heap.c

关系型数据库 Postgresql 6.5.2

	/* ----------------
	 *	first we add the user attributes..
	 * ----------------
	 */
	dpp = tupdesc->attrs;
	for (i = 0; i < natts; i++)
	{
		(*dpp)->attrelid = new_rel_oid;
		(*dpp)->attdisbursion = 0;

		tup = heap_addheader(Natts_pg_attribute,
							 ATTRIBUTE_TUPLE_SIZE,
							 (char *) *dpp);

		heap_insert(rel, tup);

		if (hasindex)
			CatalogIndexInsert(idescs, Num_pg_attr_indices, rel, tup);

		pfree(tup);
		dpp++;
	}

	/* ----------------
	 *	next we add the system attributes..
	 * ----------------
	 */
	dpp = HeapAtt;
	for (i = 0; i < -1 - FirstLowInvalidHeapAttributeNumber; i++)
	{
		(*dpp)->attrelid = new_rel_oid;
		/* (*dpp)->attdisbursion = 0;	   unneeded */

		tup = heap_addheader(Natts_pg_attribute,
							 ATTRIBUTE_TUPLE_SIZE,
							 (char *) *dpp);

		heap_insert(rel, tup);

		if (hasindex)
			CatalogIndexInsert(idescs, Num_pg_attr_indices, rel, tup);

		pfree(tup);
		dpp++;
	}

	heap_close(rel);

	/*
	 * close pg_attribute indices
	 */
	if (hasindex)
		CatalogCloseIndices(Num_pg_attr_indices, idescs);
}

/* --------------------------------
 *		AddNewRelationTuple
 *
 *		this registers the new relation in the catalogs by
 *		adding a tuple to pg_class.
 * --------------------------------
 */
static void
AddNewRelationTuple(Relation pg_class_desc,
					Relation new_rel_desc,
					Oid new_rel_oid,
					unsigned natts,
					char relkind,
					char *temp_relname)
{
	Form_pg_class new_rel_reltup;
	HeapTuple	tup;
	Relation	idescs[Num_pg_class_indices];
	bool		isBootstrap;

	/* ----------------
	 *	first we munge some of the information in our
	 *	uncataloged relation's relation descriptor.
	 * ----------------
	 */
	new_rel_reltup = new_rel_desc->rd_rel;

	/* CHECK should get new_rel_oid first via an insert then use XXX */

	/* ----------------
	 * Here we insert bogus estimates of the size of the new relation.
	 * In reality, of course, the new relation has 0 tuples and pages,
	 * and if we were tracking these statistics accurately then we'd
	 * set the fields that way.  But at present the stats will be updated
	 * only by VACUUM or CREATE INDEX, and the user might insert a lot of
	 * tuples before he gets around to doing either of those.  So, instead
	 * of saying the relation is empty, we insert guesstimates.  The point
	 * is to keep the optimizer from making really stupid choices on
	 * never-yet-vacuumed tables; so the estimates need only be large
	 * enough to discourage the optimizer from using nested-loop plans.
	 * With this hack, nested-loop plans will be preferred only after
	 * the table has been proven to be small by VACUUM or CREATE INDEX.
	 * Maintaining the stats on-the-fly would solve the problem more cleanly,
	 * but the overhead of that would likely cost more than it'd save.
	 * (NOTE: CREATE INDEX inserts the same bogus estimates if it finds the
	 * relation has 0 rows and pages. See index.c.)
	 * ----------------
	 */
	new_rel_reltup->relpages = 10;		/* bogus estimates */
	new_rel_reltup->reltuples = 1000;

	new_rel_reltup->relowner = GetUserId();
	new_rel_reltup->relkind = relkind;
	new_rel_reltup->relnatts = natts;

	/* ----------------
	 *	now form a tuple to add to pg_class
	 *	XXX Natts_pg_class_fixed is a hack - see pg_class.h
	 * ----------------
	 */
	tup = heap_addheader(Natts_pg_class_fixed,
						 CLASS_TUPLE_SIZE,
						 (char *) new_rel_reltup);
	tup->t_data->t_oid = new_rel_oid;

	/* ----------------
	 *	finally insert the new tuple and free it.
	 *
	 *	Note: I have no idea why we do a
	 *			SetProcessingMode(BootstrapProcessing);
	 *		  here -cim 6/14/90
	 * ----------------
	 */
	isBootstrap = IsBootstrapProcessingMode() ? true : false;

