heap.c

关系型数据库 Postgresql 6.5.2

	/* ----------------
	 *	create a scan key to locate the type tuple corresponding
	 *	to this relation.
	 * ----------------
	 */
	ScanKeyEntryInitialize(&key, 0,
						   Anum_pg_type_typrelid,
						   F_OIDEQ,
						   ObjectIdGetDatum(RelationGetRelid(rel)));

	pg_type_scan = heap_beginscan(pg_type_desc,
								  0,
								  SnapshotNow,
								  1,
								  &key);

	/* ----------------
	 *	use heap_getnext() to fetch the pg_type tuple.	If this
	 *	tuple is not valid then something's wrong.
	 * ----------------
	 */
	tup = heap_getnext(pg_type_scan, 0);

	if (!HeapTupleIsValid(tup))
	{
		heap_endscan(pg_type_scan);
		heap_close(pg_type_desc);
		elog(ERROR, "DeleteTypeTuple: %s type nonexistent",
			 &rel->rd_rel->relname);
	}

	/* ----------------
	 *	now scan pg_attribute.	if any other relations have
	 *	attributes of the type of the relation we are deleteing
	 *	then we have to disallow the deletion.	should talk to
	 *	stonebraker about this.  -cim 6/19/90
	 * ----------------
	 */
	typoid = tup->t_data->t_oid;

	pg_attribute_desc = heap_openr(AttributeRelationName);

	ScanKeyEntryInitialize(&attkey,
						   0,
						   Anum_pg_attribute_atttypid,
						   F_OIDEQ,
						   typoid);

	pg_attribute_scan = heap_beginscan(pg_attribute_desc,
									   0,
									   SnapshotNow,
									   1,
									   &attkey);

	/* ----------------
	 *	try and get a pg_attribute tuple.  if we succeed it means
	 *	we can't delete the relation because something depends on
	 *	the schema.
	 * ----------------
	 */
	atttup = heap_getnext(pg_attribute_scan, 0);

	if (HeapTupleIsValid(atttup))
	{
		Oid			relid = ((Form_pg_attribute) GETSTRUCT(atttup))->attrelid;

		heap_endscan(pg_type_scan);
		heap_close(pg_type_desc);
		heap_endscan(pg_attribute_scan);
		heap_close(pg_attribute_desc);

		elog(ERROR, "DeleteTypeTuple: att of type %s exists in relation %u",
			 &rel->rd_rel->relname, relid);
	}
	heap_endscan(pg_attribute_scan);
	heap_close(pg_attribute_desc);

	/* ----------------
	 *	Ok, it's safe so we delete the relation tuple
	 *	from pg_type and finish up.  But first end the scan so that
	 *	we release the read lock on pg_type.  -mer 13 Aug 1991
	 * ----------------
	 */
	heap_delete(pg_type_desc, &tup->t_self, NULL);

	heap_endscan(pg_type_scan);
	heap_close(pg_type_desc);
}

/* --------------------------------
 *		heap_destroy_with_catalog
 *
 * --------------------------------
 */
void
heap_destroy_with_catalog(char *relname)
{
	Relation	rel;
	Oid			rid;
	bool		istemp = (get_temp_rel_by_name(relname) != NULL);

	/* ----------------
	 *	first open the relation.  if the relation does exist,
	 *	heap_openr() returns NULL.
	 * ----------------
	 */
	rel = heap_openr(relname);
	if (rel == NULL)
		elog(ERROR, "Relation '%s' does not exist", relname);

	LockRelation(rel, AccessExclusiveLock);
	rid = rel->rd_id;

	/* ----------------
	 *	prevent deletion of system relations
	 * ----------------
	 */
	/* allow temp of pg_class? Guess so. */
	if (!istemp &&
		!allowSystemTableMods && IsSystemRelationName(RelationGetRelationName(rel)->data))
		elog(ERROR, "System relation '%s' cannot be destroyed",
			 &rel->rd_rel->relname);

	/* ----------------
	 *	remove inheritance information
	 * ----------------
	 */
	RelationRemoveInheritance(rel);

	/* ----------------
	 *	remove indexes if necessary
	 * ----------------
	 */
	if (rel->rd_rel->relhasindex)
		RelationRemoveIndexes(rel);

	/* ----------------
	 *	remove rules if necessary
	 * ----------------
	 */
	if (rel->rd_rules != NULL)
		RelationRemoveRules(rid);

	/* triggers */
	if (rel->rd_rel->reltriggers > 0)
		RelationRemoveTriggers(rel);

