/*
* _bt_page_recyclable() -- Is an existing page recyclable?
*
* This exists to make sure _bt_getbuf and btvacuumscan have the same
* policy about whether a page is safe to re-use.
*/
bool
_bt_page_recyclable(Page page)
{
BTPageOpaque opaque;
TransactionId cutoff;
/*
* It's possible to find an all-zeroes page in an index --- for example, a
* backend might successfully extend the relation one page and then crash
* before it is able to make a WAL entry for adding the page. If we find a
* zeroed page then reclaim it.
*/
if (PageIsNew(page))
return true;
/*
* Otherwise, recycle if deleted and too old to have any processes
* interested in it. If we are generating records for Hot Standby
* defer page recycling until RecentGlobalXmin to respect user
* controls specified by vacuum_defer_cleanup_age or hot_standby_feedback.
*/
if (XLogStandbyInfoActive())
cutoff = RecentGlobalXmin;
else
cutoff = RecentXmin;
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
if (P_ISDELETED(opaque) &&
TransactionIdPrecedesOrEquals(opaque->btpo.xact, cutoff))
return true;
return false;
}
/*
* Get new XID. For global transaction is it previsly set by dtm_begin_transaction or dtm_join_transaction.
* Local transactions are using range of local Xids obtains from DTM.
*/
static TransactionId DtmGetNextXid()
{
TransactionId xid;
LWLockAcquire(dtm->xidLock, LW_EXCLUSIVE);
if (TransactionIdIsValid(DtmNextXid))
{
XTM_INFO("Use global XID %d\n", DtmNextXid);
xid = DtmNextXid;
if (TransactionIdPrecedesOrEquals(ShmemVariableCache->nextXid, xid))
{
/* Advance ShmemVariableCache->nextXid formward until new Xid */
while (TransactionIdPrecedes(ShmemVariableCache->nextXid, xid))
{
XTM_INFO("Extend CLOG for global transaction to %d\n", ShmemVariableCache->nextXid);
ExtendCLOG(ShmemVariableCache->nextXid);
ExtendCommitTs(ShmemVariableCache->nextXid);
ExtendSUBTRANS(ShmemVariableCache->nextXid);
TransactionIdAdvance(ShmemVariableCache->nextXid);
}
dtm->nReservedXids = 0;
}
}
else
{
if (dtm->nReservedXids == 0)
{
XTM_INFO("%d: reserve new XID range\n", getpid());
dtm->nReservedXids = ArbiterReserve(ShmemVariableCache->nextXid, DtmLocalXidReserve, &dtm->nextXid);
Assert(dtm->nReservedXids > 0);
Assert(TransactionIdFollowsOrEquals(dtm->nextXid, ShmemVariableCache->nextXid));
/* Advance ShmemVariableCache->nextXid formward until new Xid */
while (TransactionIdPrecedes(ShmemVariableCache->nextXid, dtm->nextXid))
{
XTM_INFO("Extend CLOG for local transaction to %d\n", ShmemVariableCache->nextXid);
ExtendCLOG(ShmemVariableCache->nextXid);
ExtendCommitTs(ShmemVariableCache->nextXid);
ExtendSUBTRANS(ShmemVariableCache->nextXid);
TransactionIdAdvance(ShmemVariableCache->nextXid);
}
}
Assert(ShmemVariableCache->nextXid == dtm->nextXid);
xid = dtm->nextXid++;
dtm->nReservedXids -= 1;
XTM_INFO("Obtain new local XID %d\n", xid);
}
LWLockRelease(dtm->xidLock);
return xid;
}
/*
* _bt_page_recyclable() -- Is an existing page recyclable?
*
* This exists to make sure _bt_getbuf and btvacuumcleanup have the same
* policy about whether a page is safe to re-use.
*/
bool
_bt_page_recyclable(Page page)
{
BTPageOpaque opaque;
/*
* It's possible to find an all-zeroes page in an index --- for example, a
* backend might successfully extend the relation one page and then crash
* before it is able to make a WAL entry for adding the page. If we find a
* zeroed page then reclaim it.
*/
if (PageIsNew(page))
return true;
/*
* Otherwise, recycle if deleted and too old to have any processes
* interested in it.
*/
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
if (P_ISDELETED(opaque) &&
TransactionIdPrecedesOrEquals(opaque->btpo.xact, RecentXmin))
return true;
return false;
}
/*
* lazy_vacuum_rel() -- perform LAZY VACUUM for one heap relation
*
* This routine vacuums a single heap, cleans out its indexes, and
* updates its relpages and reltuples statistics.
*
* At entry, we have already established a transaction and opened
* and locked the relation.
