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clog.h File Reference
#include "access/xlogreader.h"
#include "lib/stringinfo.h"
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Data Structures

struct  xl_clog_truncate
 

Macros

#define TRANSACTION_STATUS_IN_PROGRESS   0x00
 
#define TRANSACTION_STATUS_COMMITTED   0x01
 
#define TRANSACTION_STATUS_ABORTED   0x02
 
#define TRANSACTION_STATUS_SUB_COMMITTED   0x03
 
#define CLOG_ZEROPAGE   0x00
 
#define CLOG_TRUNCATE   0x10
 

Typedefs

typedef int XidStatus
 
typedef struct xl_clog_truncate xl_clog_truncate
 

Functions

void TransactionIdSetTreeStatus (TransactionId xid, int nsubxids, TransactionId *subxids, XidStatus status, XLogRecPtr lsn)
 
XidStatus TransactionIdGetStatus (TransactionId xid, XLogRecPtr *lsn)
 
Size CLOGShmemBuffers (void)
 
Size CLOGShmemSize (void)
 
void CLOGShmemInit (void)
 
void BootStrapCLOG (void)
 
void StartupCLOG (void)
 
void TrimCLOG (void)
 
void ShutdownCLOG (void)
 
void CheckPointCLOG (void)
 
void ExtendCLOG (TransactionId newestXact)
 
void TruncateCLOG (TransactionId oldestXact, Oid oldestxid_datoid)
 
void clog_redo (XLogReaderState *record)
 
void clog_desc (StringInfo buf, XLogReaderState *record)
 
const char * clog_identify (uint8 info)
 

Macro Definition Documentation

#define CLOG_TRUNCATE   0x10

Definition at line 55 of file clog.h.

Referenced by clog_desc(), clog_identify(), clog_redo(), and WriteTruncateXlogRec().

#define CLOG_ZEROPAGE   0x00

Definition at line 54 of file clog.h.

Referenced by clog_desc(), clog_identify(), clog_redo(), and WriteZeroPageXlogRec().

#define TRANSACTION_STATUS_ABORTED   0x02
#define TRANSACTION_STATUS_IN_PROGRESS   0x00

Definition at line 26 of file clog.h.

Referenced by InitProcess(), TransactionIdSetStatusBit(), and TransactionLogFetch().

#define TRANSACTION_STATUS_SUB_COMMITTED   0x03

Typedef Documentation

Definition at line 24 of file clog.h.

Function Documentation

void BootStrapCLOG ( void  )

Definition at line 712 of file clog.c.

References Assert, ClogCtl, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), SimpleLruWritePage(), and ZeroCLOGPage().

Referenced by BootStrapXLOG().

713 {
714  int slotno;
715 
716  LWLockAcquire(CLogControlLock, LW_EXCLUSIVE);
717 
718  /* Create and zero the first page of the commit log */
719  slotno = ZeroCLOGPage(0, false);
720 
721  /* Make sure it's written out */
722  SimpleLruWritePage(ClogCtl, slotno);
723  Assert(!ClogCtl->shared->page_dirty[slotno]);
724 
725  LWLockRelease(CLogControlLock);
726 }
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1721
#define ClogCtl
Definition: clog.c:88
void SimpleLruWritePage(SlruCtl ctl, int slotno)
Definition: slru.c:578
#define Assert(condition)
Definition: c.h:681
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1117
static int ZeroCLOGPage(int pageno, bool writeXlog)
Definition: clog.c:738
void CheckPointCLOG ( void  )

Definition at line 842 of file clog.c.

References ClogCtl, fsync_fname(), and SimpleLruFlush().

Referenced by CheckPointGuts().

843 {
844  /* Flush dirty CLOG pages to disk */
845  TRACE_POSTGRESQL_CLOG_CHECKPOINT_START(true);
846  SimpleLruFlush(ClogCtl, true);
847 
848  /*
849  * fsync pg_xact to ensure that any files flushed previously are durably
850  * on disk.
851  */
852  fsync_fname("pg_xact", true);
853 
854  TRACE_POSTGRESQL_CLOG_CHECKPOINT_DONE(true);
855 }
void fsync_fname(const char *fname, bool isdir)
Definition: fd.c:572
void SimpleLruFlush(SlruCtl ctl, bool allow_redirtied)
Definition: slru.c:1103
#define ClogCtl
Definition: clog.c:88
void clog_desc ( StringInfo  buf,
XLogReaderState record 
)

Definition at line 21 of file clogdesc.c.

