heap.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

		object.objectSubId = 0;

		performDeletion(&object, behavior);

		found = true;
	}

	systable_endscan(scan);
	heap_close(attrdef_rel, RowExclusiveLock);

	if (complain && !found)
		elog(ERROR, "could not find attrdef tuple for relation %u attnum %d",
			 relid, attnum);
}

/*
 *		RemoveAttrDefaultById
 *
 * Remove a pg_attrdef entry specified by OID.	This is the guts of
 * attribute-default removal.  Note it should be called via performDeletion,
 * not directly.
 */
void
RemoveAttrDefaultById(Oid attrdefId)
{
	Relation	attrdef_rel;
	Relation	attr_rel;
	Relation	myrel;
	ScanKeyData scankeys[1];
	SysScanDesc scan;
	HeapTuple	tuple;
	Oid			myrelid;
	AttrNumber	myattnum;

	/* Grab an appropriate lock on the pg_attrdef relation */
	attrdef_rel = heap_open(AttrDefaultRelationId, RowExclusiveLock);

	/* Find the pg_attrdef tuple */
	ScanKeyInit(&scankeys[0],
				ObjectIdAttributeNumber,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(attrdefId));

	scan = systable_beginscan(attrdef_rel, AttrDefaultOidIndexId, true,
							  SnapshotNow, 1, scankeys);

	tuple = systable_getnext(scan);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "could not find tuple for attrdef %u", attrdefId);

	myrelid = ((Form_pg_attrdef) GETSTRUCT(tuple))->adrelid;
	myattnum = ((Form_pg_attrdef) GETSTRUCT(tuple))->adnum;

	/* Get an exclusive lock on the relation owning the attribute */
	myrel = relation_open(myrelid, AccessExclusiveLock);

	/* Now we can delete the pg_attrdef row */
	simple_heap_delete(attrdef_rel, &tuple->t_self);

	systable_endscan(scan);
	heap_close(attrdef_rel, RowExclusiveLock);

	/* Fix the pg_attribute row */
	attr_rel = heap_open(AttributeRelationId, RowExclusiveLock);

	tuple = SearchSysCacheCopy(ATTNUM,
							   ObjectIdGetDatum(myrelid),
							   Int16GetDatum(myattnum),
							   0, 0);
	if (!HeapTupleIsValid(tuple))		/* shouldn't happen */
		elog(ERROR, "cache lookup failed for attribute %d of relation %u",
			 myattnum, myrelid);

	((Form_pg_attribute) GETSTRUCT(tuple))->atthasdef = false;

	simple_heap_update(attr_rel, &tuple->t_self, tuple);

	/* keep the system catalog indexes current */
	CatalogUpdateIndexes(attr_rel, tuple);

	/*
	 * Our update of the pg_attribute row will force a relcache rebuild, so
	 * there's nothing else to do here.
	 */
	heap_close(attr_rel, RowExclusiveLock);

	/* Keep lock on attribute's rel until end of xact */
	relation_close(myrel, NoLock);
}

/*
 * heap_drop_with_catalog	- removes specified relation from catalogs
 *
 * Note that this routine is not responsible for dropping objects that are
 * linked to the pg_class entry via dependencies (for example, indexes and
 * constraints).  Those are deleted by the dependency-tracing logic in
 * dependency.c before control gets here.  In general, therefore, this routine
 * should never be called directly; go through performDeletion() instead.
 */
void
heap_drop_with_catalog(Oid relid)
{
	Relation	rel;

	/*
	 * Open and lock the relation.
	 */
	rel = relation_open(relid, AccessExclusiveLock);

	/*
	 * Schedule unlinking of the relation's physical file at commit.
	 */
	if (rel->rd_rel->relkind != RELKIND_VIEW &&
		rel->rd_rel->relkind != RELKIND_COMPOSITE_TYPE)
	{
		RelationOpenSmgr(rel);
		smgrscheduleunlink(rel->rd_smgr, rel->rd_istemp);
	}

	/*
	 * Close relcache entry, but *keep* AccessExclusiveLock on the relation
	 * until transaction commit.  This ensures no one else will try to do
	 * something with the doomed relation.
	 */
	relation_close(rel, NoLock);

