/*
* Record the parent of a subtransaction in the subtrans log.
*
* In some cases we may need to overwrite an existing value.
*/
void
SubTransSetParent(TransactionId xid, TransactionId parent, bool overwriteOK)
{
int pageno = TransactionIdToPage(xid);
int entryno = TransactionIdToEntry(xid);
int slotno;
TransactionId *ptr;
Assert(TransactionIdIsValid(parent));
LWLockAcquire(SubtransControlLock, LW_EXCLUSIVE);
slotno = SimpleLruReadPage(SubTransCtl, pageno, true, xid);
ptr = (TransactionId *) SubTransCtl->shared->page_buffer[slotno];
ptr += entryno;
/* Current state should be 0 */
Assert(*ptr == InvalidTransactionId ||
(*ptr == parent && overwriteOK));
*ptr = parent;
SubTransCtl->shared->page_dirty[slotno] = true;
LWLockRelease(SubtransControlLock);
}
/*
* Make sure that SUBTRANS has room for a newly-allocated XID.
*
* NB: this is called while holding XidGenLock. 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 subtrans page to make room
* in shared memory.
*/
void
ExtendSUBTRANS(TransactionId newestXact)
{
int pageno;
/*
* Caller must have already taken mirrored lock shared.
*/
/*
* No work except at first XID of a page. But beware: just after
* wraparound, the first XID of page zero is FirstNormalTransactionId.
*/
if (TransactionIdToEntry(newestXact) != 0 &&
!TransactionIdEquals(newestXact, FirstNormalTransactionId))
return;
pageno = TransactionIdToPage(newestXact);
LWLockAcquire(SubtransControlLock, LW_EXCLUSIVE);
/* Zero the page */
ZeroSUBTRANSPage(pageno);
LWLockRelease(SubtransControlLock);
}
/*
* Interrogate the parent of a transaction in the subtrans log.
*/
TransactionId
SubTransGetParent(TransactionId xid)
{
int pageno = TransactionIdToPage(xid);
int entryno = TransactionIdToEntry(xid);
int slotno;
TransactionId *ptr;
TransactionId parent;
/* Can't ask about stuff that might not be around anymore */
Assert(TransactionIdFollowsOrEquals(xid, TransactionXmin));
/* Bootstrap and frozen XIDs have no parent */
if (!TransactionIdIsNormal(xid))
return InvalidTransactionId;
/* lock is acquired by SimpleLruReadPage_ReadOnly */
slotno = SimpleLruReadPage_ReadOnly(SubTransCtl, pageno, xid);
ptr = (TransactionId *) SubTransCtl->shared->page_buffer[slotno];
ptr += entryno;
parent = *ptr;
LWLockRelease(SubtransControlLock);
return parent;
}
/*
* Record the parent of a subtransaction in the subtrans log.
*/
void
SubTransSetParent(TransactionId xid, TransactionId parent)
{
int pageno = TransactionIdToPage(xid);
int entryno = TransactionIdToEntry(xid);
int slotno;
TransactionId *ptr;
Assert(TransactionIdIsValid(parent));
Assert(TransactionIdFollows(xid, parent));
LWLockAcquire(SubtransControlLock, LW_EXCLUSIVE);
slotno = SimpleLruReadPage(SubTransCtl, pageno, true, xid);
ptr = (TransactionId *) SubTransCtl->shared->page_buffer[slotno];
ptr += entryno;
/*
* It's possible we'll try to set the parent xid multiple times but we
* shouldn't ever be changing the xid from one valid xid to another valid
* xid, which would corrupt the data structure.
*/
if (*ptr != parent)
{
Assert(*ptr == InvalidTransactionId);
*ptr = parent;
SubTransCtl->shared->page_dirty[slotno] = true;
}
LWLockRelease(SubtransControlLock);
}
/*
* Make sure that SUBTRANS has room for a newly-allocated XID.
*
* NB: this is called while holding XidGenLock. 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 subtrans page to make room
* in shared memory.