References appendStringInfo(), CLOG_TRUNCATE, CLOG_ZEROPAGE, xl_clog_truncate::oldestXact, xl_clog_truncate::pageno, XLogRecGetData, XLogRecGetInfo, and XLR_INFO_MASK.

22 {
23  char *rec = XLogRecGetData(record);
24  uint8 info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
25 
26  if (info == CLOG_ZEROPAGE)
27  {
28  int pageno;
29 
30  memcpy(&pageno, rec, sizeof(int));
31  appendStringInfo(buf, "page %d", pageno);
32  }
33  else if (info == CLOG_TRUNCATE)
34  {
35  xl_clog_truncate xlrec;
36 
37  memcpy(&xlrec, rec, sizeof(xl_clog_truncate));
38  appendStringInfo(buf, "page %d; oldestXact %u",
39  xlrec.pageno, xlrec.oldestXact);
40  }
41 }
unsigned char uint8
Definition: c.h:256
#define CLOG_ZEROPAGE
Definition: clog.h:54
#define XLogRecGetData(decoder)
Definition: xlogreader.h:226
void appendStringInfo(StringInfo str, const char *fmt,...)
Definition: stringinfo.c:78
int pageno
Definition: clog.h:33
#define CLOG_TRUNCATE
Definition: clog.h:55
#define XLogRecGetInfo(decoder)
Definition: xlogreader.h:222
TransactionId oldestXact
Definition: clog.h:34
#define XLR_INFO_MASK
Definition: xlogrecord.h:62
const char* clog_identify ( uint8  info)

Definition at line 44 of file clogdesc.c.

References CLOG_TRUNCATE, CLOG_ZEROPAGE, and XLR_INFO_MASK.

45 {
46  const char *id = NULL;
47 
48  switch (info & ~XLR_INFO_MASK)
49  {
50  case CLOG_ZEROPAGE:
51  id = "ZEROPAGE";
52  break;
53  case CLOG_TRUNCATE:
54  id = "TRUNCATE";
55  break;
56  }
57 
58  return id;
59 }
#define CLOG_ZEROPAGE
Definition: clog.h:54
#define CLOG_TRUNCATE
Definition: clog.h:55
#define XLR_INFO_MASK
Definition: xlogrecord.h:62
void clog_redo ( XLogReaderState record)

Definition at line 1003 of file clog.c.

References AdvanceOldestClogXid(), Assert, CLOG_TRUNCATE, CLOG_ZEROPAGE, ClogCtl, elog, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), xl_clog_truncate::oldestXact, xl_clog_truncate::pageno, PANIC, SimpleLruTruncate(), SimpleLruWritePage(), XLogRecGetData, XLogRecGetInfo, XLogRecHasAnyBlockRefs, XLR_INFO_MASK, and ZeroCLOGPage().