*/
void
lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
BufferAccessStrategy bstrategy)
{
LVRelStats *vacrelstats;
Relation *Irel;
int nindexes;
BlockNumber possibly_freeable;
PGRUsage ru0;
TimestampTz starttime = 0;
bool scan_all;
TransactionId freezeTableLimit;
pg_rusage_init(&ru0);
/* measure elapsed time iff autovacuum logging requires it */
if (IsAutoVacuumWorkerProcess() && Log_autovacuum_min_duration > 0)
starttime = GetCurrentTimestamp();
if (vacstmt->options & VACOPT_VERBOSE)
elevel = INFO;
else
elevel = DEBUG2;
vac_strategy = bstrategy;
vacuum_set_xid_limits(vacstmt->freeze_min_age, vacstmt->freeze_table_age,
onerel->rd_rel->relisshared,
&OldestXmin, &FreezeLimit, &freezeTableLimit);
scan_all = TransactionIdPrecedesOrEquals(onerel->rd_rel->relfrozenxid,
freezeTableLimit);
vacrelstats = (LVRelStats *) palloc0(sizeof(LVRelStats));
vacrelstats->old_rel_tuples = onerel->rd_rel->reltuples;
vacrelstats->num_index_scans = 0;
/* Open all indexes of the relation */
vac_open_indexes(onerel, RowExclusiveLock, &nindexes, &Irel);
vacrelstats->hasindex = (nindexes > 0);
/* Do the vacuuming */
lazy_scan_heap(onerel, vacrelstats, Irel, nindexes, scan_all);
/* Done with indexes */
vac_close_indexes(nindexes, Irel, NoLock);
/*
* Optionally truncate the relation.
*
* Don't even think about it unless we have a shot at releasing a goodly
* number of pages. Otherwise, the time taken isn't worth it.
*/
possibly_freeable = vacrelstats->rel_pages - vacrelstats->nonempty_pages;
if (possibly_freeable > 0 &&
(possibly_freeable >= REL_TRUNCATE_MINIMUM ||
possibly_freeable >= vacrelstats->rel_pages / REL_TRUNCATE_FRACTION))
lazy_truncate_heap(onerel, vacrelstats);
/* Vacuum the Free Space Map */
FreeSpaceMapVacuum(onerel);
/*
* Update statistics in pg_class. But don't change relfrozenxid if we
* skipped any pages.
*/
vac_update_relstats(onerel,
vacrelstats->rel_pages, vacrelstats->new_rel_tuples,
vacrelstats->hasindex,
(vacrelstats->scanned_pages < vacrelstats->rel_pages) ?
InvalidTransactionId :
FreezeLimit);
/* report results to the stats collector, too */
pgstat_report_vacuum(RelationGetRelid(onerel),
onerel->rd_rel->relisshared,
vacrelstats->new_rel_tuples);
/* and log the action if appropriate */
if (IsAutoVacuumWorkerProcess() && Log_autovacuum_min_duration >= 0)
{
if (Log_autovacuum_min_duration == 0 ||
TimestampDifferenceExceeds(starttime, GetCurrentTimestamp(),
Log_autovacuum_min_duration))
ereport(LOG,
(errmsg("automatic vacuum of table \"%s.%s.%s\": index scans: %d\n"
"pages: %d removed, %d remain\n"
"tuples: %.0f removed, %.0f remain\n"
"system usage: %s",
get_database_name(MyDatabaseId),
get_namespace_name(RelationGetNamespace(onerel)),
RelationGetRelationName(onerel),
vacrelstats->num_index_scans,
vacrelstats->pages_removed,
vacrelstats->rel_pages,
vacrelstats->tuples_deleted,
vacrelstats->new_rel_tuples,
pg_rusage_show(&ru0))));
}
}
/*
* lazy_vacuum_rel() -- perform LAZY VACUUM for one heap relation
*
* This routine vacuums a single heap, cleans out its indexes, and
* updates its relpages and reltuples statistics.
*
* At entry, we have already established a transaction and opened
* and locked the relation.
