@@ -86,12 +86,14 @@ static TransactionId DtmMinXid;
8686static bool DtmHasGlobalSnapshot ;
8787static bool DtmIsGlobalTransaction ;
8888static int DtmLocalXidReserve ;
89+ static int DtmCurcid ;
90+ static Snapshot DtmLastSnapshot ;
8991static TransactionManager DtmTM = {DtmGetTransactionStatus ,DtmSetTransactionStatus ,DtmGetSnapshot ,DtmGetNewTransactionId ,DtmGetOldestXmin };
9092
9193
9294#define XTM_TRACE (fmt , ...)
93- // #define XTM_INFO(fmt, ...) fprintf(stderr, fmt, ## __VA_ARGS__)
94- #define XTM_INFO (fmt , ...)
95+ #define XTM_INFO (fmt , ...) fprintf(stderr, fmt, ## __VA_ARGS__)
96+ // #define XTM_INFO(fmt, ...)
9597
9698static void DumpSnapshot (Snapshot s ,char * name )
9799{
@@ -100,8 +102,8 @@ static void DumpSnapshot(Snapshot s, char *name)
100102char * cursor = buf ;
101103cursor += sprintf (
102104cursor ,
103- "snapshot %s for transaction %d: xmin=%d, xmax=%d, active=[" ,
104- name ,GetCurrentTransactionId (),s -> xmin ,s -> xmax
105+ "snapshot %s(%p) for transaction %d: xmin=%d, xmax=%d, active=[" ,
106+ name ,s , GetCurrentTransactionId (),s -> xmin ,s -> xmax
105107);
106108for (i = 0 ;i < s -> xcnt ;i ++ ) {
107109if (i == 0 ) {
@@ -480,10 +482,12 @@ DtmGetNewTransactionId(bool isSubXact)
480482
481483static Snapshot DtmGetSnapshot (Snapshot snapshot )
482484{
483- if (TransactionIdIsValid (DtmNextXid )) {
484- if (!DtmHasGlobalSnapshot ) {
485+ if (TransactionIdIsValid (DtmNextXid )&& IsMVCCSnapshot ( snapshot ) && snapshot != & CatalogSnapshotData ) {
486+ if (!DtmHasGlobalSnapshot && ( snapshot != DtmLastSnapshot || DtmCurcid != snapshot -> curcid ) ) {
485487DtmGlobalGetSnapshot (DtmNextXid ,& DtmSnapshot ,& DtmMinXid );
486488}
489+ DtmCurcid = snapshot -> curcid ;
490+ DtmLastSnapshot = snapshot ;
487491DtmMergeSnapshots (snapshot ,& DtmSnapshot );
488492if (!IsolationUsesXactSnapshot ()) {
489493DtmHasGlobalSnapshot = false;
@@ -595,6 +599,7 @@ DtmXactCallback(XactEvent event, void *arg)
595599LWLockRelease (dtm -> hashLock );
596600 }
597601DtmNextXid = InvalidTransactionId ;
602+ DtmLastSnapshot = NULL ;
598603}
599604}
600605}
@@ -701,6 +706,7 @@ dtm_begin_transaction(PG_FUNCTION_ARGS)
701706
702707DtmHasGlobalSnapshot = true;
703708DtmIsGlobalTransaction = true;
709+ DtmLastSnapshot = NULL ;
704710
705711PG_RETURN_INT32 (DtmNextXid );
706712}
@@ -716,6 +722,7 @@ Datum dtm_join_transaction(PG_FUNCTION_ARGS)
716722
717723DtmHasGlobalSnapshot = true;
718724DtmIsGlobalTransaction = true;
725+ DtmLastSnapshot = NULL ;
719726
720727PG_RETURN_VOID ();
721728}