Fix asignement of next Xid

knizhnik · knizhnik · commit d7c50886b236 · 2015-09-23T11:53:59.000+03:00
diff --git a/contrib/pg_xtm/pg_dtm.c b/contrib/pg_xtm/pg_dtm.c
@@ -37,7 +37,7 @@
 typedef struct
 {
 	LWLockId hashLock;
-	LWLockId xidLock;
+	LWLockId xidLock;    
 	TransactionId nextXid;
 	size_t nReservedXids;
 } DtmState;
@@ -173,6 +173,9 @@ static void DtmMergeSnapshots(Snapshot dst, Snapshot src)
 		}
 	}
 	dst->xcnt = j;
+    if (RecentXmin > dst->xmin) { 
+        RecentXmin = dst->xmin;
+    }
 	DumpSnapshot(dst, "merged");
 }
 
@@ -187,40 +190,40 @@ static void DtmUpdateRecentXmin(void)
 		if (!TransactionIdIsNormal(xmin)) {
 			xmin = FirstNormalTransactionId;
 		}
-		if (RecentGlobalDataXmin > xmin) {
+		if (TransactionIdFollows(RecentGlobalDataXmin, xmin)) {
 			RecentGlobalDataXmin = xmin;
 		}
-		if (RecentGlobalXmin > xmin) {
+		if (TransactionIdFollows(RecentGlobalXmin, xmin)) {
 			RecentGlobalXmin = xmin;
 		}
-		if (RecentXmin > xmin) {
-			RecentXmin = xmin;
-		}
 	}
 }
 
 static TransactionId DtmGetNextXid()
 {
 	TransactionId xid;
+    LWLockAcquire(dtm->xidLock, LW_EXCLUSIVE);
 	if (TransactionIdIsValid(DtmNextXid)) {
         XTM_INFO("Use global XID %d\n", DtmNextXid);
 		xid = DtmNextXid;
-        dtm->nReservedXids = 0;
-        ShmemVariableCache->nextXid = xid;
+        if (ShmemVariableCache->nextXid <= xid) { 
+            dtm->nReservedXids = 0;
+            ShmemVariableCache->nextXid = xid;
+        }
 	} else {
-		LWLockAcquire(dtm->xidLock, LW_EXCLUSIVE);
 		if (dtm->nReservedXids == 0) {
-			dtm->nReservedXids = DtmGlobalReserve(ShmemVariableCache->nextXid, DtmLocalXidReserve, &xid);
-			ShmemVariableCache->nextXid = dtm->nextXid = xid;
+			dtm->nReservedXids = DtmGlobalReserve(ShmemVariableCache->nextXid, DtmLocalXidReserve, &dtm->nextXid);
+            Assert(dtm->nReservedXids > 0);
+            Assert(TransactionIdFollowsOrEquals(dtm->nextXid, ShmemVariableCache->nextXid));
+            ShmemVariableCache->nextXid = dtm->nextXid;
 		} else { 
-            Assert(dtm->nextXid == ShmemVariableCache->nextXid);
-            xid = ShmemVariableCache->nextXid;
+            Assert(ShmemVariableCache->nextXid == dtm->nextXid);
         }
-        XTM_INFO("Obtain new local XID %d\n", xid);
-		dtm->nextXid += 1;
+        xid = dtm->nextXid++;
 		dtm->nReservedXids -= 1;
-		LWLockRelease(dtm->xidLock);
+        XTM_INFO("Obtain new local XID %d\n", xid);
 	}
+    LWLockRelease(dtm->xidLock);
 	return xid;
 }
 
