PostgreSQL Source Code  git master
clog.h File Reference
#include "access/xlogreader.h"
#include "storage/sync.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 CheckPointCLOG (void)
 
void ExtendCLOG (TransactionId newestXact)
 
void TruncateCLOG (TransactionId oldestXact, Oid oldestxid_datoid)
 
int clogsyncfiletag (const FileTag *ftag, char *path)
 
void clog_redo (XLogReaderState *record)
 
void clog_desc (StringInfo buf, XLogReaderState *record)
 
const char * clog_identify (uint8 info)
 

Macro Definition Documentation

◆ CLOG_TRUNCATE

#define CLOG_TRUNCATE   0x10

Definition at line 57 of file clog.h.

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

◆ CLOG_ZEROPAGE

#define CLOG_ZEROPAGE   0x00

Definition at line 56 of file clog.h.

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

◆ TRANSACTION_STATUS_ABORTED

#define TRANSACTION_STATUS_ABORTED   0x02

◆ TRANSACTION_STATUS_COMMITTED

◆ TRANSACTION_STATUS_IN_PROGRESS

#define TRANSACTION_STATUS_IN_PROGRESS   0x00

Definition at line 27 of file clog.h.

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

◆ TRANSACTION_STATUS_SUB_COMMITTED

#define TRANSACTION_STATUS_SUB_COMMITTED   0x03

Typedef Documentation

◆ XidStatus

typedef int XidStatus

Definition at line 25 of file clog.h.

◆ xl_clog_truncate

Function Documentation

◆ BootStrapCLOG()

void BootStrapCLOG ( void  )

Definition at line 712 of file clog.c.

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

Referenced by BootStrapXLOG().

713 {
714  int slotno;
715 
716  LWLockAcquire(XactSLRULock, 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(XactCtl, slotno);
723  Assert(!XactCtl->shared->page_dirty[slotno]);
724 
725  LWLockRelease(XactSLRULock);
726 }
#define XactCtl
Definition: clog.c:89
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1803
void SimpleLruWritePage(SlruCtl ctl, int slotno)
Definition: slru.c:614
#define Assert(condition)
Definition: c.h:804
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1199
static int ZeroCLOGPage(int pageno, bool writeXlog)
Definition: clog.c:738

◆ CheckPointCLOG()

void CheckPointCLOG ( void  )

Definition at line 818 of file clog.c.

References SimpleLruWriteAll(), and XactCtl.

Referenced by CheckPointGuts().

819 {
820  /*
821  * Write dirty CLOG pages to disk. This may result in sync requests
822  * queued for later handling by ProcessSyncRequests(), as part of the
823  * checkpoint.
824  */
825  TRACE_POSTGRESQL_CLOG_CHECKPOINT_START(true);
826  SimpleLruWriteAll(XactCtl, true);
827  TRACE_POSTGRESQL_CLOG_CHECKPOINT_DONE(true);
828 }
#define XactCtl
Definition: clog.c:89
void SimpleLruWriteAll(SlruCtl ctl, bool allow_redirtied)
Definition: slru.c:1156

◆ clog_desc()

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:439
#define CLOG_ZEROPAGE
Definition: clog.h:56
#define XLogRecGetData(decoder)
Definition: xlogreader.h:310
void appendStringInfo(StringInfo str, const char *fmt,...)
Definition: stringinfo.c:91
int pageno
Definition: clog.h:34
#define CLOG_TRUNCATE
Definition: clog.h:57
#define XLogRecGetInfo(decoder)
Definition: xlogreader.h:305
TransactionId oldestXact
Definition: clog.h:35
#define XLR_INFO_MASK
Definition: xlogrecord.h:62

◆ clog_identify()

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:56
#define CLOG_TRUNCATE
Definition: clog.h:57
#define XLR_INFO_MASK
Definition: xlogrecord.h:62

◆ clog_redo()

void clog_redo ( XLogReaderState record)

Definition at line 986 of file clog.c.

