@@ -146,7 +146,7 @@ static bool TransactionIdIsInDoubt(TransactionId xid)
146146
147147static void DtmMergeSnapshots (Snapshot dst ,Snapshot src )
148148{
149- int i ,j , n ;
149+ int i ,j ;
150150TransactionId xid ;
151151
152152Assert (TransactionIdIsValid (src -> xmin )&& TransactionIdIsValid (src -> xmax ));
@@ -173,20 +173,17 @@ static void DtmMergeSnapshots(Snapshot dst, Snapshot src)
173173//MyPgXact->xmin = TransactionXmin = src->xmin;
174174 }
175175if (src -> xmax < dst -> xmax )dst -> xmax = src -> xmax ;
176+ // concatenate two active lists
177+ memcpy (dst -> xip + dst -> xcnt ,src -> xip ,src -> xcnt * sizeof (TransactionId ));
178+ dst -> xcnt += src -> xcnt ;
179+ Assert (dst -> xcnt <=GetMaxSnapshotXidCount ());
176180
177-
178- n = dst -> xcnt ;
179- for (xid = dst -> xmax ;xid <=src -> xmin ;xid ++ ) {
180- dst -> xip [n ++ ]= xid ;
181- }
182- memcpy (dst -> xip + n ,src -> xip ,src -> xcnt * sizeof (TransactionId ));
183- n += src -> xcnt ;
184- Assert (n <=GetMaxSnapshotXidCount ());
185-
186- qsort (dst -> xip ,n ,sizeof (TransactionId ),xidComparator );
181+ // sort the list
182+ qsort (dst -> xip ,dst -> xcnt ,sizeof (TransactionId ),xidComparator );
187183xid = InvalidTransactionId ;
188184
189- for (i = 0 ,j = 0 ;i < n && dst -> xip [i ]< dst -> xmax ;i ++ ) {
185+ // remove duplicates
186+ for (i = 0 ,j = 0 ;i < dst -> xcnt && dst -> xip [i ]< dst -> xmax ;i ++ ) {
190187if (dst -> xip [i ]!= xid ) {
191188dst -> xip [j ++ ]= xid = dst -> xip [i ];
192189}