*/
void
lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
BufferAccessStrategy bstrategy)
{
LVRelStats *vacrelstats;
Relation *Irel;
int nindexes;
BlockNumber possibly_freeable;
PGRUsage ru0;
TimestampTz starttime = 0;
long secs;
int usecs;
double read_rate,
write_rate;
bool scan_all;
TransactionId freezeTableLimit;
BlockNumber new_rel_pages;
double new_rel_tuples;
BlockNumber new_rel_allvisible;
TransactionId new_frozen_xid;
/* measure elapsed time iff autovacuum logging requires it */
if (IsAutoVacuumWorkerProcess() && Log_autovacuum_min_duration >= 0)
{
pg_rusage_init(&ru0);
starttime = GetCurrentTimestamp();
}
if (vacstmt->options & VACOPT_VERBOSE)
elevel = INFO;
else
elevel = DEBUG2;
vac_strategy = bstrategy;
vacuum_set_xid_limits(vacstmt->freeze_min_age, vacstmt->freeze_table_age,
onerel->rd_rel->relisshared,
&OldestXmin, &FreezeLimit, &freezeTableLimit);
scan_all = TransactionIdPrecedesOrEquals(onerel->rd_rel->relfrozenxid,
freezeTableLimit);
vacrelstats = (LVRelStats *) palloc0(sizeof(LVRelStats));
vacrelstats->old_rel_pages = onerel->rd_rel->relpages;
vacrelstats->old_rel_tuples = onerel->rd_rel->reltuples;
vacrelstats->num_index_scans = 0;
/* Open all indexes of the relation */
vac_open_indexes(onerel, RowExclusiveLock, &nindexes, &Irel);
vacrelstats->hasindex = (nindexes > 0);
/* Do the vacuuming */
lazy_scan_heap(onerel, vacrelstats, Irel, nindexes, scan_all);
/* Done with indexes */
vac_close_indexes(nindexes, Irel, NoLock);
/*
* Optionally truncate the relation.
*
* Don't even think about it unless we have a shot at releasing a goodly
* number of pages. Otherwise, the time taken isn't worth it.
*/
possibly_freeable = vacrelstats->rel_pages - vacrelstats->nonempty_pages;
if (possibly_freeable > 0 &&
(possibly_freeable >= REL_TRUNCATE_MINIMUM ||
possibly_freeable >= vacrelstats->rel_pages / REL_TRUNCATE_FRACTION))
lazy_truncate_heap(onerel, vacrelstats);
/* Vacuum the Free Space Map */
FreeSpaceMapVacuum(onerel);
/*
* Update statistics in pg_class.
*
* A corner case here is that if we scanned no pages at all because every
* page is all-visible, we should not update relpages/reltuples, because
* we have no new information to contribute. In particular this keeps
* us from replacing relpages=reltuples=0 (which means "unknown tuple
* density") with nonzero relpages and reltuples=0 (which means "zero
* tuple density") unless there's some actual evidence for the latter.
*
* We do update relallvisible even in the corner case, since if the
* table is all-visible we'd definitely like to know that. But clamp
* the value to be not more than what we're setting relpages to.
*
* Also, don't change relfrozenxid if we skipped any pages, since then
* we don't know for certain that all tuples have a newer xmin.
*/
new_rel_pages = vacrelstats->rel_pages;
new_rel_tuples = vacrelstats->new_rel_tuples;
if (vacrelstats->scanned_pages == 0 && new_rel_pages > 0)
{
new_rel_pages = vacrelstats->old_rel_pages;
new_rel_tuples = vacrelstats->old_rel_tuples;
}
new_rel_allvisible = visibilitymap_count(onerel);
if (new_rel_allvisible > new_rel_pages)
new_rel_allvisible = new_rel_pages;
new_frozen_xid = FreezeLimit;
if (vacrelstats->scanned_pages < vacrelstats->rel_pages)
new_frozen_xid = InvalidTransactionId;
vac_update_relstats(onerel,
new_rel_pages,
new_rel_tuples,
new_rel_allvisible,
vacrelstats->hasindex,
new_frozen_xid);
/* report results to the stats collector, too */
pgstat_report_vacuum(RelationGetRelid(onerel),
onerel->rd_rel->relisshared,
new_rel_tuples);
/* and log the action if appropriate */
if (IsAutoVacuumWorkerProcess() && Log_autovacuum_min_duration >= 0)
{
TimestampTz endtime = GetCurrentTimestamp();
if (Log_autovacuum_min_duration == 0 ||
TimestampDifferenceExceeds(starttime, endtime,
Log_autovacuum_min_duration))
{
TimestampDifference(starttime, endtime, &secs, &usecs);
read_rate = 0;
write_rate = 0;
if ((secs > 0) || (usecs > 0))
{
read_rate = (double) BLCKSZ * VacuumPageMiss / (1024 * 1024) /
(secs + usecs / 1000000.0);
write_rate = (double) BLCKSZ * VacuumPageDirty / (1024 * 1024) /
(secs + usecs / 1000000.0);
}
ereport(LOG,
(errmsg("automatic vacuum of table \"%s.%s.%s\": index scans: %d\n"
"pages: %d removed, %d remain\n"
"tuples: %.0f removed, %.0f remain\n"
"buffer usage: %d hits, %d misses, %d dirtied\n"
"avg read rate: %.3f MiB/s, avg write rate: %.3f MiB/s\n"
"system usage: %s",
get_database_name(MyDatabaseId),
get_namespace_name(RelationGetNamespace(onerel)),
RelationGetRelationName(onerel),
vacrelstats->num_index_scans,
vacrelstats->pages_removed,
vacrelstats->rel_pages,
vacrelstats->tuples_deleted,
vacrelstats->new_rel_tuples,
VacuumPageHit,
VacuumPageMiss,
VacuumPageDirty,
read_rate,write_rate,
pg_rusage_show(&ru0))));
}
}
}
/*
* Hot Standby feedback
*/
static void
ProcessStandbyHSFeedbackMessage(void)
{
StandbyHSFeedbackMessage reply;
TransactionId newxmin = InvalidTransactionId;
pq_copymsgbytes(&reply_message, (char *) &reply, sizeof(StandbyHSFeedbackMessage));
elog(DEBUG2, "hot standby feedback xmin %u epoch %u",
reply.xmin,
reply.epoch);
/*
* Update the WalSender's proc xmin to allow it to be visible to
* snapshots. This will hold back the removal of dead rows and thereby
* prevent the generation of cleanup conflicts on the standby server.