@@ -232,13 +235,13 @@ static Snapshot DtmGetSnapshot(Snapshot snapshot)
 			DtmGlobalGetSnapshot(DtmNextXid, &DtmSnapshot);
 		}
 		DtmMergeSnapshots(snapshot, &DtmSnapshot);
-		DtmUpdateRecentXmin();
         if (!IsolationUsesXactSnapshot()) {
             DtmHasGlobalSnapshot = false;
         }
 	} else { 
         snapshot = GetLocalSnapshotData(snapshot);
     }
+    DtmUpdateRecentXmin();
 	CurrentTransactionSnapshot = snapshot;
 	return snapshot;
 }
diff --git a/contrib/pg_xtm/tests/transfers.go b/contrib/pg_xtm/tests/transfers.go
@@ -8,7 +8,7 @@ import (
 )
 
 const (
-    TRANSFER_CONNECTIONS = 2
+    TRANSFER_CONNECTIONS = 8
     INIT_AMOUNT = 10000
     N_ITERATIONS = 10000
     N_ACCOUNTS = TRANSFER_CONNECTIONS//100000
diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
@@ -161,7 +161,7 @@ GetNewTransactionId(bool isSubXact)
 
 		/* Re-acquire lock and start over */
 		LWLockAcquire(XidGenLock, LW_EXCLUSIVE);
-		xid = ShmemVariableCache->nextXid;
+		xid = TM->GetNextXid();
 	}
 
 	/*
@@ -183,7 +183,11 @@ GetNewTransactionId(bool isSubXact)
 	 * want the next incoming transaction to try it again.  We cannot assign
 	 * more XIDs until there is CLOG space for them.
 	 */
-	TransactionIdAdvance(ShmemVariableCache->nextXid);
+    if (xid == ShmemVariableCache->nextXid) { 
+        TransactionIdAdvance(ShmemVariableCache->nextXid);
+    } else { 
+        Assert(TransactionIdPrecedes(xid, ShmemVariableCache->nextXid));
+    }
 
