diff options
Diffstat (limited to 'src/backend/access/transam/multixact.c')
| -rw-r--r-- | src/backend/access/transam/multixact.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c index 77f6d3cb3a9..9b10496d9bd 100644 --- a/src/backend/access/transam/multixact.c +++ b/src/backend/access/transam/multixact.c @@ -171,6 +171,8 @@ #define MULTIXACT_MEMBER_DANGER_THRESHOLD \ (MaxMultiXactOffset - MaxMultiXactOffset / 4) +#define PreviousMultiXactId(xid) \ + ((xid) == FirstMultiXactId ? MaxMultiXactId : (xid) - 1) /* * Links to shared-memory data structures for MultiXact control @@ -3076,9 +3078,15 @@ TruncateMultiXact(void) SlruScanDirectory(MultiXactMemberCtl, SlruScanDirCbRemoveMembers, &range); - /* Now we can truncate MultiXactOffset */ + /* + * Now we can truncate MultiXactOffset. We step back one multixact to + * avoid passing a cutoff page that hasn't been created yet in the rare + * case that oldestMXact would be the first item on a page and oldestMXact + * == nextMXact. In that case, if we didn't subtract one, we'd trigger + * SimpleLruTruncate's wraparound detection. + */ SimpleLruTruncate(MultiXactOffsetCtl, - MultiXactIdToOffsetPage(oldestMXact)); + MultiXactIdToOffsetPage(PreviousMultiXactId(oldestMXact))); /* * Now, and only now, we can advance the stop point for multixact members. |