*/
void
ExtendSUBTRANS(TransactionId newestXact)
{
int pageno;
/*
* No work except at first XID of a page. But beware: just after
* wraparound, the first XID of page zero is FirstNormalTransactionId.
*/
#ifdef PGXC /* PGXC_COORD || PGXC_DATANODE */
/*
* In PGXC, it may be that a node is not involved in a transaction,
* and therefore will be skipped, so we need to detect this by using
* the latest_page_number instead of the pg index.
*
* Also, there is a special case of when transactions wrap-around that
* we need to detect.
*/
pageno = TransactionIdToPage(newestXact);
/*
* The first condition makes sure we did not wrap around
* The second checks if we are still using the same page.
* Note that this value can change and we are not holding a lock,
* so we repeat the check below. We do it this way instead of
* grabbing the lock to avoid lock contention.
*/
if (SubTransCtl->shared->latest_page_number - pageno <= SUBTRANS_WRAP_CHECK_DELTA
&& pageno <= SubTransCtl->shared->latest_page_number)
return;
#else
if (TransactionIdToEntry(newestXact) != 0 &&
!TransactionIdEquals(newestXact, FirstNormalTransactionId))
return;
pageno = TransactionIdToPage(newestXact);
#endif
LWLockAcquire(SubtransControlLock, LW_EXCLUSIVE);
#ifdef PGXC
/*
* We repeat the check. Another process may have written
* out the page already and advanced the latest_page_number
* while we were waiting for the lock.
*/
if (SubTransCtl->shared->latest_page_number - pageno <= SUBTRANS_WRAP_CHECK_DELTA
&& pageno <= SubTransCtl->shared->latest_page_number)
{
LWLockRelease(SubtransControlLock);
return;
}
#endif
/* Zero the page */
ZeroSUBTRANSPage(pageno);
LWLockRelease(SubtransControlLock);
}
Datum
spoof_next_xid(PG_FUNCTION_ARGS)
{
TransactionId desiredXid = PG_GETARG_UINT32(0);
TransactionId oldXid = ShmemVariableCache->nextXid;
ShmemVariableCache->nextXid = desiredXid;
/*
* If we're raising the xid, the intent is presumably to cross some
* threshold and make assertions about expected behavior.
* On the other hand, lowering the xid is meant to be a tear down of
* a completed test case. Because of this distinction, only when
* we're raising the xid, do we take extra precaution to zero out
* the new pg_clog/pg_subtrans/pg_distributedlog files. (We don't
* want to zero out existing files...)
*/
if (TransactionIdFollows(desiredXid, oldXid))
{
/*
* The nature of xid arithmetic is such that we only bother zeroing out
* new pages of transaction files when we've crossed page boundaries.
* So, here we fool the following routines into zeroing out the desired
* pages of transaction metadata by lowering the input xid to the first
* of its corresponding page.
*/
#define CLOG_XACTS_PER_BYTE 4
#define CLOG_XACTS_PER_PAGE (BLCKSZ * CLOG_XACTS_PER_BYTE)
#define TransactionIdToPgIndex(xid) ((xid) % (TransactionId) CLOG_XACTS_PER_PAGE)
ExtendCLOG(desiredXid - TransactionIdToPgIndex(desiredXid));
#define SUBTRANS_XACTS_PER_PAGE (BLCKSZ / sizeof(SubTransData))
#define TransactionIdToEntry(xid) ((xid) % (uint32) SUBTRANS_XACTS_PER_PAGE)
ExtendSUBTRANS(desiredXid - TransactionIdToEntry(desiredXid));
#undef TransactionIdToEntry
#define ENTRIES_PER_PAGE (BLCKSZ / sizeof(DistributedLogEntry))
#define TransactionIdToEntry(localXid) ((localXid) % (TransactionId) ENTRIES_PER_PAGE)
DistributedLog_Extend(desiredXid - TransactionIdToEntry(desiredXid));
}
PG_RETURN_XID(oldXid);
}
/*
* Record the parent of a subtransaction in the subtrans log.
