Modify snapshot definition so that lazy vacuums are ignored by other
vacuums. This allows a OLTP-like system with big tables to continue regular vacuuming on small-but-frequently-updated tables while the big tables are being vacuumed. Original patch from Hannu Krossing, rewritten by Tom Lane and updated by me.
This commit is contained in:
Alvaro Herrera
parent
d6603791ea
commit
92c2ecc130
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.21 2006/07/14 14:52:17 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.22 2006/07/30 02:07:18 alvherre Exp $
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*
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* NOTES
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* Each global transaction is associated with a global transaction
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@ -279,6 +279,7 @@ MarkAsPreparing(TransactionId xid, const char *gid,
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gxact->proc.pid = 0;
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gxact->proc.databaseId = databaseid;
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gxact->proc.roleId = owner;
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gxact->proc.inVacuum = false;
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gxact->proc.lwWaiting = false;
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gxact->proc.lwExclusive = false;
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gxact->proc.lwWaitLink = NULL;
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@ -10,7 +10,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.224 2006/07/24 16:32:44 petere Exp $
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* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.225 2006/07/30 02:07:18 alvherre Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -1529,6 +1529,7 @@ CommitTransaction(void)
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LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
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MyProc->xid = InvalidTransactionId;
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MyProc->xmin = InvalidTransactionId;
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MyProc->inVacuum = false; /* must be cleared with xid/xmin */
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/* Clear the subtransaction-XID cache too while holding the lock */
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MyProc->subxids.nxids = 0;
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@ -1764,6 +1765,7 @@ PrepareTransaction(void)
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LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
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MyProc->xid = InvalidTransactionId;
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MyProc->xmin = InvalidTransactionId;
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MyProc->inVacuum = false; /* must be cleared with xid/xmin */
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/* Clear the subtransaction-XID cache too while holding the lock */
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MyProc->subxids.nxids = 0;
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@ -1927,6 +1929,7 @@ AbortTransaction(void)
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LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
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MyProc->xid = InvalidTransactionId;
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MyProc->xmin = InvalidTransactionId;
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MyProc->inVacuum = false; /* must be cleared with xid/xmin */
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/* Clear the subtransaction-XID cache too while holding the lock */
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MyProc->subxids.nxids = 0;
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.244 2006/07/14 14:52:17 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.245 2006/07/30 02:07:18 alvherre Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -5413,7 +5413,7 @@ CreateCheckPoint(bool shutdown, bool force)
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* StartupSUBTRANS hasn't been called yet.
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*/
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if (!InRecovery)
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TruncateSUBTRANS(GetOldestXmin(true));
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TruncateSUBTRANS(GetOldestXmin(true, false));
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if (!shutdown)
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ereport(DEBUG2,
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.269 2006/07/13 16:49:13 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.270 2006/07/30 02:07:18 alvherre Exp $
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*
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*
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* INTERFACE ROUTINES
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@ -1367,7 +1367,8 @@ IndexBuildHeapScan(Relation heapRelation,
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else
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{
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snapshot = SnapshotAny;
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OldestXmin = GetOldestXmin(heapRelation->rd_rel->relisshared);
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/* okay to ignore lazy VACUUMs here */
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OldestXmin = GetOldestXmin(heapRelation->rd_rel->relisshared, true);
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}
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scan = heap_beginscan(heapRelation, /* relation */
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@ -13,7 +13,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.335 2006/07/14 14:52:18 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.336 2006/07/30 02:07:18 alvherre Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -37,6 +37,7 @@
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#include "postmaster/autovacuum.h"
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#include "storage/freespace.h"
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#include "storage/pmsignal.h"
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#include "storage/proc.h"
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#include "storage/procarray.h"
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#include "utils/acl.h"
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#include "utils/builtins.h"
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@ -589,7 +590,16 @@ vacuum_set_xid_limits(VacuumStmt *vacstmt, bool sharedRel,
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{
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TransactionId limit;
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*oldestXmin = GetOldestXmin(sharedRel);
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/*
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* We can always ignore processes running lazy vacuum. This is because we
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* use these values only for deciding which tuples we must keep in the
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* tables. Since lazy vacuum doesn't write its xid to the table, it's
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* safe to ignore it. In theory it could be problematic to ignore lazy
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* vacuums on a full vacuum, but keep in mind that only one vacuum process
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* can be working on a particular table at any time, and that each vacuum
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* is always an independent transaction.