	SetProcessingMode(BootstrapProcessing);

	heap_insert(pg_class_desc, tup);

	if (temp_relname)
		create_temp_relation(temp_relname, tup);

	if (!isBootstrap)
	{

		/*
		 * First, open the catalog indices and insert index tuples for the
		 * new relation.
		 */

		CatalogOpenIndices(Num_pg_class_indices, Name_pg_class_indices, idescs);
		CatalogIndexInsert(idescs, Num_pg_class_indices, pg_class_desc, tup);
		CatalogCloseIndices(Num_pg_class_indices, idescs);
		/* now restore processing mode */
		SetProcessingMode(NormalProcessing);
	}

	pfree(tup);
}


/* --------------------------------
 *		AddNewRelationType -
 *
 *		define a complex type corresponding to the new relation
 * --------------------------------
 */
static void
AddNewRelationType(char *typeName, Oid new_rel_oid)
{
	Oid			new_type_oid;

	/*
	 * The sizes are set to oid size because it makes implementing sets
	 * MUCH easier, and no one (we hope) uses these fields to figure out
	 * how much space to allocate for the type. An oid is the type used
	 * for a set definition.  When a user requests a set, what they
	 * actually get is the oid of a tuple in the pg_proc catalog, so the
	 * size of the "set" is the size of an oid. Similarly, byval being
	 * true makes sets much easier, and it isn't used by anything else.
	 * Note the assumption that OIDs are the same size as int4s.
	 */
	new_type_oid = TypeCreate(typeName, /* type name */
							  new_rel_oid,		/* relation oid */
							  typeLen(typeidType(OIDOID)),		/* internal size */
							  typeLen(typeidType(OIDOID)),		/* external size */
							  'c',		/* type-type (catalog) */
							  ',',		/* default array delimiter */
							  "int4in", /* input procedure */
							  "int4out",		/* output procedure */
							  "int4in", /* receive procedure */
							  "int4out",		/* send procedure */
							  NULL,		/* array element type - irrelevent */
							  "-",		/* default type value */
							  (bool) 1, /* passed by value */
							  'i');		/* default alignment */
}

/* --------------------------------
 *		heap_create_with_catalog
 *
 *		creates a new cataloged relation.  see comments above.
 * --------------------------------
 */
Oid
heap_create_with_catalog(char *relname,
						 TupleDesc tupdesc,
						 char relkind,
						 bool istemp)
{
	Relation	pg_class_desc;
	Relation	new_rel_desc;
	Oid			new_rel_oid;
	int			natts = tupdesc->natts;
	char	   *temp_relname = NULL;

	/* ----------------
	 *	sanity checks
	 * ----------------
	 */
	Assert(IsNormalProcessingMode() || IsBootstrapProcessingMode());
	if (natts == 0 || natts > MaxHeapAttributeNumber)
		elog(ERROR, "Number of attributes is out of range"
			 "\n\tFrom 1 to %d attributes may be specified",
			 MaxHeapAttributeNumber);

	CheckAttributeNames(tupdesc);

	/* temp tables can mask non-temp tables */
	if ((!istemp && RelnameFindRelid(relname)) ||
		(istemp && get_temp_rel_by_name(relname) != NULL))
		elog(ERROR, "Relation '%s' already exists", relname);

	/* invalidate cache so non-temp table is masked by temp */
	if (istemp)
	{
		Oid			relid = RelnameFindRelid(relname);

		if (relid != InvalidOid)
			RelationForgetRelation(relid);
	}

	/* save user relation name because heap_create changes it */
	if (istemp)
	{
		temp_relname = pstrdup(relname);		/* save original value */
		relname = palloc(NAMEDATALEN);
		strcpy(relname, temp_relname);	/* heap_create will change this */
	}

	/* ----------------
	 *	ok, relation does not already exist so now we
	 *	create an uncataloged relation and pull its relation oid
	 *	from the newly formed relation descriptor.
	 *
	 *	Note: The call to heap_create() does all the "real" work
	 *	of creating the disk file for the relation.
	 *	This changes relname for noname and temp tables.
	 * ----------------
	 */
	new_rel_desc = heap_create(relname, tupdesc, false, istemp);

	new_rel_oid = new_rel_desc->rd_att->attrs[0]->attrelid;

	/* ----------------
	 *	since defining a relation also defines a complex type,
	 *	we add a new system type corresponding to the new relation.
	 * ----------------
	 */
	AddNewRelationType(relname, new_rel_oid);

