*
* multixact.cpp
* PostgreSQL multi-transaction-log manager
*
* The pg_multixact manager is a pg_clog-like manager that stores an array of
* MultiXactMember for each MultiXactId. It is a fundamental part of the
* shared-row-lock implementation. Each MultiXactMember is comprised of a
* TransactionId a set of flag bits(high 3 bits record status, low 60 bits record
* transactionid).
*
* The meaning of the flag bits is opaque to this module, but they are mostly
* used in heapam.cpp to identify lock modes that each of the member transactions
* is holding on any given tuple. This module just contains support to store
* and retrieve the arrays.
*
* We use two SLRU areas, one for storing the offsets at which the data
* starts for each MultiXactId in the other one. This trick allows us to
* store variable length arrays of TransactionIds. (We could alternatively
* use one area containing counts and TransactionIds, with valid MultiXactId
* values pointing at slots containing counts; but that way seems less robust
* since it would get completely confused if someone inquired about a bogus
* MultiXactId that pointed to an intermediate slot containing an XID.)
*
* XLOG interactions: this module generates an XLOG record whenever a new
* OFFSETs or MEMBERs page is initialized to zeroes, as well as an XLOG record
* whenever a new MultiXactId is defined. This allows us to completely
* rebuild the data entered since the last checkpoint during XLOG replay.
* Because this is possible, we need not follow the normal rule of
* "write WAL before data"; the only correctness guarantee needed is that
* we flush and sync all dirty OFFSETs and MEMBERs pages to disk before a
* checkpoint is considered complete. If a page does make it to disk ahead
* of corresponding WAL records, it will be forcibly zeroed before use anyway.
* Therefore, we don't need to mark our pages with LSN information; we have
* enough synchronization already.
*
* Like clog.c, and unlike subtrans.c, we have to preserve state across
* crashes and ensure that MXID and offset numbering increases monotonically
* across a crash. We do this in the same way as it's done for transaction
* IDs: the WAL record is guaranteed to contain evidence of every MXID we
* could need to worry about, and we just make sure that at the end of
* replay, the next-MXID and next-offset counters are at least as large as
* anything we saw during replay.
*
*
* Portions Copyright (c) 2020 Huawei Technologies Co.,Ltd.
* Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/gausskernel/storage/access/transam/multixact.cpp
*
* -------------------------------------------------------------------------
*/
#include "postgres.h"
#include "knl/knl_variable.h"
#include "access/multixact.h"
#include "access/slru.h"
#include "access/transam.h"
#include "access/twophase.h"
#include "access/twophase_rmgr.h"
#include "access/xact.h"
#include "access/xlog.h"
#include "access/xloginsert.h"
#include "access/xlogproc.h"
#include "lib/ilist.h"
#include "miscadmin.h"
#include "pg_trace.h"
#include "storage/smgr/fd.h"
#include "storage/lmgr.h"
#include "storage/procarray.h"
#include "utils/builtins.h"
#include "utils/memutils.h"
* MultiXact state shared across all backends. All this state is protected
* by MultiXactGenLock. (We also use SLRU bank's lock of MultiXactOffset and
* MultiXactMemberSLRULock to guard accesses to the two sets of SLRU
* buffers. For concurrency's sake, we avoid holding more than one of these
* locks at a time.)
*/
typedef struct MultiXactStateData {
MultiXactId nextMXact;
MultiXactOffset nextOffset;
MultiXactId lastTruncationPoint;
* oldest multixact that is still on disk. Anything older than this should
* not be consulted.
*/
MultiXactId oldestMultiXactId;
Oid oldestMultiXactDB;
MultiXactId multiVacLimit;
* Per-backend data starts here. We have two arrays stored in the area
* immediately following the MultiXactStateData struct. Each is indexed by
* BackendId.
*
* In both arrays, there's a slot for all normal backends (1..g_instance.shmem_cxt.MaxBackends)
* followed by a slot for max_prepared_xacts prepared transactions. Valid
* BackendIds start from 1; element zero of each array is never used.
*
* OldestMemberMXactId[k] is the oldest MultiXactId each backend's current
* transaction(s) could possibly be a member of, or InvalidMultiXactId
* when the backend has no live transaction that could possibly be a
* member of a MultiXact. Each backend sets its entry to the current
* nextMXact counter just before first acquiring a shared lock in a given
* transaction, and clears it at transaction end. (This works because only
* during or after acquiring a shared lock could an XID possibly become a
* member of a MultiXact, and that MultiXact would have to be created
* during or after the lock acquisition.)
*
* OldestVisibleMXactId[k] is the oldest MultiXactId each backend's
* current transaction(s) think is potentially live, or InvalidMultiXactId
* when not in a transaction or not in a transaction that's paid any
* attention to MultiXacts yet. This is computed when first needed in a
* given transaction, and cleared at transaction end. We can compute it
* as the minimum of the valid OldestMemberMXactId[] entries at the time
* we compute it (using nextMXact if none are valid). Each backend is
* required not to attempt to access any SLRU data for MultiXactIds older
* than its own OldestVisibleMXactId[] setting; this is necessary because
* the checkpointer could truncate away such data at any instant.
*
* The checkpointer can compute the safe truncation point as the oldest
* valid value among all the OldestMemberMXactId[] and
* OldestVisibleMXactId[] entries, or nextMXact if none are valid.
* Clearly, it is not possible for any later-computed OldestVisibleMXactId
* value to be older than this, and so there is no risk of truncating data
* that is still needed.
*/
MultiXactId perBackendXactIds[1];
} MultiXactStateData;
* Last element of OldestMemberMXactID and OldestVisibleMXactId arrays.
* Valid elements are (1..MaxOldestSlot); element 0 is never used.
*/
#define MaxOldestSlot (g_instance.shmem_cxt.MaxBackends + \
g_instance.attr.attr_storage.max_prepared_xacts * NUM_TWOPHASE_PARTITIONS)
* Definitions for the backend-local MultiXactId cache.
*
* We use this cache to store known MultiXacts, so we don't need to go to
* SLRU areas every time.
*
* The cache lasts for the duration of a single transaction, the rationale
* for this being that most entries will contain our own TransactionId and
* so they will be uninteresting by the time our next transaction starts.
* (XXX not clear that this is correct --- other members of the MultiXact
* could hang around longer than we did. However, it's not clear what a
* better policy for flushing old cache entries would be.)
*
* We allocate the cache entries in a memory context that is deleted at
* transaction end, so we don't need to do retail freeing of entries.
*/
typedef struct mXactCacheEnt {
MultiXactId multi;
int nmembers;
dlist_node node;
MultiXactMember members[FLEXIBLE_ARRAY_MEMBER];
} mXactCacheEnt;
#define MAX_CACHE_ENTRIES 256
#ifdef MULTIXACT_DEBUG
#define debug_elog2(a, b) elog(a, b)
#define debug_elog3(a, b, c) elog(a, b, c)
#define debug_elog4(a, b, c, d) elog(a, b, c, d)
#else
#define debug_elog2(a, b)
#define debug_elog3(a, b, c)
#define debug_elog4(a, b, c, d)
#endif
static void MultiXactIdSetOldestVisible(void);
static MultiXactId CreateMultiXactId(int nmembers, MultiXactMember *members);
static void RecordNewMultiXact(MultiXactId multi, MultiXactOffset offset, int nmembers, TransactionId *xidsWtihStatus);
static MultiXactId GetNewMultiXactId(int nxids, MultiXactOffset *offset);
static int MXactMemberComparator(const void *arg1, const void *arg2);
static MultiXactId mXactCacheGetBySet(int nmembers, MultiXactMember *members);
static int mXactCacheGetById(MultiXactId multi, MultiXactMember **members);
static void mXactCachePut(MultiXactId multi, int nmembers, MultiXactMember *members);
static char *mxid_to_string(MultiXactId multi, int nmembers, MultiXactMember *members);
static const char *MXStatusToString(MultiXactStatus status);
static int ZeroMultiXactOffsetPage(int64 pageno, bool writeXlog);
static int ZeroMultiXactMemberPage(int64 pageno, bool writeXlog);
static void ExtendMultiXactOffset(MultiXactId multi);
static void ExtendMultiXactMember(MultiXactOffset offset, int nmembers);
static void WriteMZeroPageXlogRec(int64 pageno, uint8 info);
* MultiXactIdCreate
* Construct a MultiXactId representing two TransactionIds.
*
* The two XIDs must be different, or be requesting different statuses.
*
* NB - we don't worry about our local MultiXactId cache here, because that
* is handled by the lower-level routines.
*/
MultiXactId MultiXactIdCreate(TransactionId xid1, MultiXactStatus status1,
TransactionId xid2, MultiXactStatus status2)
{
MultiXactId newMulti;
MultiXactMember members[2];
int nmembers = 2;
AssertArg(TransactionIdIsValid(xid1));
AssertArg(TransactionIdIsValid(xid2));
Assert(!TransactionIdEquals(xid1, xid2) || (status1 != status2));
* Note: unlike MultiXactIdExpand, we don't bother to check that both XIDs
* are still running. In typical usage, xid2 will be our own XID and the
* caller just did a check on xid1, so it'd be wasted effort.
*/
members[0].xid = xid1;
members[0].status = status1;
members[1].xid = xid2;
members[1].status = status2;
newMulti = CreateMultiXactId(2, members);
ereport(DEBUG2, (errmsg("Create: :%s", mxid_to_string(newMulti, nmembers, members))));
return newMulti;
}
* MultiXactIdExpand
* Add a TransactionId to a pre-existing MultiXactId.
*
* If the TransactionId is already a member of the passed MultiXactId with the,
* same status, just return it as-is.
*
* Note that we do NOT actually modify the membership of a pre-existing
* MultiXactId; instead we create a new one. This is necessary to avoid
* a race condition against code trying to wait for one MultiXactId to finish;
* see notes in heapam.cpp.
*
* NB - we don't worry about our local MultiXactId cache here, because that
* is handled by the lower-level routines.