1004 {
1005  uint8 info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
1006 
1007  /* Backup blocks are not used in clog records */
1008  Assert(!XLogRecHasAnyBlockRefs(record));
1009 
1010  if (info == CLOG_ZEROPAGE)
1011  {
1012  int pageno;
1013  int slotno;
1014 
1015  memcpy(&pageno, XLogRecGetData(record), sizeof(int));
1016 
1017  LWLockAcquire(CLogControlLock, LW_EXCLUSIVE);
1018 
1019  slotno = ZeroCLOGPage(pageno, false);
1020  SimpleLruWritePage(ClogCtl, slotno);
1021  Assert(!ClogCtl->shared->page_dirty[slotno]);
1022 
1023  LWLockRelease(CLogControlLock);
1024  }
1025  else if (info == CLOG_TRUNCATE)
1026  {
1027  xl_clog_truncate xlrec;
1028 
1029  memcpy(&xlrec, XLogRecGetData(record), sizeof(xl_clog_truncate));
1030 
1031  /*
1032  * During XLOG replay, latest_page_number isn't set up yet; insert a
1033  * suitable value to bypass the sanity test in SimpleLruTruncate.
1034  */
1035  ClogCtl->shared->latest_page_number = xlrec.pageno;
1036 
1038 
1040  }
1041  else
1042  elog(PANIC, "clog_redo: unknown op code %u", info);
1043 }
void SimpleLruTruncate(SlruCtl ctl, int cutoffPage)
Definition: slru.c:1168
unsigned char uint8
Definition: c.h:256
#define PANIC
Definition: elog.h:53
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1721
#define ClogCtl
Definition: clog.c:88
#define CLOG_ZEROPAGE
Definition: clog.h:54
void AdvanceOldestClogXid(TransactionId oldest_datfrozenxid)
Definition: varsup.c:271
#define XLogRecGetData(decoder)
Definition: xlogreader.h:226
void SimpleLruWritePage(SlruCtl ctl, int slotno)
Definition: slru.c:578
int pageno
Definition: clog.h:33
#define CLOG_TRUNCATE
Definition: clog.h:55
#define XLogRecGetInfo(decoder)
Definition: xlogreader.h:222
TransactionId oldestXact
Definition: clog.h:34
#define Assert(condition)
Definition: c.h:681
#define XLR_INFO_MASK
Definition: xlogrecord.h:62
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1117
static int ZeroCLOGPage(int pageno, bool writeXlog)
Definition: clog.c:738
#define XLogRecHasAnyBlockRefs(decoder)
Definition: xlogreader.h:228
#define elog
Definition: elog.h:219
Size CLOGShmemBuffers ( void  )

Definition at line 683 of file clog.c.

References Max, Min, and NBuffers.

Referenced by CLOGShmemInit(), and CLOGShmemSize().

684 {
685  return Min(128, Max(4, NBuffers / 512));
686 }
#define Min(x, y)
Definition: c.h:812
#define Max(x, y)
Definition: c.h:806
int NBuffers
Definition: globals.c:122
void CLOGShmemInit ( void  )

Definition at line 698 of file clog.c.

References CLOG_LSNS_PER_PAGE, ClogCtl, CLOGPagePrecedes(), CLOGShmemBuffers(), LWTRANCHE_CLOG_BUFFERS, and SimpleLruInit().

Referenced by CreateSharedMemoryAndSemaphores().

699 {
700  ClogCtl->PagePrecedes = CLOGPagePrecedes;
702  CLogControlLock, "pg_xact", LWTRANCHE_CLOG_BUFFERS);
703 }
#define ClogCtl
Definition: clog.c:88
#define CLOG_LSNS_PER_PAGE
Definition: clog.c:71
static bool CLOGPagePrecedes(int page1, int page2)
Definition: clog.c:952
Size CLOGShmemBuffers(void)
Definition: clog.c:683
void SimpleLruInit(SlruCtl ctl, const char *name, int nslots, int nlsns, LWLock *ctllock, const char *subdir, int tranche_id)
Definition: slru.c:165
Size CLOGShmemSize ( void  )

Definition at line 692 of file clog.c.

References CLOG_LSNS_PER_PAGE, CLOGShmemBuffers(), and SimpleLruShmemSize().

Referenced by CreateSharedMemoryAndSemaphores().

693 {
695 }
Size SimpleLruShmemSize(int nslots, int nlsns)
Definition: slru.c:145
#define CLOG_LSNS_PER_PAGE
Definition: clog.c:71
Size CLOGShmemBuffers(void)
Definition: clog.c:683
void ExtendCLOG ( TransactionId  newestXact)

Definition at line 867 of file clog.c.

References FirstNormalTransactionId, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), TransactionIdEquals, TransactionIdToPage, TransactionIdToPgIndex, and ZeroCLOGPage().

Referenced by GetNewTransactionId().

868 {
869  int pageno;
870 
871  /*
872  * No work except at first XID of a page. But beware: just after
873  * wraparound, the first XID of page zero is FirstNormalTransactionId.
874  */
875  if (TransactionIdToPgIndex(newestXact) != 0 &&
877  return;
878 
879  pageno = TransactionIdToPage(newestXact);
880 
881  LWLockAcquire(CLogControlLock, LW_EXCLUSIVE);
882 
883  /* Zero the page and make an XLOG entry about it */
884  ZeroCLOGPage(pageno, true);
885 
886  LWLockRelease(CLogControlLock);
887 }
#define TransactionIdToPage(xid)
Definition: clog.c:64
#define TransactionIdEquals(id1, id2)
Definition: transam.h:43
#define TransactionIdToPgIndex(xid)
Definition: clog.c:65
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1721
#define FirstNormalTransactionId
Definition: transam.h:34
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1117
static int ZeroCLOGPage(int pageno, bool writeXlog)
Definition: clog.c:738
void ShutdownCLOG ( void  )

Definition at line 823 of file clog.c.

