parse_coerce.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

}


/* TypeCategory()
 *		Assign a category to the specified type OID.
 *
 * NB: this must not return INVALID_TYPE.
 *
 * XXX This should be moved to system catalog lookups
 * to allow for better type extensibility.
 * - thomas 2001-09-30
 */
CATEGORY
TypeCategory(Oid inType)
{
	CATEGORY	result;

	switch (inType)
	{
		case (BOOLOID):
			result = BOOLEAN_TYPE;
			break;

		case (CHAROID):
		case (NAMEOID):
		case (BPCHAROID):
		case (VARCHAROID):
		case (TEXTOID):
			result = STRING_TYPE;
			break;

		case (BITOID):
		case (VARBITOID):
			result = BITSTRING_TYPE;
			break;

		case (OIDOID):
		case (REGPROCOID):
		case (REGPROCEDUREOID):
		case (REGOPEROID):
		case (REGOPERATOROID):
		case (REGCLASSOID):
		case (REGTYPEOID):
		case (INT2OID):
		case (INT4OID):
		case (INT8OID):
		case (FLOAT4OID):
		case (FLOAT8OID):
		case (NUMERICOID):
		case (CASHOID):
			result = NUMERIC_TYPE;
			break;

		case (DATEOID):
		case (TIMEOID):
		case (TIMETZOID):
		case (ABSTIMEOID):
		case (TIMESTAMPOID):
		case (TIMESTAMPTZOID):
			result = DATETIME_TYPE;
			break;

		case (RELTIMEOID):
		case (TINTERVALOID):
		case (INTERVALOID):
			result = TIMESPAN_TYPE;
			break;

		case (POINTOID):
		case (LSEGOID):
		case (PATHOID):
		case (BOXOID):
		case (POLYGONOID):
		case (LINEOID):
		case (CIRCLEOID):
			result = GEOMETRIC_TYPE;
			break;

		case (INETOID):
		case (CIDROID):
			result = NETWORK_TYPE;
			break;

		case (UNKNOWNOID):
		case (InvalidOid):
			result = UNKNOWN_TYPE;
			break;

		case (RECORDOID):
		case (CSTRINGOID):
		case (ANYOID):
		case (ANYARRAYOID):
		case (VOIDOID):
		case (TRIGGEROID):
		case (LANGUAGE_HANDLEROID):
		case (INTERNALOID):
		case (OPAQUEOID):
		case (ANYELEMENTOID):
			result = GENERIC_TYPE;
			break;

		default:
			result = USER_TYPE;
			break;
	}
	return result;
}	/* TypeCategory() */


/* IsPreferredType()
 *		Check if this type is a preferred type for the given category.
 *
 * If category is INVALID_TYPE, then we'll return TRUE for preferred types
 * of any category; otherwise, only for preferred types of that category.
 *
 * XXX This should be moved to system catalog lookups
 * to allow for better type extensibility.
 * - thomas 2001-09-30
 */
bool
IsPreferredType(CATEGORY category, Oid type)
{
	Oid			preftype;

	if (category == INVALID_TYPE)
		category = TypeCategory(type);
	else if (category != TypeCategory(type))
		return false;

	/*
	 * This switch should agree with TypeCategory(), above.  Note that at this
	 * point, category certainly matches the type.
	 */
	switch (category)
	{
		case (UNKNOWN_TYPE):
		case (GENERIC_TYPE):
			preftype = UNKNOWNOID;
			break;

		case (BOOLEAN_TYPE):
			preftype = BOOLOID;
			break;

		case (STRING_TYPE):
			preftype = TEXTOID;
			break;

		case (BITSTRING_TYPE):
			preftype = VARBITOID;
			break;

		case (NUMERIC_TYPE):
			if (type == OIDOID ||
				type == REGPROCOID ||
				type == REGPROCEDUREOID ||
				type == REGOPEROID ||
				type == REGOPERATOROID ||
				type == REGCLASSOID ||
				type == REGTYPEOID)
				preftype = OIDOID;
			else
				preftype = FLOAT8OID;
			break;

		case (DATETIME_TYPE):
			if (type == DATEOID)
				preftype = TIMESTAMPOID;
			else
				preftype = TIMESTAMPTZOID;
			break;

		case (TIMESPAN_TYPE):
			preftype = INTERVALOID;
			break;

