C++ relation_close函数代码示例

/*
 * 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);
		}

Datum
pg_relation_size_oid(PG_FUNCTION_ARGS)
{
	Oid			relOid = PG_GETARG_OID(0);
	Relation	rel;
	int64		size = 0;
	
	if (GP_ROLE_EXECUTE == Gp_role)
	{
		ereport(ERROR,
				(errcode(ERRCODE_GP_COMMAND_ERROR),
						errmsg("pg_relation_size: cannot be executed in segment")));
	}

	rel = try_relation_open(relOid, AccessShareLock, false);
		
	/*
	 * While we scan pg_class with an MVCC snapshot,
 	 * someone else might drop the table. It's better to return NULL for
	 * already-dropped tables than throw an error and abort the whole query.
	 */
	if (!RelationIsValid(rel))
  		PG_RETURN_NULL();
	
	if (relOid == 0 || rel->rd_node.relNode == 0)
		size = 0;
	else
		size = calculate_relation_size(rel); 
	
	relation_close(rel, AccessShareLock);

	PG_RETURN_INT64(size);
}

/*
 * 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;
}

Datum
currval_oid(PG_FUNCTION_ARGS)
{
	Oid			relid = PG_GETARG_OID(0);
	int64		result;
	SeqTable	elm;
	Relation	seqrel;

	/* open and AccessShareLock sequence */
	init_sequence(relid, &elm, &seqrel);

	if (pg_class_aclcheck(elm->relid, GetUserId(),
						  ACL_SELECT | ACL_USAGE) != ACLCHECK_OK)
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 errmsg("permission denied for sequence %s",
						RelationGetRelationName(seqrel))));

	if (!elm->last_valid)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("currval of sequence \"%s\" is not yet defined in this session",
						RelationGetRelationName(seqrel))));

	result = elm->last;

	relation_close(seqrel, NoLock);

	PG_RETURN_INT64(result);
}

Datum
pg_relation_size(PG_FUNCTION_ARGS)
{
	Oid			relOid = PG_GETARG_OID(0);
	text	   *forkName = PG_GETARG_TEXT_P(1);
	Relation	rel;
	int64		size;

	rel = try_relation_open(relOid, AccessShareLock);

	/*
	 * Before 9.2, we used to throw an error if the relation didn't exist, but
	 * that makes queries like "SELECT pg_relation_size(oid) FROM pg_class"
	 * less robust, because while we scan pg_class with an MVCC snapshot,
	 * someone else might drop the table. It's better to return NULL for
	 * already-dropped tables than throw an error and abort the whole query.
	 */
	if (rel == NULL)
		PG_RETURN_NULL();

	size = calculate_relation_size(&(rel->rd_node), rel->rd_backend,
							  forkname_to_number(text_to_cstring(forkName)));

	relation_close(rel, AccessShareLock);

	PG_RETURN_INT64(size);
}

Datum
lastval(PG_FUNCTION_ARGS)
{
	Relation	seqrel;
	int64		result;

	if (last_used_seq == NULL)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("lastval is not yet defined in this session")));

	/* Someone may have dropped the sequence since the last nextval() */
	if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(last_used_seq->relid)))
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("lastval is not yet defined in this session")));

	seqrel = open_share_lock(last_used_seq);

	/* nextval() must have already been called for this sequence */
	Assert(last_used_seq->last_valid);

	if (pg_class_aclcheck(last_used_seq->relid, GetUserId(),
						  ACL_SELECT | ACL_USAGE) != ACLCHECK_OK)
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 errmsg("permission denied for sequence %s",
						RelationGetRelationName(seqrel))));

	result = last_used_seq->last;
	relation_close(seqrel, NoLock);

	PG_RETURN_INT64(result);
}

/*
 * 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)));
}

/*
 *	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);
		}

/* 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();
}

/*
 * 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);
	}

/*
 * 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);
	}

/*
 * 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;
}

/*
 * create_distributed_table gets a table name, distribution column,
 * distribution method and colocate_with option, then it creates a
 * distributed table.
 */
Datum
create_distributed_table(PG_FUNCTION_ARGS)
{
	Oid relationId = InvalidOid;
	text *distributionColumnText = NULL;
	Oid distributionMethodOid = InvalidOid;
	text *colocateWithTableNameText = NULL;

	Relation relation = NULL;
	char *distributionColumnName = NULL;
	Var *distributionColumn = NULL;
	char distributionMethod = 0;

	char *colocateWithTableName = NULL;

	bool viaDeprecatedAPI = false;

	CheckCitusVersion(ERROR);
	EnsureCoordinator();

	relationId = PG_GETARG_OID(0);
	distributionColumnText = PG_GETARG_TEXT_P(1);
	distributionMethodOid = PG_GETARG_OID(2);
	colocateWithTableNameText = PG_GETARG_TEXT_P(3);

	/*
	 * 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 = try_relation_open(relationId, ExclusiveLock);

	if (relation == NULL)
	{
		ereport(ERROR, (errmsg("could not create distributed table: "
							   "relation does not exist")));
	}

	/*
	 * 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);

	distributionColumnName = text_to_cstring(distributionColumnText);
	distributionColumn = BuildDistributionKeyFromColumnName(relation,
															distributionColumnName);
	distributionMethod = LookupDistributionMethod(distributionMethodOid);

	colocateWithTableName = text_to_cstring(colocateWithTableNameText);

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

	relation_close(relation, NoLock);

	PG_RETURN_VOID();
}

/**
 * Given the oid of a relation, this method calculates reltuples, relpages. This only looks up
 * local information (on master or segments). It produces meaningful values for AO and
 * heap tables and returns [0.0,0.0] for all other relations.
 * Input: 
 * 	relationoid
 * Output:
 * 	array of two values [reltuples,relpages]
 */
Datum
gp_statistics_estimate_reltuples_relpages_oid(PG_FUNCTION_ARGS)
{
	
	float4		relpages = 0.0;		
	float4		reltuples = 0.0;			
	Oid			relOid = PG_GETARG_OID(0);
	Datum		values[2];
	ArrayType   *result;
	
	Relation rel = try_relation_open(relOid, AccessShareLock, false);

	if (rel != NULL)
	{
		if (rel->rd_rel->relkind == RELKIND_RELATION)
		{
			if (RelationIsHeap(rel))
			{
				gp_statistics_estimate_reltuples_relpages_heap(rel, &reltuples, &relpages);
			}
			else if (RelationIsAoRows(rel))
			{
				gp_statistics_estimate_reltuples_relpages_ao_rows(rel, &reltuples, &relpages);
			}
			else if	(RelationIsAoCols(rel))
			{
				gp_statistics_estimate_reltuples_relpages_ao_cs(rel, &reltuples, &relpages);
			}
		}
		else if (rel->rd_rel->relkind == RELKIND_INDEX)
		{
			reltuples = 1.0;
			relpages = RelationGetNumberOfBlocks(rel);
		}
		else
		{
			/**
			 * Should we silently return [0.0,0.0] or error out? Currently, we choose option 1.
			 */
		}
		relation_close(rel, AccessShareLock);
	}
	else
	{
		/**
		 * Should we silently return [0.0,0.0] or error out? Currently, we choose option 1.
		 */
	}
	
	values[0] = Float4GetDatum(reltuples);
	values[1] = Float4GetDatum(relpages);

	result = construct_array(values, 2,
					FLOAT4OID,
					sizeof(float4), true, 'i');

	PG_RETURN_ARRAYTYPE_P(result);
}