	/* ----------------
	 *	now add tuples to pg_attribute for the attributes in
	 *	our new relation.
	 * ----------------
	 */
	AddNewAttributeTuples(new_rel_oid, tupdesc);

	/* ----------------
	 *	now update the information in pg_class.
	 * ----------------
	 */
	pg_class_desc = heap_openr(RelationRelationName);

	AddNewRelationTuple(pg_class_desc,
						new_rel_desc,
						new_rel_oid,
						natts,
						relkind,
						temp_relname);

	StoreConstraints(new_rel_desc);

	if (istemp)
	{
		pfree(relname);
		pfree(temp_relname);
	}

	/* ----------------
	 *	ok, the relation has been cataloged, so close our relations
	 *	and return the oid of the newly created relation.
	 *
	 *	SOMEDAY: fill the STATISTIC relation properly.
	 * ----------------
	 */
	heap_close(new_rel_desc);
	heap_close(pg_class_desc);

	return new_rel_oid;
}


/* ----------------------------------------------------------------
 *		heap_destroy_with_catalog	- removes all record of named relation from catalogs
 *
 *		1)	open relation, check for existence, etc.
 *		2)	remove inheritance information
 *		3)	remove indexes
 *		4)	remove pg_class tuple
 *		5)	remove pg_attribute tuples
 *		6)	remove pg_type tuples
 *		7)	RemoveConstraints ()
 *		8)	unlink relation
 *
 * old comments
 *		Except for vital relations, removes relation from
 *		relation catalog, and related attributes from
 *		attribute catalog (needed?).  (Anything else?)
 *
 *		get proper relation from relation catalog (if not arg)
 *		check if relation is vital (strcmp()/reltype?)
 *		scan attribute catalog deleting attributes of reldesc
 *				(necessary?)
 *		delete relation from relation catalog
 *		(How are the tuples of the relation discarded?)
 *
 *		XXX Must fix to work with indexes.
 *		There may be a better order for doing things.
 *		Problems with destroying a deleted database--cannot create
 *		a struct reldesc without having an open file descriptor.
 * ----------------------------------------------------------------
 */

/* --------------------------------
 *		RelationRemoveInheritance
 *
 *		Note: for now, we cause an exception if relation is a
 *		superclass.  Someday, we may want to allow this and merge
 *		the type info into subclass procedures....	this seems like
 *		lots of work.
 * --------------------------------
 */
static void
RelationRemoveInheritance(Relation relation)
{
	Relation	catalogRelation;
	HeapTuple	tuple;
	HeapScanDesc scan;
	ScanKeyData entry;
	bool		found = false;

	/* ----------------
	 *	open pg_inherits
	 * ----------------
	 */
	catalogRelation = heap_openr(InheritsRelationName);

	/* ----------------
	 *	form a scan key for the subclasses of this class
	 *	and begin scanning
	 * ----------------
	 */
	ScanKeyEntryInitialize(&entry, 0x0, Anum_pg_inherits_inhparent,
						   F_OIDEQ,
						   ObjectIdGetDatum(RelationGetRelid(relation)));

	scan = heap_beginscan(catalogRelation,
						  false,
						  SnapshotNow,
						  1,
						  &entry);

	/* ----------------
	 *	if any subclasses exist, then we disallow the deletion.
	 * ----------------
	 */
	tuple = heap_getnext(scan, 0);
	if (HeapTupleIsValid(tuple))
	{
		heap_endscan(scan);
		heap_close(catalogRelation);

		elog(ERROR, "Relation '%u' inherits '%s'",
			 ((Form_pg_inherits) GETSTRUCT(tuple))->inhrel,
			 RelationGetRelationName(relation));
	}

	/* ----------------
	 *	If we get here, it means the relation has no subclasses
	 *	so we can trash it.  First we remove dead INHERITS tuples.
	 * ----------------
	 */
	entry.sk_attno = Anum_pg_inherits_inhrel;

	scan = heap_beginscan(catalogRelation,
						  false,
						  SnapshotNow,
						  1,
						  &entry);

	while (HeapTupleIsValid(tuple = heap_getnext(scan, 0)))
	{
		heap_delete(catalogRelation, &tuple->t_self, NULL);
		found = true;
	}

	heap_endscan(scan);
	heap_close(catalogRelation);

