diff options
Diffstat (limited to 'src/backend/access/transam/multixact.c')
| -rw-r--r-- | src/backend/access/transam/multixact.c | 53 |
1 files changed, 26 insertions, 27 deletions
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c index 7bccca8a17b..c2e4fa377d5 100644 --- a/src/backend/access/transam/multixact.c +++ b/src/backend/access/transam/multixact.c @@ -1173,19 +1173,25 @@ GetNewMultiXactId(int nmembers, MultiXactOffset *offset) /* * GetMultiXactIdMembers - * Returns the set of MultiXactMembers that make up a MultiXactId - * - * If the given MultiXactId is older than the value we know to be oldest, we - * return -1. The caller is expected to allow that only in permissible cases, - * i.e. when the infomask lets it presuppose that the tuple had been - * share-locked before a pg_upgrade; this means that the HEAP_XMAX_LOCK_ONLY - * needs to be set, but HEAP_XMAX_KEYSHR_LOCK and HEAP_XMAX_EXCL_LOCK are not - * set. - * - * Other border conditions, such as trying to read a value that's larger than - * the value currently known as the next to assign, raise an error. Previously - * these also returned -1, but since this can lead to the wrong visibility - * results, it is dangerous to do that. + * Return the set of MultiXactMembers that make up a MultiXactId + * + * Return value is the number of members found, or -1 if there are none, + * and *members is set to a newly palloc'ed array of members. It's the + * caller's responsibility to free it when done with it. + * + * from_pgupgrade must be passed as true if and only if only the multixact + * corresponds to a value from a tuple that was locked in a 9.2-or-older + * installation and later pg_upgrade'd (that is, the infomask is + * HEAP_LOCKED_UPGRADED). In this case, we know for certain that no members + * can still be running, so we return -1 just like for an empty multixact + * without any further checking. It would be wrong to try to resolve such a + * multixact: either the multixact is within the current valid multixact + * range, in which case the returned result would be bogus, or outside that + * range, in which case an error would be raised. + * + * In all other cases, the passed multixact must be within the known valid + * range, that is, greater to or equal than oldestMultiXactId, and less than + * nextMXact. Otherwise, an error is raised. * * onlyLock must be set to true if caller is certain that the given multi * is used only to lock tuples; can be false without loss of correctness, @@ -1194,7 +1200,7 @@ GetNewMultiXactId(int nmembers, MultiXactOffset *offset) */ int GetMultiXactIdMembers(MultiXactId multi, MultiXactMember **members, - bool allow_old, bool onlyLock) + bool from_pgupgrade, bool onlyLock) { int pageno; int prev_pageno; @@ -1213,7 +1219,7 @@ GetMultiXactIdMembers(MultiXactId multi, MultiXactMember **members, debug_elog3(DEBUG2, "GetMembers: asked for %u", multi); - if (!MultiXactIdIsValid(multi)) + if (!MultiXactIdIsValid(multi) || from_pgupgrade) return -1; /* See if the MultiXactId is in the local cache */ @@ -1246,18 +1252,11 @@ GetMultiXactIdMembers(MultiXactId multi, MultiXactMember **members, * * An ID older than MultiXactState->oldestMultiXactId cannot possibly be * useful; it has already been removed, or will be removed shortly, by - * truncation. Returning the wrong values could lead to an incorrect - * visibility result. However, to support pg_upgrade we need to allow an - * empty set to be returned regardless, if the caller is willing to accept - * it; the caller is expected to check that it's an allowed condition - * (such as ensuring that the infomask bits set on the tuple are - * consistent with the pg_upgrade scenario). If the caller is expecting - * this to be called only on recently created multis, then we raise an - * error. + * truncation. If one is passed, an error is raised. * - * Conversely, an ID >= nextMXact shouldn't ever be seen here; if it is - * seen, it implies undetected ID wraparound has occurred. This raises a - * hard error. + * Also, an ID >= nextMXact shouldn't ever be seen here; if it is seen, it + * implies undetected ID wraparound has occurred. This raises a hard + * error. * * Shared lock is enough here since we aren't modifying any global state. * Acquire it just long enough to grab the current counter values. We may @@ -1273,7 +1272,7 @@ GetMultiXactIdMembers(MultiXactId multi, MultiXactMember **members, if (MultiXactIdPrecedes(multi, oldestMXact)) { - ereport(allow_old ? DEBUG1 : ERROR, + ereport(ERROR, (errcode(ERRCODE_INTERNAL_ERROR), errmsg("MultiXactId %u does no longer exist -- apparent wraparound", multi))); |