vacuumlazy.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

					/* This is an expected case during concurrent vacuum */
					break;
				case HEAPTUPLE_DELETE_IN_PROGRESS:
					/* This is an expected case during concurrent vacuum */
					break;
				default:
					elog(ERROR, "unexpected HeapTupleSatisfiesVacuum result");
					break;
			}

			if (tupgone)
			{
				lazy_record_dead_tuple(vacrelstats, &(tuple.t_self));
				tups_vacuumed += 1;
			}
			else
			{
				num_tuples += 1;
				hastup = true;
			}
		}						/* scan along page */

		/*
		 * If we remembered any tuples for deletion, then the page will be
		 * visited again by lazy_vacuum_heap, which will compute and record
		 * its post-compaction free space.	If not, then we're done with this
		 * page, so remember its free space as-is.
		 */
		if (vacrelstats->num_dead_tuples == prev_dead_count)
		{
			lazy_record_free_space(vacrelstats, blkno,
								   PageGetFreeSpace(page));
		}

		/* Remember the location of the last page with nonremovable tuples */
		if (hastup)
			vacrelstats->nonempty_pages = blkno + 1;

		LockBuffer(buf, BUFFER_LOCK_UNLOCK);

		if (pgchanged)
			WriteBuffer(buf);
		else
			ReleaseBuffer(buf);
	}

	/* save stats for use later */
	vacrelstats->rel_tuples = num_tuples;
	vacrelstats->tuples_deleted = tups_vacuumed;

	/* If any tuples need to be deleted, perform final vacuum cycle */
	/* XXX put a threshold on min number of tuples here? */
	if (vacrelstats->num_dead_tuples > 0)
	{
		/* Remove index entries */
		for (i = 0; i < nindexes; i++)
			lazy_vacuum_index(Irel[i],
							  &index_tups_vacuumed[i],
							  &index_pages_removed[i],
							  vacrelstats);
		/* Remove tuples from heap */
		lazy_vacuum_heap(onerel, vacrelstats);
	}
	else if (!did_vacuum_index)
	{
		/* Must do post-vacuum cleanup and statistics update anyway */
		for (i = 0; i < nindexes; i++)
			lazy_scan_index(Irel[i], vacrelstats);
	}

	ereport(elevel,
			(errmsg("\"%s\": found %.0f removable, %.0f nonremovable row versions in %u pages",
					RelationGetRelationName(onerel),
					tups_vacuumed, num_tuples, nblocks),
			 errdetail("%.0f dead row versions cannot be removed yet.\n"
					   "There were %.0f unused item pointers.\n"
					   "%u pages are entirely empty.\n"
					   "%s.",
					   nkeep,
					   nunused,
					   empty_pages,
					   pg_rusage_show(&ru0))));
}


/*
 *	lazy_vacuum_heap() -- second pass over the heap
 *
 *		This routine marks dead tuples as unused and compacts out free
 *		space on their pages.  Pages not having dead tuples recorded from
 *		lazy_scan_heap are not visited at all.
 *
 * Note: the reason for doing this as a second pass is we cannot remove
 * the tuples until we've removed their index entries, and we want to
 * process index entry removal in batches as large as possible.
 */
static void
lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats)
{
	int			tupindex;
	int			npages;
	PGRUsage	ru0;

	pg_rusage_init(&ru0);
	npages = 0;

	tupindex = 0;
	while (tupindex < vacrelstats->num_dead_tuples)
	{
		BlockNumber tblk;
		Buffer		buf;
		Page		page;

		vacuum_delay_point();

		tblk = ItemPointerGetBlockNumber(&vacrelstats->dead_tuples[tupindex]);
		buf = ReadBuffer(onerel, tblk);
		LockBufferForCleanup(buf);
		tupindex = lazy_vacuum_page(onerel, tblk, buf, tupindex, vacrelstats);
		/* Now that we've compacted the page, record its available space */
		page = BufferGetPage(buf);
		lazy_record_free_space(vacrelstats, tblk,
							   PageGetFreeSpace(page));
		LockBuffer(buf, BUFFER_LOCK_UNLOCK);
		WriteBuffer(buf);
		npages++;
	}

	ereport(elevel,
			(errmsg("\"%s\": removed %d row versions in %d pages",
					RelationGetRelationName(onerel),
					tupindex, npages),
			 errdetail("%s.",
					   pg_rusage_show(&ru0))));
}

