parse_func.c

关系型数据库 Postgresql 6.5.2

	}

	/* got it */
	funcnode = makeNode(Func);
	funcnode->funcid = funcid;
	funcnode->functype = rettype;
	funcnode->funcisindex = false;
	funcnode->funcsize = 0;
	funcnode->func_fcache = NULL;
	funcnode->func_tlist = NIL;
	funcnode->func_planlist = NIL;

	/* perform the necessary typecasting */
	make_arguments(pstate, nargs, fargs, oid_array, true_oid_array);

	/*
	 * for functions returning base types, we want to project out the
	 * return value.  set up a target list to do that.	the executor will
	 * ignore these for c functions, and do the right thing for postquel
	 * functions.
	 */

	if (typeidTypeRelid(rettype) == InvalidOid)
		funcnode->func_tlist = setup_base_tlist(rettype);

	/*
	 * For sets, we want to make a targetlist to project out this
	 * attribute of the set tuples.
	 */
	if (attisset)
	{
		if (!strcmp(funcname, "*"))
			funcnode->func_tlist = expandAll(pstate, relname, refname, curr_resno);
		else
		{
			funcnode->func_tlist = setup_tlist(funcname, argrelid);
			rettype = get_atttype(argrelid, get_attnum(argrelid, funcname));
		}
	}

	/*
	 * Sequence handling.
	 */
	if (funcid == F_NEXTVAL ||
		funcid == F_CURRVAL ||
		funcid == F_SETVAL)
	{
		Const	   *seq;
		char	   *seqrel;
		text	   *seqname;
		int32		aclcheck_result = -1;

		Assert(length(fargs) == ((funcid == F_SETVAL) ? 2 : 1));
		seq = (Const *) lfirst(fargs);
		if (!IsA((Node *) seq, Const))
			elog(ERROR, "Only constant sequence names are acceptable for function '%s'", funcname);

		seqrel = textout((text *) DatumGetPointer(seq->constvalue));
		/* Do we have nextval('"Aa"')? */
		if (strlen(seqrel) >= 2 &&
			seqrel[0] == '\"' && seqrel[strlen(seqrel) - 1] == '\"')
		{
			/* strip off quotes, keep case */
			seqrel = pstrdup(seqrel + 1);
			seqrel[strlen(seqrel) - 1] = '\0';
			pfree(DatumGetPointer(seq->constvalue));
			seq->constvalue = (Datum) textin(seqrel);
		}
		else
		{
			pfree(seqrel);
			seqname = lower((text *) DatumGetPointer(seq->constvalue));
			pfree(DatumGetPointer(seq->constvalue));
			seq->constvalue = PointerGetDatum(seqname);
			seqrel = textout(seqname);
		}

		if ((aclcheck_result = pg_aclcheck(seqrel, GetPgUserName(),
					   (((funcid == F_NEXTVAL) || (funcid == F_SETVAL)) ?
						ACL_WR : ACL_RD)))
			!= ACLCHECK_OK)
			elog(ERROR, "%s.%s: %s",
			  seqrel, funcname, aclcheck_error_strings[aclcheck_result]);

		pfree(seqrel);

		if (funcid == F_NEXTVAL && pstate->p_in_where_clause)
			elog(ERROR, "Sequence function nextval is not allowed in WHERE clauses");
		if (funcid == F_SETVAL && pstate->p_in_where_clause)
			elog(ERROR, "Sequence function setval is not allowed in WHERE clauses");
	}

	expr = makeNode(Expr);
	expr->typeOid = rettype;
	expr->opType = FUNC_EXPR;
	expr->oper = (Node *) funcnode;
	expr->args = fargs;
	retval = (Node *) expr;