*/
void
SubTransSetParent(TransactionId xid, TransactionId parent)
{
MIRRORED_LOCK_DECLARE;
int pageno = TransactionIdToPage(xid);
int entryno = TransactionIdToEntry(xid);
int slotno;
SubTransData *ptr;
SubTransData subData;
/*
* Main Xact has parent and topMostParent as InvalidTransactionId
*/
if ( parent != InvalidTransactionId )
{
/* Get the topMostParent for Parent */
SubTransGetData(parent, &subData);
}
else
{
subData.topMostParent = InvalidTransactionId;
}
MIRRORED_LOCK;
LWLockAcquire(SubtransControlLock, LW_EXCLUSIVE);
slotno = SimpleLruReadPage(SubTransCtl, pageno, xid);
ptr = (SubTransData *) SubTransCtl->shared->page_buffer[slotno];
ptr += entryno;
/* Current state should be 0 */
Assert(ptr->parent == InvalidTransactionId);
Assert(ptr->topMostParent == InvalidTransactionId);
ptr->parent = parent;
ptr->topMostParent = subData.topMostParent;
SubTransCtl->shared->page_dirty[slotno] = true;
LWLockRelease(SubtransControlLock);
MIRRORED_UNLOCK;
}
/*
* A bug found in MPP-20426 was we were overrunnig to the next page
* of DistributedLog. The intention of the memset with zeors is to
* reset the reset of the current page if we are in the middle of page,
* so that we won't see uncommited data due to some recovery work.
* However, we were doing the wrong math that calculates the size of
* rest of page as the size of the part preceding to the current xid.
* The worst scenario was for the subtransaction shared memory, which
* follows distributed log shared memory to be overwritten.
*/
static MPP_20426(void **state, TransactionId nextXid)
{
char pages[BLCKSZ * DtxLogStartupNumPage];
char zeros[BLCKSZ];
int bytes;
/* Setup DistributedLogCtl */
DistributedLogCtl->shared = (SlruShared) malloc(sizeof(SlruSharedData));
DistributedLogCtl->shared->page_buffer =
(char **) malloc(DtxLogStartupNumPage * sizeof(char *));
DistributedLogCtl->shared->page_dirty =
(bool *) malloc(DtxLogStartupNumPage * sizeof(bool));
DistributedLogCtl->shared->page_buffer[0] = &pages[0];
DistributedLogCtl->shared->page_buffer[1] = &pages[BLCKSZ];
memset(pages, 0x7f, sizeof(pages));
memset(zeros, 0, sizeof(zeros));
expect_value(LWLockAcquire, lockid, DistributedLogControlLock);
expect_value(LWLockAcquire, mode, LW_EXCLUSIVE);
will_be_called(LWLockAcquire);
/* This test is only for the case xid is not on the boundary. */
expect_value(SimpleLruReadPage, ctl, DistributedLogCtl);
expect_any(SimpleLruReadPage, pageno);
expect_value(SimpleLruReadPage, xid, nextXid);
will_return(SimpleLruReadPage, 0);
expect_value(LWLockRelease, lockid, DistributedLogControlLock);
will_be_called(LWLockRelease);
/* Run the function. */
DistributedLog_Startup(nextXid, nextXid);
/* DistributedLog_Startup should not overwrite the subsequent block. */
assert_true(pages[BLCKSZ] == 0x7f);
/* Make sure the part following the xid is zeroed. */
bytes = TransactionIdToEntry(nextXid) * sizeof(DistributedLogEntry);
assert_memory_equal(&pages[bytes], zeros, BLCKSZ - bytes);
free(DistributedLogCtl->shared->page_dirty);
free(DistributedLogCtl->shared->page_buffer);
free(DistributedLogCtl->shared);
}
static void
SubTransGetData(TransactionId xid, SubTransData* subData)
{
MIRRORED_LOCK_DECLARE;
int pageno = TransactionIdToPage(xid);
int entryno = TransactionIdToEntry(xid);
int slotno;
SubTransData *ptr;
/* Can't ask about stuff that might not be around anymore */
Assert(TransactionIdFollowsOrEquals(xid, TransactionXmin));
/* Bootstrap and frozen XIDs have no parent and itself as topMostParent */
if (!TransactionIdIsNormal(xid))
{
subData->parent = InvalidTransactionId;
subData->topMostParent = xid;
return;
}
MIRRORED_LOCK;
/* lock is acquired by SimpleLruReadPage_ReadOnly */
slotno = SimpleLruReadPage_ReadOnly(SubTransCtl, pageno, xid, NULL);
ptr = (SubTransData *) SubTransCtl->shared->page_buffer[slotno];
ptr += entryno;
subData->parent = ptr->parent;
subData->topMostParent = ptr->topMostParent;
if ( subData->topMostParent == InvalidTransactionId )
{
/* Here means parent is Main XID, hence set parent itself as topMostParent */
subData->topMostParent = xid;
}
LWLockRelease(SubtransControlLock);
MIRRORED_UNLOCK;
return;
}
/*
* Make sure that DistributedLog has room for a newly-allocated XID.