	/* ----------------
	 *	delete attribute tuples
	 * ----------------
	 */
	DeleteAttributeTuples(rel);

	if (istemp)
		remove_temp_relation(rid);

	/* ----------------
	 *	delete type tuple.	here we want to see the effects
	 *	of the deletions we just did, so we use setheapoverride().
	 * ----------------
	 */
	setheapoverride(true);
	DeleteTypeTuple(rel);
	setheapoverride(false);

	/* ----------------
	 *	delete relation tuple
	 * ----------------
	 */
	/* must delete fake tuple in cache */
	DeleteRelationTuple(rel);

	/*
	 * release dirty buffers of this relation
	 */
	ReleaseRelationBuffers(rel);

	/* ----------------
	 *	flush the relation from the relcache
	 * ----------------
	 * Does nothing!!! Flushing moved below.	- vadim 06/04/97
	RelationIdInvalidateRelationCacheByRelationId(rel->rd_id);
	 */

	RemoveConstraints(rel);

	/* ----------------
	 *	unlink the relation and finish up.
	 * ----------------
	 */
	if (!(rel->rd_isnoname) || !(rel->rd_nonameunlinked))
		smgrunlink(DEFAULT_SMGR, rel);

	rel->rd_nonameunlinked = TRUE;

	UnlockRelation(rel, AccessExclusiveLock);

	heap_close(rel);

	RelationForgetRelation(rid);
}

/*
 * heap_destroy
 *	  destroy and close temporary relations
 *
 */

void
heap_destroy(Relation rel)
{
	ReleaseRelationBuffers(rel);
	if (!(rel->rd_isnoname) || !(rel->rd_nonameunlinked))
		smgrunlink(DEFAULT_SMGR, rel);
	rel->rd_nonameunlinked = TRUE;
	heap_close(rel);
	RemoveFromNoNameRelList(rel);
}


/**************************************************************
  functions to deal with the list of temporary relations
**************************************************************/

/* --------------
   InitTempRellist():

   initialize temporary relations list
   the tempRelList is a list of temporary relations that
   are created in the course of the transactions
   they need to be destroyed properly at the end of the transactions

   MODIFIES the global variable tempRels

 >> NOTE <<

   malloc is used instead of palloc because we KNOW when we are
   going to free these things.	Keeps us away from the memory context
   hairyness

*/
void
InitNoNameRelList(void)
{
	if (tempRels)
	{
		free(tempRels->rels);
		free(tempRels);
	}

	tempRels = (TempRelList *) malloc(sizeof(TempRelList));
	tempRels->size = NONAME_REL_LIST_SIZE;
	tempRels->rels = (Relation *) malloc(sizeof(Relation) * tempRels->size);
	MemSet(tempRels->rels, 0, sizeof(Relation) * tempRels->size);
	tempRels->num = 0;
}

/*
   removes a relation from the TempRelList

   MODIFIES the global variable tempRels
	  we don't really remove it, just mark it as NULL
	  and DestroyNoNameRels will look for NULLs
*/
static void
RemoveFromNoNameRelList(Relation r)
{
	int			i;

	if (!tempRels)
		return;

	for (i = 0; i < tempRels->num; i++)
	{
		if (tempRels->rels[i] == r)
		{
			tempRels->rels[i] = NULL;
			break;
		}
	}
}

/*
   add a temporary relation to the TempRelList

   MODIFIES the global variable tempRels
*/
static void
AddToNoNameRelList(Relation r)
{
	if (!tempRels)
		return;

	if (tempRels->num == tempRels->size)
	{
		tempRels->size += NONAME_REL_LIST_SIZE;
		tempRels->rels = realloc(tempRels->rels,
								 sizeof(Relation) * tempRels->size);
	}
	tempRels->rels[tempRels->num] = r;
	tempRels->num++;
}

/*
   go through the tempRels list and destroy each of the relations
*/
void
DestroyNoNameRels(void)
{
	int			i;
	Relation	rel;

	if (!tempRels)
		return;

	for (i = 0; i < tempRels->num; i++)
	{
		rel = tempRels->rels[i];
		/* rel may be NULL if it has been removed from the list already */
		if (rel)
			heap_destroy(rel);
	}
	free(tempRels->rels);
	free(tempRels);
	tempRels = NULL;
}


static void
StoreAttrDefault(Relation rel, AttrDefault *attrdef)
{
	char		str[MAX_PARSE_BUFFER];
	char		cast[2 * NAMEDATALEN] = {0};
	Form_pg_attribute atp = rel->rd_att->attrs[attrdef->adnum - 1];
	List	   *queryTree_list;
	List	   *planTree_list;
	Query	   *query;
	TargetEntry *te;
	Resdom	   *resdom;
	Node	   *expr;
	Oid			type;
	char	   *adbin;
	MemoryContext oldcxt;
	Relation	adrel;
	Relation	idescs[Num_pg_attrdef_indices];
	HeapTuple	tuple;
	Datum		values[4];
	char		nulls[4] = {' ', ' ', ' ', ' '};
	extern GlobalMemory CacheCxt;

start:

