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Small comment fixes and enhancements.

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This commit is contained in:
Heikki Linnakangas 2011-06-10 17:22:00 +03:00
parent bb8f0c4b48
commit c79c570bd8
3 changed files with 39 additions and 14 deletions
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2
src/backend/storage/lmgr/README-SSI
View File

@ -389,7 +389,7 @@ locks.
* Because PostgreSQL does not have the same concept of an "oldest
transaction ID" for all serializable transactions as assumed in the
Cahill these, we track the oldest snapshot xmin among serializable
Cahill thesis, we track the oldest snapshot xmin among serializable
transactions, and a count of how many active transactions use that
xmin. When the count hits zero we find the new oldest xmin and run a
clean-up based on that.

48
src/backend/storage/lmgr/predicate.c
View File

@ -703,8 +703,8 @@ OldSerXidInit(void)
* Set up SLRU management of the pg_serial data.
*/
OldSerXidSlruCtl->PagePrecedes = OldSerXidPagePrecedesLogically;
SimpleLruInit(OldSerXidSlruCtl, "OldSerXid SLRU Ctl", NUM_OLDSERXID_BUFFERS, 0,
OldSerXidLock, "pg_serial");
SimpleLruInit(OldSerXidSlruCtl, "OldSerXid SLRU Ctl",
NUM_OLDSERXID_BUFFERS, 0, OldSerXidLock, "pg_serial");
/* Override default assumption that writes should be fsync'd */
OldSerXidSlruCtl->do_fsync = false;
@ -2954,7 +2954,8 @@ PredicateLockPageCombine(const Relation relation, const BlockNumber oldblkno,
}
/*
* Walk the hash table and find the new xmin.
* Walk the list of in-progress serializable transactions and find the new
* xmin.
*/
static void
SetNewSxactGlobalXmin(void)
@ -3126,6 +3127,10 @@ ReleasePredicateLocks(const bool isCommit)
&& !SxactIsReadOnly(MySerializableXact)
&& SxactHasSummaryConflictOut(MySerializableXact))
{
/*
* we don't know which old committed transaction we conflicted with,
* so be conservative and use FirstNormalSerCommitSeqNo here
*/
MySerializableXact->SeqNo.earliestOutConflictCommit =
FirstNormalSerCommitSeqNo;
MySerializableXact->flags |= SXACT_FLAG_CONFLICT_OUT;
@ -3320,7 +3325,8 @@ ReleasePredicateLocksIfROSafe(void)
}
/*
* Clear old predicate locks.
* Clear old predicate locks, belonging to committed transactions that are no
* longer interesting to any in-progress transaction.
*/
static void
ClearOldPredicateLocks(void)
@ -3328,6 +3334,10 @@ ClearOldPredicateLocks(void)
SERIALIZABLEXACT *finishedSxact;
PREDICATELOCK *predlock;
/*
* Loop through finished transactions. They are in commit order, so we can
* stop as soon as we find one that's still interesting.
*/
LWLockAcquire(SerializableFinishedListLock, LW_EXCLUSIVE);
finishedSxact = (SERIALIZABLEXACT *)
SHMQueueNext(FinishedSerializableTransactions,
@ -3346,6 +3356,10 @@ ClearOldPredicateLocks(void)
|| TransactionIdPrecedesOrEquals(finishedSxact->finishedBefore,
PredXact->SxactGlobalXmin))
{
/*
* This transaction committed before any in-progress transaction
* took its snapshot. It's no longer interesting.
*/
LWLockRelease(SerializableXactHashLock);
SHMQueueDelete(&(finishedSxact->finishedLink));
ReleaseOneSerializableXact(finishedSxact, false, false);
@ -3362,7 +3376,10 @@ ClearOldPredicateLocks(void)
LWLockAcquire(SerializableXactHashLock, LW_SHARED);
}
else
{
/* Still interesting. */
break;
}
finishedSxact = nextSxact;
}
LWLockRelease(SerializableXactHashLock);
@ -3391,17 +3408,19 @@ ClearOldPredicateLocks(void)
