C++ relation_open函数代码示例

/*
 * Calculate total on-disk size of a TOAST relation, including its index.
 * Must not be applied to non-TOAST relations.
 */
static int64 calculate_toast_table_size(oid_t toastrelid)
{
	int64 size = 0;
	struct relation * toastRel;
	struct relation * toastIdxRel;
	enum fork fnr;

	toastRel = relation_open(toastrelid, ACCESS_SHR_LOCK);

	/* toast heap size, including FSM and VM size */
	for (fnr = 0; fnr <= MAX_FORK_NR; fnr++)
		size += calculate_relation_size(&(toastRel->rd_node),
			toastRel->rd_backend, fnr);

	/* toast index size, including FSM and VM size */
	toastIdxRel = relation_open(toastRel->rd_rel->reltoastidxid, ACCESS_SHR_LOCK);
	for (fnr = 0; fnr <= MAX_FORK_NR; fnr++)
		size += calculate_relation_size(&(toastIdxRel->rd_node),
			toastIdxRel->rd_backend, fnr);

	relation_close(toastIdxRel, ACCESS_SHR_LOCK);
	relation_close(toastRel, ACCESS_SHR_LOCK);

	return size;
}

/*
 * Calculate total on-disk size of all indexes attached to the given table.
 *
 * Can be applied safely to an index, but you'll just get zero.
 */
static int64
calculate_indexes_size(Oid relOid)
{
	int64		size = 0;
	Relation	rel;

	rel = relation_open(relOid, AccessShareLock);

	/*
	 * Aggregate all indexes on the given relation
	 */
	if (rel->rd_rel->relhasindex)
	{
		List	   *index_oids = RelationGetIndexList(rel);
		ListCell   *cell;

		foreach(cell, index_oids)
		{
			Oid			idxOid = lfirst_oid(cell);
			Relation	idxRel;
			ForkNumber	forkNum;

			idxRel = relation_open(idxOid, AccessShareLock);

			for (forkNum = 0; forkNum <= MAX_FORKNUM; forkNum++)
				size += calculate_relation_size(&(idxRel->rd_node),
												idxRel->rd_backend,
												forkNum);

			relation_close(idxRel, AccessShareLock);
		}

/*
 * Calculate total on-disk size of all indexes attached to the given table.
 *
 * Can be applied safely to an index, but you'll just get zero.
 */
static int64 calculate_indexes_size(oid_t relOid)
{
	int64 size = 0;
	struct relation * rel;

	rel = relation_open(relOid, ACCESS_SHR_LOCK);

	/*
	 * Aggregate all indexes on the given relation
	 */
	if (rel->rd_rel->relhasindex) {
		struct list *index_oids = rel_get_index_list(rel);
		struct list_cell *cell;

		foreach(cell, index_oids) {
			oid_t idxOid = lfirst_oid(cell);
			struct relation * idxRel;
			enum fork fnr;

			idxRel = relation_open(idxOid, ACCESS_SHR_LOCK);

			for (fnr = 0; fnr <= MAX_FORK_NR; fnr++)
				size += calculate_relation_size(&(idxRel->rd_node),
					idxRel->rd_backend, fnr);

			relation_close(idxRel, ACCESS_SHR_LOCK);
		}

		list_free(index_oids);
	}

/*
 *	Compute the on-disk size of files for the relation according to the
 *	stat function, including heap data, index data, and toast data.
 */
static int64
calculate_total_relation_size(Oid Relid)
{
	Relation	heapRel;
	Oid			toastOid;
	int64		size;
	ListCell   *cell;

	heapRel = relation_open(Relid, AccessShareLock);
	toastOid = heapRel->rd_rel->reltoastrelid;

	/* Get the heap size */
	size = calculate_relation_size(&(heapRel->rd_node));