		case (GEOMETRIC_TYPE):
			preftype = type;
			break;

		case (NETWORK_TYPE):
			preftype = INETOID;
			break;

		case (USER_TYPE):
			preftype = type;
			break;

		default:
			elog(ERROR, "unrecognized type category: %d", (int) category);
			preftype = UNKNOWNOID;
			break;
	}

	return (type == preftype);
}	/* IsPreferredType() */


/* IsBinaryCoercible()
 *		Check if srctype is binary-coercible to targettype.
 *
 * This notion allows us to cheat and directly exchange values without
 * going through the trouble of calling a conversion function.	Note that
 * in general, this should only be an implementation shortcut.	Before 7.4,
 * this was also used as a heuristic for resolving overloaded functions and
 * operators, but that's basically a bad idea.
 *
 * As of 7.3, binary coercibility isn't hardwired into the code anymore.
 * We consider two types binary-coercible if there is an implicitly
 * invokable, no-function-needed pg_cast entry.  Also, a domain is always
 * binary-coercible to its base type, though *not* vice versa (in the other
 * direction, one must apply domain constraint checks before accepting the
 * value as legitimate).  We also need to special-case the polymorphic
 * ANYARRAY type.
 *
 * This function replaces IsBinaryCompatible(), which was an inherently
 * symmetric test.	Since the pg_cast entries aren't necessarily symmetric,
 * the order of the operands is now significant.
 */
bool
IsBinaryCoercible(Oid srctype, Oid targettype)
{
	HeapTuple	tuple;
	Form_pg_cast castForm;
	bool		result;

	/* Fast path if same type */
	if (srctype == targettype)
		return true;

	/* If srctype is a domain, reduce to its base type */
	if (OidIsValid(srctype))
		srctype = getBaseType(srctype);

	/* Somewhat-fast path for domain -> base type case */
	if (srctype == targettype)
		return true;

	/* Also accept any array type as coercible to ANYARRAY */
	if (targettype == ANYARRAYOID)
		if (get_element_type(srctype) != InvalidOid)
			return true;

	/* Else look in pg_cast */
	tuple = SearchSysCache(CASTSOURCETARGET,
						   ObjectIdGetDatum(srctype),
						   ObjectIdGetDatum(targettype),
						   0, 0);
	if (!HeapTupleIsValid(tuple))
		return false;			/* no cast */
	castForm = (Form_pg_cast) GETSTRUCT(tuple);

	result = (castForm->castfunc == InvalidOid &&
			  castForm->castcontext == COERCION_CODE_IMPLICIT);

	ReleaseSysCache(tuple);

	return result;
}


/*
 * find_coercion_pathway
 *		Look for a coercion pathway between two types.
 *
 * ccontext determines the set of available casts.
 *
 * If we find a suitable entry in pg_cast, return TRUE, and set *funcid
 * to the castfunc value, which may be InvalidOid for a binary-compatible
 * coercion.
 *
 * NOTE: *funcid == InvalidOid does not necessarily mean that no work is
 * needed to do the coercion; if the target is a domain then we may need to
 * apply domain constraint checking.  If you want to check for a zero-effort
 * conversion then use IsBinaryCoercible().
 */
bool
find_coercion_pathway(Oid targetTypeId, Oid sourceTypeId,
					  CoercionContext ccontext,
					  Oid *funcid)
{
	bool		result = false;
	HeapTuple	tuple;

	*funcid = InvalidOid;

	/* Perhaps the types are domains; if so, look at their base types */
	if (OidIsValid(sourceTypeId))
		sourceTypeId = getBaseType(sourceTypeId);
	if (OidIsValid(targetTypeId))
		targetTypeId = getBaseType(targetTypeId);

	/* Domains are always coercible to and from their base type */
	if (sourceTypeId == targetTypeId)
		return true;

	/* Look in pg_cast */
	tuple = SearchSysCache(CASTSOURCETARGET,
						   ObjectIdGetDatum(sourceTypeId),
						   ObjectIdGetDatum(targetTypeId),
						   0, 0);

	if (HeapTupleIsValid(tuple))
	{
		Form_pg_cast castForm = (Form_pg_cast) GETSTRUCT(tuple);
		CoercionContext castcontext;