*
* NB: this is called while holding XidGenLock. 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 DistributedLog or xlog page
* to make room in shared memory.
*/
void
DistributedLog_Extend(TransactionId newestXact)
{
MIRRORED_LOCK_DECLARE;
int page;
/*
* No work except at first XID of a page. But beware: just after
* wraparound, the first XID of page zero is FirstNormalTransactionId.
*/
if (TransactionIdToEntry(newestXact) != 0 &&
!TransactionIdEquals(newestXact, FirstNormalTransactionId))
return;
page = TransactionIdToPage(newestXact);
elog((Debug_print_full_dtm ? LOG : DEBUG5),
"DistributedLog_Extend page %d",
page);
MIRRORED_LOCK;
LWLockAcquire(DistributedLogControlLock, LW_EXCLUSIVE);
/* Zero the page and make an XLOG entry about it */
DistributedLog_ZeroPage(page, true);
LWLockRelease(DistributedLogControlLock);
MIRRORED_UNLOCK;
elog((Debug_print_full_dtm ? LOG : DEBUG5),
"DistributedLog_Extend with newest local xid = %d to page = %d",
newestXact, page);
}
/*
* Record that a distributed transaction committed in the distributed log.
*
*/
void
DistributedLog_SetCommitted(
TransactionId localXid,
DistributedTransactionTimeStamp distribTimeStamp,
DistributedTransactionId distribXid,
bool isRedo)
{
MIRRORED_LOCK_DECLARE;
int page = TransactionIdToPage(localXid);
int entryno = TransactionIdToEntry(localXid);
int slotno;
DistributedLogEntry *ptr;
bool alreadyThere = false;
MIRRORED_LOCK;
LWLockAcquire(DistributedLogControlLock, LW_EXCLUSIVE);
if (isRedo)
{
elog((Debug_print_full_dtm ? LOG : DEBUG5),
"DistributedLog_SetCommitted check if page %d is present",
page);
if (!SimpleLruPageExists(DistributedLogCtl, page))
{
DistributedLog_ZeroPage(page, /* writeXLog */ false);
elog((Debug_print_full_dtm ? LOG : DEBUG5),
"DistributedLog_SetCommitted zeroed page %d",
page);
}
}
slotno = SimpleLruReadPage(DistributedLogCtl, page, localXid);
ptr = (DistributedLogEntry *) DistributedLogCtl->shared->page_buffer[slotno];
ptr += entryno;
if (ptr->distribTimeStamp != 0 || ptr->distribXid != 0)
{
if (ptr->distribTimeStamp != distribTimeStamp)
elog(ERROR,
"Current distributed timestamp = %u does not match input timestamp = %u for local xid = %u in distributed log (page = %d, entryno = %d)",
ptr->distribTimeStamp, distribTimeStamp, localXid, page, entryno);
if (ptr->distribXid != distribXid)
elog(ERROR,
"Current distributed xid = %u does not match input distributed xid = %u for local xid = %u in distributed log (page = %d, entryno = %d)",
ptr->distribXid, distribXid, localXid, page, entryno);
alreadyThere = true;
}
else
{
ptr->distribTimeStamp = distribTimeStamp;
ptr->distribXid = distribXid;
DistributedLogCtl->shared->page_dirty[slotno] = true;
}
LWLockRelease(DistributedLogControlLock);
MIRRORED_UNLOCK;
elog((Debug_print_full_dtm ? LOG : DEBUG5),
"DistributedLog_SetCommitted with local xid = %d (page = %d, entryno = %d) and distributed transaction xid = %u (timestamp = %u) status = %s",
localXid, page, entryno, distribXid, distribTimeStamp,
(alreadyThere ? "already there" : "set"));
}
/*
* This must be called ONCE during postmaster or standalone-backend startup,
* after StartupXLOG has initialized ShmemVariableCache->nextXid.
