diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 481d4af86bcd0bc3c9a1b562b309223785acab29..9b9fed3ed0098094b9550c7645ef15497690839b 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.21 2006/07/14 14:52:17 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.22 2006/07/30 02:07:18 alvherre Exp $
*
* NOTES
* Each global transaction is associated with a global transaction
@@ -279,6 +279,7 @@ MarkAsPreparing(TransactionId xid, const char *gid,
gxact->proc.pid = 0;
gxact->proc.databaseId = databaseid;
gxact->proc.roleId = owner;
+ gxact->proc.inVacuum = false;
gxact->proc.lwWaiting = false;
gxact->proc.lwExclusive = false;
gxact->proc.lwWaitLink = NULL;
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index e9473acaa6bd08db9abfc84d6cc686c4025f4f47..81c2583571af8d3c14ca20697bded7a155a20bd4 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -10,7 +10,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.224 2006/07/24 16:32:44 petere Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.225 2006/07/30 02:07:18 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1529,6 +1529,7 @@ CommitTransaction(void)
LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
MyProc->xid = InvalidTransactionId;
MyProc->xmin = InvalidTransactionId;
+ MyProc->inVacuum = false; /* must be cleared with xid/xmin */
/* Clear the subtransaction-XID cache too while holding the lock */
MyProc->subxids.nxids = 0;
@@ -1764,6 +1765,7 @@ PrepareTransaction(void)
LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
MyProc->xid = InvalidTransactionId;
MyProc->xmin = InvalidTransactionId;
+ MyProc->inVacuum = false; /* must be cleared with xid/xmin */
/* Clear the subtransaction-XID cache too while holding the lock */
MyProc->subxids.nxids = 0;
@@ -1927,6 +1929,7 @@ AbortTransaction(void)
LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
MyProc->xid = InvalidTransactionId;
MyProc->xmin = InvalidTransactionId;
+ MyProc->inVacuum = false; /* must be cleared with xid/xmin */
/* Clear the subtransaction-XID cache too while holding the lock */
MyProc->subxids.nxids = 0;
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index e9265dde48dc0db00ca4e1005b74a0dd2bc36296..6b5c5ac0da7e70575f255b5be2eb3f64e900907f 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.244 2006/07/14 14:52:17 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.245 2006/07/30 02:07:18 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
@@ -5413,7 +5413,7 @@ CreateCheckPoint(bool shutdown, bool force)
* StartupSUBTRANS hasn't been called yet.
*/
if (!InRecovery)
- TruncateSUBTRANS(GetOldestXmin(true));
+ TruncateSUBTRANS(GetOldestXmin(true, false));
if (!shutdown)
ereport(DEBUG2,
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 1e498ccf755bb868e07d7bed5a9c3fc4e5d408b9..829fd5e4fba2a32e428d6756f695912cae701cb6 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.269 2006/07/13 16:49:13 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.270 2006/07/30 02:07:18 alvherre Exp $
*
*
* INTERFACE ROUTINES
@@ -1367,7 +1367,8 @@ IndexBuildHeapScan(Relation heapRelation,
else
{
snapshot = SnapshotAny;
- OldestXmin = GetOldestXmin(heapRelation->rd_rel->relisshared);
+ /* okay to ignore lazy VACUUMs here */
+ OldestXmin = GetOldestXmin(heapRelation->rd_rel->relisshared, true);
}
scan = heap_beginscan(heapRelation, /* relation */
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index b1f187dc47dfadf0b3b2667fb620295e09de0585..eb0fce72edb5d70104a63ffb21aafd2f54b2e969 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -13,7 +13,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.335 2006/07/14 14:52:18 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.336 2006/07/30 02:07:18 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
@@ -37,6 +37,7 @@
#include "postmaster/autovacuum.h"
#include "storage/freespace.h"
#include "storage/pmsignal.h"
+#include "storage/proc.h"
#include "storage/procarray.h"
#include "utils/acl.h"
#include "utils/builtins.h"
@@ -589,7 +590,16 @@ vacuum_set_xid_limits(VacuumStmt *vacstmt, bool sharedRel,
{
TransactionId limit;
- *oldestXmin = GetOldestXmin(sharedRel);
+ /*
+ * We can always ignore processes running lazy vacuum. This is because we
+ * use these values only for deciding which tuples we must keep in the
+ * tables. Since lazy vacuum doesn't write its xid to the table, it's
+ * safe to ignore it. In theory it could be problematic to ignore lazy
+ * vacuums on a full vacuum, but keep in mind that only one vacuum process
+ * can be working on a particular table at any time, and that each vacuum
+ * is always an independent transaction.
