execqual.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

	 * original tuple).
	 */
	attnum = variable->varattno;

	switch (variable->varno)
	{
		case INNER:				/* get the tuple from the inner node */
			slot = econtext->ecxt_innertuple;
			Assert(attnum > 0);
			break;

		case OUTER:				/* get the tuple from the outer node */
			slot = econtext->ecxt_outertuple;
			Assert(attnum > 0);
			break;

		default:				/* get the tuple from the relation being
								 * scanned */
			slot = econtext->ecxt_scantuple;
			break;
	}

#ifdef USE_ASSERT_CHECKING

	/*
	 * Some checks that are only applied for user attribute numbers (bogus
	 * system attnums will be caught inside slot_getattr).
	 */
	if (attnum > 0)
	{
		TupleDesc	tuple_type = slot->tts_tupleDescriptor;

		/*
		 * This assert checks that the attnum is valid.
		 */
		Assert(attnum <= tuple_type->natts);

		/*
		 * This assert checks that the datatype the plan expects to get (as
		 * told by our "variable" argument) is in fact the datatype of the
		 * attribute being fetched (as seen in the current context, identified
		 * by our "econtext" argument).  Otherwise crashes are likely.
		 *
		 * Note that we can't check dropped columns, since their atttypid has
		 * been zeroed.
		 */
		Assert(variable->vartype == tuple_type->attrs[attnum - 1]->atttypid ||
			   tuple_type->attrs[attnum - 1]->attisdropped);
	}
#endif   /* USE_ASSERT_CHECKING */

	return slot_getattr(slot, attnum, isNull);
}

/* ----------------------------------------------------------------
 *		ExecEvalWholeRowVar
 *
 *		Returns a Datum for a whole-row variable.
 *
 *		This could be folded into ExecEvalVar, but we make it a separate
 *		routine so as not to slow down ExecEvalVar with tests for this
 *		uncommon case.
 * ----------------------------------------------------------------
 */
static Datum
ExecEvalWholeRowVar(ExprState *exprstate, ExprContext *econtext,
					bool *isNull, ExprDoneCond *isDone)
{
	Var		   *variable = (Var *) exprstate->expr;
	TupleTableSlot *slot;
	HeapTuple	tuple;
	TupleDesc	tupleDesc;
	HeapTupleHeader dtuple;

	if (isDone)
		*isDone = ExprSingleResult;
	*isNull = false;

	Assert(variable->varattno == InvalidAttrNumber);

	/*
	 * Whole-row Vars can only appear at the level of a relation scan, never
	 * in a join.
	 */
	Assert(variable->varno != INNER);
	Assert(variable->varno != OUTER);
	slot = econtext->ecxt_scantuple;

	tuple = ExecFetchSlotTuple(slot);
	tupleDesc = slot->tts_tupleDescriptor;

	/*
	 * We have to make a copy of the tuple so we can safely insert the Datum
	 * overhead fields, which are not set in on-disk tuples.
	 */
	dtuple = (HeapTupleHeader) palloc(tuple->t_len);
	memcpy((char *) dtuple, (char *) tuple->t_data, tuple->t_len);

	HeapTupleHeaderSetDatumLength(dtuple, tuple->t_len);

	/*
	 * If the Var identifies a named composite type, label the tuple with that
	 * type; otherwise use what is in the tupleDesc.
	 *
	 * It's likely that the slot's tupleDesc is a record type; if so, make
	 * sure it's been "blessed", so that the Datum can be interpreted later.
	 */
	if (variable->vartype != RECORDOID)
	{
		HeapTupleHeaderSetTypeId(dtuple, variable->vartype);
		HeapTupleHeaderSetTypMod(dtuple, variable->vartypmod);
	}
	else
	{
		if (tupleDesc->tdtypeid == RECORDOID &&
			tupleDesc->tdtypmod < 0)
			assign_record_type_typmod(tupleDesc);
		HeapTupleHeaderSetTypeId(dtuple, tupleDesc->tdtypeid);
		HeapTupleHeaderSetTypMod(dtuple, tupleDesc->tdtypmod);
	}

	return PointerGetDatum(dtuple);
}

/* ----------------------------------------------------------------
 *		ExecEvalConst
 *
 *		Returns the value of a constant.
 *
 *		Note that for pass-by-ref datatypes, we return a pointer to the
 *		actual constant node.  This is one of the reasons why functions
 *		must treat their input arguments as read-only.
 * ----------------------------------------------------------------
 */
static Datum
ExecEvalConst(ExprState *exprstate, ExprContext *econtext,
			  bool *isNull, ExprDoneCond *isDone)
{
	Const	   *con = (Const *) exprstate->expr;

	if (isDone)
		*isDone = ExprSingleResult;