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*/
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*oldestXmin = GetOldestXmin(sharedRel, true);
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Assert(TransactionIdIsNormal(*oldestXmin));
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@ -645,6 +655,11 @@ vacuum_set_xid_limits(VacuumStmt *vacstmt, bool sharedRel,
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* pg_class would've been obsoleted. Of course, this only works for
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* fixed-size never-null columns, but these are.
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*
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* Another reason for doing it this way is that when we are in a lazy
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* VACUUM and have inVacuum set, we mustn't do any updates --- somebody
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* vacuuming pg_class might think they could delete a tuple marked with
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* xmin = our xid.
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*
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* This routine is shared by full VACUUM, lazy VACUUM, and stand-alone
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* ANALYZE.
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*/
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@ -996,8 +1011,35 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
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/* Begin a transaction for vacuuming this relation */
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StartTransactionCommand();
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/* functions in indexes may want a snapshot set */
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ActiveSnapshot = CopySnapshot(GetTransactionSnapshot());
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if (vacstmt->full)
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{
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/* functions in indexes may want a snapshot set */
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ActiveSnapshot = CopySnapshot(GetTransactionSnapshot());
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}
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else
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{
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/*
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* During a lazy VACUUM we do not run any user-supplied functions,
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* and so it should be safe to not create a transaction snapshot.
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*
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* We can furthermore set the inVacuum flag, which lets other
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* concurrent VACUUMs know that they can ignore this one while
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* determining their OldestXmin. (The reason we don't set inVacuum
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* during a full VACUUM is exactly that we may have to run user-
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* defined functions for functional indexes, and we want to make
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* sure that if they use the snapshot set above, any tuples it
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* requires can't get removed from other tables. An index function
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* that depends on the contents of other tables is arguably broken,
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* but we won't break it here by violating transaction semantics.)
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*
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* Note: the inVacuum flag remains set until CommitTransaction or
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* AbortTransaction. We don't want to clear it until we reset
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* MyProc->xid/xmin, else OldestXmin might appear to go backwards,
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* which is probably Not Good.
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*/
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MyProc->inVacuum = true;
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}
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/*
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* Tell the cache replacement strategy that vacuum is causing all
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@ -23,7 +23,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.14 2006/07/14 14:52:22 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.15 2006/07/30 02:07:18 alvherre Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -388,20 +388,24 @@ TransactionIdIsActive(TransactionId xid)
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* If allDbs is TRUE then all backends are considered; if allDbs is FALSE
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* then only backends running in my own database are considered.
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*
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* If ignoreVacuum is TRUE then backends with inVacuum set are ignored.
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*
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* This is used by VACUUM to decide which deleted tuples must be preserved
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* in a table. allDbs = TRUE is needed for shared relations, but allDbs =
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* FALSE is sufficient for non-shared relations, since only backends in my
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* own database could ever see the tuples in them.
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* own database could ever see the tuples in them. Also, we can ignore
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* concurrently running lazy VACUUMs because (a) they must be working on other
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* tables, and (b) they don't need to do snapshot-based lookups.
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*
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* This is also used to determine where to truncate pg_subtrans. allDbs
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* must be TRUE for that case.
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* must be TRUE for that case, and ignoreVacuum FALSE.
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*
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* Note: we include the currently running xids in the set of considered xids.
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* This ensures that if a just-started xact has not yet set its snapshot,
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* when it does set the snapshot it cannot set xmin less than what we compute.
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*/
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TransactionId
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GetOldestXmin(bool allDbs)
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GetOldestXmin(bool allDbs, bool ignoreVacuum)
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{
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ProcArrayStruct *arrayP = procArray;
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TransactionId result;
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@ -425,6 +429,9 @@ GetOldestXmin(bool allDbs)
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{
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PGPROC *proc = arrayP->procs[index];
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if (ignoreVacuum && proc->inVacuum)
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continue;
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if (allDbs || proc->databaseId == MyDatabaseId)
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{
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/* Fetch xid just once - see GetNewTransactionId */
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@ -432,8 +439,18 @@ GetOldestXmin(bool allDbs)
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if (TransactionIdIsNormal(xid))
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{
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/* First consider the transaction own's Xid */
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if (TransactionIdPrecedes(xid, result))
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result = xid;
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/*
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* Also consider the transaction's Xmin, if set.
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*
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* Note that this Xmin may seem to be guaranteed to be always
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* lower than the transaction's Xid, but this is not so because
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* there is a time window on which the Xid is already assigned
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* but the Xmin has not being calculated yet.