*/
void
DistributedLog_Startup(
TransactionId oldestActiveXid,
TransactionId nextXid)
{
MIRRORED_LOCK_DECLARE;
int startPage;
int endPage;
/*
* UNDONE: We really need oldest frozen xid. If we can't get it, then
* we will need to tolerate not finiding a page in
* DistributedLog_SetCommitted and DistributedLog_IsCommitted.
*/
startPage = TransactionIdToPage(oldestActiveXid);
endPage = TransactionIdToPage(nextXid);
MIRRORED_LOCK;
LWLockAcquire(DistributedLogControlLock, LW_EXCLUSIVE);
elog((Debug_print_full_dtm ? LOG : DEBUG5),
"DistributedLog_Startup startPage %d, endPage %d",
startPage, endPage);
/*
* Initialize our idea of the latest page number.
*/
DistributedLogCtl->shared->latest_page_number = endPage;
/*
* Zero out the remainder of the current DistributedLog page. Under normal
* circumstances it should be zeroes already, but it seems at least
* theoretically possible that XLOG replay will have settled on a nextXID
* value that is less than the last XID actually used and marked by the
* previous database lifecycle (since subtransaction commit writes clog
* but makes no WAL entry). Let's just be safe. (We need not worry about
* pages beyond the current one, since those will be zeroed when first
* used. For the same reason, there is no need to do anything when
* nextXid is exactly at a page boundary; and it's likely that the
* "current" page doesn't exist yet in that case.)
*/
if (TransactionIdToEntry(nextXid) != 0)
{
int entryno = TransactionIdToEntry(nextXid);
int slotno;
DistributedLogEntry *ptr;
int remainingEntries;
slotno = SimpleLruReadPage(DistributedLogCtl, endPage, nextXid);
ptr = (DistributedLogEntry *) DistributedLogCtl->shared->page_buffer[slotno];
ptr += entryno;
/* Zero the rest of the page */
remainingEntries = ENTRIES_PER_PAGE - entryno;
MemSet(ptr, 0, remainingEntries * sizeof(DistributedLogEntry));
DistributedLogCtl->shared->page_dirty[slotno] = true;
}
LWLockRelease(DistributedLogControlLock);
MIRRORED_UNLOCK;
}
/*
* Find the next lowest transaction with a logged or recorded status.
* Currently on distributed commits are recorded.
*/
bool
DistributedLog_ScanForPrevCommitted(
TransactionId *indexXid,
DistributedTransactionTimeStamp *distribTimeStamp,
DistributedTransactionId *distribXid)
{
MIRRORED_LOCK_DECLARE;
TransactionId highXid;
int pageno;
TransactionId lowXid;
int slotno;
TransactionId xid;
*distribTimeStamp = 0; // Set it to something.
*distribXid = 0;
if ((*indexXid) == InvalidTransactionId)
return false;
highXid = (*indexXid) - 1;
if (highXid < FirstNormalTransactionId)
return false;
MIRRORED_LOCK;
while (true)
{
pageno = TransactionIdToPage(highXid);
/*
* Compute the xid floor for the page.
*/
lowXid = pageno * (TransactionId) ENTRIES_PER_PAGE;
if (lowXid == InvalidTransactionId)
lowXid = FirstNormalTransactionId;
LWLockAcquire(DistributedLogControlLock, LW_EXCLUSIVE);
/*
* Peek to see if page exists.