	/* Include any dependent indexes */
	if (heapRel->rd_rel->relhasindex)
	{
		List	   *index_oids = RelationGetIndexList(heapRel);

		foreach(cell, index_oids)
		{
			Oid			idxOid = lfirst_oid(cell);
			Relation	iRel;

			iRel = relation_open(idxOid, AccessShareLock);

			size += calculate_relation_size(&(iRel->rd_node));

			relation_close(iRel, AccessShareLock);
		}

/*
 * Calculate total on-disk size of a TOAST relation, including its index.
 * Must not be applied to non-TOAST relations.
 */
static int64
calculate_toast_table_size(Oid toastrelid)
{
	int64		size = 0;
	Relation	toastRel;
	Relation	toastIdxRel;
	ForkNumber	forkNum;

	toastRel = relation_open(toastrelid, AccessShareLock);

	/* toast heap size, including FSM and VM size */
	for (forkNum = 0; forkNum <= MAX_FORKNUM; forkNum++)
		size += calculate_relation_size(&(toastRel->rd_node),
										toastRel->rd_backend, forkNum);

	/* toast index size, including FSM and VM size */
	toastIdxRel = relation_open(toastRel->rd_rel->reltoastidxid, AccessShareLock);
	for (forkNum = 0; forkNum <= MAX_FORKNUM; forkNum++)
		size += calculate_relation_size(&(toastIdxRel->rd_node),
										toastIdxRel->rd_backend, forkNum);

	relation_close(toastIdxRel, AccessShareLock);
	relation_close(toastRel, AccessShareLock);

	return size;
}

/*
 * Calculate total on-disk size of a TOAST relation, including its indexes.
 * Must not be applied to non-TOAST relations.
 */
static int64
calculate_toast_table_size(Oid toastrelid)
{
	int64		size = 0;
	Relation	toastRel;
	ForkNumber	forkNum;
	ListCell   *lc;
	List	   *indexlist;

	toastRel = relation_open(toastrelid, AccessShareLock);

	/* toast heap size, including FSM and VM size */
	for (forkNum = 0; forkNum <= MAX_FORKNUM; forkNum++)
		size += calculate_relation_size(&(toastRel->rd_node),
										toastRel->rd_backend, forkNum);

	/* toast index size, including FSM and VM size */
	indexlist = RelationGetIndexList(toastRel);

	/* Size is calculated using all the indexes available */
	foreach(lc, indexlist)
	{
		Relation	toastIdxRel;

		toastIdxRel = relation_open(lfirst_oid(lc),
									AccessShareLock);
		for (forkNum = 0; forkNum <= MAX_FORKNUM; forkNum++)
			size += calculate_relation_size(&(toastIdxRel->rd_node),
											toastIdxRel->rd_backend, forkNum);

		relation_close(toastIdxRel, AccessShareLock);
	}

/* Returns the relation object for the index that we're going to use as key for a
 * particular table. (Indexes are relations too!) Returns null if the table is unkeyed.
 * The return value is opened with a shared lock; call relation_close() when finished. */
Relation table_key_index(Relation rel) {
    char replident = rel->rd_rel->relreplident;
    Oid repl_ident_oid;
    List *indexes;
    ListCell *index_oid;

    if (replident == REPLICA_IDENTITY_NOTHING) {
        return NULL;
    }

    if (replident == REPLICA_IDENTITY_INDEX) {
        repl_ident_oid = RelationGetReplicaIndex(rel);
        if (repl_ident_oid != InvalidOid) {
            return relation_open(repl_ident_oid, AccessShareLock);
        }
    }

    // There doesn't seem to be a convenient way of getting the primary key index for
    // a table, so we have to iterate over all the table's indexes.
    indexes = RelationGetIndexList(rel);

    foreach(index_oid, indexes) {
        Relation index_rel = relation_open(lfirst_oid(index_oid), AccessShareLock);
        Form_pg_index index = index_rel->rd_index;

        if (IndexIsValid(index) && IndexIsReady(index) && index->indisprimary) {
            list_free(indexes);
            return index_rel;
        }
        relation_close(index_rel, AccessShareLock);
    }