/*
 *	lazy_vacuum_page() -- free dead tuples on a page
 *					 and repair its fragmentation.
 *
 * Caller is expected to handle reading, locking, and writing the buffer.
 *
 * tupindex is the index in vacrelstats->dead_tuples of the first dead
 * tuple for this page.  We assume the rest follow sequentially.
 * The return value is the first tupindex after the tuples of this page.
 */
static int
lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer,
				 int tupindex, LVRelStats *vacrelstats)
{
	OffsetNumber unused[MaxOffsetNumber];
	int			uncnt;
	Page		page = BufferGetPage(buffer);
	ItemId		itemid;

	START_CRIT_SECTION();
	for (; tupindex < vacrelstats->num_dead_tuples; tupindex++)
	{
		BlockNumber tblk;
		OffsetNumber toff;

		tblk = ItemPointerGetBlockNumber(&vacrelstats->dead_tuples[tupindex]);
		if (tblk != blkno)
			break;				/* past end of tuples for this block */
		toff = ItemPointerGetOffsetNumber(&vacrelstats->dead_tuples[tupindex]);
		itemid = PageGetItemId(page, toff);
		itemid->lp_flags &= ~LP_USED;
	}

	uncnt = PageRepairFragmentation(page, unused);

	/* XLOG stuff */
	if (!onerel->rd_istemp)
	{
		XLogRecPtr	recptr;

		recptr = log_heap_clean(onerel, buffer, unused, uncnt);
		PageSetLSN(page, recptr);
		PageSetTLI(page, ThisTimeLineID);
	}
	else
	{
		/* No XLOG record, but still need to flag that XID exists on disk */
		MyXactMadeTempRelUpdate = true;
	}

	END_CRIT_SECTION();

	return tupindex;
}

/*
 *	lazy_scan_index() -- scan one index relation to update pg_class statistic.
 *
 * We use this when we have no deletions to do.
 */
static void
lazy_scan_index(Relation indrel, LVRelStats *vacrelstats)
{
	IndexBulkDeleteResult *stats;
	IndexVacuumCleanupInfo vcinfo;
	PGRUsage	ru0;

	pg_rusage_init(&ru0);

	/*
	 * Acquire appropriate type of lock on index: must be exclusive if index
	 * AM isn't concurrent-safe.
	 */
	if (indrel->rd_am->amconcurrent)
		LockRelation(indrel, RowExclusiveLock);
	else
		LockRelation(indrel, AccessExclusiveLock);

	/*
	 * Even though we're not planning to delete anything, we use the
	 * ambulkdelete call, because (a) the scan happens within the index AM for
	 * more speed, and (b) it may want to pass private statistics to the
	 * amvacuumcleanup call.
	 */
	stats = index_bulk_delete(indrel, dummy_tid_reaped, NULL);

	/* Do post-VACUUM cleanup, even though we deleted nothing */
	vcinfo.vacuum_full = false;
	vcinfo.message_level = elevel;

	stats = index_vacuum_cleanup(indrel, &vcinfo, stats);

	/*
	 * Release lock acquired above.
	 */
	if (indrel->rd_am->amconcurrent)
		UnlockRelation(indrel, RowExclusiveLock);
	else
		UnlockRelation(indrel, AccessExclusiveLock);

	if (!stats)
		return;

	/* now update statistics in pg_class */
	vac_update_relstats(RelationGetRelid(indrel),
						stats->num_pages,
						stats->num_index_tuples,
						false);

	ereport(elevel,
			(errmsg("index \"%s\" now contains %.0f row versions in %u pages",
					RelationGetRelationName(indrel),
					stats->num_index_tuples,
					stats->num_pages),
	errdetail("%u index pages have been deleted, %u are currently reusable.\n"
			  "%s.",
			  stats->pages_deleted, stats->pages_free,
			  pg_rusage_show(&ru0))));

	pfree(stats);
}

/*
 *	lazy_vacuum_index() -- vacuum one index relation.
 *
 *		Delete all the index entries pointing to tuples listed in
 *		vacrelstats->dead_tuples.
 *
 *		Increment *index_tups_vacuumed by the number of index entries
 *		removed, and *index_pages_removed by the number of pages removed.
 *
 *		Finally, we arrange to update the index relation's statistics in
 *		pg_class.
 */
static void
lazy_vacuum_index(Relation indrel,
				  double *index_tups_vacuumed,
				  BlockNumber *index_pages_removed,
				  LVRelStats *vacrelstats)
{
	IndexBulkDeleteResult *stats;
	IndexVacuumCleanupInfo vcinfo;
	PGRUsage	ru0;

	pg_rusage_init(&ru0);

