Yet another fix for limits.

Alexander Korotkov · Alexander Korotkov · commit 687bc384a81b · 2016-11-26T13:37:51.000+03:00
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
@@ -2290,7 +2290,7 @@ find_multixact_start(MultiXactId multi, MultiXactOffset *result)
  * exist.  Return false if unable to determine.
  */
 static bool
-ReadMultiXactCounts(uint32 *multixacts, MultiXactOffset *members)
+ReadMultiXactCounts(uint64 *multixacts, MultiXactOffset *members)
 {
 	MultiXactOffset nextOffset;
 	MultiXactOffset oldestOffset;
@@ -2345,12 +2345,12 @@ ReadMultiXactCounts(uint32 *multixacts, MultiXactOffset *members)
  * It's possible that these thresholds should be user-tunable, but for now
  * we keep it simple.
  */
-int
+int64
 MultiXactMemberFreezeThreshold(void)
 {
 	MultiXactOffset members;
-	uint32		multixacts;
-	uint32		victim_multixacts;
+	uint64		multixacts;
+	uint64		victim_multixacts;
 	double		fraction;
 
 	/* If we can't determine member space utilization, assume the worst. */
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
@@ -1083,6 +1083,7 @@ do_start_worker(void)
 	ListCell   *cell;
 	TransactionId xidForceLimit;
 	MultiXactId multiForceLimit;
+	int64		multiMembersThreshold;
 	bool		for_xid_wrap;
 	bool		for_multi_wrap;
 	avw_dbase  *avdb;
@@ -1122,17 +1123,18 @@ do_start_worker(void)
 	 * particular tables, but not loosened.)
 	 */
 	recentXid = ReadNewTransactionId();
-	xidForceLimit = recentXid - autovacuum_freeze_max_age;
-	/* ensure it's a "normal" XID, else TransactionIdPrecedes misbehaves */
-	/* this can cause the limit to go backwards by 3, but that's OK */
-	if (xidForceLimit < FirstNormalTransactionId)
-		xidForceLimit -= FirstNormalTransactionId;
+	if (recentXid > FirstNormalTransactionId + autovacuum_freeze_max_age)
+		xidForceLimit = recentXid - autovacuum_freeze_max_age;
+	else
+		xidForceLimit = FirstNormalTransactionId;
 
 	/* Also determine the oldest datminmxid we will consider. */
 	recentMulti = ReadNextMultiXactId();
-	multiForceLimit = recentMulti - MultiXactMemberFreezeThreshold();
-	if (multiForceLimit < FirstMultiXactId)
-		multiForceLimit -= FirstMultiXactId;
+	multiMembersThreshold = MultiXactMemberFreezeThreshold();
+	if (recentMulti > FirstMultiXactId + multiMembersThreshold)
+		multiForceLimit = recentMulti - multiMembersThreshold;
+	else
+		multiForceLimit = FirstMultiXactId;
 
 	/*
 	 * Choose a database to connect to.  We pick the database that was least
diff --git a/src/include/access/multixact.h b/src/include/access/multixact.h
@@ -138,7 +138,7 @@ extern void MultiXactSetNextMXact(MultiXactId nextMulti,
 extern void MultiXactAdvanceNextMXact(MultiXactId minMulti,
 						  MultiXactOffset minMultiOffset);
 extern void MultiXactAdvanceOldest(MultiXactId oldestMulti, Oid oldestMultiDB);
-extern int	MultiXactMemberFreezeThreshold(void);
+extern int64 MultiXactMemberFreezeThreshold(void);
 
 extern void multixact_twophase_recover(TransactionId xid, uint16 info,
 						   void *recdata, uint32 len);