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

987 {
988  uint8 info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
989 
990  /* Backup blocks are not used in clog records */
991  Assert(!XLogRecHasAnyBlockRefs(record));
992 
993  if (info == CLOG_ZEROPAGE)
994  {
995  int pageno;
996  int slotno;
997 
998  memcpy(&pageno, XLogRecGetData(record), sizeof(int));
999 
1000  LWLockAcquire(XactSLRULock, LW_EXCLUSIVE);
1001 
1002  slotno = ZeroCLOGPage(pageno, false);
1003  SimpleLruWritePage(XactCtl, slotno);
1004  Assert(!XactCtl->shared->page_dirty[slotno]);
1005 
1006  LWLockRelease(XactSLRULock);
1007  }
1008  else if (info == CLOG_TRUNCATE)
1009  {
1010  xl_clog_truncate xlrec;
1011 
1012  memcpy(&xlrec, XLogRecGetData(record), sizeof(xl_clog_truncate));
1013 
1015 
1017  }
1018  else
1019  elog(PANIC, "clog_redo: unknown op code %u", info);
1020 }
void SimpleLruTruncate(SlruCtl ctl, int cutoffPage)
Definition: slru.c:1226
#define XactCtl
Definition: clog.c:89
unsigned char uint8
Definition: c.h:439
#define PANIC
Definition: elog.h:50
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1803
#define CLOG_ZEROPAGE
Definition: clog.h:56
void AdvanceOldestClogXid(TransactionId oldest_datfrozenxid)
Definition: varsup.c:328
#define XLogRecGetData(decoder)
Definition: xlogreader.h:310
void SimpleLruWritePage(SlruCtl ctl, int slotno)
Definition: slru.c:614
int pageno
Definition: clog.h:34
#define CLOG_TRUNCATE
Definition: clog.h:57
#define XLogRecGetInfo(decoder)
Definition: xlogreader.h:305
TransactionId oldestXact
Definition: clog.h:35
#define Assert(condition)
Definition: c.h:804
#define XLR_INFO_MASK
Definition: xlogrecord.h:62
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1199
static int ZeroCLOGPage(int pageno, bool writeXlog)
Definition: clog.c:738
#define elog(elevel,...)
Definition: elog.h:232
#define XLogRecHasAnyBlockRefs(decoder)
Definition: xlogreader.h:312

◆ CLOGShmemBuffers()

Size CLOGShmemBuffers ( void  )

Definition at line 681 of file clog.c.

References Max, Min, and NBuffers.

Referenced by CLOGShmemInit(), and CLOGShmemSize().

682 {
683  return Min(128, Max(4, NBuffers / 512));
684 }
#define Min(x, y)
Definition: c.h:986
#define Max(x, y)
Definition: c.h:980
int NBuffers
Definition: globals.c:135

◆ CLOGShmemInit()

void CLOGShmemInit ( void  )

Definition at line 696 of file clog.c.

References CLOG_LSNS_PER_PAGE, CLOG_XACTS_PER_PAGE, CLOGPagePrecedes(), CLOGShmemBuffers(), LWTRANCHE_XACT_BUFFER, SimpleLruInit(), SlruPagePrecedesUnitTests, SYNC_HANDLER_CLOG, and XactCtl.

Referenced by CreateSharedMemoryAndSemaphores().

697 {
698  XactCtl->PagePrecedes = CLOGPagePrecedes;
700  XactSLRULock, "pg_xact", LWTRANCHE_XACT_BUFFER,
703 }
#define CLOG_XACTS_PER_PAGE
Definition: clog.c:62
#define XactCtl
Definition: clog.c:89
void SimpleLruInit(SlruCtl ctl, const char *name, int nslots, int nlsns, LWLock *ctllock, const char *subdir, int tranche_id, SyncRequestHandler sync_handler)
Definition: slru.c:187
#define CLOG_LSNS_PER_PAGE
Definition: clog.c:72
static bool CLOGPagePrecedes(int page1, int page2)
Definition: clog.c:934
Size CLOGShmemBuffers(void)
Definition: clog.c:681
#define SlruPagePrecedesUnitTests(ctl, per_page)
Definition: slru.h:156

◆ CLOGShmemSize()

Size CLOGShmemSize ( void  )

Definition at line 690 of file clog.c.

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

Referenced by CalculateShmemSize().