/*
 * Remove the visibility map fork for a relation.  If there turn out to be
 * any bugs in the visibility map code that require rebuilding the VM, this
 * provides users with a way to do it that is cleaner than shutting down the
 * server and removing files by hand.
 *
 * This is a cut-down version of RelationTruncate.
 */
Datum
pg_truncate_visibility_map(PG_FUNCTION_ARGS)
{
    Oid			relid = PG_GETARG_OID(0);
    Relation	rel;

    rel = relation_open(relid, AccessExclusiveLock);

    if (rel->rd_rel->relkind != RELKIND_RELATION &&
            rel->rd_rel->relkind != RELKIND_MATVIEW &&
            rel->rd_rel->relkind != RELKIND_TOASTVALUE)
        ereport(ERROR,
                (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                 errmsg("\"%s\" is not a table, materialized view, or TOAST table",
                        RelationGetRelationName(rel))));

    RelationOpenSmgr(rel);
    rel->rd_smgr->smgr_vm_nblocks = InvalidBlockNumber;

    visibilitymap_truncate(rel, 0);

    if (RelationNeedsWAL(rel))
    {
        xl_smgr_truncate xlrec;

        xlrec.blkno = 0;
        xlrec.rnode = rel->rd_node;
        xlrec.flags = SMGR_TRUNCATE_VM;

        XLogBeginInsert();
        XLogRegisterData((char *) &xlrec, sizeof(xlrec));

        XLogInsert(RM_SMGR_ID, XLOG_SMGR_TRUNCATE | XLR_SPECIAL_REL_UPDATE);
    }

    /*
     * Release the lock right away, not at commit time.
     *
     * It would be a problem to release the lock prior to commit if this
     * truncate operation sends any transactional invalidation messages. Other
     * backends would potentially be able to lock the relation without
     * processing them in the window of time between when we release the lock
     * here and when we sent the messages at our eventual commit.  However,
     * we're currently only sending a non-transactional smgr invalidation,
     * which will have been posted to shared memory immediately from within
     * visibilitymap_truncate.  Therefore, there should be no race here.
     *
     * The reason why it's desirable to release the lock early here is because
     * of the possibility that someone will need to use this to blow away many
     * visibility map forks at once.  If we can't release the lock until
     * commit time, the transaction doing this will accumulate
     * AccessExclusiveLocks on all of those relations at the same time, which
     * is undesirable. However, if this turns out to be unsafe we may have no
     * choice...
     */
    relation_close(rel, AccessExclusiveLock);

    /* Nothing to return. */
    PG_RETURN_VOID();
}

/*
 * Visibility map information for a single block of a relation.
 */
Datum
pg_visibility_map(PG_FUNCTION_ARGS)
{
	Oid			relid = PG_GETARG_OID(0);
	int64		blkno = PG_GETARG_INT64(1);
	int32		mapbits;
	Relation	rel;
	Buffer		vmbuffer = InvalidBuffer;
	TupleDesc	tupdesc;
	Datum		values[2];
	bool		nulls[2];

	rel = relation_open(relid, AccessShareLock);

	if (blkno < 0 || blkno > MaxBlockNumber)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("invalid block number")));

	tupdesc = pg_visibility_tupdesc(false, false);
	MemSet(nulls, 0, sizeof(nulls));

	mapbits = (int32) visibilitymap_get_status(rel, blkno, &vmbuffer);
	if (vmbuffer != InvalidBuffer)
		ReleaseBuffer(vmbuffer);
	values[0] = BoolGetDatum((mapbits & VISIBILITYMAP_ALL_VISIBLE) != 0);
	values[1] = BoolGetDatum((mapbits & VISIBILITYMAP_ALL_FROZEN) != 0);

	relation_close(rel, AccessShareLock);

	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
}

/*
 * Calculate total on-disk size of a given table,
 * including FSM and VM, plus TOAST table if any.
 * Indexes other than the TOAST table's index are not included.
 *
 * Note that this also behaves sanely if applied to an index or toast table;
 * those won't have attached toast tables, but they can have multiple forks.
 */
static int64
calculate_table_size(Oid relOid)
{
	int64		size = 0;
	Relation	rel;
	ForkNumber	forkNum;

	rel = relation_open(relOid, AccessShareLock);

	/*
	 * heap size, including FSM and VM
	 */
	for (forkNum = 0; forkNum <= MAX_FORKNUM; forkNum++)
		size += calculate_relation_size(&(rel->rd_node), rel->rd_backend,
										forkNum);

