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snapbuild.h File Reference
#include "access/xlogdefs.h"
#include "utils/snapmgr.h"
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Typedefs

typedef struct SnapBuild SnapBuild
 

Enumerations

enum  SnapBuildState { SNAPBUILD_START = -1, SNAPBUILD_BUILDING_SNAPSHOT = 0, SNAPBUILD_FULL_SNAPSHOT = 1, SNAPBUILD_CONSISTENT = 2 }
 

Functions

void CheckPointSnapBuild (void)
 
SnapBuildAllocateSnapshotBuilder (struct ReorderBuffer *cache, TransactionId xmin_horizon, XLogRecPtr start_lsn, bool need_full_snapshot)
 
void FreeSnapshotBuilder (SnapBuild *cache)
 
void SnapBuildSnapDecRefcount (Snapshot snap)
 
Snapshot SnapBuildInitialSnapshot (SnapBuild *builder)
 
const char * SnapBuildExportSnapshot (SnapBuild *snapstate)
 
void SnapBuildClearExportedSnapshot (void)
 
SnapBuildState SnapBuildCurrentState (SnapBuild *snapstate)
 
Snapshot SnapBuildGetOrBuildSnapshot (SnapBuild *builder, TransactionId xid)
 
bool SnapBuildXactNeedsSkip (SnapBuild *snapstate, XLogRecPtr ptr)
 
void SnapBuildCommitTxn (SnapBuild *builder, XLogRecPtr lsn, TransactionId xid, int nsubxacts, TransactionId *subxacts)
 
bool SnapBuildProcessChange (SnapBuild *builder, TransactionId xid, XLogRecPtr lsn)
 
void SnapBuildProcessNewCid (SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *cid)
 
void SnapBuildProcessRunningXacts (SnapBuild *builder, XLogRecPtr lsn, struct xl_running_xacts *running)
 
void SnapBuildSerializationPoint (SnapBuild *builder, XLogRecPtr lsn)
 

Typedef Documentation

◆ SnapBuild

typedef struct SnapBuild SnapBuild

Definition at line 51 of file snapbuild.h.

Enumeration Type Documentation

◆ SnapBuildState

Enumerator
SNAPBUILD_START 
SNAPBUILD_BUILDING_SNAPSHOT 
SNAPBUILD_FULL_SNAPSHOT 
SNAPBUILD_CONSISTENT 

Definition at line 18 of file snapbuild.h.

19 {
20  /*
21  * Initial state, we can't do much yet.
22  */
23  SNAPBUILD_START = -1,
24 
25  /*
26  * Collecting committed transactions, to build the initial catalog
27  * snapshot.
28  */
30 
31  /*
32  * We have collected enough information to decode tuples in transactions
33  * that started after this.
34  *
35  * Once we reached this we start to collect changes. We cannot apply them
36  * yet, because they might be based on transactions that were still
37  * running when FULL_SNAPSHOT was reached.
38  */
40 
41  /*
42  * Found a point after SNAPBUILD_FULL_SNAPSHOT where all transactions that
43  * were running at that point finished. Till we reach that we hold off
44  * calling any commit callbacks.
45  */
SnapBuildState
Definition: snapbuild.h:18

Function Documentation

◆ AllocateSnapshotBuilder()

SnapBuild* AllocateSnapshotBuilder ( struct ReorderBuffer cache,
TransactionId  xmin_horizon,
XLogRecPtr  start_lsn,
bool  need_full_snapshot 
)

Definition at line 310 of file snapbuild.c.

References ALLOCSET_DEFAULT_SIZES, AllocSetContextCreate, SnapBuild::building_full_snapshot, SnapBuild::committed, SnapBuild::context, CurrentMemoryContext, SnapBuild::includes_all_transactions, SnapBuild::initial_xmin_horizon, MemoryContextSwitchTo(), palloc0(), SnapBuild::reorder, SNAPBUILD_START, SnapBuild::start_decoding_at, SnapBuild::state, SnapBuild::xcnt, SnapBuild::xcnt_space, and SnapBuild::xip.

Referenced by StartupDecodingContext().