References ClogCtl, fsync_fname(), and SimpleLruFlush().

Referenced by ShutdownXLOG().

824 {
825  /* Flush dirty CLOG pages to disk */
826  TRACE_POSTGRESQL_CLOG_CHECKPOINT_START(false);
827  SimpleLruFlush(ClogCtl, false);
828 
829  /*
830  * fsync pg_xact to ensure that any files flushed previously are durably
831  * on disk.
832  */
833  fsync_fname("pg_xact", true);
834 
835  TRACE_POSTGRESQL_CLOG_CHECKPOINT_DONE(false);
836 }
void fsync_fname(const char *fname, bool isdir)
Definition: fd.c:572
void SimpleLruFlush(SlruCtl ctl, bool allow_redirtied)
Definition: slru.c:1103
#define ClogCtl
Definition: clog.c:88
void StartupCLOG ( void  )

Definition at line 755 of file clog.c.

References ClogCtl, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), VariableCacheData::nextXid, ShmemVariableCache, and TransactionIdToPage.

Referenced by StartupXLOG().

756 {
758  int pageno = TransactionIdToPage(xid);
759 
760  LWLockAcquire(CLogControlLock, LW_EXCLUSIVE);
761 
762  /*
763  * Initialize our idea of the latest page number.
764  */
765  ClogCtl->shared->latest_page_number = pageno;
766 
767  LWLockRelease(CLogControlLock);
768 }
#define TransactionIdToPage(xid)
Definition: clog.c:64
uint32 TransactionId
Definition: c.h:391
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1721
#define ClogCtl
Definition: clog.c:88
TransactionId nextXid
Definition: transam.h:117
VariableCache ShmemVariableCache
Definition: varsup.c:34
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1117
XidStatus TransactionIdGetStatus ( TransactionId  xid,
XLogRecPtr lsn 
)

Definition at line 641 of file clog.c.

References CLOG_BITS_PER_XACT, CLOG_XACT_BITMASK, ClogCtl, GetLSNIndex, LWLockRelease(), SimpleLruReadPage_ReadOnly(), status(), TransactionIdToBIndex, TransactionIdToByte, and TransactionIdToPage.

Referenced by TransactionIdGetCommitLSN(), and TransactionLogFetch().

642 {
643  int pageno = TransactionIdToPage(xid);
644  int byteno = TransactionIdToByte(xid);
645  int bshift = TransactionIdToBIndex(xid) * CLOG_BITS_PER_XACT;
646  int slotno;
647  int lsnindex;
648  char *byteptr;
650 
651  /* lock is acquired by SimpleLruReadPage_ReadOnly */
652 
653  slotno = SimpleLruReadPage_ReadOnly(ClogCtl, pageno, xid);
654  byteptr = ClogCtl->shared->page_buffer[slotno] + byteno;
655 
656  status = (*byteptr >> bshift) & CLOG_XACT_BITMASK;
657 
658  lsnindex = GetLSNIndex(slotno, xid);
659  *lsn = ClogCtl->shared->group_lsn[lsnindex];
660 
661  LWLockRelease(CLogControlLock);
662 
663  return status;
664 }
#define TransactionIdToBIndex(xid)
Definition: clog.c:67
#define CLOG_XACT_BITMASK
Definition: clog.c:62
#define TransactionIdToPage(xid)
Definition: clog.c:64
#define GetLSNIndex(slotno, xid)
Definition: clog.c:73
int XidStatus
Definition: clog.h:24
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1721
#define ClogCtl
Definition: clog.c:88
#define CLOG_BITS_PER_XACT
Definition: clog.c:59
int SimpleLruReadPage_ReadOnly(SlruCtl ctl, int pageno, TransactionId xid)
Definition: slru.c:467
#define TransactionIdToByte(xid)
Definition: clog.c:66
static void static void status(const char *fmt,...) pg_attribute_printf(1
Definition: pg_regress.c:225
void TransactionIdSetTreeStatus ( TransactionId  xid,
int  nsubxids,
TransactionId subxids,
XidStatus  status,
XLogRecPtr  lsn 
)

Definition at line 163 of file clog.c.