	/*
	 * if the function returns a set of values, then we need to iterate
	 * over all the returned values in the executor, so we stick an iter
	 * node here.  if it returns a singleton, then we don't need the iter
	 * node.
	 */

	if (retset)
	{
		Iter	   *iter = makeNode(Iter);

		iter->itertype = rettype;
		iter->iterexpr = retval;
		retval = (Node *) iter;
	}

	return retval;
}

static Oid
funcid_get_rettype(Oid funcid)
{
	HeapTuple	func_tuple = NULL;
	Oid			funcrettype = InvalidOid;

	func_tuple = SearchSysCacheTuple(PROOID,
									 ObjectIdGetDatum(funcid),
									 0, 0, 0);

	if (!HeapTupleIsValid(func_tuple))
		elog(ERROR, "Function OID %u does not exist", funcid);

	funcrettype = (Oid)
		((Form_pg_proc) GETSTRUCT(func_tuple))->prorettype;

	return funcrettype;
}


/* func_get_candidates()
 * get a list of all argument type vectors for which a function named
 * funcname taking nargs arguments exists
 */
static CandidateList
func_get_candidates(char *funcname, int nargs)
{
	Relation	heapRelation;
	Relation	idesc;
	ScanKeyData skey;
	HeapTupleData tuple;
	IndexScanDesc sd;
	RetrieveIndexResult indexRes;
	Form_pg_proc pgProcP;
	CandidateList candidates = NULL;
	CandidateList current_candidate;
	int			i;

	heapRelation = heap_openr(ProcedureRelationName);
	ScanKeyEntryInitialize(&skey,
						   (bits16) 0x0,
						   (AttrNumber) 1,
						   (RegProcedure) F_NAMEEQ,
						   (Datum) funcname);

	idesc = index_openr(ProcedureNameIndex);

	sd = index_beginscan(idesc, false, 1, &skey);

	do
	{
		indexRes = index_getnext(sd, ForwardScanDirection);
		if (indexRes)
		{
			Buffer		buffer;

			tuple.t_self = indexRes->heap_iptr;
			heap_fetch(heapRelation, SnapshotNow, &tuple, &buffer);
			pfree(indexRes);
			if (tuple.t_data != NULL)
			{
				pgProcP = (Form_pg_proc) GETSTRUCT(&tuple);
				if (pgProcP->pronargs == nargs)
				{
					current_candidate = (CandidateList)
						palloc(sizeof(struct _CandidateList));
					current_candidate->args = (Oid *)
						palloc(MAXFARGS * sizeof(Oid));
					MemSet(current_candidate->args, 0, MAXFARGS * sizeof(Oid));
					for (i = 0; i < nargs; i++)
						current_candidate->args[i] = pgProcP->proargtypes[i];

					current_candidate->next = candidates;
					candidates = current_candidate;
				}
				ReleaseBuffer(buffer);
			}
		}
	} while (indexRes);

	index_endscan(sd);
	index_close(idesc);
	heap_close(heapRelation);

	return candidates;
}


/* match_argtypes()
 * Given a list of possible typeid arrays to a function and an array of
 * input typeids, produce a shortlist of those function typeid arrays
 * that match the input typeids (either exactly or by coercion), and
 * return the number of such arrays
 */
static int
match_argtypes(int nargs,
			   Oid *input_typeids,
			   CandidateList function_typeids,
			   CandidateList *candidates)		/* return value */
{
	CandidateList current_candidate;
	CandidateList matching_candidate;
	Oid		   *current_typeids;
	int			ncandidates = 0;

	*candidates = NULL;

	for (current_candidate = function_typeids;
		 current_candidate != NULL;
		 current_candidate = current_candidate->next)
	{
		current_typeids = current_candidate->args;
		if (can_coerce_type(nargs, input_typeids, current_typeids))
		{
			matching_candidate = (CandidateList)
				palloc(sizeof(struct _CandidateList));
			matching_candidate->args = current_typeids;
			matching_candidate->next = *candidates;
			*candidates = matching_candidate;
			ncandidates++;
		}
	}

