execqual.c

PostgreSQL7.4.6 for Linux

		{
			if (DatumGetBool(thisresult))
			{
				result = BoolGetDatum(true);
				resultnull = false;
				break;			/* needn't look at any more elements */
			}
		}
		else
		{
			if (!DatumGetBool(thisresult))
			{
				result = BoolGetDatum(false);
				resultnull = false;
				break;			/* needn't look at any more elements */
			}
		}
	}

	*isNull = resultnull;
	return result;
}

/* ----------------------------------------------------------------
 *		ExecEvalNot
 *		ExecEvalOr
 *		ExecEvalAnd
 *
 *		Evaluate boolean expressions, with appropriate short-circuiting.
 *
 *		The query planner reformulates clause expressions in the
 *		qualification to conjunctive normal form.  If we ever get
 *		an AND to evaluate, we can be sure that it's not a top-level
 *		clause in the qualification, but appears lower (as a function
 *		argument, for example), or in the target list.	Not that you
 *		need to know this, mind you...
 * ----------------------------------------------------------------
 */
static Datum
ExecEvalNot(BoolExprState *notclause, ExprContext *econtext, bool *isNull)
{
	ExprState  *clause;
	Datum		expr_value;

	clause = lfirst(notclause->args);

	expr_value = ExecEvalExpr(clause, econtext, isNull, NULL);

	/*
	 * if the expression evaluates to null, then we just cascade the null
	 * back to whoever called us.
	 */
	if (*isNull)
		return expr_value;

	/*
	 * evaluation of 'not' is simple.. expr is false, then return 'true'
	 * and vice versa.
	 */
	return BoolGetDatum(!DatumGetBool(expr_value));
}

/* ----------------------------------------------------------------
 *		ExecEvalOr
 * ----------------------------------------------------------------
 */
static Datum
ExecEvalOr(BoolExprState *orExpr, ExprContext *econtext, bool *isNull)
{
	List	   *clauses;
	List	   *clause;
	bool		AnyNull;
	Datum		clause_value;

	clauses = orExpr->args;
	AnyNull = false;

	/*
	 * If any of the clauses is TRUE, the OR result is TRUE regardless of
	 * the states of the rest of the clauses, so we can stop evaluating
	 * and return TRUE immediately.  If none are TRUE and one or more is
	 * NULL, we return NULL; otherwise we return FALSE.  This makes sense
	 * when you interpret NULL as "don't know": if we have a TRUE then the
	 * OR is TRUE even if we aren't sure about some of the other inputs.
	 * If all the known inputs are FALSE, but we have one or more "don't
	 * knows", then we have to report that we "don't know" what the OR's
	 * result should be --- perhaps one of the "don't knows" would have
	 * been TRUE if we'd known its value.  Only when all the inputs are
	 * known to be FALSE can we state confidently that the OR's result is
	 * FALSE.
	 */
	foreach(clause, clauses)
	{
		clause_value = ExecEvalExpr((ExprState *) lfirst(clause),
									econtext, isNull, NULL);

		/*
		 * if we have a non-null true result, then return it.
		 */
		if (*isNull)
			AnyNull = true;		/* remember we got a null */
		else if (DatumGetBool(clause_value))
			return clause_value;
	}

	/* AnyNull is true if at least one clause evaluated to NULL */
	*isNull = AnyNull;
	return BoolGetDatum(false);
}

/* ----------------------------------------------------------------
 *		ExecEvalAnd
 * ----------------------------------------------------------------
 */
static Datum
ExecEvalAnd(BoolExprState *andExpr, ExprContext *econtext, bool *isNull)
{
	List	   *clauses;
	List	   *clause;
	bool		AnyNull;
	Datum		clause_value;

	clauses = andExpr->args;
	AnyNull = false;

	/*
	 * If any of the clauses is FALSE, the AND result is FALSE regardless
	 * of the states of the rest of the clauses, so we can stop evaluating
	 * and return FALSE immediately.  If none are FALSE and one or more is
	 * NULL, we return NULL; otherwise we return TRUE.	This makes sense
	 * when you interpret NULL as "don't know", using the same sort of
	 * reasoning as for OR, above.
	 */
	foreach(clause, clauses)
	{
		clause_value = ExecEvalExpr((ExprState *) lfirst(clause),
									econtext, isNull, NULL);

		/*
		 * if we have a non-null false result, then return it.
		 */
		if (*isNull)
			AnyNull = true;		/* remember we got a null */
		else if (!DatumGetBool(clause_value))
			return clause_value;
	}

	/* AnyNull is true if at least one clause evaluated to NULL */
	*isNull = AnyNull;
	return BoolGetDatum(!AnyNull);
}