*/
MultiXactId MultiXactIdExpand(MultiXactId multi, TransactionId xid, MultiXactStatus status)
{
MultiXactId newMulti;
MultiXactMember *members = NULL;
MultiXactMember *newMembers = NULL;
int nmembers;
int i;
int j;
AssertArg(MultiXactIdIsValid(multi));
AssertArg(TransactionIdIsValid(xid));
ereport(DEBUG2, (errmsg("Expand: received multi " XID_FMT ", xid " XID_FMT ", status %s", multi, xid,
MXStatusToString(status))));
nmembers = GetMultiXactIdMembers(multi, &members);
if (nmembers < 0) {
* The MultiXactId is obsolete. This can only happen if all the
* MultiXactId members stop running between the caller checking and
* passing it to us. It would be better to return that fact to the
* caller, but it would complicate the API and it's unlikely to happen
* too often, so just deal with it by creating a singleton MultiXact.
*/
MultiXactMember member;
member.xid = xid;
member.status = status;
newMulti = CreateMultiXactId(1, &member);
ereport(DEBUG2, (errmsg("Expand: " XID_FMT " has no members, create singleton " XID_FMT, multi, newMulti)));
return newMulti;
}
* If the TransactionId is already a member of the MultiXactId with the
* same status, just return the existing MultiXactId.
*/
for (i = 0; i < nmembers; i++) {
if (TransactionIdEquals(members[i].xid, xid) && members[i].status == status) {
ereport(DEBUG2, (errmsg("Expand: " XID_FMT " is already a member of " XID_FMT, xid, multi)));
pfree(members);
members = NULL;
return multi;
}
}
* Determine which of the members of the MultiXactId are still of interest.
* This is any running transaction, and also any transaction that grabbed
* something stronger than just a lock and was committed. (An update that
* aborted is of no interest here.)
*
* (Removing dead members is just an optimization, but a useful one.
* Note we have the same race condition here as above: j could be 0 at the
* end of the loop.)
*/
newMembers = (MultiXactMember *)palloc(sizeof(MultiXactMember) * (unsigned)(nmembers + 1));
for (i = 0, j = 0; i < nmembers; i++) {
if (TransactionIdIsInProgress(members[i].xid) ||
(ISUPDATE_from_mxstatus(members[i].status) && TransactionIdDidCommit(members[i].xid))) {
newMembers[j].xid = members[i].xid;
newMembers[j++].status = members[i].status;
}
}
newMembers[j].xid = xid;
newMembers[j++].status = status;
newMulti = CreateMultiXactId(j, newMembers);
pfree(members);
pfree(newMembers);
members = NULL;
newMembers = NULL;
ereport(DEBUG2, (errmsg("Expand: returning new multi " XID_FMT, newMulti)));
return newMulti;
}
* MultiXactIdIsRunning
* Returns whether a MultiXactId is "running".
*
* We return true if at least one member of the given MultiXactId is still
* running. Note that a "false" result is certain not to change,
* because it is not legal to add members to an existing MultiXactId.
*/
bool MultiXactIdIsRunning(MultiXactId multi)
{
MultiXactMember *members = NULL;
int nmembers;
int i;
ereport(DEBUG2, (errmsg("IsRunning " XID_FMT "?", multi)));
nmembers = GetMultiXactIdMembers(multi, &members);
if (nmembers <= 0) {
ereport(DEBUG2, (errmsg("IsRunning: no members")));
return false;
}
* Checking for myself is cheap compared to looking in shared memory;
* return true if any live subtransaction of the current top-level
* transaction is a member.
*
* This is not needed for correctness, it's just a fast path.
*/
for (i = 0; i < nmembers; i++) {
if (TransactionIdIsCurrentTransactionId(members[i].xid)) {
ereport(DEBUG2, (errmsg("IsRunning: I (%d) am running!", i)));
pfree(members);
members = NULL;
return true;
}
}
* This could be made faster by having another entry point in procarray.c,
* walking the PGPROC array only once for all the members. But in most
* cases nmembers should be small enough that it doesn't much matter.
*/
for (i = 0; i < nmembers; i++) {
if (TransactionIdIsInProgress(members[i].xid)) {
ereport(DEBUG2, (errmsg("IsRunning: member %d (" XID_FMT ") is running", i, members[i].xid)));
pfree(members);
members = NULL;
return true;
}
}
pfree(members);
members = NULL;
ereport(DEBUG2, (errmsg("IsRunning: " XID_FMT " is not running", multi)));
return false;
}
* MultiXactIdIsCurrent
* Returns true if the current transaction is a member of the MultiXactId.
*
* We return true if any live subtransaction of the current top-level
* transaction is a member. This is appropriate for the same reason that a
* lock held by any such subtransaction is globally equivalent to a lock
* held by the current subtransaction: no such lock could be released without
* aborting this subtransaction, and hence releasing its locks. So it's not
* necessary to add the current subxact to the MultiXact separately.
*/
bool MultiXactIdIsCurrent(MultiXactId multi)
{
bool result = false;
MultiXactMember *members = NULL;
int nmembers;
int i;
nmembers = GetMultiXactIdMembers(multi, &members);
if (nmembers < 0) {
return false;
}
for (i = 0; i < nmembers; i++) {
if (TransactionIdIsCurrentTransactionId(members[i].xid)) {
result = true;
break;
}
}
pfree(members);
members = NULL;
return result;
}
* MultiXactIdSetOldestMember
* Save the oldest MultiXactId this transaction could be a member of.
*
* We set the OldestMemberMXactId for a given transaction the first time it's
* going to do some operation that might require a MultiXactId (tuple lock,
* update or delete). We need to do this even if we end up using a
* TransactionId instead of a MultiXactId, because there is a chance that
* another transaction would add our XID to a MultiXactId.
*
* The value to set is the next-to-be-assigned MultiXactId, so this is meant to
* be called just before doing any such possibly-MultiXactId-able operation.
*/
void MultiXactIdSetOldestMember(void)
{
if (!MultiXactIdIsValid(t_thrd.shemem_ptr_cxt.OldestMemberMXactId[t_thrd.proc_cxt.MyBackendId])) {
MultiXactId nextMXact;
* You might think we don't need to acquire a lock here, since
* fetching and storing of TransactionIds is probably atomic, but in
* fact we do: suppose we pick up nextMXact and then lose the CPU for
* a long time. Someone else could advance nextMXact, and then
* another someone else could compute an OldestVisibleMXactId that
* would be after the value we are going to store when we get control
* back. Which would be wrong.
*
* Note that a shared lock is sufficient, because it's enough to stop
* someone from advancing nextMXact; and nobody else could be trying to
* write to our OldestMember entry, only reading (and we assume storing
* it is atomic.)
*/
(void)LWLockAcquire(MultiXactGenLock, LW_SHARED);
* We have to beware of the possibility that nextMXact is in the
* wrapped-around state. We don't fix the counter itself here, but we
* must be sure to store a valid value in our array entry.
*/
nextMXact = t_thrd.shemem_ptr_cxt.MultiXactState->nextMXact;
if (nextMXact < FirstMultiXactId)
nextMXact = FirstMultiXactId;
t_thrd.shemem_ptr_cxt.OldestMemberMXactId[t_thrd.proc_cxt.MyBackendId] = nextMXact;
LWLockRelease(MultiXactGenLock);
ereport(DEBUG2, (errmsg("MultiXact: setting OldestMember[%d] = %lu", t_thrd.proc_cxt.MyBackendId, nextMXact)));
}
}
* MultiXactIdSetOldestVisible
* Save the oldest MultiXactId this transaction considers possibly live.
*
* We set the OldestVisibleMXactId for a given transaction the first time
* it's going to inspect any MultiXactId. Once we have set this, we are
* guaranteed that the checkpointer won't truncate off SLRU data for
* MultiXactIds at or after our OldestVisibleMXactId.
*
* The value to set is the oldest of nextMXact and all the valid per-backend
* OldestMemberMXactId[] entries. Because of the locking we do, we can be
* certain that no subsequent call to MultiXactIdSetOldestMember can set
* an OldestMemberMXactId[] entry older than what we compute here. Therefore
* there is no live transaction, now or later, that can be a member of any
* MultiXactId older than the OldestVisibleMXactId we compute here.
*/
static void MultiXactIdSetOldestVisible(void)
{
if (ENABLE_DMS && t_thrd.role == DMS_WORKER) {
return;
}
if (!MultiXactIdIsValid(t_thrd.shemem_ptr_cxt.OldestVisibleMXactId[t_thrd.proc_cxt.MyBackendId])) {
MultiXactId oldestMXact;
int i;
(void)LWLockAcquire(MultiXactGenLock, LW_EXCLUSIVE);
* We have to beware of the possibility that nextMXact is in the
* wrapped-around state. We don't fix the counter itself here, but we
* must be sure to store a valid value in our array entry.
*/
oldestMXact = t_thrd.shemem_ptr_cxt.MultiXactState->nextMXact;
if (oldestMXact < FirstMultiXactId)
oldestMXact = FirstMultiXactId;
for (i = 1; i <= MaxOldestSlot; i++) {
MultiXactId thisoldest = t_thrd.shemem_ptr_cxt.OldestMemberMXactId[i];
if (MultiXactIdIsValid(thisoldest) && MultiXactIdPrecedes(thisoldest, oldestMXact))
oldestMXact = thisoldest;
}
t_thrd.shemem_ptr_cxt.OldestVisibleMXactId[t_thrd.proc_cxt.MyBackendId] = oldestMXact;
LWLockRelease(MultiXactGenLock);
ereport(DEBUG2,
(errmsg("MultiXact: setting OldestVisible[%d] = %lu", t_thrd.proc_cxt.MyBackendId, oldestMXact)));
}
}
* ReadNextMultiXactId
* Return the next MultiXactId to be assigned, but don't allocate it
*/
MultiXactId ReadNextMultiXactId(void)
{
MultiXactId mxid;
LWLockAcquire(MultiXactGenLock, LW_SHARED);
mxid = t_thrd.shemem_ptr_cxt.MultiXactState->nextMXact;
LWLockRelease(MultiXactGenLock);
if (mxid < FirstMultiXactId)
mxid = FirstMultiXactId;
return mxid;
}
* DoMultiXactIdWait
* Actual implementation for the two functions below.