	/*
	 * Forget any ON COMMIT action for the rel
	 */
	remove_on_commit_action(relid);

	/*
	 * Flush the relation from the relcache.  We want to do this before
	 * starting to remove catalog entries, just to be certain that no relcache
	 * entry rebuild will happen partway through.  (That should not really
	 * matter, since we don't do CommandCounterIncrement here, but let's be
	 * safe.)
	 */
	RelationForgetRelation(relid);

	/*
	 * remove inheritance information
	 */
	RelationRemoveInheritance(relid);

	/*
	 * delete statistics
	 */
	RemoveStatistics(relid, 0);

	/*
	 * delete attribute tuples
	 */
	DeleteAttributeTuples(relid);

	/*
	 * delete relation tuple
	 */
	DeleteRelationTuple(relid);
}


/*
 * Store a default expression for column attnum of relation rel.
 * The expression must be presented as a nodeToString() string.
 */
void
StoreAttrDefault(Relation rel, AttrNumber attnum, char *adbin)
{
	Node	   *expr;
	char	   *adsrc;
	Relation	adrel;
	HeapTuple	tuple;
	Datum		values[4];
	static char nulls[4] = {' ', ' ', ' ', ' '};
	Relation	attrrel;
	HeapTuple	atttup;
	Form_pg_attribute attStruct;
	Oid			attrdefOid;
	ObjectAddress colobject,
				defobject;

	/*
	 * Need to construct source equivalent of given node-string.
	 */
	expr = stringToNode(adbin);

	/*
	 * deparse it
	 */
	adsrc = deparse_expression(expr,
							deparse_context_for(RelationGetRelationName(rel),
												RelationGetRelid(rel)),
							   false, false);

	/*
	 * Make the pg_attrdef entry.
	 */
	values[Anum_pg_attrdef_adrelid - 1] = RelationGetRelid(rel);
	values[Anum_pg_attrdef_adnum - 1] = attnum;
	values[Anum_pg_attrdef_adbin - 1] = DirectFunctionCall1(textin,
													 CStringGetDatum(adbin));
	values[Anum_pg_attrdef_adsrc - 1] = DirectFunctionCall1(textin,
													 CStringGetDatum(adsrc));

	adrel = heap_open(AttrDefaultRelationId, RowExclusiveLock);

	tuple = heap_formtuple(adrel->rd_att, values, nulls);
	attrdefOid = simple_heap_insert(adrel, tuple);

	CatalogUpdateIndexes(adrel, tuple);

	defobject.classId = AttrDefaultRelationId;
	defobject.objectId = attrdefOid;
	defobject.objectSubId = 0;

	heap_close(adrel, RowExclusiveLock);

	/* now can free some of the stuff allocated above */
	pfree(DatumGetPointer(values[Anum_pg_attrdef_adbin - 1]));
	pfree(DatumGetPointer(values[Anum_pg_attrdef_adsrc - 1]));
	heap_freetuple(tuple);
	pfree(adsrc);

	/*
	 * Update the pg_attribute entry for the column to show that a default
	 * exists.
	 */
	attrrel = heap_open(AttributeRelationId, RowExclusiveLock);
	atttup = SearchSysCacheCopy(ATTNUM,
								ObjectIdGetDatum(RelationGetRelid(rel)),
								Int16GetDatum(attnum),
								0, 0);
	if (!HeapTupleIsValid(atttup))
		elog(ERROR, "cache lookup failed for attribute %d of relation %u",
			 attnum, RelationGetRelid(rel));
	attStruct = (Form_pg_attribute) GETSTRUCT(atttup);
	if (!attStruct->atthasdef)
	{
		attStruct->atthasdef = true;
		simple_heap_update(attrrel, &atttup->t_self, atttup);
		/* keep catalog indexes current */
		CatalogUpdateIndexes(attrrel, atttup);
	}
	heap_close(attrrel, RowExclusiveLock);
	heap_freetuple(atttup);

