lsyscache.c

来自「postgresql8.3.4源码,开源数据库」· C语言 代码 · 共 2,698 行 · 第 1/5 页

 * or that it is in the database's default tablespace.
 */
Oid
get_rel_tablespace(Oid relid)
{
	HeapTuple	tp;

	tp = SearchSysCache(RELOID,
						ObjectIdGetDatum(relid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_class reltup = (Form_pg_class) GETSTRUCT(tp);
		Oid			result;

		result = reltup->reltablespace;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return InvalidOid;
}


/*				---------- TYPE CACHE ----------						 */

/*
 * get_typisdefined
 *
 *		Given the type OID, determine whether the type is defined
 *		(if not, it's only a shell).
 */
bool
get_typisdefined(Oid typid)
{
	HeapTuple	tp;

	tp = SearchSysCache(TYPEOID,
						ObjectIdGetDatum(typid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
		bool		result;

		result = typtup->typisdefined;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return false;
}

/*
 * get_typlen
 *
 *		Given the type OID, return the length of the type.
 */
int16
get_typlen(Oid typid)
{
	HeapTuple	tp;

	tp = SearchSysCache(TYPEOID,
						ObjectIdGetDatum(typid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
		int16		result;

		result = typtup->typlen;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return 0;
}

/*
 * get_typbyval
 *
 *		Given the type OID, determine whether the type is returned by value or
 *		not.  Returns true if by value, false if by reference.
 */
bool
get_typbyval(Oid typid)
{
	HeapTuple	tp;

	tp = SearchSysCache(TYPEOID,
						ObjectIdGetDatum(typid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
		bool		result;

		result = typtup->typbyval;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return false;
}

/*
 * get_typlenbyval
 *
 *		A two-fer: given the type OID, return both typlen and typbyval.
 *
 *		Since both pieces of info are needed to know how to copy a Datum,
 *		many places need both.	Might as well get them with one cache lookup
 *		instead of two.  Also, this routine raises an error instead of
 *		returning a bogus value when given a bad type OID.
 */
void
get_typlenbyval(Oid typid, int16 *typlen, bool *typbyval)
{
	HeapTuple	tp;
	Form_pg_type typtup;

	tp = SearchSysCache(TYPEOID,
						ObjectIdGetDatum(typid),
						0, 0, 0);
	if (!HeapTupleIsValid(tp))
		elog(ERROR, "cache lookup failed for type %u", typid);
	typtup = (Form_pg_type) GETSTRUCT(tp);
	*typlen = typtup->typlen;
	*typbyval = typtup->typbyval;
	ReleaseSysCache(tp);
}

/*
 * get_typlenbyvalalign
 *
 *		A three-fer: given the type OID, return typlen, typbyval, typalign.
 */
void
get_typlenbyvalalign(Oid typid, int16 *typlen, bool *typbyval,
					 char *typalign)
{
	HeapTuple	tp;
	Form_pg_type typtup;

	tp = SearchSysCache(TYPEOID,
						ObjectIdGetDatum(typid),
						0, 0, 0);
	if (!HeapTupleIsValid(tp))
		elog(ERROR, "cache lookup failed for type %u", typid);
	typtup = (Form_pg_type) GETSTRUCT(tp);
	*typlen = typtup->typlen;
	*typbyval = typtup->typbyval;
	*typalign = typtup->typalign;
	ReleaseSysCache(tp);
}

/*
 * getTypeIOParam
 *		Given a pg_type row, select the type OID to pass to I/O functions
 *
 * Formerly, all I/O functions were passed pg_type.typelem as their second
 * parameter, but we now have a more complex rule about what to pass.
 * This knowledge is intended to be centralized here --- direct references
 * to typelem elsewhere in the code are wrong, if they are associated with
 * I/O calls and not with actual subscripting operations!  (But see
 * bootstrap.c's boot_get_type_io_data() if you need to change this.)
 *
 * As of PostgreSQL 8.1, output functions receive only the value itself
 * and not any auxiliary parameters, so the name of this routine is now
 * a bit of a misnomer ... it should be getTypeInputParam.
 */
Oid
getTypeIOParam(HeapTuple typeTuple)
{
	Form_pg_type typeStruct = (Form_pg_type) GETSTRUCT(typeTuple);

	/*
	 * Array types get their typelem as parameter; everybody else gets their
	 * own type OID as parameter.  (As of 8.2, domains must get their own OID
	 * even if their base type is an array.)
	 */
	if (typeStruct->typtype == TYPTYPE_BASE && OidIsValid(typeStruct->typelem))
		return typeStruct->typelem;
	else
		return HeapTupleGetOid(typeTuple);
}

