/*-------------------------------------------------------------------------
 *
 * istrat.c
 *	  index scan strategy manipulation code and index strategy manipulation
 *	  operator code.
 *
 * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/access/index/Attic/istrat.c,v 1.60 2003/08/04 02:39:57 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/istrat.h"


#ifdef USE_ASSERT_CHECKING
static bool StrategyEvaluationIsValid(StrategyEvaluation evaluation);
static bool StrategyExpressionIsValid(StrategyExpression expression,
						  StrategyNumber maxStrategy);
static bool StrategyOperatorIsValid(StrategyOperator operator,
						StrategyNumber maxStrategy);
static bool StrategyTermIsValid(StrategyTerm term,
					StrategyNumber maxStrategy);
#endif


/* ----------------------------------------------------------------
 *				   misc strategy support routines
 * ----------------------------------------------------------------
 */

/*
 *		StrategyNumberIsValid
 *		StrategyNumberIsInBounds
 *		StrategyMapIsValid
 *		StrategyTransformMapIsValid
 *		IndexStrategyIsValid
 *
 *				... are now macros in istrat.h -cim 4/27/91
 */

/*
 * StrategyMapGetScanKeyEntry
 *		Returns a scan key entry of a index strategy mapping member.
 *
 * Note:
 *		Assumes that the index strategy mapping is valid.
 *		Assumes that the index strategy number is valid.
 *		Bounds checking should be done outside this routine.
 */
ScanKey
StrategyMapGetScanKeyEntry(StrategyMap map,
						   StrategyNumber strategyNumber)
{
	Assert(StrategyMapIsValid(map));
	Assert(StrategyNumberIsValid(strategyNumber));
	return &map->entry[strategyNumber - 1];
}

/*
 * IndexStrategyGetStrategyMap
 *		Returns an index strategy mapping of an index strategy.
 *
 * Note:
 *		Assumes that the index strategy is valid.
 *		Assumes that the number of index strategies is valid.
 *		Bounds checking should be done outside this routine.
 */
StrategyMap
IndexStrategyGetStrategyMap(IndexStrategy indexStrategy,
							StrategyNumber maxStrategyNum,
							AttrNumber attrNum)
{
	Assert(IndexStrategyIsValid(indexStrategy));
	Assert(StrategyNumberIsValid(maxStrategyNum));
	Assert(AttributeNumberIsValid(attrNum));

	maxStrategyNum = AMStrategies(maxStrategyNum);		/* XXX */
	return &indexStrategy->strategyMapData[maxStrategyNum * (attrNum - 1)];
}

/*
 * AttributeNumberGetIndexStrategySize
 *		Computes the size of an index strategy.
 */
Size
AttributeNumberGetIndexStrategySize(AttrNumber maxAttributeNumber,
									StrategyNumber maxStrategyNumber)
{
	maxStrategyNumber = AMStrategies(maxStrategyNumber);		/* XXX */
	return maxAttributeNumber * maxStrategyNumber * sizeof(ScanKeyData);
}

#ifdef USE_ASSERT_CHECKING
/*
 * StrategyTransformMapIsValid is now a macro in istrat.h -cim 4/27/91
 */

/* ----------------
 *		StrategyOperatorIsValid
 * ----------------
 */
static bool
StrategyOperatorIsValid(StrategyOperator operator,
						StrategyNumber maxStrategy)
{
	return (bool)
		(PointerIsValid(operator) &&
		 StrategyNumberIsInBounds(operator->strategy, maxStrategy) &&
		 !(operator->flags & ~(SK_NEGATE | SK_COMMUTE)));
}

/* ----------------
 *		StrategyTermIsValid
 * ----------------
 */
static bool
StrategyTermIsValid(StrategyTerm term,
					StrategyNumber maxStrategy)
{
	Index		index;

	if (!PointerIsValid(term) || term->degree == 0)
		return false;

	for (index = 0; index < term->degree; index += 1)
	{
		if (!StrategyOperatorIsValid(&term->operatorData[index],
									 maxStrategy))
			return false;
	}

	return true;
}

/* ----------------
 *		StrategyExpressionIsValid
 * ----------------
 */
static bool
StrategyExpressionIsValid(StrategyExpression expression,
						  StrategyNumber maxStrategy)
{
	StrategyTerm *termP;

	if (!PointerIsValid(expression))
		return true;

	if (!StrategyTermIsValid(expression->term[0], maxStrategy))
		return false;

	termP = &expression->term[1];
	while (StrategyTermIsValid(*termP, maxStrategy))
		termP += 1;

	return (bool)
		(!PointerIsValid(*termP));
}

/* ----------------
 *		StrategyEvaluationIsValid
 * ----------------
 */
static bool
StrategyEvaluationIsValid(StrategyEvaluation evaluation)
{
	Index		index;

	if (!PointerIsValid(evaluation) ||
		!StrategyNumberIsValid(evaluation->maxStrategy) ||
		!StrategyTransformMapIsValid(evaluation->negateTransform) ||
		!StrategyTransformMapIsValid(evaluation->commuteTransform) ||
		!StrategyTransformMapIsValid(evaluation->negateCommuteTransform))
		return false;

	for (index = 0; index < evaluation->maxStrategy; index += 1)
	{
		if (!StrategyExpressionIsValid(evaluation->expression[index],
									   evaluation->maxStrategy))
			return false;
	}
	return true;
}
#endif

