diff options
Diffstat (limited to 'src/backend/access/transam/multixact.c')
| -rw-r--r-- | src/backend/access/transam/multixact.c | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c index 377d0842bdd..1933a87d656 100644 --- a/src/backend/access/transam/multixact.c +++ b/src/backend/access/transam/multixact.c @@ -173,6 +173,8 @@ #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 @@ -3057,10 +3059,15 @@ 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. |