/* ----------------------------------------------------------------
 *		ExecEvalCase
 *
 *		Evaluate a CASE clause. Will have boolean expressions
 *		inside the WHEN clauses, and will have expressions
 *		for results.
 *		- thomas 1998-11-09
 * ----------------------------------------------------------------
 */
static Datum
ExecEvalCase(CaseExprState *caseExpr, ExprContext *econtext,
			 bool *isNull, ExprDoneCond *isDone)
{
	List	   *clauses;
	List	   *clause;
	Datum		clause_value;

	clauses = caseExpr->args;

	/*
	 * we evaluate each of the WHEN clauses in turn, as soon as one is
	 * true we return the corresponding result. If none are true then we
	 * return the value of the default clause, or NULL if there is none.
	 */
	foreach(clause, clauses)
	{
		CaseWhenState *wclause = lfirst(clause);

		clause_value = ExecEvalExpr(wclause->expr,
									econtext,
									isNull,
									NULL);

		/*
		 * if we have a true test, then we return the result, since the
		 * case statement is satisfied.  A NULL result from the test is
		 * not considered true.
		 */
		if (DatumGetBool(clause_value) && !*isNull)
		{
			return ExecEvalExpr(wclause->result,
								econtext,
								isNull,
								isDone);
		}
	}

	if (caseExpr->defresult)
	{
		return ExecEvalExpr(caseExpr->defresult,
							econtext,
							isNull,
							isDone);
	}

	*isNull = true;
	return (Datum) 0;
}

/* ----------------------------------------------------------------
 *		ExecEvalArray - ARRAY[] expressions
 *
 * NOTE: currently, if any input value is NULL then we return a NULL array,
 * so the ARRAY[] construct can be considered strict.  Eventually this will
 * change; when it does, be sure to fix contain_nonstrict_functions().
 * ----------------------------------------------------------------
 */
static Datum
ExecEvalArray(ArrayExprState *astate, ExprContext *econtext,
			  bool *isNull)
{
	ArrayExpr  *arrayExpr = (ArrayExpr *) astate->xprstate.expr;
	ArrayType  *result;
	List	   *element;
	Oid			element_type = arrayExpr->element_typeid;
	int			ndims = 0;
	int			dims[MAXDIM];
	int			lbs[MAXDIM];

	if (!arrayExpr->multidims)
	{
		/* Elements are presumably of scalar type */
		int			nelems;
		Datum	   *dvalues;
		int			i = 0;

		ndims = 1;
		nelems = length(astate->elements);

		/* Shouldn't happen here, but if length is 0, return NULL */
		if (nelems == 0)
		{
			*isNull = true;
			return (Datum) 0;
		}

		dvalues = (Datum *) palloc(nelems * sizeof(Datum));

		/* loop through and build array of datums */
		foreach(element, astate->elements)
		{
			ExprState  *e = (ExprState *) lfirst(element);
			bool		eisnull;

			dvalues[i++] = ExecEvalExpr(e, econtext, &eisnull, NULL);
			if (eisnull)
			{
				*isNull = true;
				return (Datum) 0;
			}
		}

		/* setup for 1-D array of the given length */
		dims[0] = nelems;
		lbs[0] = 1;

		result = construct_md_array(dvalues, ndims, dims, lbs,
									element_type,
									astate->elemlength,
									astate->elembyval,
									astate->elemalign);
	}
	else
	{
		/* Must be nested array expressions */
		char	   *dat = NULL;
		Size		ndatabytes = 0;
		int			nbytes;
		int			outer_nelems = length(astate->elements);
		int			elem_ndims = 0;
		int		   *elem_dims = NULL;
		int		   *elem_lbs = NULL;
		bool		firstone = true;
		int			i;

		/* loop through and get data area from each element */
		foreach(element, astate->elements)
		{
			ExprState  *e = (ExprState *) lfirst(element);
			bool		eisnull;
			Datum		arraydatum;
			ArrayType  *array;
			int			elem_ndatabytes;

			arraydatum = ExecEvalExpr(e, econtext, &eisnull, NULL);
			if (eisnull)
			{
				*isNull = true;
				return (Datum) 0;
			}

			array = DatumGetArrayTypeP(arraydatum);

			/* run-time double-check on element type */
			if (element_type != ARR_ELEMTYPE(array))
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
						 errmsg("cannot merge incompatible arrays"),
						 errdetail("Array with element type %s cannot be "
								   "included in ARRAY construct with element type %s.",
								   format_type_be(ARR_ELEMTYPE(array)),
								   format_type_be(element_type))));

			if (firstone)
			{
				/* Get sub-array details from first member */
				elem_ndims = ARR_NDIM(array);
				ndims = elem_ndims + 1;
				if (ndims <= 0 || ndims > MAXDIM)
					ereport(ERROR,
							(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
							 errmsg("number of array dimensions (%d) exceeds " \
									"the maximum allowed (%d)", ndims, MAXDIM)));