	/*
	 * Size of toast relation
	 */
	if (OidIsValid(rel->rd_rel->reltoastrelid))
		size += calculate_toast_table_size(rel->rd_rel->reltoastrelid);

	relation_close(rel, AccessShareLock);

	return size;
}

/*
 * Open the sequence and acquire AccessShareLock if needed
 *
 * If we haven't touched the sequence already in this transaction,
 * we need to acquire AccessShareLock.  We arrange for the lock to
 * be owned by the top transaction, so that we don't need to do it
 * more than once per xact.
 */
static Relation
open_share_lock(SeqTable seq)
{
	LocalTransactionId thislxid = MyProc->lxid;

	/* Get the lock if not already held in this xact */
	if (seq->lxid != thislxid)
	{
		ResourceOwner currentOwner;

		currentOwner = CurrentResourceOwner;
		PG_TRY();
		{
			CurrentResourceOwner = TopTransactionResourceOwner;
			LockRelationOid(seq->relid, AccessShareLock);
		}
		PG_CATCH();
		{
			/* Ensure CurrentResourceOwner is restored on error */
			CurrentResourceOwner = currentOwner;
			PG_RE_THROW();
		}
		PG_END_TRY();
		CurrentResourceOwner = currentOwner;

		/* Flag that we have a lock in the current xact */
		seq->lxid = thislxid;
	}

	/* We now know we have AccessShareLock, and can safely open the rel */
	return relation_open(seq->relid, NoLock);
}

/*
 * Collect visibility data about a relation.
 */
static vbits *
collect_visibility_data(Oid relid, bool include_pd)
{
	Relation	rel;
	BlockNumber	nblocks;
	vbits	   *info;
	BlockNumber	blkno;
	Buffer		vmbuffer = InvalidBuffer;
	BufferAccessStrategy	bstrategy = GetAccessStrategy(BAS_BULKREAD);

	rel = relation_open(relid, AccessShareLock);

	nblocks = RelationGetNumberOfBlocks(rel);
	info = palloc0(offsetof(vbits, bits) + nblocks);
	info->next = 0;
	info->count = nblocks;

	for (blkno = 0; blkno < nblocks; ++blkno)
	{
		int32		mapbits;

		/* Make sure we are interruptible. */
		CHECK_FOR_INTERRUPTS();

		/* Get map info. */
		mapbits = (int32) visibilitymap_get_status(rel, blkno, &vmbuffer);
		if ((mapbits & VISIBILITYMAP_ALL_VISIBLE) != 0)
			info->bits[blkno] |= (1 << 0);
		if ((mapbits & VISIBILITYMAP_ALL_FROZEN) != 0)
			info->bits[blkno] |= (1 << 1);

		/*
		 * Page-level data requires reading every block, so only get it if
		 * the caller needs it.  Use a buffer access strategy, too, to prevent
		 * cache-trashing.
		 */
		if (include_pd)
		{
			Buffer		buffer;
			Page		page;

			buffer = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_NORMAL,
										bstrategy);
			LockBuffer(buffer, BUFFER_LOCK_SHARE);

			page = BufferGetPage(buffer, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
			if (PageIsAllVisible(page))
				info->bits[blkno] |= (1 << 2);

			UnlockReleaseBuffer(buffer);
		}
	}

	/* Clean up. */
	if (vmbuffer != InvalidBuffer)
		ReleaseBuffer(vmbuffer);
	relation_close(rel, AccessShareLock);

	return info;
}

/*
 * CreateReferenceTable creates a distributed table with the given relationId. The
 * created table has one shard and replication factor is set to the active worker
 * count. In fact, the above is the definition of a reference table in Citus.
 */
Datum
create_reference_table(PG_FUNCTION_ARGS)
{
	Oid relationId = PG_GETARG_OID(0);

	Relation relation = NULL;
	char *colocateWithTableName = NULL;
	List *workerNodeList = NIL;
	int workerCount = 0;
	Var *distributionColumn = NULL;

	bool viaDeprecatedAPI = false;

	EnsureCoordinator();
	CheckCitusVersion(ERROR);

	/*
	 * Ensure schema exists on each worker node. We can not run this function
	 * transactionally, since we may create shards over separate sessions and
	 * shard creation depends on the schema being present and visible from all
	 * sessions.
	 */
	EnsureSchemaExistsOnAllNodes(relationId);