canDoPartialCleanup = (predlock->commitSeqNo <= PredXact->CanPartialClearThrough);
LWLockRelease(SerializableXactHashLock);
/*
* If this lock originally belonged to an old enough transaction, we
* can release it.
*/
if (canDoPartialCleanup)
{
PREDICATELOCKTAG tag;
SHM_QUEUE *targetLink;
PREDICATELOCKTARGET *target;
PREDICATELOCKTARGETTAG targettag;
uint32 targettaghash;
LWLockId partitionLock;
tag = predlock->tag;
targetLink = &(predlock->targetLink);
target = tag.myTarget;
targettag = target->tag;
targettaghash = PredicateLockTargetTagHashCode(&targettag);
@ -3409,7 +3428,7 @@ ClearOldPredicateLocks(void)
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
SHMQueueDelete(targetLink);
SHMQueueDelete(&(predlock->targetLink));
SHMQueueDelete(&(predlock->xactLink));
hash_search_with_hash_value(PredicateLockHash, &tag,
@ -3437,9 +3456,9 @@ ClearOldPredicateLocks(void)
* delete the transaction.
*
* When the partial flag is set, we can release all predicate locks and
* out-conflict information -- we've established that there are no longer
* in-conflict information -- we've established that there are no longer
* any overlapping read write transactions for which this transaction could
* matter.
* matter -- but keep the transaction entry itself and any outConflicts.
*
* When the summarize flag is set, we've run short of room for sxact data
* and must summarize to the SLRU. Predicate locks are transferred to a
@ -3460,6 +3479,10 @@ ReleaseOneSerializableXact(SERIALIZABLEXACT *sxact, bool partial,
Assert(SxactIsRolledBack(sxact) || SxactIsCommitted(sxact));
Assert(LWLockHeldByMe(SerializableFinishedListLock));
/*
* First release all the predicate locks held by this xact (or transfer
* them to OldCommittedSxact if summarize is true)
*/
LWLockAcquire(SerializablePredicateLockListLock, LW_SHARED);
predlock = (PREDICATELOCK *)
SHMQueueNext(&(sxact->predicateLocks),
@ -3545,9 +3568,9 @@ ReleaseOneSerializableXact(SERIALIZABLEXACT *sxact, bool partial,
sxidtag.xid = sxact->topXid;
LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
/* Release all outConflicts (unless 'partial' is true) */
if (!partial)
{
/* Release all outConflicts. */
conflict = (RWConflict)
SHMQueueNext(&sxact->outConflicts,
&sxact->outConflicts,
@ -3582,9 +3605,9 @@ ReleaseOneSerializableXact(SERIALIZABLEXACT *sxact, bool partial,
conflict = nextConflict;
}
/* Finally, get rid of the xid and the record of the transaction itself. */
if (!partial)
{
/* Get rid of the xid and the record of the transaction itself. */
if (sxidtag.xid != InvalidTransactionId)
hash_search(SerializableXidHash, &sxidtag, HASH_REMOVE, NULL);
ReleasePredXact(sxact);
@ -3844,7 +3867,8 @@ CheckForSerializableConflictOut(const bool visible, const Relation relation,
}
/*
* Check a particular target for rw-dependency conflict in.
* Check a particular target for rw-dependency conflict in. A subroutine of
* CheckForSerializableConflictIn().
*/
static void
CheckTargetForConflictsIn(PREDICATELOCKTARGETTAG *targettag)

3
src/include/storage/predicate_internals.h
View File

@ -134,7 +134,8 @@ typedef struct PredXactListData
/*
* These global variables are maintained when registering and cleaning up
* serializable transactions. They must be global across all backends,
* but are not needed outside the predicate.c source file.
* but are not needed outside the predicate.c source file. Protected
* by SerializableXactHashLock.
*/
TransactionId SxactGlobalXmin; /* global xmin for active serializable
* transactions */