*/
if (!SimpleLruPageExists(DistributedLogCtl, pageno))
{
LWLockRelease(DistributedLogControlLock);
MIRRORED_UNLOCK;
*indexXid = InvalidTransactionId;
*distribTimeStamp = 0; // Set it to something.
*distribXid = 0;
return false;
}
slotno = SimpleLruReadPage(DistributedLogCtl, pageno, highXid);
for (xid = highXid; xid >= lowXid; xid--)
{
int entryno = TransactionIdToEntry(xid);
DistributedLogEntry *ptr;
ptr = (DistributedLogEntry *) DistributedLogCtl->shared->page_buffer[slotno];
ptr += entryno;
if (ptr->distribTimeStamp != 0 && ptr->distribXid != 0)
{
*indexXid = xid;
*distribTimeStamp = ptr->distribTimeStamp;
*distribXid = ptr->distribXid;
LWLockRelease(DistributedLogControlLock);
MIRRORED_UNLOCK;
return true;
}
}
LWLockRelease(DistributedLogControlLock);
if (lowXid == FirstNormalTransactionId)
{
MIRRORED_UNLOCK;
*indexXid = InvalidTransactionId;
*distribTimeStamp = 0; // Set it to something.
*distribXid = 0;
return false;
}
highXid = lowXid - 1; // Go to last xid of previous page.
}
MIRRORED_UNLOCK;
return false; // We'll never reach this.
}
/*
* Determine if a distributed transaction committed in the distributed log.
*/
bool
DistributedLog_CommittedCheck(
TransactionId localXid,
DistributedTransactionTimeStamp *distribTimeStamp,
DistributedTransactionId *distribXid)
{
MIRRORED_LOCK_DECLARE;
int page = TransactionIdToPage(localXid);
int entryno = TransactionIdToEntry(localXid);
int slotno;
DistributedLogEntry *ptr;
MIRRORED_LOCK;
LWLockAcquire(DistributedLogControlLock, LW_EXCLUSIVE);
if (DistributedLogShared->knowHighestUnusedPage &&
page <= DistributedLogShared->highestUnusedPage)
{
/*
* We prevously discovered we didn't have the page...
*/
LWLockRelease(DistributedLogControlLock);
MIRRORED_UNLOCK;
*distribTimeStamp = 0; // Set it to something.
*distribXid = 0;
return false;
}
/*
* Peek to see if page exists.
*/
if (!SimpleLruPageExists(DistributedLogCtl, page))
{
if (DistributedLogShared->knowHighestUnusedPage)
{
if (DistributedLogShared->highestUnusedPage > page)
DistributedLogShared->highestUnusedPage = page;
}
else
{
DistributedLogShared->knowHighestUnusedPage = true;
DistributedLogShared->highestUnusedPage = page;
}
LWLockRelease(DistributedLogControlLock);
MIRRORED_UNLOCK;
*distribTimeStamp = 0; // Set it to something.
*distribXid = 0;
return false;
}
slotno = SimpleLruReadPage(DistributedLogCtl, page, localXid);
ptr = (DistributedLogEntry *) DistributedLogCtl->shared->page_buffer[slotno];
ptr += entryno;
*distribTimeStamp = ptr->distribTimeStamp;
*distribXid = ptr->distribXid;
ptr = NULL;
LWLockRelease(DistributedLogControlLock);
MIRRORED_UNLOCK;
if (*distribTimeStamp != 0 && *distribXid != 0)
{
return true;
}
else if (*distribTimeStamp == 0 && *distribXid == 0)
{
// Not found.
return false;
}
else
{
if (*distribTimeStamp == 0)
elog(ERROR, "Found zero timestamp for local xid = %u in distributed log (distributed xid = %u, page = %d, entryno = %d)",
localXid, *distribXid, page, entryno);
elog(ERROR, "Found zero distributed xid for local xid = %u in distributed log (dtx start time = %u, page = %d, entryno = %d)",
localXid, *distribTimeStamp, page, entryno);
return false; // We'll never reach here.
}
}