314 {
315  MemoryContext context;
316  MemoryContext oldcontext;
317  SnapBuild *builder;
318 
319  /* allocate memory in own context, to have better accountability */
321  "snapshot builder context",
323  oldcontext = MemoryContextSwitchTo(context);
324 
325  builder = palloc0(sizeof(SnapBuild));
326 
327  builder->state = SNAPBUILD_START;
328  builder->context = context;
329  builder->reorder = reorder;
330  /* Other struct members initialized by zeroing via palloc0 above */
331 
332  builder->committed.xcnt = 0;
333  builder->committed.xcnt_space = 128; /* arbitrary number */
334  builder->committed.xip =
335  palloc0(builder->committed.xcnt_space * sizeof(TransactionId));
336  builder->committed.includes_all_transactions = true;
337 
338  builder->initial_xmin_horizon = xmin_horizon;
339  builder->start_decoding_at = start_lsn;
340  builder->building_full_snapshot = need_full_snapshot;
341 
342  MemoryContextSwitchTo(oldcontext);
343 
344  return builder;
345 }
#define AllocSetContextCreate
Definition: memutils.h:170
struct SnapBuild::@24 committed
uint32 TransactionId
Definition: c.h:514
bool building_full_snapshot
Definition: snapbuild.c:174
static MemoryContext MemoryContextSwitchTo(MemoryContext context)
Definition: palloc.h:109
size_t xcnt_space
Definition: snapbuild.c:221
size_t xcnt
Definition: snapbuild.c:218
SnapBuildState state
Definition: snapbuild.c:150
#define ALLOCSET_DEFAULT_SIZES
Definition: memutils.h:192
ReorderBuffer * reorder
Definition: snapbuild.c:189
TransactionId initial_xmin_horizon
Definition: snapbuild.c:171
TransactionId * xip
Definition: snapbuild.c:244
bool includes_all_transactions
Definition: snapbuild.c:228
MemoryContext CurrentMemoryContext
Definition: mcxt.c:38
void * palloc0(Size size)
Definition: mcxt.c:980
MemoryContext context
Definition: snapbuild.c:153
XLogRecPtr start_decoding_at
Definition: snapbuild.c:165

◆ CheckPointSnapBuild()

void CheckPointSnapBuild ( void  )

Definition at line 1932 of file snapbuild.c.

References AllocateDir(), dirent::d_name, DEBUG1, elog, ereport, errcode_for_file_access(), errmsg(), FreeDir(), GetRedoRecPtr(), InvalidXLogRecPtr, LOG, lstat, MAXPGPATH, ReadDir(), ReplicationSlotsComputeLogicalRestartLSN(), S_ISREG, snprintf, and stat.

Referenced by CheckPointGuts().