	*isNull = con->constisnull;
	return con->constvalue;
}

/* ----------------------------------------------------------------
 *		ExecEvalParam
 *
 *		Returns the value of a parameter.  A param node contains
 *		something like ($.name) and the expression context contains
 *		the current parameter bindings (name = "sam") (age = 34)...
 *		so our job is to find and return the appropriate datum ("sam").
 *
 *		Q: if we have a parameter ($.foo) without a binding, i.e.
 *		   there is no (foo = xxx) in the parameter list info,
 *		   is this a fatal error or should this be a "not available"
 *		   (in which case we could return NULL)?	-cim 10/13/89
 * ----------------------------------------------------------------
 */
static Datum
ExecEvalParam(ExprState *exprstate, ExprContext *econtext,
			  bool *isNull, ExprDoneCond *isDone)
{
	Param	   *expression = (Param *) exprstate->expr;
	int			thisParamKind = expression->paramkind;
	AttrNumber	thisParamId = expression->paramid;

	if (isDone)
		*isDone = ExprSingleResult;

	if (thisParamKind == PARAM_EXEC)
	{
		/*
		 * PARAM_EXEC params (internal executor parameters) are stored in the
		 * ecxt_param_exec_vals array, and can be accessed by array index.
		 */
		ParamExecData *prm;

		prm = &(econtext->ecxt_param_exec_vals[thisParamId]);
		if (prm->execPlan != NULL)
		{
			/* Parameter not evaluated yet, so go do it */
			ExecSetParamPlan(prm->execPlan, econtext);
			/* ExecSetParamPlan should have processed this param... */
			Assert(prm->execPlan == NULL);
		}
		*isNull = prm->isnull;
		return prm->value;
	}
	else
	{
		/*
		 * All other parameter types must be sought in ecxt_param_list_info.
		 */
		ParamListInfo paramInfo;

		paramInfo = lookupParam(econtext->ecxt_param_list_info,
								thisParamKind,
								expression->paramname,
								thisParamId,
								false);
		Assert(paramInfo->ptype == expression->paramtype);
		*isNull = paramInfo->isnull;
		return paramInfo->value;
	}
}


/* ----------------------------------------------------------------
 *		ExecEvalOper / ExecEvalFunc support routines
 * ----------------------------------------------------------------
 */

/*
 *		GetAttributeByName
 *		GetAttributeByNum
 *
 *		These functions return the value of the requested attribute
 *		out of the given tuple Datum.
 *		C functions which take a tuple as an argument are expected
 *		to use these.  Ex: overpaid(EMP) might call GetAttributeByNum().
 *		Note: these are actually rather slow because they do a typcache
 *		lookup on each call.
 */
Datum
GetAttributeByNum(HeapTupleHeader tuple,
				  AttrNumber attrno,
				  bool *isNull)
{
	Datum		result;
	Oid			tupType;
	int32		tupTypmod;
	TupleDesc	tupDesc;
	HeapTupleData tmptup;

	if (!AttributeNumberIsValid(attrno))
		elog(ERROR, "invalid attribute number %d", attrno);

	if (isNull == NULL)
		elog(ERROR, "a NULL isNull pointer was passed");

	if (tuple == NULL)
	{
		/* Kinda bogus but compatible with old behavior... */
		*isNull = true;
		return (Datum) 0;
	}

	tupType = HeapTupleHeaderGetTypeId(tuple);
	tupTypmod = HeapTupleHeaderGetTypMod(tuple);
	tupDesc = lookup_rowtype_tupdesc(tupType, tupTypmod);

	/*
	 * heap_getattr needs a HeapTuple not a bare HeapTupleHeader.  We set all
	 * the fields in the struct just in case user tries to inspect system
	 * columns.
	 */
	tmptup.t_len = HeapTupleHeaderGetDatumLength(tuple);
	ItemPointerSetInvalid(&(tmptup.t_self));
	tmptup.t_tableOid = InvalidOid;
	tmptup.t_data = tuple;

	result = heap_getattr(&tmptup,
						  attrno,
						  tupDesc,
						  isNull);
	return result;
}

Datum
GetAttributeByName(HeapTupleHeader tuple, const char *attname, bool *isNull)
{
	AttrNumber	attrno;
	Datum		result;
	Oid			tupType;
	int32		tupTypmod;
	TupleDesc	tupDesc;
	HeapTupleData tmptup;
	int			i;

	if (attname == NULL)
		elog(ERROR, "invalid attribute name");

	if (isNull == NULL)
		elog(ERROR, "a NULL isNull pointer was passed");

	if (tuple == NULL)
	{
		/* Kinda bogus but compatible with old behavior... */
		*isNull = true;
		return (Datum) 0;
	}

	tupType = HeapTupleHeaderGetTypeId(tuple);
	tupTypmod = HeapTupleHeaderGetTypMod(tuple);
	tupDesc = lookup_rowtype_tupdesc(tupType, tupTypmod);

	attrno = InvalidAttrNumber;
	for (i = 0; i < tupDesc->natts; i++)
	{
		if (namestrcmp(&(tupDesc->attrs[i]->attname), attname) == 0)
		{
			attrno = tupDesc->attrs[i]->attnum;
			break;
		}
	}

	if (attrno == InvalidAttrNumber)
		elog(ERROR, "attribute \"%s\" does not exist", attname);