*/
if (TransactionIdIsValid(reply.xmin))
{
TransactionId nextXid;
uint32 nextEpoch;
bool epochOK = false;
GetNextXidAndEpoch(&nextXid, &nextEpoch);
/*
* Epoch of oldestXmin should be same as standby or if the counter has
* wrapped, then one less than reply.
*/
if (reply.xmin <= nextXid)
{
if (reply.epoch == nextEpoch)
epochOK = true;
}
else
{
if (nextEpoch > 0 && reply.epoch == nextEpoch - 1)
epochOK = true;
}
/*
* Feedback from standby must not go backwards, nor should it go
* forwards further than our most recent xid.
*/
if (epochOK && TransactionIdPrecedesOrEquals(reply.xmin, nextXid))
{
if (!TransactionIdIsValid(MyProc->xmin))
{
TransactionId oldestXmin = GetOldestXmin(true, true);
if (TransactionIdPrecedes(oldestXmin, reply.xmin))
newxmin = reply.xmin;
else
newxmin = oldestXmin;
}
else
{
if (TransactionIdPrecedes(MyProc->xmin, reply.xmin))
newxmin = reply.xmin;
else
newxmin = MyProc->xmin; /* stay the same */
}
}
}
/*
* Grab the ProcArrayLock to set xmin, or invalidate for bad reply
*/
if (MyProc->xmin != newxmin)
{
LWLockAcquire(ProcArrayLock, LW_SHARED);
MyProc->xmin = newxmin;
LWLockRelease(ProcArrayLock);
}
}
/*
* Hot Standby feedback
*/
static void
ProcessStandbyHSFeedbackMessage(void)
{
StandbyHSFeedbackMessage reply;
TransactionId nextXid;
uint32 nextEpoch;
/* Decipher the reply message */
pq_copymsgbytes(&reply_message, (char *) &reply,
sizeof(StandbyHSFeedbackMessage));
elog(DEBUG2, "hot standby feedback xmin %u epoch %u",
reply.xmin,
reply.epoch);
/* Ignore invalid xmin (can't actually happen with current walreceiver) */
if (!TransactionIdIsNormal(reply.xmin))
return;
/*
* Check that the provided xmin/epoch are sane, that is, not in the future
* and not so far back as to be already wrapped around. Ignore if not.
*
* Epoch of nextXid should be same as standby, or if the counter has
* wrapped, then one greater than standby.
*/
GetNextXidAndEpoch(&nextXid, &nextEpoch);
if (reply.xmin <= nextXid)
{
if (reply.epoch != nextEpoch)
return;
}
else
{
if (reply.epoch + 1 != nextEpoch)
return;
}
if (!TransactionIdPrecedesOrEquals(reply.xmin, nextXid))
return; /* epoch OK, but it's wrapped around */
/*
* Set the WalSender's xmin equal to the standby's requested xmin, so that
* the xmin will be taken into account by GetOldestXmin. This will hold
* back the removal of dead rows and thereby prevent the generation of
* cleanup conflicts on the standby server.
*
* There is a small window for a race condition here: although we just
* checked that reply.xmin precedes nextXid, the nextXid could have gotten
* advanced between our fetching it and applying the xmin below, perhaps
* far enough to make reply.xmin wrap around. In that case the xmin we
* set here would be "in the future" and have no effect. No point in
* worrying about this since it's too late to save the desired data
* anyway. Assuming that the standby sends us an increasing sequence of
* xmins, this could only happen during the first reply cycle, else our
* own xmin would prevent nextXid from advancing so far.
*
* We don't bother taking the ProcArrayLock here. Setting the xmin field
* is assumed atomic, and there's no real need to prevent a concurrent
* GetOldestXmin. (If we're moving our xmin forward, this is obviously
* safe, and if we're moving it backwards, well, the data is at risk
* already since a VACUUM could have just finished calling GetOldestXmin.)
*/
MyPgXact->xmin = reply.xmin;
}