1933 {
1934  XLogRecPtr cutoff;
1935  XLogRecPtr redo;
1936  DIR *snap_dir;
1937  struct dirent *snap_de;
1938  char path[MAXPGPATH + 21];
1939 
1940  /*
1941  * We start off with a minimum of the last redo pointer. No new
1942  * replication slot will start before that, so that's a safe upper bound
1943  * for removal.
1944  */
1945  redo = GetRedoRecPtr();
1946 
1947  /* now check for the restart ptrs from existing slots */
1949 
1950  /* don't start earlier than the restart lsn */
1951  if (redo < cutoff)
1952  cutoff = redo;
1953 
1954  snap_dir = AllocateDir("pg_logical/snapshots");
1955  while ((snap_de = ReadDir(snap_dir, "pg_logical/snapshots")) != NULL)
1956  {
1957  uint32 hi;
1958  uint32 lo;
1959  XLogRecPtr lsn;
1960  struct stat statbuf;
1961 
1962  if (strcmp(snap_de->d_name, ".") == 0 ||
1963  strcmp(snap_de->d_name, "..") == 0)
1964  continue;
1965 
1966  snprintf(path, sizeof(path), "pg_logical/snapshots/%s", snap_de->d_name);
1967 
1968  if (lstat(path, &statbuf) == 0 && !S_ISREG(statbuf.st_mode))
1969  {
1970  elog(DEBUG1, "only regular files expected: %s", path);
1971  continue;
1972  }
1973 
1974  /*
1975  * temporary filenames from SnapBuildSerialize() include the LSN and
1976  * everything but are postfixed by .$pid.tmp. We can just remove them
1977  * the same as other files because there can be none that are
1978  * currently being written that are older than cutoff.
1979  *
1980  * We just log a message if a file doesn't fit the pattern, it's
1981  * probably some editors lock/state file or similar...
1982  */
1983  if (sscanf(snap_de->d_name, "%X-%X.snap", &hi, &lo) != 2)
1984  {
1985  ereport(LOG,
1986  (errmsg("could not parse file name \"%s\"", path)));
1987  continue;
1988  }
1989 
1990  lsn = ((uint64) hi) << 32 | lo;
1991 
1992  /* check whether we still need it */
1993  if (lsn < cutoff || cutoff == InvalidXLogRecPtr)
1994  {
1995  elog(DEBUG1, "removing snapbuild snapshot %s", path);
1996 
1997  /*
1998  * It's not particularly harmful, though strange, if we can't
1999  * remove the file here. Don't prevent the checkpoint from
2000  * completing, that'd be a cure worse than the disease.
2001  */
2002  if (unlink(path) < 0)
2003  {
2004  ereport(LOG,
2006  errmsg("could not remove file \"%s\": %m",
2007  path)));
2008  continue;
2009  }
2010  }
2011  }
2012  FreeDir(snap_dir);
2013 }
#define InvalidXLogRecPtr
Definition: xlogdefs.h:28
#define DEBUG1
Definition: elog.h:25
#define LOG
Definition: elog.h:26
Definition: dirent.h:9
Definition: dirent.c:25
#define MAXPGPATH
int errcode_for_file_access(void)
Definition: elog.c:631
XLogRecPtr ReplicationSlotsComputeLogicalRestartLSN(void)
Definition: slot.c:791
unsigned int uint32
Definition: c.h:359
DIR * AllocateDir(const char *dirname)
Definition: fd.c:2503
#define ereport(elevel, rest)
Definition: elog.h:141
#define S_ISREG(m)
Definition: win32_port.h:299
#define stat(a, b)
Definition: win32_port.h:255
uint64 XLogRecPtr
Definition: xlogdefs.h:21
struct dirent * ReadDir(DIR *dir, const char *dirname)
Definition: fd.c:2569
XLogRecPtr GetRedoRecPtr(void)
Definition: xlog.c:8208
#define lstat(path, sb)
Definition: win32_port.h:244
int errmsg(const char *fmt,...)
Definition: elog.c:822
#define elog(elevel,...)
Definition: elog.h:228
char d_name[MAX_PATH]
Definition: dirent.h:14
#define snprintf
Definition: port.h:192
int FreeDir(DIR *dir)
Definition: fd.c:2621

◆ FreeSnapshotBuilder()

void FreeSnapshotBuilder ( SnapBuild cache)

Definition at line 351 of file snapbuild.c.

References SnapBuild::context, MemoryContextDelete(), SnapBuildSnapDecRefcount(), and SnapBuild::snapshot.

Referenced by FreeDecodingContext().

352 {
353  MemoryContext context = builder->context;
354 
355  /* free snapshot explicitly, that contains some error checking */
356  if (builder->snapshot != NULL)
357  {
358  SnapBuildSnapDecRefcount(builder->snapshot);
359  builder->snapshot = NULL;
360  }
361 
362  /* other resources are deallocated via memory context reset */
363  MemoryContextDelete(context);
364 }
void MemoryContextDelete(MemoryContext context)
Definition: mcxt.c:211
void SnapBuildSnapDecRefcount(Snapshot snap)
Definition: snapbuild.c:428

◆ SnapBuildClearExportedSnapshot()

void SnapBuildClearExportedSnapshot ( void  )

Definition at line 692 of file snapbuild.c.

References AbortCurrentTransaction(), CurrentResourceOwner, elog, ERROR, ExportInProgress, IsTransactionState(), and SavedResourceOwnerDuringExport.

Referenced by exec_replication_command().