691 {
693 }
Size SimpleLruShmemSize(int nslots, int nlsns)
Definition: slru.c:156
#define CLOG_LSNS_PER_PAGE
Definition: clog.c:72
Size CLOGShmemBuffers(void)
Definition: clog.c:681

◆ clogsyncfiletag()

int clogsyncfiletag ( const FileTag ftag,
char *  path 
)

Definition at line 1026 of file clog.c.

References SlruSyncFileTag(), and XactCtl.

1027 {
1028  return SlruSyncFileTag(XactCtl, ftag, path);
1029 }
int SlruSyncFileTag(SlruCtl ctl, const FileTag *ftag, char *path)
Definition: slru.c:1593
#define XactCtl
Definition: clog.c:89

◆ ExtendCLOG()

void ExtendCLOG ( TransactionId  newestXact)

Definition at line 840 of file clog.c.

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

Referenced by GetNewTransactionId().

841 {
842  int pageno;
843 
844  /*
845  * No work except at first XID of a page. But beware: just after
846  * wraparound, the first XID of page zero is FirstNormalTransactionId.
847  */
848  if (TransactionIdToPgIndex(newestXact) != 0 &&
850  return;
851 
852  pageno = TransactionIdToPage(newestXact);
853 
854  LWLockAcquire(XactSLRULock, LW_EXCLUSIVE);
855 
856  /* Zero the page and make an XLOG entry about it */
857  ZeroCLOGPage(pageno, true);
858 
859  LWLockRelease(XactSLRULock);
860 }
#define TransactionIdToPage(xid)
Definition: clog.c:65
#define TransactionIdEquals(id1, id2)
Definition: transam.h:43
#define TransactionIdToPgIndex(xid)
Definition: clog.c:66
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1803
#define FirstNormalTransactionId
Definition: transam.h:34
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1199
static int ZeroCLOGPage(int pageno, bool writeXlog)
Definition: clog.c:738

◆ StartupCLOG()

void StartupCLOG ( void  )

Definition at line 755 of file clog.c.

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

Referenced by StartupXLOG().

756 {
758  int pageno = TransactionIdToPage(xid);
759 
760  LWLockAcquire(XactSLRULock, LW_EXCLUSIVE);
761 
762  /*
763  * Initialize our idea of the latest page number.
764  */
765  XactCtl->shared->latest_page_number = pageno;
766 
767  LWLockRelease(XactSLRULock);
768 }
#define TransactionIdToPage(xid)
Definition: clog.c:65
uint32 TransactionId
Definition: c.h:587
#define XactCtl
Definition: clog.c:89
FullTransactionId nextXid
Definition: transam.h:220
#define XidFromFullTransactionId(x)
Definition: transam.h:48
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1803
VariableCache ShmemVariableCache
Definition: varsup.c:34
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1199

◆ TransactionIdGetStatus()

XidStatus TransactionIdGetStatus ( TransactionId  xid,
XLogRecPtr lsn 
)

Definition at line 639 of file clog.c.

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

Referenced by TransactionIdGetCommitLSN(), and TransactionLogFetch().

640 {
641  int pageno = TransactionIdToPage(xid);
642  int byteno = TransactionIdToByte(xid);
643  int bshift = TransactionIdToBIndex(xid) * CLOG_BITS_PER_XACT;
644  int slotno;
645  int lsnindex;
646  char *byteptr;
648 
649  /* lock is acquired by SimpleLruReadPage_ReadOnly */
650 
651  slotno = SimpleLruReadPage_ReadOnly(XactCtl, pageno, xid);
652  byteptr = XactCtl->shared->page_buffer[slotno] + byteno;
653 
654  status = (*byteptr >> bshift) & CLOG_XACT_BITMASK;
655 
656  lsnindex = GetLSNIndex(slotno, xid);
657  *lsn = XactCtl->shared->group_lsn[lsnindex];
658 
659  LWLockRelease(XactSLRULock);
660 
661  return status;
662 }
#define TransactionIdToBIndex(xid)
Definition: clog.c:68
#define CLOG_XACT_BITMASK
Definition: clog.c:63
#define TransactionIdToPage(xid)
Definition: clog.c:65
#define GetLSNIndex(slotno, xid)
Definition: clog.c:74
#define XactCtl
Definition: clog.c:89
int XidStatus
Definition: clog.h:25
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1803
#define CLOG_BITS_PER_XACT
Definition: clog.c:60
int SimpleLruReadPage_ReadOnly(SlruCtl ctl, int pageno, TransactionId xid)
Definition: slru.c:495
#define TransactionIdToByte(xid)
Definition: clog.c:67
static void static void status(const char *fmt,...) pg_attribute_printf(1
Definition: pg_regress.c:227