References Assert, i, set_status_by_pages(), TRANSACTION_STATUS_ABORTED, TRANSACTION_STATUS_COMMITTED, TRANSACTION_STATUS_SUB_COMMITTED, TransactionIdSetPageStatus(), and TransactionIdToPage.

Referenced by TransactionIdAbortTree(), TransactionIdAsyncCommitTree(), and TransactionIdCommitTree().

165 {
166  int pageno = TransactionIdToPage(xid); /* get page of parent */
167  int i;
168 
171 
172  /*
173  * See how many subxids, if any, are on the same page as the parent, if
174  * any.
175  */
176  for (i = 0; i < nsubxids; i++)
177  {
178  if (TransactionIdToPage(subxids[i]) != pageno)
179  break;
180  }
181 
182  /*
183  * Do all items fit on a single page?
184  */
185  if (i == nsubxids)
186  {
187  /*
188  * Set the parent and all subtransactions in a single call
189  */
190  TransactionIdSetPageStatus(xid, nsubxids, subxids, status, lsn,
191  pageno, true);
192  }
193  else
194  {
195  int nsubxids_on_first_page = i;
196 
197  /*
198  * If this is a commit then we care about doing this correctly (i.e.
199  * using the subcommitted intermediate status). By here, we know
200  * we're updating more than one page of clog, so we must mark entries
201  * that are *not* on the first page so that they show as subcommitted
202  * before we then return to update the status to fully committed.
203  *
204  * To avoid touching the first page twice, skip marking subcommitted
205  * for the subxids on that first page.
206  */
208  set_status_by_pages(nsubxids - nsubxids_on_first_page,
209  subxids + nsubxids_on_first_page,
211 
212  /*
213  * Now set the parent and subtransactions on same page as the parent,
214  * if any
215  */
216  pageno = TransactionIdToPage(xid);
217  TransactionIdSetPageStatus(xid, nsubxids_on_first_page, subxids, status,
218  lsn, pageno, false);
219 
220  /*
221  * Now work through the rest of the subxids one clog page at a time,
222  * starting from the second page onwards, like we did above.
223  */
224  set_status_by_pages(nsubxids - nsubxids_on_first_page,
225  subxids + nsubxids_on_first_page,
226  status, lsn);
227  }
228 }
#define TransactionIdToPage(xid)
Definition: clog.c:64
#define TRANSACTION_STATUS_COMMITTED
Definition: clog.h:27
#define TRANSACTION_STATUS_ABORTED
Definition: clog.h:28
#define TRANSACTION_STATUS_SUB_COMMITTED
Definition: clog.h:29
static void set_status_by_pages(int nsubxids, TransactionId *subxids, XidStatus status, XLogRecPtr lsn)
Definition: clog.c:237
#define Assert(condition)
Definition: c.h:681
static void TransactionIdSetPageStatus(TransactionId xid, int nsubxids, TransactionId *subxids, XidStatus status, XLogRecPtr lsn, int pageno, bool all_xact_same_page)
Definition: clog.c:273
int i
static void static void status(const char *fmt,...) pg_attribute_printf(1
Definition: pg_regress.c:225
void TrimCLOG ( void  )

Definition at line 774 of file clog.c.

References CLOG_BITS_PER_XACT, ClogCtl, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MemSet, VariableCacheData::nextXid, ShmemVariableCache, SimpleLruReadPage(), TransactionIdToBIndex, TransactionIdToByte, TransactionIdToPage, and TransactionIdToPgIndex.

Referenced by StartupXLOG().