				elem_dims = (int *) palloc(elem_ndims * sizeof(int));
				memcpy(elem_dims, ARR_DIMS(array), elem_ndims * sizeof(int));
				elem_lbs = (int *) palloc(elem_ndims * sizeof(int));
				memcpy(elem_lbs, ARR_LBOUND(array), elem_ndims * sizeof(int));

				firstone = false;
			}
			else
			{
				/* Check other sub-arrays are compatible */
				if (elem_ndims != ARR_NDIM(array) ||
					memcmp(elem_dims, ARR_DIMS(array),
						   elem_ndims * sizeof(int)) != 0 ||
					memcmp(elem_lbs, ARR_LBOUND(array),
						   elem_ndims * sizeof(int)) != 0)
					ereport(ERROR,
							(errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
						errmsg("multidimensional arrays must have array "
							   "expressions with matching dimensions")));
			}

			elem_ndatabytes = ARR_SIZE(array) - ARR_OVERHEAD(elem_ndims);
			ndatabytes += elem_ndatabytes;
			if (dat == NULL)
				dat = (char *) palloc(ndatabytes);
			else
				dat = (char *) repalloc(dat, ndatabytes);

			memcpy(dat + (ndatabytes - elem_ndatabytes),
				   ARR_DATA_PTR(array),
				   elem_ndatabytes);
		}

		/* setup for multi-D array */
		dims[0] = outer_nelems;
		lbs[0] = 1;
		for (i = 1; i < ndims; i++)
		{
			dims[i] = elem_dims[i - 1];
			lbs[i] = elem_lbs[i - 1];
		}

		nbytes = ndatabytes + ARR_OVERHEAD(ndims);
		result = (ArrayType *) palloc(nbytes);

		result->size = nbytes;
		result->ndim = ndims;
		result->flags = 0;
		result->elemtype = element_type;
		memcpy(ARR_DIMS(result), dims, ndims * sizeof(int));
		memcpy(ARR_LBOUND(result), lbs, ndims * sizeof(int));
		if (ndatabytes > 0)
			memcpy(ARR_DATA_PTR(result), dat, ndatabytes);

		if (dat != NULL)
			pfree(dat);
	}

	return PointerGetDatum(result);
}

/* ----------------------------------------------------------------
 *		ExecEvalCoalesce
 * ----------------------------------------------------------------
 */
static Datum
ExecEvalCoalesce(CoalesceExprState *coalesceExpr, ExprContext *econtext,
				 bool *isNull)
{
	List	   *arg;

	/* Simply loop through until something NOT NULL is found */
	foreach(arg, coalesceExpr->args)
	{
		ExprState  *e = (ExprState *) lfirst(arg);
		Datum		value;

		value = ExecEvalExpr(e, econtext, isNull, NULL);
		if (!*isNull)
			return value;
	}

	/* Else return NULL */
	*isNull = true;
	return (Datum) 0;
}

/* ----------------------------------------------------------------
 *		ExecEvalNullIf
 *
 * Note that this is *always* derived from the equals operator,
 * but since we need special processing of the arguments
 * we can not simply reuse ExecEvalOper() or ExecEvalFunc().
 * ----------------------------------------------------------------
 */
static Datum
ExecEvalNullIf(FuncExprState *fcache, ExprContext *econtext,
			   bool *isNull)
{
	Datum		result;
	FunctionCallInfoData fcinfo;
	ExprDoneCond argDone;
	List	   *argList;

	/*
	 * Initialize function cache if first time through
	 */
	if (fcache->func.fn_oid == InvalidOid)
	{
		NullIfExpr *op = (NullIfExpr *) fcache->xprstate.expr;

		init_fcache(op->opfuncid, fcache, econtext->ecxt_per_query_memory);
		Assert(!fcache->func.fn_retset);
	}

	/*
	 * extract info from fcache
	 */
	argList = fcache->args;

	/* Need to prep callinfo structure */
	MemSet(&fcinfo, 0, sizeof(fcinfo));
	fcinfo.flinfo = &(fcache->func);
	argDone = ExecEvalFuncArgs(&fcinfo, argList, econtext);
	if (argDone != ExprSingleResult)
		ereport(ERROR,
				(errcode(ERRCODE_DATATYPE_MISMATCH),
				 errmsg("NULLIF does not support set arguments")));
	Assert(fcinfo.nargs == 2);

	/* if either argument is NULL they can't be equal */
	if (!fcinfo.argnull[0] && !fcinfo.argnull[1])
	{
		fcinfo.isnull = false;
		result = FunctionCallInvoke(&fcinfo);
		/* if the arguments are equal return null */
		if (!fcinfo.isnull && DatumGetBool(result))
		{
			*isNull = true;
			return (Datum) 0;
		}
	}

	/* else return first argument */
	*isNull = fcinfo.argnull[0];
	return fcinfo.arg[0];
}

/* ----------------------------------------------------------------
 *		ExecEvalNullTest