693 {
694  /* nothing exported, that is the usual case */
695  if (!ExportInProgress)
696  return;
697 
698  if (!IsTransactionState())
699  elog(ERROR, "clearing exported snapshot in wrong transaction state");
700 
701  /* make sure nothing could have ever happened */
703 
706  ExportInProgress = false;
707 }
void AbortCurrentTransaction(void)
Definition: xact.c:3162
ResourceOwner CurrentResourceOwner
Definition: resowner.c:142
static ResourceOwner SavedResourceOwnerDuringExport
Definition: snapbuild.c:252
#define ERROR
Definition: elog.h:43
static bool ExportInProgress
Definition: snapbuild.c:253
bool IsTransactionState(void)
Definition: xact.c:355
#define elog(elevel,...)
Definition: elog.h:228

◆ SnapBuildCommitTxn()

void SnapBuildCommitTxn ( SnapBuild builder,
XLogRecPtr  lsn,
TransactionId  xid,
int  nsubxacts,
TransactionId subxacts 
)

Definition at line 923 of file snapbuild.c.

References Assert, SnapBuild::building_full_snapshot, SnapBuild::committed, DEBUG1, DEBUG2, elog, SnapBuild::includes_all_transactions, NormalTransactionIdFollows, SnapBuild::reorder, ReorderBufferSetBaseSnapshot(), ReorderBufferXidHasBaseSnapshot(), ReorderBufferXidHasCatalogChanges(), SNAPBUILD_BUILDING_SNAPSHOT, SNAPBUILD_CONSISTENT, SNAPBUILD_FULL_SNAPSHOT, SNAPBUILD_START, SnapBuildAddCommittedTxn(), SnapBuildBuildSnapshot(), SnapBuildDistributeNewCatalogSnapshot(), SnapBuildNextPhaseAt(), SnapBuildSnapDecRefcount(), SnapBuildSnapIncRefcount(), SnapBuild::snapshot, SnapBuild::start_decoding_at, SnapBuild::state, TransactionIdAdvance, TransactionIdFollowsOrEquals(), TransactionIdIsValid, TransactionIdPrecedes(), and SnapBuild::xmax.

Referenced by DecodeCommit().