+ */
+ *oldestXmin = GetOldestXmin(sharedRel, true);
Assert(TransactionIdIsNormal(*oldestXmin));
@@ -645,6 +655,11 @@ vacuum_set_xid_limits(VacuumStmt *vacstmt, bool sharedRel,
* pg_class would've been obsoleted. Of course, this only works for
* fixed-size never-null columns, but these are.
*
+ * Another reason for doing it this way is that when we are in a lazy
+ * VACUUM and have inVacuum set, we mustn't do any updates --- somebody
+ * vacuuming pg_class might think they could delete a tuple marked with
+ * xmin = our xid.
+ *
* This routine is shared by full VACUUM, lazy VACUUM, and stand-alone
* ANALYZE.
*/
@@ -996,8 +1011,35 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
/* Begin a transaction for vacuuming this relation */
StartTransactionCommand();
- /* functions in indexes may want a snapshot set */
- ActiveSnapshot = CopySnapshot(GetTransactionSnapshot());
+
+ if (vacstmt->full)
+ {
+ /* functions in indexes may want a snapshot set */
+ ActiveSnapshot = CopySnapshot(GetTransactionSnapshot());
+ }
+ else
+ {
+ /*
+ * During a lazy VACUUM we do not run any user-supplied functions,
+ * and so it should be safe to not create a transaction snapshot.
+ *
+ * We can furthermore set the inVacuum flag, which lets other
+ * concurrent VACUUMs know that they can ignore this one while
+ * determining their OldestXmin. (The reason we don't set inVacuum
+ * during a full VACUUM is exactly that we may have to run user-
+ * defined functions for functional indexes, and we want to make
+ * sure that if they use the snapshot set above, any tuples it
+ * requires can't get removed from other tables. An index function
+ * that depends on the contents of other tables is arguably broken,
+ * but we won't break it here by violating transaction semantics.)
+ *
+ * Note: the inVacuum flag remains set until CommitTransaction or
+ * AbortTransaction. We don't want to clear it until we reset
+ * MyProc->xid/xmin, else OldestXmin might appear to go backwards,
+ * which is probably Not Good.
+ */
+ MyProc->inVacuum = true;
+ }
/*
* Tell the cache replacement strategy that vacuum is causing all
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index c8a173fbee363987a531f07661d406f8af3e3b16..e9d0da12ff0d705a7b7cfe751c9005dcf9f4bfbd 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -23,7 +23,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.14 2006/07/14 14:52:22 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.15 2006/07/30 02:07:18 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
@@ -388,20 +388,24 @@ TransactionIdIsActive(TransactionId xid)
* If allDbs is TRUE then all backends are considered; if allDbs is FALSE
* then only backends running in my own database are considered.
*
+ * If ignoreVacuum is TRUE then backends with inVacuum set are ignored.
+ *
* This is used by VACUUM to decide which deleted tuples must be preserved
* in a table. allDbs = TRUE is needed for shared relations, but allDbs =
* FALSE is sufficient for non-shared relations, since only backends in my
- * own database could ever see the tuples in them.
+ * own database could ever see the tuples in them. Also, we can ignore
+ * concurrently running lazy VACUUMs because (a) they must be working on other
+ * tables, and (b) they don't need to do snapshot-based lookups.
*
* This is also used to determine where to truncate pg_subtrans. allDbs
- * must be TRUE for that case.
+ * must be TRUE for that case, and ignoreVacuum FALSE.
*
* Note: we include the currently running xids in the set of considered xids.
* This ensures that if a just-started xact has not yet set its snapshot,
* when it does set the snapshot it cannot set xmin less than what we compute.
*/
TransactionId
-GetOldestXmin(bool allDbs)
+GetOldestXmin(bool allDbs, bool ignoreVacuum)
{
ProcArrayStruct *arrayP = procArray;
TransactionId result;
@@ -425,6 +429,9 @@ GetOldestXmin(bool allDbs)
{
PGPROC *proc = arrayP->procs[index];
+ if (ignoreVacuum && proc->inVacuum)
+ continue;
+
if (allDbs || proc->databaseId == MyDatabaseId)
{
/* Fetch xid just once - see GetNewTransactionId */
@@ -432,8 +439,18 @@ GetOldestXmin(bool allDbs)
if (TransactionIdIsNormal(xid))
{
+ /* First consider the transaction own's Xid */
if (TransactionIdPrecedes(xid, result))
result = xid;
+
+ /*
+ * Also consider the transaction's Xmin, if set.
+ *
+ * Note that this Xmin may seem to be guaranteed to be always
+ * lower than the transaction's Xid, but this is not so because
+ * there is a time window on which the Xid is already assigned
+ * but the Xmin has not being calculated yet.
