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kelvichkelvich
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some comments and cleanups
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‎src/backend/access/transam/twophase.c

Lines changed: 38 additions & 73 deletions
Original file line numberDiff line numberDiff line change
@@ -122,7 +122,7 @@ typedef struct GlobalTransactionData
122122
TimestampTz prepared_at; /* time of preparation */
123123
XLogRecPtr prepare_lsn; /* XLOG offset of prepare record end */
124124
XLogRecPtr prepare_xlogptr; /* XLOG offset of prepare record start
125-
* or NULL if twophase data moved to file
125+
* or NULL if twophase data moved to file
126126
* after checkpoint.
127127
*/
128128
Oid owner; /* ID of user that executed the xact */
@@ -587,41 +587,6 @@ RemoveGXact(GlobalTransaction gxact)
587587
elog(ERROR, "failed to find %p in GlobalTransaction array", gxact);
588588
}
589589

590-
/*
591-
* TransactionIdIsPrepared
592-
* True iff transaction associated with the identifier is prepared
593-
* for two-phase commit
594-
*
595-
* Note: only gxacts marked "valid" are considered; but notice we do not
596-
* check the locking status.
597-
*
598-
* This is not currently exported, because it is only needed internally.
599-
*/
600-
static bool
601-
TransactionIdIsPrepared(TransactionId xid)
602-
{
603-
bool result = false;
604-
int i;
605-
606-
LWLockAcquire(TwoPhaseStateLock, LW_SHARED);
607-
608-
for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
609-
{
610-
GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
611-
PGXACT *pgxact = &ProcGlobal->allPgXact[gxact->pgprocno];
612-
613-
if (gxact->valid && pgxact->xid == xid)
614-
{
615-
result = true;
616-
break;
617-
}
618-
}
619-
620-
LWLockRelease(TwoPhaseStateLock);
621-
622-
return result;
623-
}
624-
625590
/*
626591
* Returns an array of all prepared transactions for the user-level
627592
* function pg_prepared_xact.
@@ -1244,6 +1209,36 @@ ReadTwoPhaseFile(TransactionId xid, bool give_warnings)
12441209
return buf;
12451210
}
12461211

1212+
1213+
/*
1214+
* Reads 2PC data from xlog. During checkpoint this data will be moved to
1215+
* twophase files and ReadTwoPhaseFile should be used instead.
1216+
*/
1217+
static void
1218+
XlogReadTwoPhaseData(XLogRecPtr lsn, char **buf, int *len)
1219+
{
1220+
XLogRecord *record;
1221+
XLogReaderState *xlogreader;
1222+
char *errormsg;
1223+
1224+
xlogreader = XLogReaderAllocate(&logical_read_local_xlog_page, NULL);
1225+
if (xlogreader == NULL)
1226+
elog(ERROR, "failed to open xlogreader for reading 2PC data");
1227+
1228+
record = XLogReadRecord(xlogreader, lsn, &errormsg);
1229+
if (record == NULL)
1230+
elog(ERROR, "failed to read 2PC record from xlog");
1231+
1232+
if (len != NULL)
1233+
*len = XLogRecGetDataLen(xlogreader);
1234+
1235+
*buf = palloc(sizeof(char)*XLogRecGetDataLen(xlogreader));
1236+
memcpy(*buf, XLogRecGetData(xlogreader), sizeof(char)*XLogRecGetDataLen(xlogreader));
1237+
1238+
XLogReaderFree(xlogreader);
1239+
}
1240+
1241+
12471242
/*
12481243
* Confirms an xid is prepared, during recovery
12491244
*/
@@ -1306,13 +1301,9 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
13061301

13071302
/*
13081303
* Read and validate 2PC state data.
1309-
* State data can be stored in xlog or files depending on checkpoint
1310-
* status. One way to read that data is to delay checkpoint (delayChkpt) and
1311-
* compare gxact->prepare_lsn with current xlog horizon. But having in mind
1312-
* that most of 2PC transactions will be commited right after prepare, we
1313-
* can just try to read xlog and in case of error read file. Also that is
1314-
* happening under LockGXact, so nobody can commit our transaction between
1315-
* xlog and file reads.
1304+
* State data can be stored in xlog or in files after xlog checkpoint.
1305+
* While checkpointing we set gxact->prepare_lsn to NULL to signalize
1306+
* that 2PC data is moved to files.
13161307
*/
13171308
if (gxact->prepare_lsn)
13181309
{
@@ -1480,7 +1471,8 @@ RemoveTwoPhaseFile(TransactionId xid, bool giveWarning)
14801471
}
14811472

14821473
/*
1483-
* Recreates a state file. This is used in WAL replay.
1474+
* Recreates a state file. This is used in WAL replay and during
1475+
* checkpoint creation.
14841476
*
14851477
* Note: content and len don't include CRC.
14861478
*/
@@ -1574,12 +1566,11 @@ CheckPointTwoPhase(XLogRecPtr redo_horizon)
15741566

15751567
/*
15761568
* Here we doing whole I/O while holding TwoPhaseStateLock.
1577-
* It's also possible to move I/O out of the lock, but on
1569+
* It's also possible to move I/O out of the lock, but on
15781570
* every error we should check whether somebody commited our
15791571
* transaction in different backend. Let's leave this optimisation
1580-
* for future, if somebody will spot that this place cause
1572+
* for future, if somebody will spot that this place cause
15811573
* bottleneck.
1582-
*
15831574
*/
15841575
LWLockAcquire(TwoPhaseStateLock, LW_SHARED);
15851576
for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
@@ -2107,29 +2098,3 @@ RecordTransactionAbortPrepared(TransactionId xid,
21072098
*/
21082099
SyncRepWaitForLSN(recptr);
21092100
}
2110-
2111-
/**********************************************************************************/
2112-
2113-
static void
2114-
XlogReadTwoPhaseData(XLogRecPtr lsn, char **buf, int *len)
2115-
{
2116-
XLogRecord *record;
2117-
XLogReaderState *xlogreader;
2118-
char *errormsg;
2119-
2120-
xlogreader = XLogReaderAllocate(&logical_read_local_xlog_page, NULL);
2121-
if (xlogreader == NULL)
2122-
elog(ERROR, "failed to open xlogreader for reading 2PC data");
2123-
2124-
record = XLogReadRecord(xlogreader, lsn, &errormsg);
2125-
if (record == NULL)
2126-
elog(ERROR, "failed to read 2PC record from xlog");
2127-
2128-
if (len != NULL)
2129-
*len = XLogRecGetDataLen(xlogreader);
2130-
2131-
*buf = palloc(sizeof(char)*XLogRecGetDataLen(xlogreader));
2132-
memcpy(*buf, XLogRecGetData(xlogreader), sizeof(char)*XLogRecGetDataLen(xlogreader));
2133-
2134-
XLogReaderFree(xlogreader);
2135-
}

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