*
* We do this by sleeping on each member using XactLockTableWait. Any
* members that belong to the current backend are *not* waited for, however;
* this would not merely be useless but would lead to Assert failure inside
* XactLockTableWait. By the time this returns, it is certain that all
* transactions *of other backends* that were members of the MultiXactId
* that conflict with the requested status are dead (and no new ones can have
* been added, since it is not legal to add members to an existing
* MultiXactId).
*
* But by the time we finish sleeping, someone else may have changed the Xmax
* of the containing tuple, so the caller needs to iterate on us somehow.
*
* Note that in case we return false, the number of remaining members is
* not to be trusted.
*/
bool DoMultiXactIdWait(MultiXactId multi, MultiXactStatus status, int *remaining, bool nowait, int waitSec)
{
bool result = true;
MultiXactMember *members = NULL;
int nmembers;
int remain = 0;
nmembers = GetMultiXactIdMembers(multi, &members);
for (int i = 0; i < nmembers; i++) {
TransactionId memxid = members[i].xid;
MultiXactStatus memstatus = members[i].status;
if (TransactionIdIsCurrentTransactionId(memxid)) {
remain++;
continue;
}
if (!DoLockModesConflict(LOCKMODE_FROM_MXSTATUS(memstatus), LOCKMODE_FROM_MXSTATUS(status))) {
if (remaining && TransactionIdIsInProgress(memxid))
remain++;
continue;
}
* This member conflicts with our multi, so we have to sleep (or
* return failure, if asked to avoid waiting.)
*/
if (nowait) {
result = ConditionalXactLockTableWait(memxid);
if (!result) {
break;
}
} else {
XactLockTableWait(memxid, true, waitSec);
}
}
pfree_ext(members);
if (remaining)
*remaining = remain;
return result;
}
* MultiXactIdWait
* Sleep on a MultiXactId.
*
* By the time we finish sleeping, someone else may have changed the Xmax
* of the containing tuple, so the caller needs to iterate on us somehow.
*
* We return (in *remaining, if not NULL) the number of members that are still
* running, including any (non-aborted) subtransactions of our own transaction.
*/
void MultiXactIdWait(MultiXactId multi, MultiXactStatus status, int *remaining, int waitSec)
{
DoMultiXactIdWait(multi, status, remaining, false, waitSec);
}
* ConditionalMultiXactIdWait
* As above, but only lock if we can get the lock without blocking.
*
* By the time we finish sleeping, someone else may have changed the Xmax
* of the containing tuple, so the caller needs to iterate on us somehow.
*
* If the multixact is now all gone, return true. Returns false if some
* transactions might still be running.
*
* We return (in *remaining, if not NULL) the number of members that are still
* running, including any (non-aborted) subtransactions of our own transaction.
*/
bool ConditionalMultiXactIdWait(MultiXactId multi, MultiXactStatus status, int *remaining)
{
return DoMultiXactIdWait(multi, status, remaining, true);
}
* CreateMultiXactId
* Make a new MultiXactId
*
* Make XLOG, SLRU and cache entries for a new MultiXactId, recording the
* given TransactionIds as members. Returns the newly created MultiXactId.
*
* NB: the passed members[] array will be sorted in-place.
*/
static MultiXactId CreateMultiXactId(int nmembers, MultiXactMember *members)
{
MultiXactId multi;
MultiXactOffset offset;
TransactionId *xidsWithStatus;
xl_multixact_create xlrec;
if (t_thrd.proc->workingVersionNum < ENHANCED_TUPLE_LOCK_VERSION_NUM) {
for (int i = 0; i < nmembers; ++i) {
if (members[i].status != MultiXactStatusForShare) {
ereport(ERROR, (errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("New MultiXact feature isn't support in this version. Please upgrade to version: %d",
ENHANCED_TUPLE_LOCK_VERSION_NUM)));
}
}
}
debug_elog3(DEBUG2, "Create: %s", mxid_to_string(InvalidMultiXactId, nmembers, members));
* See if the same set of members already exists in our cache; if so, just
* re-use that MultiXactId. (Note: it might seem that looking in our
* cache is insufficient, and we ought to search disk to see if a
* duplicate definition already exists. But since we only ever create
* MultiXacts containing our own XID, in most cases any such MultiXacts
* were in fact created by us, and so will be in our cache. There are
* corner cases where someone else added us to a MultiXact without our
* knowledge, but it's not worth checking for.)
*/
multi = mXactCacheGetBySet(nmembers, members);
if (MultiXactIdIsValid(multi)) {
ereport(DEBUG2, (errmsg("Create: in cache!")));
return multi;
}
{
int i;
bool has_update = false;
for (i = 0; i < nmembers; i++) {
if (ISUPDATE_from_mxstatus(members[i].status)) {
if (has_update)
ereport(ERROR, (errmsg("new multixact has more than one updating member")));
has_update = true;
}
}
}
xidsWithStatus = (TransactionId *)palloc((unsigned)nmembers * sizeof(TransactionId));
for (int i = 0; i < nmembers; ++i) {
xidsWithStatus[i] = GET_SLRU_XID_FROM_MULTIXACT_MEMBER(members + i);
}
* Assign the MXID and offsets range to use, and make sure there is space
* in the OFFSETs and MEMBERs files. NB: this routine does START_CRIT_SECTION().
*/
multi = GetNewMultiXactId(nmembers, &offset);
* Make an XLOG entry describing the new MXID.
*
* Note: we need not flush this XLOG entry to disk before proceeding. The
* only way for the MXID to be referenced from any data page is for
* heap_lock_tuple() to have put it there, and heap_lock_tuple() generates
* an XLOG record that must follow ours. The normal LSN interlock between
* the data page and that XLOG record will ensure that our XLOG record
* reaches disk first. If the SLRU members/offsets data reaches disk
* sooner than the XLOG record, we do not care because we'll overwrite it
* with zeroes unless the XLOG record is there too; see notes at top of
* this file.
*/
xlrec.mid = multi;
xlrec.moff = offset;
xlrec.nxids = nmembers;
XLogBeginInsert();
XLogRegisterData((char *)(&xlrec), MinSizeOfMultiXactCreate);
XLogRegisterData((char *)xidsWithStatus, (unsigned)nmembers * sizeof(TransactionId));
(void)XLogInsert(RM_MULTIXACT_ID, XLOG_MULTIXACT_CREATE_ID);
RecordNewMultiXact(multi, offset, nmembers, xidsWithStatus);
END_CRIT_SECTION();
mXactCachePut(multi, nmembers, members);
pfree(xidsWithStatus);
ereport(DEBUG2, (errmsg("Create: all done")));
return multi;
}
* RecordNewMultiXact
* Write info about a new multixact into the offsets and members files
*
* This is broken out of CreateMultiXactId so that xlog replay can use it.
*/
static void RecordNewMultiXact(MultiXactId multi, MultiXactOffset offset, int nmembers, TransactionId *xidsWithStatus)
{
if (SS_STANDBY_MODE) {
ereport(WARNING, (errmodule(MOD_DMS), errmsg("DMS standby can't set newmultixact status")));
return;
}
int64 pageno;
int64 prev_pageno;
int entryno;
int slotno;
MultiXactOffset *offptr = NULL;
int i;
LWLock* lock;
LWLock* prevlock = NULL;
pageno = (int64)MultiXactIdToOffsetPage(multi);
entryno = MultiXactIdToOffsetEntry(multi);
lock = SimpleLruGetBankLock(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, pageno);
LWLockAcquire(lock, LW_EXCLUSIVE);
* Note: we pass the MultiXactId to SimpleLruReadPage as the "transaction"
* to complain about if there's any I/O error. This is kinda bogus, but
* since the errors will always give the full pathname, it should be clear
* enough that a MultiXactId is really involved. Perhaps someday we'll
* take the trouble to generalize the slru.c error reporting code.
*/
slotno = SimpleLruReadPage(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, pageno, true, multi);
offptr = (MultiXactOffset *)t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl->shared->page_buffer[slotno];
offptr += entryno;
*offptr = offset;
t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl->shared->page_dirty[slotno] = true;
LWLockRelease(lock);
prev_pageno = -1;
for (i = 0; i < nmembers; i++, offset++) {
TransactionId *memberptr = NULL;
pageno = (int64)MXOffsetToMemberPage(offset);
entryno = MXOffsetToMemberEntry(offset);
if (pageno != prev_pageno) {
* MultiXactMember SLRU page is changed so check if this new page
* fall into the different SLRU bank then release the old bank's
* lock and acquire lock on the new bank.
*/
lock = SimpleLruGetBankLock(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, pageno);
SlruBankLockSwitch(prevlock, lock, LW_EXCLUSIVE);
slotno = SimpleLruReadPage(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, pageno, true, multi);
prev_pageno = pageno;
}
memberptr = (TransactionId *)t_thrd.shemem_ptr_cxt.MultiXactMemberCtl->shared->page_buffer[slotno];
memberptr += entryno;
*memberptr = xidsWithStatus[i];
t_thrd.shemem_ptr_cxt.MultiXactMemberCtl->shared->page_dirty[slotno] = true;
}
if (prevlock != NULL) {
LWLockRelease(prevlock);
}
}
* GetNewMultiXactId
* Get the next MultiXactId.
*
* Also, reserve the needed amount of space in the "members" area. The
* starting offset of the reserved space is returned in *offset.
*
* This may generate XLOG records for expansion of the offsets and/or members
* files. Unfortunately, we have to do that while holding MultiXactGenLock
* to avoid race conditions --- the XLOG record for zeroing a page must appear
* before any backend can possibly try to store data in that page!
*
* We start a critical section before advancing the shared counters. The
* caller must end the critical section after writing SLRU data.
*/
static MultiXactId GetNewMultiXactId(int nmembers, MultiXactOffset *offset)
{
MultiXactId result;
MultiXactOffset nextOffset;
ereport(DEBUG2, (errmsg("GetNew: for %d xids", nmembers)));
Assert(MultiXactIdIsValid(t_thrd.shemem_ptr_cxt.OldestMemberMXactId[t_thrd.proc_cxt.MyBackendId]));
(void)LWLockAcquire(MultiXactGenLock, LW_EXCLUSIVE);
if (t_thrd.shemem_ptr_cxt.MultiXactState->nextMXact < FirstMultiXactId)
t_thrd.shemem_ptr_cxt.MultiXactState->nextMXact = FirstMultiXactId;
* Assign the MXID, and make sure there is room for it in the file.