◆ TransactionIdSetTreeStatus()

void TransactionIdSetTreeStatus ( TransactionId  xid,
int  nsubxids,
TransactionId subxids,
XidStatus  status,
XLogRecPtr  lsn 
)

Definition at line 164 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().

166 {
167  int pageno = TransactionIdToPage(xid); /* get page of parent */
168  int i;
169 
172 
173  /*
174  * See how many subxids, if any, are on the same page as the parent, if
175  * any.
176  */
177  for (i = 0; i < nsubxids; i++)
178  {
179  if (TransactionIdToPage(subxids[i]) != pageno)
180  break;
181  }
182 
183  /*
184  * Do all items fit on a single page?
185  */
186  if (i == nsubxids)
187  {
188  /*
189  * Set the parent and all subtransactions in a single call
190  */
191  TransactionIdSetPageStatus(xid, nsubxids, subxids, status, lsn,
192  pageno, true);
193  }
194  else
195  {
196  int nsubxids_on_first_page = i;
197 
198  /*
199  * If this is a commit then we care about doing this correctly (i.e.
200  * using the subcommitted intermediate status). By here, we know
201  * we're updating more than one page of clog, so we must mark entries
202  * that are *not* on the first page so that they show as subcommitted
203  * before we then return to update the status to fully committed.
204  *
205  * To avoid touching the first page twice, skip marking subcommitted
206  * for the subxids on that first page.
207  */
209  set_status_by_pages(nsubxids - nsubxids_on_first_page,
210  subxids + nsubxids_on_first_page,
212 
213  /*
214  * Now set the parent and subtransactions on same page as the parent,
215  * if any
216  */
217  pageno = TransactionIdToPage(xid);
218  TransactionIdSetPageStatus(xid, nsubxids_on_first_page, subxids, status,
219  lsn, pageno, false);
220 
221  /*
222  * Now work through the rest of the subxids one clog page at a time,
223  * starting from the second page onwards, like we did above.
224  */
225  set_status_by_pages(nsubxids - nsubxids_on_first_page,
226  subxids + nsubxids_on_first_page,
227  status, lsn);
228  }
229 }
#define TransactionIdToPage(xid)
Definition: clog.c:65
#define TRANSACTION_STATUS_COMMITTED
Definition: clog.h:28
#define TRANSACTION_STATUS_ABORTED
Definition: clog.h:29
#define TRANSACTION_STATUS_SUB_COMMITTED
Definition: clog.h:30
static void set_status_by_pages(int nsubxids, TransactionId *subxids, XidStatus status, XLogRecPtr lsn)
Definition: clog.c:238
#define Assert(condition)
Definition: c.h:804
static void TransactionIdSetPageStatus(TransactionId xid, int nsubxids, TransactionId *subxids, XidStatus status, XLogRecPtr lsn, int pageno, bool all_xact_same_page)
Definition: clog.c:274
int i
static void static void status(const char *fmt,...) pg_attribute_printf(1
Definition: pg_regress.c:227

◆ TrimCLOG()

void TrimCLOG ( void  )

Definition at line 774 of file clog.c.

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

Referenced by StartupXLOG().