+ */
xid = proc->xmin;
if (TransactionIdIsNormal(xid))
if (TransactionIdPrecedes(xid, result))
@@ -471,8 +488,8 @@ GetOldestXmin(bool allDbs)
* RecentXmin: the xmin computed for the most recent snapshot. XIDs
* older than this are known not running any more.
* RecentGlobalXmin: the global xmin (oldest TransactionXmin across all
- * running transactions). This is the same computation done by
- * GetOldestXmin(TRUE).
+ * running transactions, except those running LAZY VACUUM). This is
+ * the same computation done by GetOldestXmin(true, false).
*----------
*/
Snapshot
@@ -561,15 +578,17 @@ GetSnapshotData(Snapshot snapshot, bool serializable)
/*
* Ignore my own proc (dealt with my xid above), procs not running a
- * transaction, and xacts started since we read the next transaction
- * ID. There's no need to store XIDs above what we got from
- * ReadNewTransactionId, since we'll treat them as running anyway. We
- * also assume that such xacts can't compute an xmin older than ours,
- * so they needn't be considered in computing globalxmin.
+ * transaction, xacts started since we read the next transaction
+ * ID, and xacts executing LAZY VACUUM. There's no need to store XIDs
+ * above what we got from ReadNewTransactionId, since we'll treat them
+ * as running anyway. We also assume that such xacts can't compute an
+ * xmin older than ours, so they needn't be considered in computing
+ * globalxmin.
*/
if (proc == MyProc ||
!TransactionIdIsNormal(xid) ||
- TransactionIdFollowsOrEquals(xid, xmax))
+ TransactionIdFollowsOrEquals(xid, xmax) ||
+ proc->inVacuum)
continue;
if (TransactionIdPrecedes(xid, xmin))
diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
index 04cd338aac7e29308b5f5b344f33bdfeabdd0c75..07fc3e3d2555b25f7979dcdd510f2ea0be56f605 100644
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.178 2006/07/23 23:08:46 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.179 2006/07/30 02:07:18 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
@@ -257,6 +257,7 @@ InitProcess(void)
/* databaseId and roleId will be filled in later */
MyProc->databaseId = InvalidOid;
MyProc->roleId = InvalidOid;
+ MyProc->inVacuum = false;
MyProc->lwWaiting = false;
MyProc->lwExclusive = false;
MyProc->lwWaitLink = NULL;
@@ -388,6 +389,7 @@ InitDummyProcess(void)
MyProc->xmin = InvalidTransactionId;
MyProc->databaseId = InvalidOid;
MyProc->roleId = InvalidOid;
+ MyProc->inVacuum = false;
MyProc->lwWaiting = false;
MyProc->lwExclusive = false;
MyProc->lwWaitLink = NULL;
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index 83816dd05ddc83a86854a15966ce48b9265639ba..0345b42f977eb60116b5d85a72d5dd6adfe5f891 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/storage/proc.h,v 1.89 2006/07/13 16:49:20 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/storage/proc.h,v 1.90 2006/07/30 02:07:18 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
@@ -66,13 +66,16 @@ struct PGPROC
* this proc */
TransactionId xmin; /* minimal running XID as it was when we were
- * starting our xact: vacuum must not remove
- * tuples deleted by xid >= xmin ! */
+ * starting our xact, excluding LAZY VACUUM:
+ * vacuum must not remove tuples deleted by
+ * xid >= xmin ! */
int pid; /* This backend's process id, or 0 */
Oid databaseId; /* OID of database this backend is using */
Oid roleId; /* OID of role using this backend */
+ bool inVacuum; /* true if current xact is a LAZY VACUUM */
+
/* Info about LWLock the process is currently waiting for, if any. */
bool lwWaiting; /* true if waiting for an LW lock */
bool lwExclusive; /* true if waiting for exclusive access */
diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h
index e1710701a1d642fd42f558009c1e16d9f66451cc..b9da4db9180b2e939a6ef0a79a350cc2b4d64b29 100644
--- a/src/include/storage/procarray.h
+++ b/src/include/storage/procarray.h
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/storage/procarray.h,v 1.9 2006/06/19 01:51:22 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/storage/procarray.h,v 1.10 2006/07/30 02:07:18 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
@@ -24,7 +24,7 @@ extern void ProcArrayRemove(PGPROC *proc);
extern bool TransactionIdIsInProgress(TransactionId xid);
extern bool TransactionIdIsActive(TransactionId xid);
-extern TransactionId GetOldestXmin(bool allDbs);
+extern TransactionId GetOldestXmin(bool allDbs, bool ignoreVacuum);
extern PGPROC *BackendPidGetProc(int pid);
extern int BackendXidGetPid(TransactionId xid);