*/
result = t_thrd.shemem_ptr_cxt.MultiXactState->nextMXact;
ExtendMultiXactOffset(result);
* Reserve the members space, similarly to above. Also, be careful not to
* return zero as the starting offset for any multixact. See
* GetMultiXactIdMembers() for motivation.
*/
nextOffset = t_thrd.shemem_ptr_cxt.MultiXactState->nextOffset;
if (nextOffset == 0) {
*offset = 1;
nmembers++;
} else
*offset = nextOffset;
ExtendMultiXactMember(nextOffset, nmembers);
* Critical section from here until caller has written the data into the
* just-reserved SLRU space; we don't want to error out with a partly
* written MultiXact structure. (In particular, failing to write our
* start offset after advancing nextMXact would effectively corrupt the
* previous MultiXact.)
*/
START_CRIT_SECTION();
* Advance counters. As in GetNewTransactionId(), this must not happen
* until after file extension has succeeded!
*
* Note that nextMXact may be InvalidMultiXactId after this routine exits,
* so anyone else looking at the variable must be prepared to deal with that.
* Similarly, nextOffset may be zero, but we won't use that as the
* actual start offset of the next multixact.
*/
(t_thrd.shemem_ptr_cxt.MultiXactState->nextMXact)++;
t_thrd.shemem_ptr_cxt.MultiXactState->nextOffset += (unsigned)nmembers;
LWLockRelease(MultiXactGenLock);
ereport(DEBUG2, (errmsg("GetNew: returning %lu offset %lu", result, *offset)));
return result;
}
* 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.
*
* 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.
*/
int GetMultiXactIdMembers(MultiXactId multi, MultiXactMember **members)
{
int64 pageno;
int64 prev_pageno;
int entryno;
int slotno;
MultiXactOffset *offptr = NULL;
MultiXactOffset offset;
int length;
int truelength;
MultiXactId nextMXact;
MultiXactId tmpMXact;
MultiXactOffset nextOffset;
MultiXactMember *ptr = NULL;
MultiXactId oldestMXact;
LWLock* lock;
ereport(DEBUG2, (errmsg("GetMembers: asked for " XID_FMT, multi)));
Assert(MultiXactIdIsValid(multi));
length = mXactCacheGetById(multi, members);
if (length >= 0) {
debug_elog3(DEBUG2, "GetMembers: found %s in the cache", mxid_to_string(multi, length, *members));
return length;
}
MultiXactIdSetOldestVisible();
* We check known limits on MultiXact before resorting to the SLRU area.
*
* An ID >= nextMXact shouldn't ever be seen here;
*
* 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
* need both nextMXact and nextOffset; see below.
*/
(void)LWLockAcquire(MultiXactGenLock, LW_SHARED);
oldestMXact = t_thrd.shemem_ptr_cxt.MultiXactState->oldestMultiXactId;
nextMXact = t_thrd.shemem_ptr_cxt.MultiXactState->nextMXact;
nextOffset = t_thrd.shemem_ptr_cxt.MultiXactState->nextOffset;
LWLockRelease(MultiXactGenLock);
if (MultiXactIdPrecedes(multi, oldestMXact)) {
ereport(DEBUG2, (errmsg("MultiXactId %lu does no longer exist -- apparent wraparound", multi)));
*members = NULL;
return -1;
}
if (!MultiXactIdPrecedes(multi, nextMXact)) {
ereport(DEBUG2, (errmsg("MultiXactId %lu has not been created yet -- apparent wraparound", multi)));
*members = NULL;
return -1;
}
* Find out the offset at which we need to start reading MultiXactMembers
* and the number of members in the multixact. We determine the latter as
* the difference between this multixact's starting offset and the next
* one's. However, there are some corner cases to worry about:
*
* 1. This multixact may be the latest one created, in which case there is
* no next one to look at. In this case the nextOffset value we just
* saved is the correct endpoint.
*
* 2. The next multixact may still be in process of being filled in: that
* is, another process may have done GetNewMultiXactId but not yet written
* the offset entry for that ID. In that scenario, it is guaranteed that
* the offset entry for that multixact exists (because GetNewMultiXactId
* won't release MultiXactGenLock until it does) but contains zero
* (because we are careful to pre-zero offset pages). Because
* GetNewMultiXactId will never return zero as the starting offset for a
* multixact, when we read zero as the next multixact's offset, we know we
* have this case. We sleep for a bit and try again.
*
* 3. Because GetNewMultiXactId increments offset zero to offset one to
* handle case #2, there is an ambiguity near the point of offset
* wraparound. If we see next multixact's offset is one, is that our multixact's actual
* endpoint, or did it end at zero with a subsequent increment? We
* handle this using the knowledge that if the zero'th member slot wasn't
* filled, it'll contain zero, and zero isn't a valid transaction ID so it can't
* be a multixact member. Therefore, if we read a zero from the
* members array, just ignore it.
*
* This is all pretty messy, but the mess occurs only in infrequent corner
* cases, so it seems better than holding the MultiXactGenLock for a long
* time on every multixact creation.
*/
retry:
pageno = MultiXactIdToOffsetPage(multi);
entryno = MultiXactIdToOffsetEntry(multi);
lock = SimpleLruGetBankLock(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, pageno);
LWLockAcquire(lock, LW_EXCLUSIVE);
slotno = SimpleLruReadPage(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, pageno, true, multi);
offptr = (MultiXactOffset *)t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl->shared->page_buffer[slotno];
offptr += entryno;
offset = *offptr;
Assert(offset != 0);
tmpMXact = multi + 1;
if (nextMXact == tmpMXact) {
length = nextOffset - offset;
} else {
MultiXactOffset nextMXOffset;
prev_pageno = pageno;
pageno = (int64)MultiXactIdToOffsetPage(tmpMXact);
entryno = MultiXactIdToOffsetEntry(tmpMXact);
if (pageno != prev_pageno) {
LWLock* newLock;
* Since we're going to access a different SLRU page, if this page
* falls under a different bank, release the old bank's lock and
* acquire the lock of the new bank.
*/
newLock = SimpleLruGetBankLock(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, pageno);
if (newLock != lock) {
LWLockRelease(lock);
LWLockAcquire(newLock, LW_EXCLUSIVE);
lock = newLock;
}
slotno = SimpleLruReadPage(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, pageno, true, tmpMXact);
}
offptr = (MultiXactOffset *)t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl->shared->page_buffer[slotno];
offptr += entryno;
nextMXOffset = *offptr;
if (nextMXOffset == 0) {
LWLockRelease(lock);
lock = NULL;
pg_usleep(1000L);
goto retry;
}
length = nextMXOffset - offset;
}
LWLockRelease(lock);
lock = NULL;
ptr = (MultiXactMember *)palloc((unsigned)length * sizeof(MultiXactMember));
*members = ptr;
truelength = 0;
prev_pageno = -1;
for (int i = 0; i < length; i++, offset++) {
TransactionId *xactptr = NULL;
TransactionId memberXid;
pageno = (int64)MXOffsetToMemberPage(offset);
entryno = MXOffsetToMemberEntry(offset);
if (pageno != prev_pageno) {
LWLock* newLock;
* Since we're going to access a different SLRU page, if this page
* falls under a different bank, release the old bank's lock and
* acquire the lock of the new bank.
*/
newLock = SimpleLruGetBankLock(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, pageno);
SlruBankLockSwitch(lock, newLock, LW_EXCLUSIVE);
slotno = SimpleLruReadPage(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, pageno, true, multi);
prev_pageno = pageno;
}
xactptr = (TransactionId *)t_thrd.shemem_ptr_cxt.MultiXactMemberCtl->shared->page_buffer[slotno];
xactptr += entryno;
memberXid = GET_MEMBER_XID_FROM_SLRU_XID(*xactptr);
if (!TransactionIdIsValid(memberXid)) {
Assert(offset == 0);
continue;
}
ptr[truelength].xid = memberXid;
ptr[truelength].status = GET_MEMBER_STATUS_FROM_SLRU_XID(*xactptr);
++truelength;
}
LWLockRelease(lock);
* Copy the result into the local cache.
*/
mXactCachePut(multi, truelength, ptr);
debug_elog3(DEBUG2, "GetMembers: no cache for %s", mxid_to_string(multi, truelength, ptr));
return truelength;
}
* MXactMemberComparator
* qsort comparison function for MultiXactMember
*/
static int MXactMemberComparator(const void *arg1, const void *arg2)
{
MultiXactMember member1 = *(const MultiXactMember *)arg1;
MultiXactMember member2 = *(const MultiXactMember *)arg2;
if (member1.xid > member2.xid) {
return 1;
}
if (member1.xid < member2.xid) {
return -1;
}
* Because of compatibility, we set MultiXactStatusForShare = 0x00.
* But for status strength, MultiXactStatusForKeyShare = 0x01 is
* weaker thean MultiXactStatusForShare, so we exchange these two
* value.
*/
int status1 = (member1.status == MultiXactStatusForShare) ? 1 :
((member1.status == MultiXactStatusForKeyShare) ? 0 : (int)(member1.status));
int status2 = (member2.status == MultiXactStatusForShare) ? 1 :
((member2.status == MultiXactStatusForKeyShare) ? 0 : (int)(member2.status));
if (status1 > status2) {
return 1;
}
if (status1 < status2) {
return -1;
}
return 0;
}
* mXactCacheGetBySet
* returns a MultiXactId from the cache based on the set of
* TransactionIds that compose it, or InvalidMultiXactId if
* none matches.
*
* This is helpful, for example, if two transactions want to lock a huge
* table. By using the cache, the second will use the same MultiXactId
* for the majority of tuples, thus keeping MultiXactId usage low (saving
* both I/O).
*
* NB: the passed members[] array will be sorted in-place.
