diff options
Diffstat (limited to 'src/backend/access/transam/multixact.c')
| -rw-r--r-- | src/backend/access/transam/multixact.c | 31 |
1 files changed, 25 insertions, 6 deletions
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c index 9f259bb54eb..33346c76643 100644 --- a/src/backend/access/transam/multixact.c +++ b/src/backend/access/transam/multixact.c @@ -428,7 +428,7 @@ MultiXactIdExpand(MultiXactId multi, TransactionId xid, MultiXactStatus status) * caller of this function does a check that the multixact is no longer * running. */ - nmembers = GetMultiXactIdMembers(multi, &members, false); + nmembers = GetMultiXactIdMembers(multi, &members, false, false); if (nmembers < 0) { @@ -517,7 +517,7 @@ MultiXactIdExpand(MultiXactId multi, TransactionId xid, MultiXactStatus status) * a pg_upgraded share-locked tuple. */ bool -MultiXactIdIsRunning(MultiXactId multi) +MultiXactIdIsRunning(MultiXactId multi, bool isLockOnly) { MultiXactMember *members; int nmembers; @@ -529,7 +529,7 @@ MultiXactIdIsRunning(MultiXactId multi) * "false" here means we assume our callers have checked that the given * multi cannot possibly come from a pg_upgraded database. */ - nmembers = GetMultiXactIdMembers(multi, &members, false); + nmembers = GetMultiXactIdMembers(multi, &members, false, isLockOnly); if (nmembers < 0) { @@ -1095,10 +1095,15 @@ GetNewMultiXactId(int nmembers, MultiXactOffset *offset) * 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. + * + * 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, + * but passing a true means we can return quickly without checking for + * old updates. */ int GetMultiXactIdMembers(MultiXactId multi, MultiXactMember **members, - bool allow_old) + bool allow_old, bool onlyLock) { int pageno; int prev_pageno; @@ -1133,6 +1138,19 @@ GetMultiXactIdMembers(MultiXactId multi, MultiXactMember **members, MultiXactIdSetOldestVisible(); /* + * If we know the multi is used only for locking and not for updates, + * then we can skip checking if the value is older than our oldest + * visible multi. It cannot possibly still be running. + */ + if (onlyLock && + MultiXactIdPrecedes(multi, OldestVisibleMXactId[MyBackendId])) + { + debug_elog2(DEBUG2, "GetMembers: a locker-only multi is too old"); + *members = NULL; + return -1; + } + + /* * We check known limits on MultiXact before resorting to the SLRU area. * * An ID older than MultiXactState->oldestMultiXactId cannot possibly be @@ -1335,7 +1353,7 @@ MultiXactHasRunningRemoteMembers(MultiXactId multi) int nmembers; int i; - nmembers = GetMultiXactIdMembers(multi, &members, true); + nmembers = GetMultiXactIdMembers(multi, &members, true, false); if (nmembers <= 0) return false; @@ -2807,7 +2825,8 @@ pg_get_multixact_members(PG_FUNCTION_ARGS) multi = palloc(sizeof(mxact)); /* no need to allow for old values here */ - multi->nmembers = GetMultiXactIdMembers(mxid, &multi->members, false); + multi->nmembers = GetMultiXactIdMembers(mxid, &multi->members, false, + false); multi->iter = 0; tupdesc = CreateTemplateTupleDesc(2, false); |