	/*
	 * Surround table name with double quotes to allow mixed-case and
	 * whitespaces in names. - BGA 1998-11-14
	 */
	snprintf(str, MAX_PARSE_BUFFER,
			 "select %s%s from \"%.*s\"", attrdef->adsrc, cast,
			 NAMEDATALEN, rel->rd_rel->relname.data);
	setheapoverride(true);
	planTree_list = pg_parse_and_plan(str, NULL, 0,
									  &queryTree_list, None, FALSE);
	setheapoverride(false);
	query = (Query *) lfirst(queryTree_list);

	if (length(query->rtable) > 1 ||
		flatten_tlist(query->targetList) != NIL)
		elog(ERROR, "Cannot use attribute(s) in DEFAULT clause");
	te = (TargetEntry *) lfirst(query->targetList);
	resdom = te->resdom;
	expr = te->expr;
	type = exprType(expr);

	if (type != atp->atttypid)
	{
		if (IS_BINARY_COMPATIBLE(type, atp->atttypid))
			;					/* use without change */
		else if (can_coerce_type(1, &(type), &(atp->atttypid)))
			expr = coerce_type(NULL, (Node *) expr, type, atp->atttypid,
							   atp->atttypmod);
		else if (IsA(expr, Const))
		{
			if (*cast != 0)
				elog(ERROR, "DEFAULT clause const type '%s' mismatched with column type '%s'",
					 typeidTypeName(type), typeidTypeName(atp->atttypid));
			snprintf(cast, 2 * NAMEDATALEN, ":: %s", typeidTypeName(atp->atttypid));
			goto start;
		}
		else
			elog(ERROR, "DEFAULT clause type '%s' mismatched with column type '%s'",
				 typeidTypeName(type), typeidTypeName(atp->atttypid));
	}

	adbin = nodeToString(expr);
	oldcxt = MemoryContextSwitchTo((MemoryContext) CacheCxt);
	attrdef->adbin = pstrdup(adbin);
	(void) MemoryContextSwitchTo(oldcxt);
	pfree(adbin);

	values[Anum_pg_attrdef_adrelid - 1] = rel->rd_id;
	values[Anum_pg_attrdef_adnum - 1] = attrdef->adnum;
	values[Anum_pg_attrdef_adbin - 1] = PointerGetDatum(textin(attrdef->adbin));
	values[Anum_pg_attrdef_adsrc - 1] = PointerGetDatum(textin(attrdef->adsrc));
	adrel = heap_openr(AttrDefaultRelationName);
	tuple = heap_formtuple(adrel->rd_att, values, nulls);
	CatalogOpenIndices(Num_pg_attrdef_indices, Name_pg_attrdef_indices, idescs);
	heap_insert(adrel, tuple);
	CatalogIndexInsert(idescs, Num_pg_attrdef_indices, adrel, tuple);
	CatalogCloseIndices(Num_pg_attrdef_indices, idescs);
	heap_close(adrel);

	pfree(DatumGetPointer(values[Anum_pg_attrdef_adbin - 1]));
	pfree(DatumGetPointer(values[Anum_pg_attrdef_adsrc - 1]));
	pfree(tuple);

}

static void
StoreRelCheck(Relation rel, ConstrCheck *check)
{
	char		str[MAX_PARSE_BUFFER];
	List	   *queryTree_list;
	List	   *planTree_list;
	Query	   *query;
	Plan	   *plan;
	List	   *qual;
	char	   *ccbin;
	MemoryContext oldcxt;
	Relation	rcrel;
	Relation	idescs[Num_pg_relcheck_indices];
	HeapTuple	tuple;
	Datum		values[4];
	char		nulls[4] = {' ', ' ', ' ', ' '};
	extern GlobalMemory CacheCxt;