 	/*
 	 * We must store the new XID into the shared ProcArray before releasing

Original file line number	Diff line number	Diff line change
`@@ -37,7 +37,7 @@`
`37`	`37`	`typedef struct`
`38`	`38`	`{`
`39`	`39`	`LWLockId hashLock;`
`40`		`- LWLockId xidLock;`
	`40`	`+ LWLockId xidLock;`
`41`	`41`	`TransactionId nextXid;`
`42`	`42`	`size_t nReservedXids;`
`43`	`43`	`} DtmState;`
`@@ -173,6 +173,9 @@ static void DtmMergeSnapshots(Snapshot dst, Snapshot src)`
`173`	`173`	`}`
`174`	`174`	`}`
`175`	`175`	`dst->xcnt = j;`
	`176`	`+ if (RecentXmin > dst->xmin) {`
	`177`	`+ RecentXmin = dst->xmin;`
	`178`	`+ }`
`176`	`179`	`DumpSnapshot(dst, "merged");`
`177`	`180`	`}`
`178`	`181`
`@@ -187,40 +190,40 @@ static void DtmUpdateRecentXmin(void)`
`187`	`190`	`if (!TransactionIdIsNormal(xmin)) {`
`188`	`191`	`xmin = FirstNormalTransactionId;`
`189`	`192`	`}`
`190`		`- if (RecentGlobalDataXmin > xmin) {`
	`193`	`+ if (TransactionIdFollows(RecentGlobalDataXmin, xmin)) {`
`191`	`194`	`RecentGlobalDataXmin = xmin;`
`192`	`195`	`}`
`193`		`- if (RecentGlobalXmin > xmin) {`
	`196`	`+ if (TransactionIdFollows(RecentGlobalXmin, xmin)) {`
`194`	`197`	`RecentGlobalXmin = xmin;`
`195`	`198`	`}`
`196`		`- if (RecentXmin > xmin) {`
`197`		`- RecentXmin = xmin;`
`198`		`- }`
`199`	`199`	`}`
`200`	`200`	`}`
`201`	`201`
`202`	`202`	`static TransactionId DtmGetNextXid()`
`203`	`203`	`{`
`204`	`204`	`TransactionId xid;`
	`205`	`+ LWLockAcquire(dtm->xidLock, LW_EXCLUSIVE);`
`205`	`206`	`if (TransactionIdIsValid(DtmNextXid)) {`
`206`	`207`	`XTM_INFO("Use global XID %d\n", DtmNextXid);`
`207`	`208`	`xid = DtmNextXid;`
`208`		`- dtm->nReservedXids = 0;`
`209`		`- ShmemVariableCache->nextXid = xid;`
	`209`	`+ if (ShmemVariableCache->nextXid <= xid) {`
	`210`	`+ dtm->nReservedXids = 0;`
	`211`	`+ ShmemVariableCache->nextXid = xid;`
	`212`	`+ }`
`210`	`213`	`} else {`
`211`		`- LWLockAcquire(dtm->xidLock, LW_EXCLUSIVE);`
`212`	`214`	`if (dtm->nReservedXids == 0) {`
`213`		`- dtm->nReservedXids = DtmGlobalReserve(ShmemVariableCache->nextXid, DtmLocalXidReserve, &xid);`
`214`		`- ShmemVariableCache->nextXid = dtm->nextXid = xid;`
	`215`	`+ dtm->nReservedXids = DtmGlobalReserve(ShmemVariableCache->nextXid, DtmLocalXidReserve, &dtm->nextXid);`
	`216`	`+ Assert(dtm->nReservedXids > 0);`
	`217`	`+ Assert(TransactionIdFollowsOrEquals(dtm->nextXid, ShmemVariableCache->nextXid));`
	`218`	`+ ShmemVariableCache->nextXid = dtm->nextXid;`
`215`	`219`	`} else {`
`216`		`- Assert(dtm->nextXid == ShmemVariableCache->nextXid);`
`217`		`- xid = ShmemVariableCache->nextXid;`
	`220`	`+ Assert(ShmemVariableCache->nextXid == dtm->nextXid);`
`218`	`221`	`}`
`219`		`- XTM_INFO("Obtain new local XID %d\n", xid);`
`220`		`- dtm->nextXid += 1;`
	`222`	`+ xid = dtm->nextXid++;`
`221`	`223`	`dtm->nReservedXids -= 1;`
`222`		`- LWLockRelease(dtm->xidLock);`
	`224`	`+ XTM_INFO("Obtain new local XID %d\n", xid);`
`223`	`225`	`}`
	`226`	`+ LWLockRelease(dtm->xidLock);`
`224`	`227`	`return xid;`
`225`	`228`	`}`
`226`	`229`
`@@ -232,13 +235,13 @@ static Snapshot DtmGetSnapshot(Snapshot snapshot)`
`232`	`235`	`DtmGlobalGetSnapshot(DtmNextXid, &DtmSnapshot);`
`233`	`236`	`}`
`234`	`237`	`DtmMergeSnapshots(snapshot, &DtmSnapshot);`
`235`		`- DtmUpdateRecentXmin();`
`236`	`238`	`if (!IsolationUsesXactSnapshot()) {`
`237`	`239`	`DtmHasGlobalSnapshot = false;`
`238`	`240`	`}`
`239`	`241`	`} else {`
`240`	`242`	`snapshot = GetLocalSnapshotData(snapshot);`
`241`	`243`	`}`
	`244`	`+ DtmUpdateRecentXmin();`
`242`	`245`	`CurrentTransactionSnapshot = snapshot;`
`243`	`246`	`return snapshot;`
`244`	`247`	`}`
Original file line number	Diff line number	Diff line change
`@@ -8,7 +8,7 @@ import (`
`8`	`8`	`)`
`9`	`9`
`10`	`10`	`const (`
`11`		`- TRANSFER_CONNECTIONS = 2`
	`11`	`+ TRANSFER_CONNECTIONS = 8`
`12`	`12`	`INIT_AMOUNT = 10000`
`13`	`13`	`N_ITERATIONS = 10000`
`14`	`14`	`N_ACCOUNTS = TRANSFER_CONNECTIONS//100000`