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*/
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xid = proc->xmin;
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if (TransactionIdIsNormal(xid))
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if (TransactionIdPrecedes(xid, result))
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@ -471,8 +488,8 @@ GetOldestXmin(bool allDbs)
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* RecentXmin: the xmin computed for the most recent snapshot. XIDs
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* older than this are known not running any more.
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* RecentGlobalXmin: the global xmin (oldest TransactionXmin across all
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* running transactions). This is the same computation done by
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* GetOldestXmin(TRUE).
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* running transactions, except those running LAZY VACUUM). This is
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* the same computation done by GetOldestXmin(true, false).
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*----------
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*/
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Snapshot
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@ -561,15 +578,17 @@ GetSnapshotData(Snapshot snapshot, bool serializable)
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/*
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* Ignore my own proc (dealt with my xid above), procs not running a
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* transaction, and xacts started since we read the next transaction
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* ID. There's no need to store XIDs above what we got from
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* ReadNewTransactionId, since we'll treat them as running anyway. We
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* also assume that such xacts can't compute an xmin older than ours,
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* so they needn't be considered in computing globalxmin.
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* transaction, xacts started since we read the next transaction
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* ID, and xacts executing LAZY VACUUM. There's no need to store XIDs
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* above what we got from ReadNewTransactionId, since we'll treat them
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* as running anyway. We also assume that such xacts can't compute an
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* xmin older than ours, so they needn't be considered in computing
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* globalxmin.
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*/
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if (proc == MyProc ||
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!TransactionIdIsNormal(xid) ||
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TransactionIdFollowsOrEquals(xid, xmax))
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TransactionIdFollowsOrEquals(xid, xmax) ||
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proc->inVacuum)
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continue;
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if (TransactionIdPrecedes(xid, xmin))
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.178 2006/07/23 23:08:46 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.179 2006/07/30 02:07:18 alvherre Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -257,6 +257,7 @@ InitProcess(void)
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/* databaseId and roleId will be filled in later */
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MyProc->databaseId = InvalidOid;
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MyProc->roleId = InvalidOid;
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MyProc->inVacuum = false;
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MyProc->lwWaiting = false;
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MyProc->lwExclusive = false;
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MyProc->lwWaitLink = NULL;
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@ -388,6 +389,7 @@ InitDummyProcess(void)
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MyProc->xmin = InvalidTransactionId;
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MyProc->databaseId = InvalidOid;
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MyProc->roleId = InvalidOid;
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MyProc->inVacuum = false;
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MyProc->lwWaiting = false;
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MyProc->lwExclusive = false;
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MyProc->lwWaitLink = NULL;
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/storage/proc.h,v 1.89 2006/07/13 16:49:20 momjian Exp $
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* $PostgreSQL: pgsql/src/include/storage/proc.h,v 1.90 2006/07/30 02:07:18 alvherre Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -66,13 +66,16 @@ struct PGPROC
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* this proc */
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TransactionId xmin; /* minimal running XID as it was when we were
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* starting our xact: vacuum must not remove
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* tuples deleted by xid >= xmin ! */
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* starting our xact, excluding LAZY VACUUM:
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* vacuum must not remove tuples deleted by
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* xid >= xmin ! */
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int pid; /* This backend's process id, or 0 */
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Oid databaseId; /* OID of database this backend is using */
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Oid roleId; /* OID of role using this backend */
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bool inVacuum; /* true if current xact is a LAZY VACUUM */
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/* Info about LWLock the process is currently waiting for, if any. */
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bool lwWaiting; /* true if waiting for an LW lock */
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bool lwExclusive; /* true if waiting for exclusive access */
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/storage/procarray.h,v 1.9 2006/06/19 01:51:22 tgl Exp $
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* $PostgreSQL: pgsql/src/include/storage/procarray.h,v 1.10 2006/07/30 02:07:18 alvherre Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -24,7 +24,7 @@ extern void ProcArrayRemove(PGPROC *proc);
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extern bool TransactionIdIsInProgress(TransactionId xid);
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extern bool TransactionIdIsActive(TransactionId xid);
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extern TransactionId GetOldestXmin(bool allDbs);
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extern TransactionId GetOldestXmin(bool allDbs, bool ignoreVacuum);
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extern PGPROC *BackendPidGetProc(int pid);
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extern int BackendXidGetPid(TransactionId xid);
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Loading…
Reference in New Issue