	/*
	 * Make a dependency so that the pg_attrdef entry goes away if the column
	 * (or whole table) is deleted.
	 */
	colobject.classId = RelationRelationId;
	colobject.objectId = RelationGetRelid(rel);
	colobject.objectSubId = attnum;

	recordDependencyOn(&defobject, &colobject, DEPENDENCY_AUTO);

	/*
	 * Record dependencies on objects used in the expression, too.
	 */
	recordDependencyOnExpr(&defobject, expr, NIL, DEPENDENCY_NORMAL);
}

/*
 * Store a check-constraint expression for the given relation.
 * The expression must be presented as a nodeToString() string.
 *
 * Caller is responsible for updating the count of constraints
 * in the pg_class entry for the relation.
 */
static void
StoreRelCheck(Relation rel, char *ccname, char *ccbin)
{
	Node	   *expr;
	char	   *ccsrc;
	List	   *varList;
	int			keycount;
	int16	   *attNos;

	/*
	 * Convert condition to an expression tree.
	 */
	expr = stringToNode(ccbin);

	/*
	 * deparse it
	 */
	ccsrc = deparse_expression(expr,
							deparse_context_for(RelationGetRelationName(rel),
												RelationGetRelid(rel)),
							   false, false);

	/*
	 * Find columns of rel that are used in ccbin
	 *
	 * NB: pull_var_clause is okay here only because we don't allow subselects
	 * in check constraints; it would fail to examine the contents of
	 * subselects.
	 */
	varList = pull_var_clause(expr, false);
	keycount = list_length(varList);

	if (keycount > 0)
	{
		ListCell   *vl;
		int			i = 0;

		attNos = (int16 *) palloc(keycount * sizeof(int16));
		foreach(vl, varList)
		{
			Var		   *var = (Var *) lfirst(vl);
			int			j;

			for (j = 0; j < i; j++)
				if (attNos[j] == var->varattno)
					break;
			if (j == i)
				attNos[i++] = var->varattno;
		}
		keycount = i;
	}
	else
		attNos = NULL;

	/*
	 * Create the Check Constraint
	 */
	CreateConstraintEntry(ccname,		/* Constraint Name */
						  RelationGetNamespace(rel),	/* namespace */
						  CONSTRAINT_CHECK,		/* Constraint Type */
						  false,	/* Is Deferrable */
						  false,	/* Is Deferred */
						  RelationGetRelid(rel),		/* relation */
						  attNos,		/* attrs in the constraint */
						  keycount,		/* # attrs in the constraint */
						  InvalidOid,	/* not a domain constraint */
						  InvalidOid,	/* Foreign key fields */
						  NULL,
						  0,
						  ' ',
						  ' ',
						  ' ',
						  InvalidOid,	/* no associated index */
						  expr, /* Tree form check constraint */
						  ccbin,	/* Binary form check constraint */
						  ccsrc);		/* Source form check constraint */

	pfree(ccsrc);
}

/*
 * Store defaults and constraints passed in via the tuple constraint struct.
 *
 * NOTE: only pre-cooked expressions will be passed this way, which is to
 * say expressions inherited from an existing relation.  Newly parsed
 * expressions can be added later, by direct calls to StoreAttrDefault
 * and StoreRelCheck (see AddRelationRawConstraints()).
 */
static void
StoreConstraints(Relation rel, TupleDesc tupdesc)
{
	TupleConstr *constr = tupdesc->constr;
	int			i;

	if (!constr)
		return;					/* nothing to do */

	/*
	 * Deparsing of constraint expressions will fail unless the just-created
	 * pg_attribute tuples for this relation are made visible.	So, bump the
	 * command counter.  CAUTION: this will cause a relcache entry rebuild.
	 */
	CommandCounterIncrement();

	for (i = 0; i < constr->num_defval; i++)
		StoreAttrDefault(rel, constr->defval[i].adnum,
						 constr->defval[i].adbin);

	for (i = 0; i < constr->num_check; i++)
		StoreRelCheck(rel, constr->check[i].ccname,
					  constr->check[i].ccbin);

