diff options
| -rw-r--r-- | src/backend/storage/ipc/procarray.c | 7 | ||||
| -rw-r--r-- | src/backend/utils/adt/xid.c | 26 | ||||
| -rw-r--r-- | src/include/utils/builtins.h | 1 |
3 files changed, 33 insertions, 1 deletions
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index 9a8429169fc..f047f9a242c 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -1164,8 +1164,13 @@ ProcArrayApplyRecoveryInfo(RunningTransactions running) /* * Sort the array so that we can add them safely into * KnownAssignedXids. + * + * We have to sort them logically, because in KnownAssignedXidsAdd we + * call TransactionIdFollowsOrEquals and so on. But we know these XIDs + * come from RUNNING_XACTS, which means there are only normal XIDs from + * the same epoch, so this is safe. */ - qsort(xids, nxids, sizeof(TransactionId), xidComparator); + qsort(xids, nxids, sizeof(TransactionId), xidLogicalComparator); /* * Add the sorted snapshot into KnownAssignedXids. The running-xacts diff --git a/src/backend/utils/adt/xid.c b/src/backend/utils/adt/xid.c index 24c1c937326..faa7737508c 100644 --- a/src/backend/utils/adt/xid.c +++ b/src/backend/utils/adt/xid.c @@ -145,6 +145,32 @@ xidComparator(const void *arg1, const void *arg2) return 0; } +/* + * xidLogicalComparator + * qsort comparison function for XIDs + * + * This is used to compare only XIDs from the same epoch (e.g. for backends + * running at the same time). So there must be only normal XIDs, so there's + * no issue with triangle inequality. + */ +int +xidLogicalComparator(const void *arg1, const void *arg2) +{ + TransactionId xid1 = *(const TransactionId *) arg1; + TransactionId xid2 = *(const TransactionId *) arg2; + + Assert(TransactionIdIsNormal(xid1)); + Assert(TransactionIdIsNormal(xid2)); + + if (TransactionIdPrecedes(xid1, xid2)) + return -1; + + if (TransactionIdPrecedes(xid2, xid1)) + return 1; + + return 0; +} + Datum xid8toxid(PG_FUNCTION_ARGS) { diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h index 40fcb0ab6d7..4329925f1e3 100644 --- a/src/include/utils/builtins.h +++ b/src/include/utils/builtins.h @@ -88,6 +88,7 @@ extern void text_to_cstring_buffer(const text *src, char *dst, size_t dst_len); /* xid.c */ extern int xidComparator(const void *arg1, const void *arg2); +extern int xidLogicalComparator(const void *arg1, const void *arg2); /* inet_cidr_ntop.c */ extern char *pg_inet_cidr_ntop(int af, const void *src, int bits, |