*/
static MultiXactId mXactCacheGetBySet(int nmembers, MultiXactMember *members)
{
dlist_iter iter;
debug_elog3(DEBUG2, "CacheGet: looking for %s", mxid_to_string(InvalidMultiXactId, nmembers, members));
qsort(members, nmembers, sizeof(MultiXactMember), MXactMemberComparator);
dlist_foreach(iter, &t_thrd.xact_cxt.MXactCache) {
mXactCacheEnt *entry = dlist_container(mXactCacheEnt, node, iter.cur);
if (entry->nmembers != nmembers)
continue;
if (memcmp(members, entry->members, (unsigned)nmembers * sizeof(MultiXactMember)) == 0) {
ereport(DEBUG2, (errmsg("CacheGet: found " XID_FMT, entry->multi)));
dlist_move_head(&t_thrd.xact_cxt.MXactCache, iter.cur);
return entry->multi;
}
}
ereport(DEBUG2, (errmsg("CacheGet: not found :-(")));
return InvalidMultiXactId;
}
* mXactCacheGetById
* returns the composing MultiXactMember set from the cache for a
* given MultiXactId, if present.
*
* If successful, *members is set to the address of a palloc'd copy of the
* MultiXactMember set. Return value is number of members, or -1 on failure.
*/
static int mXactCacheGetById(MultiXactId multi, MultiXactMember **members)
{
if (ENABLE_DMS && t_thrd.role == DMS_WORKER) {
return -1;
}
dlist_iter iter;
errno_t rc = EOK;
ereport(DEBUG2, (errmsg("CacheGet: looking for " XID_FMT, multi)));
dlist_foreach(iter, &t_thrd.xact_cxt.MXactCache) {
mXactCacheEnt *entry = dlist_container(mXactCacheEnt, node, iter.cur);
if (entry->multi == multi) {
MultiXactMember *ptr = NULL;
Size size;
size = sizeof(MultiXactMember) * (unsigned)entry->nmembers;
ptr = (MultiXactMember *)palloc(size);
*members = ptr;
rc = memcpy_s(ptr, size, entry->members, size);
securec_check(rc, "", "");
debug_elog3(DEBUG2, "CacheGet: found %s", mxid_to_string(multi, entry->nmembers, entry->members));
* Note we modify the list while not using a modifyable iterator.
* This is acceptable only because we exit the iteration
* immediately afterwards.
*/
dlist_move_head(&t_thrd.xact_cxt.MXactCache, iter.cur);
return entry->nmembers;
}
}
ereport(DEBUG2, (errmsg("CacheGet: not found")));
return -1;
}
* mXactCachePut
* Add a new MultiXactId and its composing set into the local cache.
*/
static void mXactCachePut(MultiXactId multi, int nmembers, MultiXactMember *members)
{
if (ENABLE_DMS && t_thrd.role == DMS_WORKER) {
return;
}
mXactCacheEnt *entry = NULL;
errno_t rc = EOK;
debug_elog3(DEBUG2, "CachePut: storing %s", mxid_to_string(multi, nmembers, members));
if (t_thrd.xact_cxt.MXactContext == NULL) {
ereport(DEBUG2, (errmsg("CachePut: initializing memory context")));
t_thrd.xact_cxt.MXactContext = AllocSetContextCreate(u_sess->top_transaction_mem_cxt, "MultiXact Cache Context",
ALLOCSET_SMALL_MINSIZE, ALLOCSET_SMALL_INITSIZE,
ALLOCSET_SMALL_MAXSIZE);
}
entry = (mXactCacheEnt *)MemoryContextAlloc(t_thrd.xact_cxt.MXactContext,
offsetof(mXactCacheEnt, members) + (unsigned)nmembers * sizeof(MultiXactMember));
entry->multi = multi;
entry->nmembers = nmembers;
rc = memcpy_s(entry->members, (unsigned)nmembers * sizeof(MultiXactMember), members,
(unsigned)nmembers * sizeof(MultiXactMember));
securec_check(rc, "", "");
qsort(entry->members, nmembers, sizeof(MultiXactMember), MXactMemberComparator);
dlist_push_head(&t_thrd.xact_cxt.MXactCache, &entry->node);
if (t_thrd.xact_cxt.MXactCacheMembers++ >= MAX_CACHE_ENTRIES) {
dlist_node *node;
node = dlist_tail_node(&t_thrd.xact_cxt.MXactCache);
dlist_delete(node);
t_thrd.xact_cxt.MXactCacheMembers--;
entry = dlist_container(mXactCacheEnt, node, node);
debug_elog3(DEBUG2, "CachePut: pruning cached multi %u", entry->multi);
pfree(entry);
}
}
static const char *MXStatusToString(MultiXactStatus status)
{
switch (status) {
case MultiXactStatusForKeyShare:
return "keysh";
case MultiXactStatusForShare:
return "sh";
case MultiXactStatusForNoKeyUpdate:
return "fornokeyupd";
case MultiXactStatusForUpdate:
return "forupd";
case MultiXactStatusNoKeyUpdate:
return "nokeyupd";
case MultiXactStatusUpdate:
return "upd";
default:
elog(ERROR, "unrecognized multixact status %d", (int)status);
return "";
}
}
static char *mxid_to_string(MultiXactId multi, int nmembers, MultiXactMember *members)
{
char *str = NULL;
StringInfoData buf;
int i;
initStringInfo(&buf);
appendStringInfo(&buf, XID_FMT " %d[" XID_FMT " (%s)", multi, nmembers,
members[0].xid, MXStatusToString(members[0].status));
for (i = 1; i < nmembers; i++) {
appendStringInfo(&buf, ", " XID_FMT " (%s)", members[i].xid, MXStatusToString(members[i].status));
}
appendStringInfoChar(&buf, ']');
str = MemoryContextStrdup(SESS_GET_MEM_CXT_GROUP(MEMORY_CONTEXT_STORAGE), buf.data);
pfree(buf.data);
return str;
}
* AtEOXact_MultiXact
* Handle transaction end for MultiXact
*
* This is called at top transaction commit or abort (we don't care which).
*/
void AtEOXact_MultiXact(void)
{
* Reset our OldestMemberMXactId and OldestVisibleMXactId values, both of
* which should only be valid while within a transaction.
*
* We assume that storing a MultiXactId is atomic and so we need not take
* MultiXactGenLock to do this.
*/
t_thrd.shemem_ptr_cxt.OldestMemberMXactId[t_thrd.proc_cxt.MyBackendId] = InvalidMultiXactId;
t_thrd.shemem_ptr_cxt.OldestVisibleMXactId[t_thrd.proc_cxt.MyBackendId] = InvalidMultiXactId;
* Discard the local MultiXactId cache. Since MXactContext was created as
* a child of u_sess->top_transaction_mem_cxt, we needn't delete it explicitly.
*/
t_thrd.xact_cxt.MXactContext = NULL;
dlist_init(&t_thrd.xact_cxt.MXactCache);
t_thrd.xact_cxt.MXactCacheMembers = 0;
}
* AtPrepare_MultiXact
* Save multixact state at 2PC transaction prepare
*
* In this phase, we only store our OldestMemberMXactId value in the two-phase
* state file.
*/
void AtPrepare_MultiXact(void)
{
MultiXactId myOldestMember = t_thrd.shemem_ptr_cxt.OldestMemberMXactId[t_thrd.proc_cxt.MyBackendId];
if (MultiXactIdIsValid(myOldestMember))
RegisterTwoPhaseRecord(TWOPHASE_RM_MULTIXACT_ID, 0, &myOldestMember, sizeof(MultiXactId));
}
* PostPrepare_MultiXact
* Clean up after successful PREPARE TRANSACTION
*/
void PostPrepare_MultiXact(TransactionId xid)
{
MultiXactId myOldestMember;
* Transfer our OldestMemberMXactId value to the slot reserved for the
* prepared transaction.
*/
myOldestMember = t_thrd.shemem_ptr_cxt.OldestMemberMXactId[t_thrd.proc_cxt.MyBackendId];
if (MultiXactIdIsValid(myOldestMember)) {
BackendId dummyBackendId = TwoPhaseGetDummyBackendId(xid);
* Even though storing MultiXactId is atomic, acquire lock to make
* sure others see both changes, not just the reset of the slot of the
* current backend. Using a volatile pointer might suffice, but this
* isn't a hot spot.
*/
(void)LWLockAcquire(MultiXactGenLock, LW_EXCLUSIVE);
t_thrd.shemem_ptr_cxt.OldestMemberMXactId[dummyBackendId] = myOldestMember;
t_thrd.shemem_ptr_cxt.OldestMemberMXactId[t_thrd.proc_cxt.MyBackendId] = InvalidMultiXactId;
LWLockRelease(MultiXactGenLock);
}
* We don't need to transfer OldestVisibleMXactId value, because the
* transaction is not going to be looking at any more multixacts once it's
* prepared.
*
* We assume that storing a MultiXactId is atomic and so we need not take
* MultiXactGenLock to do this.
*/
t_thrd.shemem_ptr_cxt.OldestVisibleMXactId[t_thrd.proc_cxt.MyBackendId] = InvalidMultiXactId;
* Discard the local MultiXactId cache like in AtEOX_MultiXact
*/
t_thrd.xact_cxt.MXactContext = NULL;
dlist_init(&t_thrd.xact_cxt.MXactCache);
t_thrd.xact_cxt.MXactCacheMembers = 0;
}
* multixact_twophase_recover
* Recover the state of a prepared transaction at startup
*/
void multixact_twophase_recover(TransactionId xid, uint16 info, void *recdata, uint32 len)
{
BackendId dummyBackendId = TwoPhaseGetDummyBackendId(xid);
MultiXactId oldestMember;
* Get the oldest member XID from the state file record, and set it in the
* OldestMemberMXactId slot reserved for this prepared transaction.
*/
Assert(len == sizeof(MultiXactId));
oldestMember = *((MultiXactId *)recdata);
t_thrd.shemem_ptr_cxt.OldestMemberMXactId[dummyBackendId] = oldestMember;
}
* multixact_twophase_postcommit
* Similar to AtEOX_MultiXact but for COMMIT PREPARED
*/
void multixact_twophase_postcommit(TransactionId xid, uint16 info, void *recdata, uint32 len)
{
BackendId dummyBackendId = TwoPhaseGetDummyBackendId(xid);
Assert(len == sizeof(MultiXactId));
t_thrd.shemem_ptr_cxt.OldestMemberMXactId[dummyBackendId] = InvalidMultiXactId;
}
* multixact_twophase_postabort
* This is actually just the same as the COMMIT case.