775 {
777  int pageno = TransactionIdToPage(xid);
778 
779  LWLockAcquire(XactSLRULock, LW_EXCLUSIVE);
780 
781  /*
782  * Zero out the remainder of the current clog page. Under normal
783  * circumstances it should be zeroes already, but it seems at least
784  * theoretically possible that XLOG replay will have settled on a nextXID
785  * value that is less than the last XID actually used and marked by the
786  * previous database lifecycle (since subtransaction commit writes clog
787  * but makes no WAL entry). Let's just be safe. (We need not worry about
788  * pages beyond the current one, since those will be zeroed when first
789  * used. For the same reason, there is no need to do anything when
790  * nextXid is exactly at a page boundary; and it's likely that the
791  * "current" page doesn't exist yet in that case.)
792  */
793  if (TransactionIdToPgIndex(xid) != 0)
794  {
795  int byteno = TransactionIdToByte(xid);
796  int bshift = TransactionIdToBIndex(xid) * CLOG_BITS_PER_XACT;
797  int slotno;
798  char *byteptr;
799 
800  slotno = SimpleLruReadPage(XactCtl, pageno, false, xid);
801  byteptr = XactCtl->shared->page_buffer[slotno] + byteno;
802 
803  /* Zero so-far-unused positions in the current byte */
804  *byteptr &= (1 << bshift) - 1;
805  /* Zero the rest of the page */
806  MemSet(byteptr + 1, 0, BLCKSZ - byteno - 1);
807 
808  XactCtl->shared->page_dirty[slotno] = true;
809  }
810 
811  LWLockRelease(XactSLRULock);
812 }
#define TransactionIdToBIndex(xid)
Definition: clog.c:68
#define TransactionIdToPage(xid)
Definition: clog.c:65
uint32 TransactionId
Definition: c.h:587
#define TransactionIdToPgIndex(xid)
Definition: clog.c:66
#define XactCtl
Definition: clog.c:89
#define MemSet(start, val, len)
Definition: c.h:1008
FullTransactionId nextXid
Definition: transam.h:220
#define XidFromFullTransactionId(x)
Definition: transam.h:48
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1803
int SimpleLruReadPage(SlruCtl ctl, int pageno, bool write_ok, TransactionId xid)
Definition: slru.c:395
VariableCache ShmemVariableCache
Definition: varsup.c:34
#define CLOG_BITS_PER_XACT
Definition: clog.c:60
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1199
#define TransactionIdToByte(xid)
Definition: clog.c:67

◆ TruncateCLOG()

void TruncateCLOG ( TransactionId  oldestXact,
Oid  oldestxid_datoid 
)

Definition at line 879 of file clog.c.

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

Referenced by vac_truncate_clog().

880 {
881  int cutoffPage;
882 
883  /*
884  * The cutoff point is the start of the segment containing oldestXact. We
885  * pass the *page* containing oldestXact to SimpleLruTruncate.
886  */
887  cutoffPage = TransactionIdToPage(oldestXact);
888 
889  /* Check to see if there's any files that could be removed */
891  return; /* nothing to remove */
892 
893  /*
894  * Advance oldestClogXid before truncating clog, so concurrent xact status
895  * lookups can ensure they don't attempt to access truncated-away clog.
896  *
897  * It's only necessary to do this if we will actually truncate away clog
898  * pages.
899  */
900  AdvanceOldestClogXid(oldestXact);
901 
902  /*
903  * Write XLOG record and flush XLOG to disk. We record the oldest xid
904  * we're keeping information about here so we can ensure that it's always
905  * ahead of clog truncation in case we crash, and so a standby finds out
906  * the new valid xid before the next checkpoint.
907  */
908  WriteTruncateXlogRec(cutoffPage, oldestXact, oldestxid_datoid);
909 
910  /* Now we can remove the old CLOG segment(s) */
911  SimpleLruTruncate(XactCtl, cutoffPage);
912 }
#define TransactionIdToPage(xid)
Definition: clog.c:65
void SimpleLruTruncate(SlruCtl ctl, int cutoffPage)
Definition: slru.c:1226
#define XactCtl
Definition: clog.c:89
void AdvanceOldestClogXid(TransactionId oldest_datfrozenxid)
Definition: varsup.c:328
static void WriteTruncateXlogRec(int pageno, TransactionId oldestXact, Oid oldestXactDb)
Definition: clog.c:967
bool SlruScanDirCbReportPresence(SlruCtl ctl, char *filename, int segpage, void *data)
Definition: slru.c:1500
bool SlruScanDirectory(SlruCtl ctl, SlruScanCallback callback, void *data)
Definition: slru.c:1553