	/* ----------------
	 *	now remove dead IPL tuples
	 * ----------------
	 */
	catalogRelation = heap_openr(InheritancePrecidenceListRelationName);

	entry.sk_attno = Anum_pg_ipl_iplrel;

	scan = heap_beginscan(catalogRelation,
						  false,
						  SnapshotNow,
						  1,
						  &entry);

	while (HeapTupleIsValid(tuple = heap_getnext(scan, 0)))
		heap_delete(catalogRelation, &tuple->t_self, NULL);

	heap_endscan(scan);
	heap_close(catalogRelation);
}

/* --------------------------------
 *		RelationRemoveIndexes
 *
 * --------------------------------
 */
static void
RelationRemoveIndexes(Relation relation)
{
	Relation	indexRelation;
	HeapTuple	tuple;
	HeapScanDesc scan;
	ScanKeyData entry;

	indexRelation = heap_openr(IndexRelationName);

	ScanKeyEntryInitialize(&entry, 0x0, Anum_pg_index_indrelid,
						   F_OIDEQ,
						   ObjectIdGetDatum(RelationGetRelid(relation)));

	scan = heap_beginscan(indexRelation,
						  false,
						  SnapshotNow,
						  1,
						  &entry);

	while (HeapTupleIsValid(tuple = heap_getnext(scan, 0)))
		index_destroy(((Form_pg_index) GETSTRUCT(tuple))->indexrelid);

	heap_endscan(scan);
	heap_close(indexRelation);
}

/* --------------------------------
 *		DeleteRelationTuple
 *
 * --------------------------------
 */
static void
DeleteRelationTuple(Relation rel)
{
	Relation	pg_class_desc;
	HeapTuple	tup;

	/* ----------------
	 *	open pg_class
	 * ----------------
	 */
	pg_class_desc = heap_openr(RelationRelationName);

	tup = SearchSysCacheTupleCopy(RELOID,
					   ObjectIdGetDatum(rel->rd_att->attrs[0]->attrelid),
								  0, 0, 0);
	if (!HeapTupleIsValid(tup))
	{
		heap_close(pg_class_desc);
		elog(ERROR, "Relation '%s' does not exist",
			 &rel->rd_rel->relname);
	}

	/* ----------------
	 *	delete the relation tuple from pg_class, and finish up.
	 * ----------------
	 */
	heap_delete(pg_class_desc, &tup->t_self, NULL);
	pfree(tup);

	heap_close(pg_class_desc);
}

/* --------------------------------
 *		DeleteAttributeTuples
 *
 * --------------------------------
 */
static void
DeleteAttributeTuples(Relation rel)
{
	Relation	pg_attribute_desc;
	HeapTuple	tup;
	int2		attnum;

	/* ----------------
	 *	open pg_attribute
	 * ----------------
	 */
	pg_attribute_desc = heap_openr(AttributeRelationName);

	/* -----------------
	 * Get a write lock _before_ getting the read lock in the scan
	 * ----------------
	 */
	LockRelation(pg_attribute_desc, AccessExclusiveLock);

	for (attnum = FirstLowInvalidHeapAttributeNumber + 1;
		 attnum <= rel->rd_att->natts;
		 attnum++)
	{
		if (HeapTupleIsValid(tup = SearchSysCacheTupleCopy(ATTNUM,
								 ObjectIdGetDatum(RelationGetRelid(rel)),
												   Int16GetDatum(attnum),
														   0, 0)))
		{
			heap_delete(pg_attribute_desc, &tup->t_self, NULL);
			pfree(tup);
		}
	}

	/* ----------------
	 * Release the write lock
	 * ----------------
	 */
	UnlockRelation(pg_attribute_desc, AccessExclusiveLock);
	heap_close(pg_attribute_desc);
}

/* --------------------------------
 *		DeleteTypeTuple
 *
 *		If the user attempts to destroy a relation and there
 *		exists attributes in other relations of type
 *		"relation we are deleting", then we have to do something
 *		special.  presently we disallow the destroy.
 * --------------------------------
 */
static void
DeleteTypeTuple(Relation rel)
{
	Relation	pg_type_desc;
	HeapScanDesc pg_type_scan;
	Relation	pg_attribute_desc;
	HeapScanDesc pg_attribute_scan;
	ScanKeyData key;
	ScanKeyData attkey;
	HeapTuple	tup;
	HeapTuple	atttup;
	Oid			typoid;

	/* ----------------
	 *	open pg_type
	 * ----------------
	 */
	pg_type_desc = heap_openr(TypeRelationName);