*/
void multixact_twophase_postabort(TransactionId xid, uint16 info, void *recdata, uint32 len)
{
multixact_twophase_postcommit(xid, info, recdata, len);
}
* Initialization of shared memory for MultiXact. We use two SLRU areas,
* thus double memory. Also, reserve space for the shared MultiXactState
* struct and the per-backend MultiXactId arrays (two of those, too).
*/
Size MultiXactShmemSize(void)
{
Size size;
#define SHARED_MULTIXACT_STATE_SIZE \
add_size(sizeof(MultiXactStateData), mul_size(sizeof(MultiXactId) * 2, MaxOldestSlot))
size = SHARED_MULTIXACT_STATE_SIZE;
if (ENABLE_DSS) {
size = add_size(size, SimpleLruShmemSize(DSS_MAX_MXACTOFFSET, 0, true));
size = add_size(size, SimpleLruShmemSize(DSS_MAX_MXACTMEMBER, 0, true));
} else {
size = add_size(size, SimpleLruShmemSize(MULTIXACT_OFFSET_BUFFERS, 0, true));
size = add_size(size, SimpleLruShmemSize(MULTIXACT_MEMBER_BUFFERS, 0, true));
}
return size;
}
void MultiXactShmemInit(void)
{
bool found = false;
errno_t rc = EOK;
char path[MAXPGPATH];
debug_elog2(DEBUG2, "Shared Memory Init for MultiXact");
rc = snprintf_s(path, MAXPGPATH, MAXPGPATH - 1, "%s/offsets", MULTIXACTDIR);
securec_check_ss(rc, "\0", "\0");
if (ENABLE_DSS) {
SimpleLruInit(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, GetBuiltInTrancheName(LWTRANCHE_MULTIXACTOFFSET_CTL),
LWTRANCHE_MULTIXACTOFFSET_CTL, LWTRANCHE_MULTIXACTOFFSET_SLRU, DSS_MAX_MXACTOFFSET, 0,
MultiXactOffsetControlLock, path, 0, true);
} else {
SimpleLruInit(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, GetBuiltInTrancheName(LWTRANCHE_MULTIXACTOFFSET_CTL),
LWTRANCHE_MULTIXACTOFFSET_CTL, LWTRANCHE_MULTIXACTOFFSET_SLRU, MULTIXACT_OFFSET_BUFFERS, 0,
MultiXactOffsetControlLock, path, 0, true);
}
rc = snprintf_s(path, MAXPGPATH, MAXPGPATH - 1, "%s/members", MULTIXACTDIR);
securec_check_ss(rc, "\0", "\0");
if (ENABLE_DSS) {
SimpleLruInit(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, GetBuiltInTrancheName(LWTRANCHE_MULTIXACTMEMBER_CTL),
LWTRANCHE_MULTIXACTMEMBER_CTL, LWTRANCHE_MULTIXACTMEMBER_SLRU, DSS_MAX_MXACTMEMBER, 0,
MultiXactMemberControlLock, path, 0, true);
} else {
SimpleLruInit(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, GetBuiltInTrancheName(LWTRANCHE_MULTIXACTMEMBER_CTL),
LWTRANCHE_MULTIXACTMEMBER_CTL, LWTRANCHE_MULTIXACTMEMBER_SLRU, MULTIXACT_MEMBER_BUFFERS, 0,
MultiXactMemberControlLock, path, 0, true);
}
t_thrd.shemem_ptr_cxt.MultiXactState = (MultiXactStateData *)ShmemInitStruct("Shared MultiXact State",
SHARED_MULTIXACT_STATE_SIZE, &found);
if (!IsUnderPostmaster) {
Assert(!found);
rc = memset_s(t_thrd.shemem_ptr_cxt.MultiXactState, SHARED_MULTIXACT_STATE_SIZE, 0,
SHARED_MULTIXACT_STATE_SIZE);
securec_check(rc, "", "");
} else
Assert(found);
* Set up array pointers. Note that perBackendXactIds[0] is wasted space
* since we only use indexes 1..MaxOldestSlot in each array.
*/
t_thrd.shemem_ptr_cxt.OldestMemberMXactId = t_thrd.shemem_ptr_cxt.MultiXactState->perBackendXactIds;
t_thrd.shemem_ptr_cxt.OldestVisibleMXactId = t_thrd.shemem_ptr_cxt.OldestMemberMXactId + MaxOldestSlot;
}
* This func must be called ONCE on system install. It creates the initial
* MultiXact segments. (The MultiXacts directories are assumed to have been
* created by initdb, and MultiXactShmemInit must have been called already.)
*/
void BootStrapMultiXact(void)
{
int slotno;
LWLock* lock;
lock = SimpleLruGetBankLock(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, 0);
LWLockAcquire(lock, LW_EXCLUSIVE);
slotno = ZeroMultiXactOffsetPage(0, false);
SimpleLruWritePage(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, slotno);
Assert(!t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl->shared->page_dirty[slotno]);
LWLockRelease(lock);
lock = SimpleLruGetBankLock(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, 0);
LWLockAcquire(lock, LW_EXCLUSIVE);
slotno = ZeroMultiXactMemberPage(0, false);
SimpleLruWritePage(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, slotno);
Assert(!t_thrd.shemem_ptr_cxt.MultiXactMemberCtl->shared->page_dirty[slotno]);
LWLockRelease(lock);
}
* Initialize (or reinitialize) a page of MultiXactOffset to zeroes.
* If writeXlog is TRUE, also emit an XLOG record saying we did this.
*
* The page is not actually written, just set up in shared memory.
* The slot number of the new page is returned.
*
* Control lock must be held at entry, and will be held at exit.
*/
static int ZeroMultiXactOffsetPage(int64 pageno, bool writeXlog)
{
int slotno;
slotno = SimpleLruZeroPage(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, pageno, NULL);
if (writeXlog)
WriteMZeroPageXlogRec(pageno, XLOG_MULTIXACT_ZERO_OFF_PAGE);
return slotno;
}
* Ditto, for MultiXactMember
*/
static int ZeroMultiXactMemberPage(int64 pageno, bool writeXlog)
{
int slotno;
bool bPZeroPage = true;
slotno = SimpleLruZeroPage(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, pageno, &bPZeroPage);
if (writeXlog && bPZeroPage)
WriteMZeroPageXlogRec(pageno, XLOG_MULTIXACT_ZERO_MEM_PAGE);
return slotno;
}
* This must be called ONCE during postmaster or standalone-backend startup.
*
* StartupXLOG has already established nextMXact/nextOffset by calling
* MultiXactSetNextMXact and/or MultiXactAdvanceNextMXact. Note that we
* may already have replayed WAL data into the SLRU files.
*
* We don't need any locks here, really; the SLRU locks are taken
* only because slru.c expects to be called with locks held.
*/
void StartupMultiXact(void)
{
MultiXactId multi = t_thrd.shemem_ptr_cxt.MultiXactState->nextMXact;
MultiXactOffset offset = t_thrd.shemem_ptr_cxt.MultiXactState->nextOffset;
errno_t rc = EOK;
int64 pageno;
int64 entryno;
* Initialize our idea of the latest page number.
*/
pageno = (int64)MultiXactIdToOffsetPage(multi);
t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl->shared->latest_page_number = pageno;
* Zero out the remainder of the current offsets page. See notes in
* StartupCLOG() for motivation.
*/
entryno = (int64)MultiXactIdToOffsetEntry(multi);
if (entryno != 0) {
int slotno;
MultiXactOffset *offptr = NULL;
LWLock* lock = SimpleLruGetBankLock(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, pageno);
LWLockAcquire(lock, LW_EXCLUSIVE);
slotno = SimpleLruReadPage(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, pageno, true, multi);
offptr = (MultiXactOffset *)t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl->shared->page_buffer[slotno];
offptr += entryno;
rc = memset_s(offptr, BLCKSZ - ((unsigned)entryno * sizeof(MultiXactOffset)), 0,
BLCKSZ - ((unsigned)entryno * sizeof(MultiXactOffset)));
securec_check(rc, "", "");
t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl->shared->page_dirty[slotno] = true;
LWLockRelease(lock);
}
* Initialize our idea of the latest page number.
*/
pageno = (int64)MXOffsetToMemberPage(offset);
t_thrd.shemem_ptr_cxt.MultiXactMemberCtl->shared->latest_page_number = pageno;
* Zero out the remainder of the current members page. See notes in
* TrimCLOG() for motivation.
*/
entryno = (int64)MXOffsetToMemberEntry(offset);
if (entryno != 0) {
int slotno;
TransactionId *xidptr = NULL;
LWLock* lock = SimpleLruGetBankLock(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, pageno);
LWLockAcquire(lock, LW_EXCLUSIVE);
slotno = SimpleLruReadPage(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, pageno, true, offset);
xidptr = (TransactionId *)t_thrd.shemem_ptr_cxt.MultiXactMemberCtl->shared->page_buffer[slotno];
xidptr += entryno;
rc = memset_s(xidptr, BLCKSZ - ((unsigned)entryno * sizeof(TransactionId)), 0,
BLCKSZ - ((unsigned)entryno * sizeof(TransactionId)));
securec_check(rc, "", "");
t_thrd.shemem_ptr_cxt.MultiXactMemberCtl->shared->page_dirty[slotno] = true;
LWLockRelease(lock);
}
* Initialize lastTruncationPoint to invalid, ensuring that the first
* checkpoint will try to do truncation.