/*
 * get_type_io_data
 *
 *		A six-fer:	given the type OID, return typlen, typbyval, typalign,
 *					typdelim, typioparam, and IO function OID. The IO function
 *					returned is controlled by IOFuncSelector
 */
void
get_type_io_data(Oid typid,
				 IOFuncSelector which_func,
				 int16 *typlen,
				 bool *typbyval,
				 char *typalign,
				 char *typdelim,
				 Oid *typioparam,
				 Oid *func)
{
	HeapTuple	typeTuple;
	Form_pg_type typeStruct;

	/*
	 * In bootstrap mode, pass it off to bootstrap.c.  This hack allows us to
	 * use array_in and array_out during bootstrap.
	 */
	if (IsBootstrapProcessingMode())
	{
		Oid			typinput;
		Oid			typoutput;

		boot_get_type_io_data(typid,
							  typlen,
							  typbyval,
							  typalign,
							  typdelim,
							  typioparam,
							  &typinput,
							  &typoutput);
		switch (which_func)
		{
			case IOFunc_input:
				*func = typinput;
				break;
			case IOFunc_output:
				*func = typoutput;
				break;
			default:
				elog(ERROR, "binary I/O not supported during bootstrap");
				break;
		}
		return;
	}

	typeTuple = SearchSysCache(TYPEOID,
							   ObjectIdGetDatum(typid),
							   0, 0, 0);
	if (!HeapTupleIsValid(typeTuple))
		elog(ERROR, "cache lookup failed for type %u", typid);
	typeStruct = (Form_pg_type) GETSTRUCT(typeTuple);

	*typlen = typeStruct->typlen;
	*typbyval = typeStruct->typbyval;
	*typalign = typeStruct->typalign;
	*typdelim = typeStruct->typdelim;
	*typioparam = getTypeIOParam(typeTuple);
	switch (which_func)
	{
		case IOFunc_input:
			*func = typeStruct->typinput;
			break;
		case IOFunc_output:
			*func = typeStruct->typoutput;
			break;
		case IOFunc_receive:
			*func = typeStruct->typreceive;
			break;
		case IOFunc_send:
			*func = typeStruct->typsend;
			break;
	}
	ReleaseSysCache(typeTuple);
}

#ifdef NOT_USED
char
get_typalign(Oid typid)
{
	HeapTuple	tp;

	tp = SearchSysCache(TYPEOID,
						ObjectIdGetDatum(typid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
		char		result;

		result = typtup->typalign;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return 'i';
}
#endif

char
get_typstorage(Oid typid)
{
	HeapTuple	tp;

	tp = SearchSysCache(TYPEOID,
						ObjectIdGetDatum(typid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
		char		result;

		result = typtup->typstorage;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return 'p';
}

/*
 * get_typdefault
 *	  Given a type OID, return the type's default value, if any.
 *
 *	  The result is a palloc'd expression node tree, or NULL if there
 *	  is no defined default for the datatype.
 *
 * NB: caller should be prepared to coerce result to correct datatype;
 * the returned expression tree might produce something of the wrong type.
 */
Node *
get_typdefault(Oid typid)
{
	HeapTuple	typeTuple;
	Form_pg_type type;
	Datum		datum;
	bool		isNull;
	Node	   *expr;

	typeTuple = SearchSysCache(TYPEOID,
							   ObjectIdGetDatum(typid),
							   0, 0, 0);
	if (!HeapTupleIsValid(typeTuple))
		elog(ERROR, "cache lookup failed for type %u", typid);
	type = (Form_pg_type) GETSTRUCT(typeTuple);

	/*
	 * typdefault and typdefaultbin are potentially null, so don't try to
	 * access 'em as struct fields. Must do it the hard way with
	 * SysCacheGetAttr.
	 */
	datum = SysCacheGetAttr(TYPEOID,
							typeTuple,
							Anum_pg_type_typdefaultbin,
							&isNull);

	if (!isNull)
	{
		/* We have an expression default */
		expr = stringToNode(DatumGetCString(DirectFunctionCall1(textout,
																datum)));
	}
	else
	{
		/* Perhaps we have a plain literal default */
		datum = SysCacheGetAttr(TYPEOID,
								typeTuple,
								Anum_pg_type_typdefault,
								&isNull);

		if (!isNull)
		{
			char	   *strDefaultVal;