775 {
777  int pageno = TransactionIdToPage(xid);
778 
779  LWLockAcquire(CLogControlLock, LW_EXCLUSIVE);
780 
781  /*
782  * Re-Initialize our idea of the latest page number.
783  */
784  ClogCtl->shared->latest_page_number = pageno;
785 
786  /*
787  * Zero out the remainder of the current clog page. Under normal
788  * circumstances it should be zeroes already, but it seems at least
789  * theoretically possible that XLOG replay will have settled on a nextXID
790  * value that is less than the last XID actually used and marked by the
791  * previous database lifecycle (since subtransaction commit writes clog
792  * but makes no WAL entry). Let's just be safe. (We need not worry about
793  * pages beyond the current one, since those will be zeroed when first
794  * used. For the same reason, there is no need to do anything when
795  * nextXid is exactly at a page boundary; and it's likely that the
796  * "current" page doesn't exist yet in that case.)
797  */
798  if (TransactionIdToPgIndex(xid) != 0)
799  {
800  int byteno = TransactionIdToByte(xid);
801  int bshift = TransactionIdToBIndex(xid) * CLOG_BITS_PER_XACT;
802  int slotno;
803  char *byteptr;
804 
805  slotno = SimpleLruReadPage(ClogCtl, pageno, false, xid);
806  byteptr = ClogCtl->shared->page_buffer[slotno] + byteno;
807 
808  /* Zero so-far-unused positions in the current byte */
809  *byteptr &= (1 << bshift) - 1;
810  /* Zero the rest of the page */
811  MemSet(byteptr + 1, 0, BLCKSZ - byteno - 1);
812 
813  ClogCtl->shared->page_dirty[slotno] = true;
814  }
815 
816  LWLockRelease(CLogControlLock);
817 }
#define TransactionIdToBIndex(xid)
Definition: clog.c:67
#define TransactionIdToPage(xid)
Definition: clog.c:64
uint32 TransactionId
Definition: c.h:391
#define TransactionIdToPgIndex(xid)
Definition: clog.c:65
#define MemSet(start, val, len)
Definition: c.h:863
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1721
#define ClogCtl
Definition: clog.c:88
TransactionId nextXid
Definition: transam.h:117
int SimpleLruReadPage(SlruCtl ctl, int pageno, bool write_ok, TransactionId xid)
Definition: slru.c:375
VariableCache ShmemVariableCache
Definition: varsup.c:34
#define CLOG_BITS_PER_XACT
Definition: clog.c:59
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1117
#define TransactionIdToByte(xid)
Definition: clog.c:66
void TruncateCLOG ( TransactionId  oldestXact,
Oid  oldestxid_datoid 
)

Definition at line 906 of file clog.c.

References AdvanceOldestClogXid(), ClogCtl, SimpleLruTruncate(), SlruScanDirCbReportPresence(), SlruScanDirectory(), TransactionIdToPage, and WriteTruncateXlogRec().

Referenced by vac_truncate_clog().

907 {
908  int cutoffPage;
909 
910  /*
911  * The cutoff point is the start of the segment containing oldestXact. We
912  * pass the *page* containing oldestXact to SimpleLruTruncate.
913  */
914  cutoffPage = TransactionIdToPage(oldestXact);
915 
916  /* Check to see if there's any files that could be removed */
918  return; /* nothing to remove */
919 
920  /*
921  * Advance oldestClogXid before truncating clog, so concurrent xact status
922  * lookups can ensure they don't attempt to access truncated-away clog.
923  *
924  * It's only necessary to do this if we will actually truncate away clog
925  * pages.
926  */
927  AdvanceOldestClogXid(oldestXact);
928 
929  /*
930  * Write XLOG record and flush XLOG to disk. We record the oldest xid
931  * we're keeping information about here so we can ensure that it's always
932  * ahead of clog truncation in case we crash, and so a standby finds out
933  * the new valid xid before the next checkpoint.
934  */
935  WriteTruncateXlogRec(cutoffPage, oldestXact, oldestxid_datoid);
936 
937  /* Now we can remove the old CLOG segment(s) */
938  SimpleLruTruncate(ClogCtl, cutoffPage);
939 }
#define TransactionIdToPage(xid)
Definition: clog.c:64
void SimpleLruTruncate(SlruCtl ctl, int cutoffPage)
Definition: slru.c:1168
#define ClogCtl
Definition: clog.c:88
void AdvanceOldestClogXid(TransactionId oldest_datfrozenxid)
Definition: varsup.c:271
bool SlruScanDirCbReportPresence(SlruCtl ctl, char *filename, int segpage, void *data)
Definition: slru.c:1321
bool SlruScanDirectory(SlruCtl ctl, SlruScanCallback callback, void *data)
Definition: slru.c:1376
static void WriteTruncateXlogRec(int pageno, TransactionId oldestXact, Oid oldestXidDb)
Definition: clog.c:984