	return ncandidates;
}	/* match_argtypes() */


/* func_select_candidate()
 * Given the input argtype array and more than one candidate
 * for the function argtype array, attempt to resolve the conflict.
 * returns the selected argtype array if the conflict can be resolved,
 * otherwise returns NULL.
 *
 * If all input Oids are UNKNOWNOID, then try matching with TEXTOID.
 * Otherwise, could return first function arguments on list of candidates.
 * But for now, return NULL and make the user give a better hint.
 * - thomas 1998-03-17
 */
static Oid *
func_select_candidate(int nargs,
					  Oid *input_typeids,
					  CandidateList candidates)
{
	CandidateList current_candidate;
	CandidateList last_candidate;
	Oid		   *current_typeids;
	int			i;

	int			ncandidates;
	int			nbestMatch,
				nmatch,
				nident;

	CATEGORY	slot_category,
				current_category;
	Oid			slot_type,
				current_type;

/*
 * Run through all candidates and keep those with the most matches
 *	on explicit types. Keep all candidates if none match.
 */
	ncandidates = 0;
	nbestMatch = 0;
	last_candidate = NULL;
	for (current_candidate = candidates;
		 current_candidate != NULL;
		 current_candidate = current_candidate->next)
	{
		current_typeids = current_candidate->args;
		nmatch = 0;
		nident = 0;
		for (i = 0; i < nargs; i++)
		{
			if ((input_typeids[i] != UNKNOWNOID)
				&& (current_typeids[i] == input_typeids[i]))
				nmatch++;
			else if (IS_BINARY_COMPATIBLE(current_typeids[i], input_typeids[i]))
				nident++;
		}

		if ((nmatch + nident) == nargs)
			return current_candidate->args;

		if ((nmatch > nbestMatch) || (last_candidate == NULL))
		{
			nbestMatch = nmatch;
			candidates = current_candidate;
			last_candidate = current_candidate;
			ncandidates = 1;
		}
		else if (nmatch == nbestMatch)
		{
			last_candidate->next = current_candidate;
			last_candidate = current_candidate;
			ncandidates++;
		}
		else
			last_candidate->next = NULL;
	}

	if (ncandidates == 1)
		return candidates->args;

/*
 * Still too many candidates?
 * Try assigning types for the unknown columns.
 */
	for (i = 0; i < nargs; i++)
	{
		if (input_typeids[i] == UNKNOWNOID)
		{
			slot_category = INVALID_TYPE;
			slot_type = InvalidOid;
			for (current_candidate = candidates;
				 current_candidate != NULL;
				 current_candidate = current_candidate->next)
			{
				current_typeids = current_candidate->args;
				current_type = current_typeids[i];
				current_category = TypeCategory(current_typeids[i]);

				if (slot_category == InvalidOid)
				{
					slot_category = current_category;
					slot_type = current_type;
				}
				else if ((current_category != slot_category)
						 && IS_BUILTIN_TYPE(current_type))
					return NULL;
				else if (current_type != slot_type)
				{
					if (IsPreferredType(slot_category, current_type))
					{
						slot_type = current_type;
						candidates = current_candidate;
					}
					else if (IsPreferredType(slot_category, slot_type))
						candidates->next = current_candidate->next;
				}
			}

			if (slot_type != InvalidOid)
				input_typeids[i] = slot_type;
		}
		else
		{
		}
	}

	ncandidates = 0;
	for (current_candidate = candidates;
		 current_candidate != NULL;
		 current_candidate = current_candidate->next)
		ncandidates++;

	if (ncandidates == 1)
		return candidates->args;

