Restore rule for getting global snapshot

knizhnik · kelvich · commit 81035a765274 · 2016-02-08T14:31:36.000+03:00
diff --git a/contrib/multimaster/multimaster.c b/contrib/multimaster/multimaster.c
@@ -123,6 +123,7 @@ static TransactionId DtmNextXid;
 static SnapshotData DtmSnapshot = { HeapTupleSatisfiesMVCC };
 static bool DtmHasGlobalSnapshot;
 static int DtmLocalXidReserve;
+static CommandId DtmCurcid;
 static Snapshot DtmLastSnapshot;
 static TransactionManager DtmTM = {
 	DtmGetTransactionStatus,
@@ -630,11 +631,12 @@ static Snapshot DtmGetSnapshot(Snapshot snapshot)
 {
 	if (TransactionIdIsValid(DtmNextXid) && snapshot != &CatalogSnapshotData)
 	{
-		if (!DtmHasGlobalSnapshot) {
+		if (!DtmHasGlobalSnapshot && (snapshot != DtmLastSnapshot || DtmCurcid != GetCurrentCommandId(false))) {
 			DtmGlobalGetSnapshot(DtmNextXid, &DtmSnapshot, &dtm->minXid);
         }
 		DtmLastSnapshot = snapshot;
 		DtmMergeWithGlobalSnapshot(snapshot);
+		DtmCurcid = snapshot->curcid;
 		if (!IsolationUsesXactSnapshot())
 		{
 			/* Use single global snapshot during all transaction for repeatable read isolation level,
diff --git a/contrib/pg_dtm/pg_dtm.c b/contrib/pg_dtm/pg_dtm.c
@@ -107,6 +107,7 @@ static SnapshotData DtmSnapshot = { HeapTupleSatisfiesMVCC };
 static bool DtmHasGlobalSnapshot;
 static bool DtmGlobalXidAssigned;
 static int DtmLocalXidReserve;
+static CommandId DtmCurcid;
 static Snapshot DtmLastSnapshot;
 static TransactionManager DtmTM = {
 	DtmGetTransactionStatus,
@@ -600,7 +601,6 @@ DtmGetNewTransactionId(bool isSubXact)
 	return xid;
 }
 
-
 static Snapshot DtmGetSnapshot(Snapshot snapshot)
 {
 	if (DtmGlobalXidAssigned)
@@ -613,11 +613,13 @@ static Snapshot DtmGetSnapshot(Snapshot snapshot)
 	}
 	if (TransactionIdIsValid(DtmNextXid) && snapshot != &CatalogSnapshotData)
 	{
+		// if (!DtmHasGlobalSnapshot && (snapshot != DtmLastSnapshot || DtmCurcid != GetCurrentCommandId(false))) {
 		if (!DtmHasGlobalSnapshot) { 
 			ArbiterGetSnapshot(DtmNextXid, &DtmSnapshot, &dtm->minXid);
 		}
 		DtmLastSnapshot = snapshot;
 		DtmMergeWithGlobalSnapshot(snapshot);
+		DtmCurcid = snapshot->curcid;
 		if (!IsolationUsesXactSnapshot())
 		{
 			/* Use single global snapshot during all transaction for repeatable read isolation level,
diff --git a/contrib/pg_dtm/tests/dtmbench.cpp b/contrib/pg_dtm/tests/dtmbench.cpp
@@ -70,7 +70,7 @@ struct config
         nWriters = 10;
         nIterations = 1000;
         nAccounts = 1000;      
-        isolationLevel = "read committed";
+        isolationLevel = "repeatable read";//"read committed";
     }
 };
 