*/
t_thrd.shemem_ptr_cxt.MultiXactState->lastTruncationPoint = InvalidMultiXactId;
}
* This must be called ONCE during postmaster or standalone-backend shutdown
*/
void ShutdownMultiXact(void)
{
TRACE_POSTGRESQL_MULTIXACT_CHECKPOINT_START(false);
(void)SimpleLruFlush(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, false);
(void)SimpleLruFlush(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, false);
TRACE_POSTGRESQL_MULTIXACT_CHECKPOINT_DONE(false);
}
* Get the next MultiXactId and offset to save in a checkpoint record
*/
void MultiXactGetCheckptMulti(bool is_shutdown, MultiXactId *nextMulti, MultiXactOffset *nextMultiOffset)
{
(void)LWLockAcquire(MultiXactGenLock, LW_SHARED);
*nextMulti = t_thrd.shemem_ptr_cxt.MultiXactState->nextMXact;
*nextMultiOffset = t_thrd.shemem_ptr_cxt.MultiXactState->nextOffset;
LWLockRelease(MultiXactGenLock);
ereport(DEBUG2, (errmsg("MultiXact: checkpoint is nextMulti %lu, nextOffset %lu", *nextMulti, *nextMultiOffset)));
}
* Perform a checkpoint --- either during shutdown, or on-the-fly
*/
void CheckPointMultiXact(void)
{
TRACE_POSTGRESQL_MULTIXACT_CHECKPOINT_START(true);
int flush_num;
flush_num = SimpleLruFlush(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, true);
g_instance.ckpt_cxt_ctl->ckpt_view.ckpt_multixact_flush_num += flush_num;
flush_num = SimpleLruFlush(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, true);
g_instance.ckpt_cxt_ctl->ckpt_view.ckpt_multixact_flush_num += flush_num;
#ifdef ENABLE_MULTIPLE_NODES
* Truncate the SLRU files. This could be done at any time, but
* checkpoint seems a reasonable place for it. There is one exception: if
* we are called during xlog recovery, then shared->latest_page_number
* isn't valid (because StartupMultiXact hasn't been called yet) and so
* SimpleLruTruncate would get confused. It seems best not to risk
* removing any data during recovery anyway, so don't truncate.
*/
if (!RecoveryInProgress())
TruncateMultiXact();
#endif
TRACE_POSTGRESQL_MULTIXACT_CHECKPOINT_DONE(true);
}
* Set the next-to-be-assigned MultiXactId and offset
*
* This is used when we can determine the correct next ID/offset exactly
* from a checkpoint record. Although this is only called during bootstrap
* and XLog replay, we take the lock in case any hot-standby backends are
* examining the values.
*/
void MultiXactSetNextMXact(MultiXactId nextMulti, MultiXactOffset nextMultiOffset)
{
debug_elog4(DEBUG2, "MultiXact: setting next multi to %u offset %u", nextMulti, nextMultiOffset);
(void)LWLockAcquire(MultiXactGenLock, LW_EXCLUSIVE);
t_thrd.shemem_ptr_cxt.MultiXactState->nextMXact = nextMulti;
t_thrd.shemem_ptr_cxt.MultiXactState->nextOffset = nextMultiOffset;
LWLockRelease(MultiXactGenLock);
}
* Determine the last safe MultiXactId to allocate given the currently oldest
* datminmxid (ie, the oldest MultiXactId that might exist in any database
* of our cluster), and the OID of the (or a) database with that value.
*/
void SetMultiXactIdLimit(MultiXactId oldest_datminmxid, Oid oldest_datoid)
{
MultiXactId multiVacLimit;
MultiXactId curMulti;
Assert(MultiXactIdIsValid(oldest_datminmxid));
* We'll start trying to force autovacuums when oldest_datminmxid gets
* to be more than autovacuum_freeze_max_age mxids old.
*
* It's a bit ugly to just reuse limits for xids that way, but it doesn't
* seem worth adding separate GUCs for that purpose.
*/
multiVacLimit = oldest_datminmxid + g_instance.attr.attr_storage.autovacuum_freeze_max_age;
if (multiVacLimit < FirstMultiXactId)
multiVacLimit += FirstMultiXactId;
LWLockAcquire(MultiXactGenLock, LW_EXCLUSIVE);
t_thrd.shemem_ptr_cxt.MultiXactState->oldestMultiXactId = oldest_datminmxid;
t_thrd.shemem_ptr_cxt.MultiXactState->oldestMultiXactDB = oldest_datoid;
t_thrd.shemem_ptr_cxt.MultiXactState->multiVacLimit = multiVacLimit;
curMulti = t_thrd.shemem_ptr_cxt.MultiXactState->nextMXact;
LWLockRelease(MultiXactGenLock);
* If past the autovacuum force point, immediately signal an autovac
* request. The reason for this is that autovac only processes one
* database per invocation. Once it's finished cleaning up the oldest
* database, it'll call here, and we'll signal the postmaster to start
* another iteration immediately if there are still any old databases.
*/
if (MultiXactIdPrecedes(multiVacLimit, curMulti) && IsUnderPostmaster && !t_thrd.xlog_cxt.InRecovery)
SendPostmasterSignal(PMSIGNAL_START_AUTOVAC_LAUNCHER);
}
* Ensure the next-to-be-assigned MultiXactId is at least minMulti,
* and similarly nextOffset is at least minMultiOffset.
*
* This is used when we can determine minimum safe values from an XLog
* record (either an on-line checkpoint or an mxact creation log entry).
* Although this is only called during XLog replay, we take the lock in case
* any hot-standby backends are examining the values.
*/
void MultiXactAdvanceNextMXact(MultiXactId minMulti, MultiXactOffset minMultiOffset)
{
(void)LWLockAcquire(MultiXactGenLock, LW_EXCLUSIVE);
if (MultiXactIdPrecedes(t_thrd.shemem_ptr_cxt.MultiXactState->nextMXact, minMulti)) {
ereport(DEBUG2, (errmsg("MultiXact: setting next multi to %lu", minMulti)));
t_thrd.shemem_ptr_cxt.MultiXactState->nextMXact = minMulti;
}
if (t_thrd.shemem_ptr_cxt.MultiXactState->nextOffset < minMultiOffset) {
ereport(DEBUG2, (errmsg("MultiXact: setting next offset to %lu", minMultiOffset)));
t_thrd.shemem_ptr_cxt.MultiXactState->nextOffset = minMultiOffset;
}
LWLockRelease(MultiXactGenLock);
}
* Update our oldestMultiXactId value, but only if it's more recent than
* what we had.
*/
void MultiXactAdvanceOldest(MultiXactId oldestMulti, Oid oldestMultiDB)
{
if (MultiXactIdPrecedes(t_thrd.shemem_ptr_cxt.MultiXactState->oldestMultiXactId, oldestMulti))
SetMultiXactIdLimit(oldestMulti, oldestMultiDB);
}
* Make sure that MultiXactOffset has room for a newly-allocated MultiXactId.
*
* NB: this is called while holding MultiXactGenLock. We want it to be very
* fast most of the time; even when it's not so fast, no actual I/O need
* happen unless we're forced to write out a dirty log or xlog page to make
* room in shared memory.
*/
static void ExtendMultiXactOffset(MultiXactId multi)
{
int64 pageno;
LWLock* lock;
* No work except at first MultiXactId of a page.
*/
if (MultiXactIdToOffsetEntry(multi) != 0 && multi != FirstMultiXactId)
return;
pageno = (int64)MultiXactIdToOffsetPage(multi);
lock = SimpleLruGetBankLock(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, pageno);
(void)LWLockAcquire(lock, LW_EXCLUSIVE);
ZeroMultiXactOffsetPage(pageno, true);
LWLockRelease(lock);
}
* Make sure that MultiXactMember has room for the members of a newly-
* allocated MultiXactId.
*
* Like the above routine, this is called while holding MultiXactGenLock;
* same comments apply.
*/
static void ExtendMultiXactMember(MultiXactOffset offset, int nmembers)
{
* It's possible that the members span more than one page of the members
* file, so we loop to ensure we consider each page. The coding is not
* optimal if the members span several pages, but that seems unusual
* enough to not worry much about.
*/
while (nmembers > 0) {
int entryno;
* Only zero when at first entry of a page.
*/
entryno = MXOffsetToMemberEntry(offset);
if (entryno == 0) {
int64 pageno;
LWLock* lock;
pageno = (int64)MXOffsetToMemberPage(offset);
lock = SimpleLruGetBankLock(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, pageno);
(void)LWLockAcquire(lock, LW_EXCLUSIVE);
ZeroMultiXactMemberPage(pageno, true);
LWLockRelease(lock);
}
offset += (MULTIXACT_MEMBERS_PER_PAGE - entryno);
nmembers -= (MULTIXACT_MEMBERS_PER_PAGE - entryno);
}
}
* GetOldestMultiXactId
*
* Return the oldest MultiXactId that's still possibly still seen as live by
* any running transaction. Older ones might still exist on disk, but they no
* longer have any running member transaction.
*
* It's not safe to truncate MultiXact SLRU segments on the value returned by
* this function; however, it can be used by a full-table vacuum to set the
* point at which it will be possible to truncate SLRU for that table.
*/
MultiXactId GetOldestMultiXactId(void)
{
MultiXactId oldestMXact;
MultiXactId nextMXact;
int i;
* This is the oldest valid value among all the OldestMemberMXactId[] and
* OldestVisibleMXactId[] entries, or nextMXact if none are valid.
*/
(void)LWLockAcquire(MultiXactGenLock, LW_SHARED);
* We have to beware of the possibility that nextMXact is in the
* wrapped-around state. We don't fix the counter itself here, but we
* must be sure to use a valid value in our calculation.
*/
nextMXact = t_thrd.shemem_ptr_cxt.MultiXactState->nextMXact;
if (nextMXact < FirstMultiXactId)
nextMXact = FirstMultiXactId;
oldestMXact = nextMXact;
for (i = 1; i <= MaxOldestSlot; i++) {
MultiXactId thisoldest;
thisoldest = t_thrd.shemem_ptr_cxt.OldestMemberMXactId[i];
if (MultiXactIdIsValid(thisoldest) && MultiXactIdPrecedes(thisoldest, oldestMXact))
oldestMXact = thisoldest;
thisoldest = t_thrd.shemem_ptr_cxt.OldestVisibleMXactId[i];
if (MultiXactIdIsValid(thisoldest) && MultiXactIdPrecedes(thisoldest, oldestMXact))
oldestMXact = thisoldest;
}
LWLockRelease(MultiXactGenLock);
return oldestMXact;
}
#ifndef ENABLE_MULTIPLE_NODES
typedef struct mxtruncinfo {
int earliestExistingPage;
} mxtruncinfo;
* Decide whether a MultiXactOffset page number is "older" for truncation
* purposes. Analogous to CLOGPagePrecedes().