	return NULL;
}	/* func_select_candidate() */


/* func_get_detail()
 * Find the named function in the system catalogs.
 *
 * Attempt to find the named function in the system catalogs with
 *	arguments exactly as specified, so that the normal case
 *	(exact match) is as quick as possible.
 *
 * If an exact match isn't found:
 *	1) get a vector of all possible input arg type arrays constructed
 *	   from the superclasses of the original input arg types
 *	2) get a list of all possible argument type arrays to the function
 *	   with given name and number of arguments
 *	3) for each input arg type array from vector #1:
 *	 a) find how many of the function arg type arrays from list #2
 *		it can be coerced to
 *	 b) if the answer is one, we have our function
 *	 c) if the answer is more than one, attempt to resolve the conflict
 *	 d) if the answer is zero, try the next array from vector #1
 */
static bool
func_get_detail(char *funcname,
				int nargs,
				Oid *oid_array,
				Oid *funcid,	/* return value */
				Oid *rettype,	/* return value */
				bool *retset,	/* return value */
				Oid **true_typeids)		/* return value */
{
	Oid		  **input_typeid_vector;
	Oid		   *current_input_typeids;
	CandidateList function_typeids;
	CandidateList current_function_typeids;
	HeapTuple	ftup;
	Form_pg_proc pform;

	/* attempt to find with arguments exactly as specified... */
	ftup = SearchSysCacheTuple(PRONAME,
							   PointerGetDatum(funcname),
							   Int32GetDatum(nargs),
							   PointerGetDatum(oid_array),
							   0);
	*true_typeids = oid_array;

	/* didn't find an exact match, so now try to match up candidates... */
	if (!HeapTupleIsValid(ftup))
	{
		function_typeids = func_get_candidates(funcname, nargs);

		/* found something, so let's look through them... */
		if (function_typeids != NULL)
		{
			int			ncandidates;

			input_typeid_vector = argtype_inherit(nargs, oid_array);
			current_input_typeids = oid_array;

			do
			{
				ncandidates = match_argtypes(nargs, current_input_typeids,
											 function_typeids,
											 &current_function_typeids);

				/* one match only? then run with it... */
				if (ncandidates == 1)
				{
					*true_typeids = current_function_typeids->args;
					ftup = SearchSysCacheTuple(PRONAME,
											   PointerGetDatum(funcname),
											   Int32GetDatum(nargs),
										  PointerGetDatum(*true_typeids),
											   0);
					Assert(HeapTupleIsValid(ftup));
				}

				/*
				 * multiple candidates? then better decide or throw an
				 * error...
				 */
				else if (ncandidates > 1)
				{
					*true_typeids = func_select_candidate(nargs,
												   current_input_typeids,
											   current_function_typeids);

					/* couldn't decide, so quit */
					if (*true_typeids == NULL)
					{
						func_error(NULL, funcname, nargs, oid_array,
								   "Unable to identify a function which satisfies the given argument types"
								   "\n\tYou will have to retype your query using explicit typecasts");
					}

					/* found something, so use the first one... */
					else
					{
						ftup = SearchSysCacheTuple(PRONAME,
											   PointerGetDatum(funcname),
												   Int32GetDatum(nargs),
										  PointerGetDatum(*true_typeids),
												   0);
						Assert(HeapTupleIsValid(ftup));
					}
				}
				current_input_typeids = *input_typeid_vector++;
			}
			while (current_input_typeids != InvalidOid && ncandidates == 0);
		}
	}

	if (!HeapTupleIsValid(ftup))
	{
		Type		tp;

		if (nargs == 1)
		{
			tp = typeidType(oid_array[0]);
			if (typeTypeFlag(tp) == 'c')
				elog(ERROR, "No such attribute or function '%s'", funcname);
		}
	}
	else
	{
		pform = (Form_pg_proc) GETSTRUCT(ftup);
		*funcid = ftup->t_data->t_oid;
		*rettype = pform->prorettype;
		*retset = pform->proretset;

		return true;
	}

	/* shouldn't reach here */
	return false;
}	/* func_get_detail() */

/*
 *	argtype_inherit() -- Construct an argtype vector reflecting the
 *						 inheritance properties of the supplied argv.
 *
 *		This function is used to disambiguate among functions with the
 *		same name but different signatures.  It takes an array of eight
 *		type ids.  For each type id in the array that's a complex type
 *		(a class), it walks up the inheritance tree, finding all
 *		superclasses of that type.	A vector of new Oid type arrays