Original file line number	Diff line number	Diff line change
`@@ -123,6 +123,7 @@ static TransactionId DtmNextXid;`
`123`	`123`	`static SnapshotData DtmSnapshot = { HeapTupleSatisfiesMVCC };`
`124`	`124`	`static bool DtmHasGlobalSnapshot;`
`125`	`125`	`static int DtmLocalXidReserve;`
	`126`	`+static CommandId DtmCurcid;`
`126`	`127`	`static Snapshot DtmLastSnapshot;`
`127`	`128`	`static TransactionManager DtmTM = {`
`128`	`129`	`DtmGetTransactionStatus,`
`@@ -630,11 +631,12 @@ static Snapshot DtmGetSnapshot(Snapshot snapshot)`
`630`	`631`	`{`
`631`	`632`	`if (TransactionIdIsValid(DtmNextXid) && snapshot != &CatalogSnapshotData)`
`632`	`633`	`{`
`633`		`- if (!DtmHasGlobalSnapshot) {`
	`634`	`+ if (!DtmHasGlobalSnapshot && (snapshot != DtmLastSnapshot \|\| DtmCurcid != GetCurrentCommandId(false))) {`
`634`	`635`	`DtmGlobalGetSnapshot(DtmNextXid, &DtmSnapshot, &dtm->minXid);`
`635`	`636`	`}`
`636`	`637`	`DtmLastSnapshot = snapshot;`
`637`	`638`	`DtmMergeWithGlobalSnapshot(snapshot);`
	`639`	`+ DtmCurcid = snapshot->curcid;`
`638`	`640`	`if (!IsolationUsesXactSnapshot())`
`639`	`641`	`{`
`640`	`642`	`/* Use single global snapshot during all transaction for repeatable read isolation level,`
Original file line number	Diff line number	Diff line change
`@@ -107,6 +107,7 @@ static SnapshotData DtmSnapshot = { HeapTupleSatisfiesMVCC };`
`107`	`107`	`static bool DtmHasGlobalSnapshot;`
`108`	`108`	`static bool DtmGlobalXidAssigned;`
`109`	`109`	`static int DtmLocalXidReserve;`
	`110`	`+static CommandId DtmCurcid;`
`110`	`111`	`static Snapshot DtmLastSnapshot;`
`111`	`112`	`static TransactionManager DtmTM = {`
`112`	`113`	`DtmGetTransactionStatus,`
`@@ -600,7 +601,6 @@ DtmGetNewTransactionId(bool isSubXact)`
`600`	`601`	`return xid;`
`601`	`602`	`}`
`602`	`603`
`603`		`-`
`604`	`604`	`static Snapshot DtmGetSnapshot(Snapshot snapshot)`
`605`	`605`	`{`
`606`	`606`	`if (DtmGlobalXidAssigned)`
`@@ -613,11 +613,13 @@ static Snapshot DtmGetSnapshot(Snapshot snapshot)`
`613`	`613`	`}`
`614`	`614`	`if (TransactionIdIsValid(DtmNextXid) && snapshot != &CatalogSnapshotData)`
`615`	`615`	`{`
	`616`	`+ // if (!DtmHasGlobalSnapshot && (snapshot != DtmLastSnapshot \|\| DtmCurcid != GetCurrentCommandId(false))) {`
`616`	`617`	`if (!DtmHasGlobalSnapshot) {`
`617`	`618`	`ArbiterGetSnapshot(DtmNextXid, &DtmSnapshot, &dtm->minXid);`
`618`	`619`	`}`
`619`	`620`	`DtmLastSnapshot = snapshot;`
`620`	`621`	`DtmMergeWithGlobalSnapshot(snapshot);`
	`622`	`+ DtmCurcid = snapshot->curcid;`
`621`	`623`	`if (!IsolationUsesXactSnapshot())`
`622`	`624`	`{`
`623`	`625`	`/* Use single global snapshot during all transaction for repeatable read isolation level,`
Original file line number	Diff line number	Diff line change
`@@ -70,7 +70,7 @@ struct config`
`70`	`70`	`nWriters = 10;`
`71`	`71`	`nIterations = 1000;`
`72`	`72`	`nAccounts = 1000;`
`73`		`- isolationLevel = "read committed";`
	`73`	`+ isolationLevel = "repeatable read";//"read committed";`
`74`	`74`	`}`
`75`	`75`	`};`
`76`	`76`