#ifdef NOT_USED
/* ----------------
 *		StrategyTermEvaluate
 * ----------------
 */
static bool
StrategyTermEvaluate(StrategyTerm term,
					 StrategyMap map,
					 Datum left,
					 Datum right)
{
	bool		result = false;
	Index		index;
	StrategyOperator operator;

	for (index = 0, operator = &term->operatorData[0];
		 index < term->degree; index += 1, operator += 1)
	{
		ScanKey		entry;

		entry = &map->entry[operator->strategy - 1];

		Assert(RegProcedureIsValid(entry->sk_procedure));

		switch (operator->flags ^ entry->sk_flags)
		{
			case 0x0:
				result = DatumGetBool(FunctionCall2(&entry->sk_func,
													left, right));
				break;

			case SK_NEGATE:
				result = !DatumGetBool(FunctionCall2(&entry->sk_func,
													 left, right));
				break;

			case SK_COMMUTE:
				result = DatumGetBool(FunctionCall2(&entry->sk_func,
													right, left));
				break;

			case SK_NEGATE | SK_COMMUTE:
				result = !DatumGetBool(FunctionCall2(&entry->sk_func,
													 right, left));
				break;

			default:
				elog(ERROR, "impossible strategy case: %d",
					 operator->flags ^ entry->sk_flags);
		}
		if (!result)
			return result;
	}

	return result;
}
#endif

/* ----------------
 *		RelationGetStrategy
 *
 * Identify strategy number that describes given procedure, if there is one.
 * ----------------
 */
StrategyNumber
RelationGetStrategy(Relation relation,
					AttrNumber attributeNumber,
					StrategyEvaluation evaluation,
					RegProcedure procedure)
{
	StrategyNumber strategy;
	StrategyMap strategyMap;
	ScanKey		entry;
	Index		index;
	int			numattrs;

	Assert(RelationIsValid(relation));
	numattrs = RelationGetNumberOfAttributes(relation);

	Assert(relation->rd_rel->relkind == RELKIND_INDEX); /* XXX use accessor */
	Assert((attributeNumber >= 1) && (attributeNumber <= numattrs));

	Assert(StrategyEvaluationIsValid(evaluation));
	Assert(RegProcedureIsValid(procedure));

	strategyMap = IndexStrategyGetStrategyMap(RelationGetIndexStrategy(relation),
											  evaluation->maxStrategy,
											  attributeNumber);

	/* get a strategy number for the procedure ignoring flags for now */
	for (index = 0; index < evaluation->maxStrategy; index += 1)
	{
		if (strategyMap->entry[index].sk_procedure == procedure)
			break;
	}

	if (index == evaluation->maxStrategy)
		return InvalidStrategy;

	strategy = 1 + index;
	entry = StrategyMapGetScanKeyEntry(strategyMap, strategy);

	Assert(!(entry->sk_flags & ~(SK_NEGATE | SK_COMMUTE)));

	switch (entry->sk_flags & (SK_NEGATE | SK_COMMUTE))
	{
		case 0x0:
			return strategy;

		case SK_NEGATE:
			strategy = evaluation->negateTransform->strategy[strategy - 1];
			break;

		case SK_COMMUTE:
			strategy = evaluation->commuteTransform->strategy[strategy - 1];
			break;

		case SK_NEGATE | SK_COMMUTE:
			strategy = evaluation->negateCommuteTransform->strategy[strategy - 1];
			break;

		default:
			elog(ERROR, "impossible strategy case: %d",
				 entry->sk_flags);
	}

	if (!StrategyNumberIsInBounds(strategy, evaluation->maxStrategy))
	{
		if (!StrategyNumberIsValid(strategy))
			elog(ERROR, "corrupted strategy evaluation");
	}

	return strategy;
}

#ifdef NOT_USED
/* ----------------
 *		RelationInvokeStrategy
 * ----------------
 */
bool							/* XXX someday, this may return Datum */
RelationInvokeStrategy(Relation relation,
					   StrategyEvaluation evaluation,
					   AttrNumber attributeNumber,
					   StrategyNumber strategy,
					   Datum left,
					   Datum right)
{
	StrategyNumber newStrategy;
	StrategyMap strategyMap;
	ScanKey		entry;
	StrategyTermData termData;
	int			numattrs;