	if (constr->num_check > 0)
		SetRelationNumChecks(rel, constr->num_check);
}

/*
 * AddRelationRawConstraints
 *
 * Add raw (not-yet-transformed) column default expressions and/or constraint
 * check expressions to an existing relation.  This is defined to do both
 * for efficiency in DefineRelation, but of course you can do just one or
 * the other by passing empty lists.
 *
 * rel: relation to be modified
 * rawColDefaults: list of RawColumnDefault structures
 * rawConstraints: list of Constraint nodes
 *
 * All entries in rawColDefaults will be processed.  Entries in rawConstraints
 * will be processed only if they are CONSTR_CHECK type and contain a "raw"
 * expression.
 *
 * Returns a list of CookedConstraint nodes that shows the cooked form of
 * the default and constraint expressions added to the relation.
 *
 * NB: caller should have opened rel with AccessExclusiveLock, and should
 * hold that lock till end of transaction.	Also, we assume the caller has
 * done a CommandCounterIncrement if necessary to make the relation's catalog
 * tuples visible.
 */
List *
AddRelationRawConstraints(Relation rel,
						  List *rawColDefaults,
						  List *rawConstraints)
{
	List	   *cookedConstraints = NIL;
	TupleDesc	tupleDesc;
	TupleConstr *oldconstr;
	int			numoldchecks;
	ParseState *pstate;
	RangeTblEntry *rte;
	int			numchecks;
	List	   *checknames;
	ListCell   *cell;
	Node	   *expr;
	CookedConstraint *cooked;

	/*
	 * Get info about existing constraints.
	 */
	tupleDesc = RelationGetDescr(rel);
	oldconstr = tupleDesc->constr;
	if (oldconstr)
		numoldchecks = oldconstr->num_check;
	else
		numoldchecks = 0;

	/*
	 * Create a dummy ParseState and insert the target relation as its sole
	 * rangetable entry.  We need a ParseState for transformExpr.
	 */
	pstate = make_parsestate(NULL);
	rte = addRangeTableEntryForRelation(pstate,
										rel,
										NULL,
										false,
										true);
	addRTEtoQuery(pstate, rte, true, true, true);

	/*
	 * Process column default expressions.
	 */
	foreach(cell, rawColDefaults)
	{
		RawColumnDefault *colDef = (RawColumnDefault *) lfirst(cell);
		Form_pg_attribute atp = rel->rd_att->attrs[colDef->attnum - 1];

		expr = cookDefault(pstate, colDef->raw_default,
						   atp->atttypid, atp->atttypmod,
						   NameStr(atp->attname));

		StoreAttrDefault(rel, colDef->attnum, nodeToString(expr));

		cooked = (CookedConstraint *) palloc(sizeof(CookedConstraint));
		cooked->contype = CONSTR_DEFAULT;
		cooked->name = NULL;
		cooked->attnum = colDef->attnum;
		cooked->expr = expr;
		cookedConstraints = lappend(cookedConstraints, cooked);
	}

	/*
	 * Process constraint expressions.
	 */
	numchecks = numoldchecks;
	checknames = NIL;
	foreach(cell, rawConstraints)
	{
		Constraint *cdef = (Constraint *) lfirst(cell);
		char	   *ccname;

		if (cdef->contype != CONSTR_CHECK || cdef->raw_expr == NULL)
			continue;
		Assert(cdef->cooked_expr == NULL);

		/*
		 * Transform raw parsetree to executable expression.
		 */
		expr = transformExpr(pstate, cdef->raw_expr);

		/*
		 * Make sure it yields a boolean result.
		 */
		expr = coerce_to_boolean(pstate, expr, "CHECK");

		/*
		 * Make sure no outside relations are referred to.
		 */
		if (list_length(pstate->p_rtable) != 1)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
			errmsg("only table \"%s\" can be referenced in check constraint",
				   RelationGetRelationName(rel))));

		/*
		 * No subplans or aggregates, either...
		 */
		if (pstate->p_hasSubLinks)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("cannot use subquery in check constraint")));
		if (pstate->p_hasAggs)
			ereport(ERROR,
					(errcode(ERRCODE_GROUPING_ERROR),
			   errmsg("cannot use aggregate function in check constraint")));

		/*
		 * Check name uniqueness, or generate a name if none was given.
		 */
		if (cdef->name != NULL)
		{