		/* convert char value for castcontext to CoercionContext enum */
		switch (castForm->castcontext)
		{
			case COERCION_CODE_IMPLICIT:
				castcontext = COERCION_IMPLICIT;
				break;
			case COERCION_CODE_ASSIGNMENT:
				castcontext = COERCION_ASSIGNMENT;
				break;
			case COERCION_CODE_EXPLICIT:
				castcontext = COERCION_EXPLICIT;
				break;
			default:
				elog(ERROR, "unrecognized castcontext: %d",
					 (int) castForm->castcontext);
				castcontext = 0;	/* keep compiler quiet */
				break;
		}

		/* Rely on ordering of enum for correct behavior here */
		if (ccontext >= castcontext)
		{
			*funcid = castForm->castfunc;
			result = true;
		}

		ReleaseSysCache(tuple);
	}
	else
	{
		/*
		 * If there's no pg_cast entry, perhaps we are dealing with a pair of
		 * array types.  If so, and if the element types have a suitable cast,
		 * use array_type_coerce() or array_type_length_coerce().
		 *
		 * Hack: disallow coercions to oidvector and int2vector, which
		 * otherwise tend to capture coercions that should go to "real" array
		 * types.  We want those types to be considered "real" arrays for many
		 * purposes, but not this one.	(Also, array_type_coerce isn't
		 * guaranteed to produce an output that meets the restrictions of
		 * these datatypes, such as being 1-dimensional.)
		 */
		Oid			targetElemType;
		Oid			sourceElemType;
		Oid			elemfuncid;

		if (targetTypeId == OIDVECTOROID || targetTypeId == INT2VECTOROID)
			return false;

		if ((targetElemType = get_element_type(targetTypeId)) != InvalidOid &&
			(sourceElemType = get_element_type(sourceTypeId)) != InvalidOid)
		{
			if (find_coercion_pathway(targetElemType, sourceElemType,
									  ccontext, &elemfuncid))
			{
				if (!OidIsValid(elemfuncid))
				{
					/* binary-compatible element type conversion */
					*funcid = F_ARRAY_TYPE_COERCE;
				}
				else
				{
					/* does the function take a typmod arg? */
					if (get_func_nargs(elemfuncid) > 1)
						*funcid = F_ARRAY_TYPE_LENGTH_COERCE;
					else
						*funcid = F_ARRAY_TYPE_COERCE;
				}
				result = true;
			}
		}
	}

	return result;
}


/*
 * find_typmod_coercion_function -- does the given type need length coercion?
 *
 * If the target type possesses a pg_cast function from itself to itself,
 * it must need length coercion.
 *
 * "bpchar" (ie, char(N)) and "numeric" are examples of such types.
 *
 * If the given type is a varlena array type, we do not look for a coercion
 * function associated directly with the array type, but instead look for
 * one associated with the element type.  If one exists, we report
 * array_length_coerce() as the coercion function to use.
 */
Oid
find_typmod_coercion_function(Oid typeId)
{
	Oid			funcid = InvalidOid;
	bool		isArray = false;
	Type		targetType;
	Form_pg_type typeForm;
	HeapTuple	tuple;

	targetType = typeidType(typeId);
	typeForm = (Form_pg_type) GETSTRUCT(targetType);

	/* Check for a varlena array type (and not a domain) */
	if (typeForm->typelem != InvalidOid &&
		typeForm->typlen == -1 &&
		typeForm->typtype != 'd')
	{
		/* Yes, switch our attention to the element type */
		typeId = typeForm->typelem;
		isArray = true;
	}
	ReleaseSysCache(targetType);

	/* Look in pg_cast */
	tuple = SearchSysCache(CASTSOURCETARGET,
						   ObjectIdGetDatum(typeId),
						   ObjectIdGetDatum(typeId),
						   0, 0);

	if (HeapTupleIsValid(tuple))
	{
		Form_pg_cast castForm = (Form_pg_cast) GETSTRUCT(tuple);

		funcid = castForm->castfunc;
		ReleaseSysCache(tuple);
	}

	/*
	 * Now, if we did find a coercion function for an array element type,
	 * report array_length_coerce() as the function to use.
	 */
	if (isArray && OidIsValid(funcid))
		funcid = F_ARRAY_LENGTH_COERCE;

	return funcid;
}