	/*
	 * heap_getattr needs a HeapTuple not a bare HeapTupleHeader.  We set all
	 * the fields in the struct just in case user tries to inspect system
	 * columns.
	 */
	tmptup.t_len = HeapTupleHeaderGetDatumLength(tuple);
	ItemPointerSetInvalid(&(tmptup.t_self));
	tmptup.t_tableOid = InvalidOid;
	tmptup.t_data = tuple;

	result = heap_getattr(&tmptup,
						  attrno,
						  tupDesc,
						  isNull);
	return result;
}

/*
 * init_fcache - initialize a FuncExprState node during first use
 */
void
init_fcache(Oid foid, FuncExprState *fcache, MemoryContext fcacheCxt)
{
	AclResult	aclresult;

	/* Check permission to call function */
	aclresult = pg_proc_aclcheck(foid, GetUserId(), ACL_EXECUTE);
	if (aclresult != ACLCHECK_OK)
		aclcheck_error(aclresult, ACL_KIND_PROC, get_func_name(foid));

	/*
	 * Safety check on nargs.  Under normal circumstances this should never
	 * fail, as parser should check sooner.  But possibly it might fail if
	 * server has been compiled with FUNC_MAX_ARGS smaller than some functions
	 * declared in pg_proc?
	 */
	if (list_length(fcache->args) > FUNC_MAX_ARGS)
		ereport(ERROR,
				(errcode(ERRCODE_TOO_MANY_ARGUMENTS),
				 errmsg("cannot pass more than %d arguments to a function",
						FUNC_MAX_ARGS)));

	/* Set up the primary fmgr lookup information */
	fmgr_info_cxt(foid, &(fcache->func), fcacheCxt);

	/* Initialize additional info */
	fcache->setArgsValid = false;
	fcache->shutdown_reg = false;
	fcache->func.fn_expr = (Node *) fcache->xprstate.expr;
}

/*
 * callback function in case a FuncExpr returning a set needs to be shut down
 * before it has been run to completion
 */
static void
ShutdownFuncExpr(Datum arg)
{
	FuncExprState *fcache = (FuncExprState *) DatumGetPointer(arg);

	/* Clear any active set-argument state */
	fcache->setArgsValid = false;

	/* execUtils will deregister the callback... */
	fcache->shutdown_reg = false;
}

/*
 * Evaluate arguments for a function.
 */
static ExprDoneCond
ExecEvalFuncArgs(FunctionCallInfo fcinfo,
				 List *argList,
				 ExprContext *econtext)
{
	ExprDoneCond argIsDone;
	int			i;
	ListCell   *arg;

	argIsDone = ExprSingleResult;		/* default assumption */

	i = 0;
	foreach(arg, argList)
	{
		ExprState  *argstate = (ExprState *) lfirst(arg);
		ExprDoneCond thisArgIsDone;

		fcinfo->arg[i] = ExecEvalExpr(argstate,
									  econtext,
									  &fcinfo->argnull[i],
									  &thisArgIsDone);

		if (thisArgIsDone != ExprSingleResult)
		{
			/*
			 * We allow only one argument to have a set value; we'd need much
			 * more complexity to keep track of multiple set arguments (cf.
			 * ExecTargetList) and it doesn't seem worth it.
			 */
			if (argIsDone != ExprSingleResult)
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("functions and operators can take at most one set argument")));
			argIsDone = thisArgIsDone;
		}
		i++;
	}

	fcinfo->nargs = i;

	return argIsDone;
}

/*
 *		ExecMakeFunctionResult
 *
 * Evaluate the arguments to a function and then the function itself.
 */
Datum
ExecMakeFunctionResult(FuncExprState *fcache,
					   ExprContext *econtext,
					   bool *isNull,
					   ExprDoneCond *isDone)
{
	List	   *arguments = fcache->args;
	Datum		result;
	FunctionCallInfoData fcinfo;
	ReturnSetInfo rsinfo;		/* for functions returning sets */
	ExprDoneCond argDone;
	bool		hasSetArg;
	int			i;

	/* Guard against stack overflow due to overly complex expressions */
	check_stack_depth();

	/*
	 * arguments is a list of expressions to evaluate before passing to the
	 * function manager.  We skip the evaluation if it was already done in the
	 * previous call (ie, we are continuing the evaluation of a set-valued
	 * function).  Otherwise, collect the current argument values into fcinfo.
	 */
	if (!fcache->setArgsValid)
	{