	/*
	 * Lock target relation with an exclusive lock - there's no way to make
	 * sense of this table until we've committed, and we don't want multiple
	 * backends manipulating this relation.
	 */
	relation = relation_open(relationId, ExclusiveLock);

	/*
	 * We should do this check here since the codes in the following lines rely
	 * on this relation to have a supported relation kind. More extensive checks
	 * will be performed in CreateDistributedTable.
	 */
	EnsureRelationKindSupported(relationId);

	workerNodeList = ActivePrimaryNodeList();
	workerCount = list_length(workerNodeList);

	/* if there are no workers, error out */
	if (workerCount == 0)
	{
		char *relationName = get_rel_name(relationId);

		ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
						errmsg("cannot create reference table \"%s\"", relationName),
						errdetail("There are no active worker nodes.")));
	}

	CreateDistributedTable(relationId, distributionColumn, DISTRIBUTE_BY_NONE,
						   colocateWithTableName, viaDeprecatedAPI);

	relation_close(relation, NoLock);

	PG_RETURN_VOID();
}

Datum
check_SPI_gettype(PG_FUNCTION_ARGS)
{
	int		fnumber = PG_GETARG_INT32(0);
	Relation	rel = relation_open(RelationRelationId, AccessShareLock);
	char		*name = SPI_gettype(RelationGetDescr(rel), fnumber);
	relation_close(rel, AccessShareLock);

	PG_RETURN_TEXT_P(cstring_to_text(name));
}

Datum
lock_test2(PG_FUNCTION_ARGS)
{
	Oid			table_oid;
	text	   *lock_type;
	float8		sleep_time;
	const char *lock_type_str;
	LOCKMODE	lockmode;
	Relation	heapRelation;

	table_oid	= PG_GETARG_OID(0);
	lock_type	= PG_GETARG_TEXT_P(1);
	sleep_time	= PG_GETARG_FLOAT8(2);

	lock_type_str = text_to_cstring(lock_type);

	if (pg_strcasecmp(lock_type_str, "NOLOCK") == 0)
		lockmode = NoLock;
	else if (pg_strcasecmp(lock_type_str, "ACCESSSHARELOCK") == 0)
		lockmode = AccessShareLock;
	else if (pg_strcasecmp(lock_type_str, "ROWSHARELOCK") == 0)
		lockmode = RowShareLock;
	else if (pg_strcasecmp(lock_type_str, "ROWEXCLUSIVELOCK") == 0)
		lockmode = RowExclusiveLock;
	else if (pg_strcasecmp(lock_type_str, "SHAREUPDATEEXCLUSIVELOCK") == 0)
		lockmode = ShareUpdateExclusiveLock;
	else if (pg_strcasecmp(lock_type_str, "SHARELOCK") == 0)
		lockmode = ShareLock;
	else if (pg_strcasecmp(lock_type_str, "SHAREEXCLUSIVELOCK") == 0)
		lockmode = ShareRowExclusiveLock;
	else if (pg_strcasecmp(lock_type_str, "EXCLUSIVELOCK") == 0)
		lockmode = ExclusiveLock;
	else if (pg_strcasecmp(lock_type_str, "ACCESSEXCLUSIVELOCK") == 0)
		lockmode = AccessExclusiveLock;
	else
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("\"lock_mode\" is set to invalid string: %s", lock_type_str),
				 errhint("\"lock_mode\" must select one among NoLock, AccessShareLock, RowShareLock, RowExclusiveLock, ShareUpdateExclusiveLock, ShareLock, ShareExclusiveLock, ExclusiveLock, and AccessExclusiveLock")));

	elog(NOTICE, "enter lock %d as %s", table_oid, lock_type_str);

	heapRelation = relation_open(table_oid, lockmode);

	elog(NOTICE, "succeed locking %d as %s", table_oid, lock_type_str);

	pg_usleep(sleep_time * 1000000L);

	relation_close(heapRelation, lockmode);

	elog(NOTICE, "exit lock %d as %s", table_oid, lock_type_str);

	PG_RETURN_VOID();
}