMultiTxnContext() {}

public:

	BOOL IsEmpty() const 
	{ 
		return const_cast<CRUMultiTxnContext*>(this)->
				stack_.IsEmpty(); 
	}
	
	Int32 GetNumOfRows() const 
	{ 
		return const_cast<CRUMultiTxnContext*>(this)->
				stack_.GetCount(); 
	}

public:

	enum { ROW_DOES_NOT_EXIST = -1 };

	// This function return ROW_DOES_NOT_EXIST if no such row exists
	// index == 0 is the top row in the stack
	TInt32 GetRowByIndex(Lng32 index);
	TInt32 GetTargetEpochOfFirstRow() { return GetRowByIndex(0); }
	TInt32 GetTargetEpochOfSecondRow() { return GetRowByIndex(1); }


public:

	// Read the "@EPOCH" column from the context table
	void ReadRowsFromContextLog(CDMPreparedStatement *readStmt);
	
	//  This function Adds a catchup line to the context 
	void Push(TInt32 epoch) 
	{
		stack_.AddHead(epoch); 
	}
	
	void Pop() 
	{ 
		stack_.RemoveHead(); 
	}

	//----------------------------------//
	//	Private Members
	//----------------------------------//		

private:
	// The rows of the context table are orderd when retrieved by begin_epoch desc
	// so it allows us to look at the rows as a stack of context rows
	CDSList<TInt32> stack_;

};

#endif