*
* Offsetting the values is optional, because MultiXactIdPrecedes() has
* translational symmetry.
*/
static bool MultiXactOffsetPagePrecedes(int page1, int page2)
{
MultiXactId multi1;
MultiXactId multi2;
multi1 = ((MultiXactId) page1) * MULTIXACT_OFFSETS_PER_PAGE;
multi1 += FirstMultiXactId + 1;
multi2 = ((MultiXactId) page2) * MULTIXACT_OFFSETS_PER_PAGE;
multi2 += FirstMultiXactId + 1;
return (MultiXactIdPrecedes(multi1, multi2) &&
MultiXactIdPrecedes(multi1, multi2 + MULTIXACT_OFFSETS_PER_PAGE - 1));
}
* SlruScanDirectory callback
* This callback determines the earliest existing page number.
*/
static bool SlruScanDirCbFindEarliest(SlruCtl ctl, const char* filename, int64 segpage, const void* data)
{
mxtruncinfo *trunc = (mxtruncinfo *)data;
if (trunc->earliestExistingPage == -1 || MultiXactOffsetPagePrecedes(segpage, trunc->earliestExistingPage)) {
trunc->earliestExistingPage = segpage;
}
return false;
}
#endif
* Remove all MultiXactOffset and MultiXactMember segments before the oldest
* ones still of interest.
*
* This is called by vacuum after it has successfully advanced a database's
* datminmxid value; the cutoff value we're passed is the minimum of all
* databases' datminmxid values.
*/
void TruncateMultiXact(MultiXactId oldestMXact)
{
if (SS_STANDBY_MODE) {
ereport(WARNING, (errmodule(MOD_DMS), errmsg("DMS standby can't truncate multixact status")));
return;
}
MultiXactOffset oldestOffset;
#ifndef ENABLE_MULTIPLE_NODES
mxtruncinfo trunc;
MultiXactId earliest;
* Note we can't just plow ahead with the truncation; it's possible that
* there are no segments to truncate, which is a problem because we are
* going to attempt to read the offsets page to determine where to truncate
* the members SLRU. So we first scan the directory to determine the
* earliest offsets page number that we can read without error.
*/
trunc.earliestExistingPage = -1;
SlruScanDirectory(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, SlruScanDirCbFindEarliest, &trunc);
earliest = trunc.earliestExistingPage * MULTIXACT_OFFSETS_PER_PAGE;
if (MultiXactIdPrecedes(oldestMXact, earliest))
return;
#else
MultiXactOffset nextOffset;
MultiXactId nextMXact;
oldestMXact = GetOldestMultiXactId();
(void)LWLockAcquire(MultiXactGenLock, LW_SHARED);
nextMXact = t_thrd.shemem_ptr_cxt.MultiXactState->nextMXact;
if (nextMXact < FirstMultiXactId)
nextMXact = FirstMultiXactId;
nextOffset = t_thrd.shemem_ptr_cxt.MultiXactState->nextOffset;
LWLockRelease(MultiXactGenLock);
ereport(DEBUG2, (errmsg("MultiXact: truncation point = %lu", oldestMXact)));
* If we already truncated at this point, do nothing. This saves time
* when no MultiXacts are getting used, which is probably not uncommon.
*/
if (t_thrd.shemem_ptr_cxt.MultiXactState->lastTruncationPoint == oldestMXact)
return;
* We need to determine where to truncate MultiXactMember. If we found a
* valid oldest MultiXactId, read its starting offset; otherwise we use
* the nextOffset value we saved above.
*/
if (oldestMXact == nextMXact)
oldestOffset = nextOffset;
else
#endif
* First, compute the safe truncation point for MultiXactMember.
* This is the starting offset of the multixact we were passed
* as MultiXactOffset cutoff.
*/
{
int64 pageno;
int slotno;
int entryno;
MultiXactOffset *offptr = NULL;
pageno = (int64)MultiXactIdToOffsetPage(oldestMXact);
entryno = MultiXactIdToOffsetEntry(oldestMXact);
slotno = SimpleLruReadPage_ReadOnly(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, pageno, oldestMXact);
offptr = (MultiXactOffset *)t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl->shared->page_buffer[slotno];
offptr += entryno;
oldestOffset = *offptr;
LWLockRelease(MultiXactOffsetControlLock);
}
SimpleLruTruncate(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, MultiXactIdToOffsetPage(oldestMXact),
NUM_SLRU_DEFAULT_PARTITION);
SimpleLruTruncate(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, MXOffsetToMemberPage(oldestOffset),
NUM_SLRU_DEFAULT_PARTITION);
* Set the last known truncation point. We don't need a lock for this
* since only one backend does checkpoints at a time.
*/
t_thrd.shemem_ptr_cxt.MultiXactState->lastTruncationPoint = oldestMXact;
}
* Write an xlog record reflecting the zeroing of either a MEMBERs or
* OFFSETs page (info shows which)
*/
static void WriteMZeroPageXlogRec(int64 pageno, uint8 info)
{
XLogBeginInsert();
if (t_thrd.proc->workingVersionNum >= 92068) {
info |= XLOG_MULTIXACT_INT64_PAGENO;
XLogRegisterData((char *)(&pageno), sizeof(int64));
} else {
XLogRegisterData((char *)(&pageno), sizeof(int));
}
(void)XLogInsert(RM_MULTIXACT_ID, info);
}
void get_multixact_pageno(uint8 info, int64 *pageno, XLogReaderState *record)
{
errno_t rc = EOK;
if ((info & XLOG_MULTIXACT_INT64_PAGENO) != 0) {
rc = memcpy_s(pageno, sizeof(int64), XLogRecGetData(record), sizeof(int64));
securec_check(rc, "", "");
} else {
rc = memcpy_s(pageno, sizeof(int64), XLogRecGetData(record), sizeof(int));
securec_check(rc, "", "");
}
}
* MULTIXACT resource manager's routines
*/
void multixact_redo(XLogReaderState *record)
{
uint8 info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
uint8 mask_info = info & XLOG_MULTIXACT_MASK;
Assert(!XLogRecHasAnyBlockRefs(record));
if (mask_info == XLOG_MULTIXACT_ZERO_OFF_PAGE) {
int64 pageno = 0;
int slotno;
LWLock* lock;
get_multixact_pageno(info, &pageno, record);
lock = SimpleLruGetBankLock(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, pageno);
LWLockAcquire(lock, LW_EXCLUSIVE);
slotno = ZeroMultiXactOffsetPage(pageno, false);
SimpleLruWritePage(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl, slotno);
Assert(!t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl->shared->page_dirty[slotno]);
LWLockRelease(lock);
} else if (mask_info == XLOG_MULTIXACT_ZERO_MEM_PAGE) {
int64 pageno = 0;
int slotno;
LWLock* lock;
get_multixact_pageno(info, &pageno, record);
lock = SimpleLruGetBankLock(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, pageno);
LWLockAcquire(lock, LW_EXCLUSIVE);
slotno = ZeroMultiXactMemberPage(pageno, false);
SimpleLruWritePage(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl, slotno);
Assert(!t_thrd.shemem_ptr_cxt.MultiXactMemberCtl->shared->page_dirty[slotno]);
LWLockRelease(lock);
} else if (mask_info == XLOG_MULTIXACT_CREATE_ID) {
xl_multixact_create *xlrec = (xl_multixact_create *)XLogRecGetData(record);
TransactionId *xidsWithStatus = xlrec->xids;
TransactionId max_xid;
int i;
RecordNewMultiXact(xlrec->mid, xlrec->moff, xlrec->nxids, xidsWithStatus);
MultiXactAdvanceNextMXact(xlrec->mid + 1, xlrec->moff + xlrec->nxids);
* Make sure nextXid is beyond any XID mentioned in the record. This
* should be unnecessary, since any XID found here ought to have other
* evidence in the XLOG, but let's be safe.
*/
max_xid = XLogRecGetXid(record);
for (i = 0; i < xlrec->nxids; i++) {
TransactionId memberXid = GET_MEMBER_XID_FROM_SLRU_XID(xidsWithStatus[i]);
if (TransactionIdPrecedes(max_xid, memberXid))
max_xid = memberXid;
}
* We don't expect anyone else to modify nextXid, hence startup
* process doesn't need to hold a lock while checking this. We still
* acquire the lock to modify it, though.
*/
if (TransactionIdFollowsOrEquals(max_xid, t_thrd.xact_cxt.ShmemVariableCache->nextXid)) {
(void)LWLockAcquire(XidGenLock, LW_EXCLUSIVE);
if (TransactionIdFollowsOrEquals(max_xid, t_thrd.xact_cxt.ShmemVariableCache->nextXid)) {
t_thrd.xact_cxt.ShmemVariableCache->nextXid = max_xid;
TransactionIdAdvance(t_thrd.xact_cxt.ShmemVariableCache->nextXid);
}
LWLockRelease(XidGenLock);
}
} else {
ereport(PANIC, (errmsg("multixact_redo: unknown op code %u", (uint32)info)));
}
}
void SSMultiXactShmemClear(void)
{
errno_t rc = EOK;
char path[MAXPGPATH];
debug_elog2(DEBUG2, "Shared Memory Init for MultiXact");
rc = snprintf_s(path, MAXPGPATH, MAXPGPATH - 1, "%s/offsets", MULTIXACTDIR);
securec_check_ss(rc, "\0", "\0");
SimpleLruSetPageEmpty(t_thrd.shemem_ptr_cxt.MultiXactOffsetCtl,
GetBuiltInTrancheName(LWTRANCHE_MULTIXACTOFFSET_CTL), LWTRANCHE_MULTIXACTOFFSET_CTL,
DSS_MAX_MXACTOFFSET, 0, path);
rc = snprintf_s(path, MAXPGPATH, MAXPGPATH - 1, "%s/members", MULTIXACTDIR);
securec_check_ss(rc, "\0", "\0");
SimpleLruSetPageEmpty(t_thrd.shemem_ptr_cxt.MultiXactMemberCtl,
GetBuiltInTrancheName(LWTRANCHE_MULTIXACTMEMBER_CTL), LWTRANCHE_MULTIXACTMEMBER_CTL,
DSS_MAX_MXACTMEMBER, 0, path);
}