	/*
	 * Acquire appropriate type of lock on index: must be exclusive if index
	 * AM isn't concurrent-safe.
	 */
	if (indrel->rd_am->amconcurrent)
		LockRelation(indrel, RowExclusiveLock);
	else
		LockRelation(indrel, AccessExclusiveLock);

	/* Do bulk deletion */
	stats = index_bulk_delete(indrel, lazy_tid_reaped, (void *) vacrelstats);

	/* Do post-VACUUM cleanup */
	vcinfo.vacuum_full = false;
	vcinfo.message_level = elevel;

	stats = index_vacuum_cleanup(indrel, &vcinfo, stats);

	/*
	 * Release lock acquired above.
	 */
	if (indrel->rd_am->amconcurrent)
		UnlockRelation(indrel, RowExclusiveLock);
	else
		UnlockRelation(indrel, AccessExclusiveLock);

	if (!stats)
		return;

	/* accumulate total removed over multiple index-cleaning cycles */
	*index_tups_vacuumed += stats->tuples_removed;
	*index_pages_removed += stats->pages_removed;

	/* now update statistics in pg_class */
	vac_update_relstats(RelationGetRelid(indrel),
						stats->num_pages,
						stats->num_index_tuples,
						false);

	ereport(elevel,
			(errmsg("index \"%s\" now contains %.0f row versions in %u pages",
					RelationGetRelationName(indrel),
					stats->num_index_tuples,
					stats->num_pages),
			 errdetail("%.0f index row versions were removed.\n"
			 "%u index pages have been deleted, %u are currently reusable.\n"
					   "%s.",
					   stats->tuples_removed,
					   stats->pages_deleted, stats->pages_free,
					   pg_rusage_show(&ru0))));

	pfree(stats);
}

/*
 * lazy_truncate_heap - try to truncate off any empty pages at the end
 */
static void
lazy_truncate_heap(Relation onerel, LVRelStats *vacrelstats)
{
	BlockNumber old_rel_pages = vacrelstats->rel_pages;
	BlockNumber new_rel_pages;
	PageFreeSpaceInfo *pageSpaces;
	int			n;
	int			i,
				j;
	PGRUsage	ru0;

	pg_rusage_init(&ru0);

	/*
	 * We need full exclusive lock on the relation in order to do truncation.
	 * If we can't get it, give up rather than waiting --- we don't want to
	 * block other backends, and we don't want to deadlock (which is quite
	 * possible considering we already hold a lower-grade lock).
	 */
	if (!ConditionalLockRelation(onerel, AccessExclusiveLock))
		return;

	/*
	 * Now that we have exclusive lock, look to see if the rel has grown
	 * whilst we were vacuuming with non-exclusive lock.  If so, give up; the
	 * newly added pages presumably contain non-deletable tuples.
	 */
	new_rel_pages = RelationGetNumberOfBlocks(onerel);
	if (new_rel_pages != old_rel_pages)
	{
		/* might as well use the latest news when we update pg_class stats */
		vacrelstats->rel_pages = new_rel_pages;
		UnlockRelation(onerel, AccessExclusiveLock);
		return;
	}

	/*
	 * Scan backwards from the end to verify that the end pages actually
	 * contain nothing we need to keep.  This is *necessary*, not optional,
	 * because other backends could have added tuples to these pages whilst we
	 * were vacuuming.
	 */
	new_rel_pages = count_nondeletable_pages(onerel, vacrelstats);

	if (new_rel_pages >= old_rel_pages)
	{
		/* can't do anything after all */
		UnlockRelation(onerel, AccessExclusiveLock);
		return;
	}

	/*
	 * Okay to truncate.
	 */
	RelationTruncate(onerel, new_rel_pages);

	/*
	 * Drop free-space info for removed blocks; these must not get entered
	 * into the FSM!
	 */
	pageSpaces = vacrelstats->free_pages;
	n = vacrelstats->num_free_pages;
	j = 0;
	for (i = 0; i < n; i++)
	{