	/*
	 * Check for table's existance. Surround table name with double-quotes
	 * to allow mixed-case and whitespace names. - thomas 1998-11-12
	 */
	snprintf(str, MAX_PARSE_BUFFER,
			 "select 1 from \"%.*s\" where %s",
			 NAMEDATALEN, rel->rd_rel->relname.data, check->ccsrc);
	setheapoverride(true);
	planTree_list = pg_parse_and_plan(str, NULL, 0,
									  &queryTree_list, None, FALSE);
	setheapoverride(false);
	query = (Query *) lfirst(queryTree_list);

	if (length(query->rtable) > 1)
		elog(ERROR, "Only relation '%.*s' can be referenced",
			 NAMEDATALEN, rel->rd_rel->relname.data);

	plan = (Plan *) lfirst(planTree_list);
	qual = plan->qual;

	ccbin = nodeToString(qual);
	oldcxt = MemoryContextSwitchTo((MemoryContext) CacheCxt);
	check->ccbin = (char *) palloc(strlen(ccbin) + 1);
	strcpy(check->ccbin, ccbin);
	(void) MemoryContextSwitchTo(oldcxt);
	pfree(ccbin);

	values[Anum_pg_relcheck_rcrelid - 1] = rel->rd_id;
	values[Anum_pg_relcheck_rcname - 1] = PointerGetDatum(namein(check->ccname));
	values[Anum_pg_relcheck_rcbin - 1] = PointerGetDatum(textin(check->ccbin));
	values[Anum_pg_relcheck_rcsrc - 1] = PointerGetDatum(textin(check->ccsrc));
	rcrel = heap_openr(RelCheckRelationName);
	tuple = heap_formtuple(rcrel->rd_att, values, nulls);
	CatalogOpenIndices(Num_pg_relcheck_indices, Name_pg_relcheck_indices, idescs);
	heap_insert(rcrel, tuple);
	CatalogIndexInsert(idescs, Num_pg_relcheck_indices, rcrel, tuple);
	CatalogCloseIndices(Num_pg_relcheck_indices, idescs);
	heap_close(rcrel);

	pfree(DatumGetPointer(values[Anum_pg_relcheck_rcname - 1]));
	pfree(DatumGetPointer(values[Anum_pg_relcheck_rcbin - 1]));
	pfree(DatumGetPointer(values[Anum_pg_relcheck_rcsrc - 1]));
	pfree(tuple);

	return;
}

static void
StoreConstraints(Relation rel)
{
	TupleConstr *constr = rel->rd_att->constr;
	int			i;

	if (!constr)
		return;

	if (constr->num_defval > 0)
	{
		for (i = 0; i < constr->num_defval; i++)
			StoreAttrDefault(rel, &(constr->defval[i]));
	}

	if (constr->num_check > 0)
	{
		for (i = 0; i < constr->num_check; i++)
			StoreRelCheck(rel, &(constr->check[i]));
	}

	return;
}

static void
RemoveAttrDefault(Relation rel)
{
	Relation	adrel;
	HeapScanDesc adscan;
	ScanKeyData key;
	HeapTuple	tup;

	adrel = heap_openr(AttrDefaultRelationName);

	ScanKeyEntryInitialize(&key, 0, Anum_pg_attrdef_adrelid,
						   F_OIDEQ, rel->rd_id);

	LockRelation(adrel, AccessExclusiveLock);

	adscan = heap_beginscan(adrel, 0, SnapshotNow, 1, &key);

	while (HeapTupleIsValid(tup = heap_getnext(adscan, 0)))
		heap_delete(adrel, &tup->t_self, NULL);

	heap_endscan(adscan);

	UnlockRelation(adrel, AccessExclusiveLock);
	heap_close(adrel);

}

static void
RemoveRelCheck(Relation rel)
{
	Relation	rcrel;
	HeapScanDesc rcscan;
	ScanKeyData key;
	HeapTuple	tup;

	rcrel = heap_openr(RelCheckRelationName);

	ScanKeyEntryInitialize(&key, 0, Anum_pg_relcheck_rcrelid,
						   F_OIDEQ, rel->rd_id);

	LockRelation(rcrel, AccessExclusiveLock);

	rcscan = heap_beginscan(rcrel, 0, SnapshotNow, 1, &key);

	while (HeapTupleIsValid(tup = heap_getnext(rcscan, 0)))
		heap_delete(rcrel, &tup->t_self, NULL);

	heap_endscan(rcscan);

	UnlockRelation(rcrel, AccessExclusiveLock);
	heap_close(rcrel);

}

static void
RemoveConstraints(Relation rel)
{
	TupleConstr *constr = rel->rd_att->constr;

	if (!constr)
		return;

	if (constr->num_defval > 0)
		RemoveAttrDefault(rel);

	if (constr->num_check > 0)
		RemoveRelCheck(rel);

	return;
}