			/* Convert text datum to C string */
			strDefaultVal = DatumGetCString(DirectFunctionCall1(textout,
																datum));
			/* Convert C string to a value of the given type */
			datum = OidInputFunctionCall(type->typinput, strDefaultVal,
										 getTypeIOParam(typeTuple), -1);
			/* Build a Const node containing the value */
			expr = (Node *) makeConst(typid,
									  -1,
									  type->typlen,
									  datum,
									  false,
									  type->typbyval);
			pfree(strDefaultVal);
		}
		else
		{
			/* No default */
			expr = NULL;
		}
	}

	ReleaseSysCache(typeTuple);

	return expr;
}

/*
 * getBaseType
 *		If the given type is a domain, return its base type;
 *		otherwise return the type's own OID.
 */
Oid
getBaseType(Oid typid)
{
	int32		typmod = -1;

	return getBaseTypeAndTypmod(typid, &typmod);
}

/*
 * getBaseTypeAndTypmod
 *		If the given type is a domain, return its base type and typmod;
 *		otherwise return the type's own OID, and leave *typmod unchanged.
 *
 * Note that the "applied typmod" should be -1 for every domain level
 * above the bottommost; therefore, if the passed-in typid is indeed
 * a domain, *typmod should be -1.
 */
Oid
getBaseTypeAndTypmod(Oid typid, int32 *typmod)
{
	/*
	 * We loop to find the bottom base type in a stack of domains.
	 */
	for (;;)
	{
		HeapTuple	tup;
		Form_pg_type typTup;

		tup = SearchSysCache(TYPEOID,
							 ObjectIdGetDatum(typid),
							 0, 0, 0);
		if (!HeapTupleIsValid(tup))
			elog(ERROR, "cache lookup failed for type %u", typid);
		typTup = (Form_pg_type) GETSTRUCT(tup);
		if (typTup->typtype != TYPTYPE_DOMAIN)
		{
			/* Not a domain, so done */
			ReleaseSysCache(tup);
			break;
		}

		Assert(*typmod == -1);
		typid = typTup->typbasetype;
		*typmod = typTup->typtypmod;

		ReleaseSysCache(tup);
	}

	return typid;
}

/*
 * get_typavgwidth
 *
 *	  Given a type OID and a typmod value (pass -1 if typmod is unknown),
 *	  estimate the average width of values of the type.  This is used by
 *	  the planner, which doesn't require absolutely correct results;
 *	  it's OK (and expected) to guess if we don't know for sure.
 */
int32
get_typavgwidth(Oid typid, int32 typmod)
{
	int			typlen = get_typlen(typid);
	int32		maxwidth;

	/*
	 * Easy if it's a fixed-width type
	 */
	if (typlen > 0)
		return typlen;

	/*
	 * type_maximum_size knows the encoding of typmod for some datatypes;
	 * don't duplicate that knowledge here.
	 */
	maxwidth = type_maximum_size(typid, typmod);
	if (maxwidth > 0)
	{
		/*
		 * For BPCHAR, the max width is also the only width.  Otherwise we
		 * need to guess about the typical data width given the max. A sliding
		 * scale for percentage of max width seems reasonable.
		 */
		if (typid == BPCHAROID)
			return maxwidth;
		if (maxwidth <= 32)
			return maxwidth;	/* assume full width */
		if (maxwidth < 1000)
			return 32 + (maxwidth - 32) / 2;	/* assume 50% */

		/*
		 * Beyond 1000, assume we're looking at something like
		 * "varchar(10000)" where the limit isn't actually reached often, and
		 * use a fixed estimate.
		 */
		return 32 + (1000 - 32) / 2;
	}

	/*
	 * Ooops, we have no idea ... wild guess time.
	 */
	return 32;
}

/*
 * get_typtype
 *
 *		Given the type OID, find if it is a basic type, a complex type, etc.
 *		It returns the null char if the cache lookup fails...
 */
char
get_typtype(Oid typid)
{
	HeapTuple	tp;

	tp = SearchSysCache(TYPEOID,
						ObjectIdGetDatum(typid),
						0, 0, 0);
	if (HeapTupleIsValid(tp))
	{
		Form_pg_type typtup = (Form_pg_type) GETSTRUCT(tp);
		char		result;

		result = typtup->typtype;
		ReleaseSysCache(tp);
		return result;
	}
	else
		return '\0';
}

/*
 * type_is_rowtype
 *
 *		Convenience function to determine whether a type OID represents
 *		a "rowtype" type --- either RECORD or a named composite type.
 */
bool
type_is_rowtype(Oid typid)
{