	Assert(RelationIsValid(relation));
	Assert(relation->rd_rel->relkind == RELKIND_INDEX); /* XXX use accessor */
	numattrs = RelationGetNumberOfAttributes(relation);

	Assert(StrategyEvaluationIsValid(evaluation));
	Assert(AttributeNumberIsValid(attributeNumber));
	Assert((attributeNumber >= 1) && (attributeNumber < 1 + numattrs));

	Assert(StrategyNumberIsInBounds(strategy, evaluation->maxStrategy));

	termData.degree = 1;

	strategyMap = IndexStrategyGetStrategyMap(RelationGetIndexStrategy(relation),
											  evaluation->maxStrategy,
											  attributeNumber);

	entry = StrategyMapGetScanKeyEntry(strategyMap, strategy);

	if (RegProcedureIsValid(entry->sk_procedure))
	{
		termData.operatorData[0].strategy = strategy;
		termData.operatorData[0].flags = 0x0;

		return StrategyTermEvaluate(&termData, strategyMap, left, right);
	}


	newStrategy = evaluation->negateTransform->strategy[strategy - 1];
	if (newStrategy != strategy && StrategyNumberIsValid(newStrategy))
	{
		entry = StrategyMapGetScanKeyEntry(strategyMap, newStrategy);

		if (RegProcedureIsValid(entry->sk_procedure))
		{
			termData.operatorData[0].strategy = newStrategy;
			termData.operatorData[0].flags = SK_NEGATE;

			return StrategyTermEvaluate(&termData, strategyMap, left, right);
		}
	}

	newStrategy = evaluation->commuteTransform->strategy[strategy - 1];
	if (newStrategy != strategy && StrategyNumberIsValid(newStrategy))
	{
		entry = StrategyMapGetScanKeyEntry(strategyMap, newStrategy);

		if (RegProcedureIsValid(entry->sk_procedure))
		{
			termData.operatorData[0].strategy = newStrategy;
			termData.operatorData[0].flags = SK_COMMUTE;

			return StrategyTermEvaluate(&termData, strategyMap, left, right);
		}
	}

	newStrategy = evaluation->negateCommuteTransform->strategy[strategy - 1];
	if (newStrategy != strategy && StrategyNumberIsValid(newStrategy))
	{
		entry = StrategyMapGetScanKeyEntry(strategyMap, newStrategy);

		if (RegProcedureIsValid(entry->sk_procedure))
		{
			termData.operatorData[0].strategy = newStrategy;
			termData.operatorData[0].flags = SK_NEGATE | SK_COMMUTE;

			return StrategyTermEvaluate(&termData, strategyMap, left, right);
		}
	}

	if (PointerIsValid(evaluation->expression[strategy - 1]))
	{
		StrategyTerm *termP;

		termP = &evaluation->expression[strategy - 1]->term[0];
		while (PointerIsValid(*termP))
		{
			Index		index;

			for (index = 0; index < (*termP)->degree; index += 1)
			{
				entry = StrategyMapGetScanKeyEntry(strategyMap,
								 (*termP)->operatorData[index].strategy);

				if (!RegProcedureIsValid(entry->sk_procedure))
					break;
			}

			if (index == (*termP)->degree)
				return StrategyTermEvaluate(*termP, strategyMap, left, right);

			termP += 1;
		}
	}

	elog(ERROR, "cannot evaluate strategy %d", strategy);

	/* not reached, just to make compiler happy */
	return FALSE;
}
#endif

/* ----------------
 *		IndexStrategyDisplay
 * ----------------
 */
#ifdef	ISTRATDEBUG
int
IndexStrategyDisplay(IndexStrategy indexStrategy,
					 StrategyNumber numberOfStrategies,
					 int numberOfAttributes)
{
	StrategyMap strategyMap;
	AttrNumber	attributeNumber;
	StrategyNumber strategyNumber;

	for (attributeNumber = 1; attributeNumber <= numberOfAttributes;
		 attributeNumber += 1)
	{
		strategyMap = IndexStrategyGetStrategyMap(indexStrategy,
												  numberOfStrategies,
												  attributeNumber);

		for (strategyNumber = 1;
			 strategyNumber <= AMStrategies(numberOfStrategies);
			 strategyNumber += 1)
		{
			printf(":att %d\t:str %d\t:opr 0x%x(%d)\n",
				   attributeNumber, strategyNumber,
				   strategyMap->entry[strategyNumber - 1].sk_procedure,
				   strategyMap->entry[strategyNumber - 1].sk_procedure);
		}
	}
}

#endif   /* defined(ISTRATDEBUG) */