diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/access/transam/multixact.c | 14 | ||||
| -rw-r--r-- | src/backend/access/transam/subtrans.c | 7 | ||||
| -rw-r--r-- | src/include/access/multixact.h | 1 |
3 files changed, 17 insertions, 5 deletions
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c index b90c110dcad..5182b4acb53 100644 --- a/src/backend/access/transam/multixact.c +++ b/src/backend/access/transam/multixact.c @@ -90,6 +90,8 @@ #define MXOffsetToMemberEntry(xid) \ ((xid) % (TransactionId) MULTIXACT_MEMBERS_PER_PAGE) +#define PreviousMultiXactId(xid) \ + ((xid) == FirstMultiXactId ? MaxMultiXactId : (xid) - 1) /* * Links to shared-memory data structures for MultiXact control @@ -1902,17 +1904,21 @@ TruncateMultiXact(void) } /* - * The cutoff point is the start of the segment containing oldestMXact. We - * pass the *page* containing oldestMXact to SimpleLruTruncate. + * The cutoff point is the start of the segment containing oldestMXact. + * 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. */ - cutoffPage = MultiXactIdToOffsetPage(oldestMXact); + cutoffPage = MultiXactIdToOffsetPage(PreviousMultiXactId(oldestMXact)); SimpleLruTruncate(MultiXactOffsetCtl, cutoffPage); /* * Also truncate MultiXactMember at the previously determined offset. */ - cutoffPage = MXOffsetToMemberPage(oldestOffset); + cutoffPage = MXOffsetToMemberPage(oldestOffset - 1); SimpleLruTruncate(MultiXactMemberCtl, cutoffPage); diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/subtrans.c index c6fa2419c63..39e0f10866f 100644 --- a/src/backend/access/transam/subtrans.c +++ b/src/backend/access/transam/subtrans.c @@ -340,8 +340,13 @@ TruncateSUBTRANS(TransactionId oldestXact) /* * The cutoff point is the start of the segment containing oldestXact. We - * pass the *page* containing oldestXact to SimpleLruTruncate. + * pass the *page* containing oldestXact to SimpleLruTruncate. We step + * back one transaction to avoid passing a cutoff page that hasn't been + * created yet in the rare case that oldestXact would be the first item on + * a page and oldestXact == next XID. In that case, if we didn't subtract + * one, we'd trigger SimpleLruTruncate's wraparound detection. */ + TransactionIdRetreat(oldestXact); cutoffPage = TransactionIdToPage(oldestXact); SimpleLruTruncate(SubTransCtl, cutoffPage); diff --git a/src/include/access/multixact.h b/src/include/access/multixact.h index c86aeee44ef..a96e6531ef8 100644 --- a/src/include/access/multixact.h +++ b/src/include/access/multixact.h @@ -15,6 +15,7 @@ #define InvalidMultiXactId ((MultiXactId) 0) #define FirstMultiXactId ((MultiXactId) 1) +#define MaxMultiXactId ((MultiXactId) 0xFFFFFFFF) #define MultiXactIdIsValid(multi) ((multi) != InvalidMultiXactId) |