925 {
926  int nxact;
927 
928  bool needs_snapshot = false;
929  bool needs_timetravel = false;
930  bool sub_needs_timetravel = false;
931 
932  TransactionId xmax = xid;
933 
934  /*
935  * Transactions preceding BUILDING_SNAPSHOT will neither be decoded, nor
936  * will they be part of a snapshot. So we don't need to record anything.
937  */
938  if (builder->state == SNAPBUILD_START ||
939  (builder->state == SNAPBUILD_BUILDING_SNAPSHOT &&
941  {
942  /* ensure that only commits after this are getting replayed */
943  if (builder->start_decoding_at <= lsn)
944  builder->start_decoding_at = lsn + 1;
945  return;
946  }
947 
948  if (builder->state < SNAPBUILD_CONSISTENT)
949  {
950  /* ensure that only commits after this are getting replayed */
951  if (builder->start_decoding_at <= lsn)
952  builder->start_decoding_at = lsn + 1;
953 
954  /*
955  * If building an exportable snapshot, force xid to be tracked, even
956  * if the transaction didn't modify the catalog.
957  */
958  if (builder->building_full_snapshot)
959  {
960  needs_timetravel = true;
961  }
962  }
963 
964  for (nxact = 0; nxact < nsubxacts; nxact++)
965  {
966  TransactionId subxid = subxacts[nxact];
967 
968  /*
969  * Add subtransaction to base snapshot if catalog modifying, we don't
970  * distinguish to toplevel transactions there.
971  */
972  if (ReorderBufferXidHasCatalogChanges(builder->reorder, subxid))
973  {
974  sub_needs_timetravel = true;
975  needs_snapshot = true;
976 
977  elog(DEBUG1, "found subtransaction %u:%u with catalog changes",
978  xid, subxid);
979 
980  SnapBuildAddCommittedTxn(builder, subxid);
981 
982  if (NormalTransactionIdFollows(subxid, xmax))
983  xmax = subxid;
984  }
985 
986  /*
987  * If we're forcing timetravel we also need visibility information
988  * about subtransaction, so keep track of subtransaction's state, even
989  * if not catalog modifying. Don't need to distribute a snapshot in
990  * that case.
991  */
992  else if (needs_timetravel)
993  {
994  SnapBuildAddCommittedTxn(builder, subxid);
995  if (NormalTransactionIdFollows(subxid, xmax))
996  xmax = subxid;
997  }
998  }
999 
1000  /* if top-level modified catalog, it'll need a snapshot */
1001  if (ReorderBufferXidHasCatalogChanges(builder->reorder, xid))
1002  {
1003  elog(DEBUG2, "found top level transaction %u, with catalog changes",
1004  xid);
1005  needs_snapshot = true;
1006  needs_timetravel = true;
1007  SnapBuildAddCommittedTxn(builder, xid);
1008  }
1009  else if (sub_needs_timetravel)
1010  {
1011  /* track toplevel txn as well, subxact alone isn't meaningful */
1012  SnapBuildAddCommittedTxn(builder, xid);
1013  }
1014  else if (needs_timetravel)
1015  {
1016  elog(DEBUG2, "forced transaction %u to do timetravel", xid);
1017 
1018  SnapBuildAddCommittedTxn(builder, xid);
1019  }
1020 
1021  if (!needs_timetravel)
1022  {
1023  /* record that we cannot export a general snapshot anymore */
1024  builder->committed.includes_all_transactions = false;
1025  }
1026 
1027  Assert(!needs_snapshot || needs_timetravel);
1028 
1029  /*
1030  * Adjust xmax of the snapshot builder, we only do that for committed,
1031  * catalog modifying, transactions, everything else isn't interesting for
1032  * us since we'll never look at the respective rows.
1033  */
1034  if (needs_timetravel &&
1035  (!TransactionIdIsValid(builder->xmax) ||
1036  TransactionIdFollowsOrEquals(xmax, builder->xmax)))
1037  {
1038  builder->xmax = xmax;
1039  TransactionIdAdvance(builder->xmax);
1040  }
1041 
1042  /* if there's any reason to build a historic snapshot, do so now */
1043  if (needs_snapshot)
1044  {
1045  /*
1046  * If we haven't built a complete snapshot yet there's no need to hand
1047  * it out, it wouldn't (and couldn't) be used anyway.
1048  */
1049  if (builder->state < SNAPBUILD_FULL_SNAPSHOT)
1050  return;
1051 
1052  /*
1053  * Decrease the snapshot builder's refcount of the old snapshot, note
1054  * that it still will be used if it has been handed out to the
1055  * reorderbuffer earlier.
1056  */
1057  if (builder->snapshot)
1059 
1060  builder->snapshot = SnapBuildBuildSnapshot(builder);
1061 
1062  /* we might need to execute invalidations, add snapshot */
1063  if (!ReorderBufferXidHasBaseSnapshot(builder->reorder, xid))
1064  {
1066  ReorderBufferSetBaseSnapshot(builder->reorder, xid, lsn,
1067  builder->snapshot);
1068  }
1069 
1070  /* refcount of the snapshot builder for the new snapshot */
1072 
1073  /* add a new catalog snapshot to all currently running transactions */
1075  }
1076 }
#define TransactionIdAdvance(dest)
Definition: transam.h:75
bool ReorderBufferXidHasBaseSnapshot(ReorderBuffer *rb, TransactionId xid)
struct SnapBuild::@24 committed
#define DEBUG1
Definition: elog.h:25
static void SnapBuildAddCommittedTxn(SnapBuild *builder, TransactionId xid)
Definition: snapbuild.c:853
uint32 TransactionId
Definition: c.h:514
Snapshot snapshot
Definition: snapbuild.c:179
bool building_full_snapshot
Definition: snapbuild.c:174
void ReorderBufferSetBaseSnapshot(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn, Snapshot snap)
bool TransactionIdFollowsOrEquals(TransactionId id1, TransactionId id2)
Definition: transam.c:349
SnapBuildState state
Definition: snapbuild.c:150
static void SnapBuildDistributeNewCatalogSnapshot(SnapBuild *builder, XLogRecPtr lsn)
Definition: snapbuild.c:807
#define DEBUG2
Definition: elog.h:24
ReorderBuffer * reorder
Definition: snapbuild.c:189
static Snapshot SnapBuildBuildSnapshot(SnapBuild *builder)
Definition: snapbuild.c:460
bool includes_all_transactions
Definition: snapbuild.c:228
bool ReorderBufferXidHasCatalogChanges(ReorderBuffer *rb, TransactionId xid)
bool TransactionIdPrecedes(TransactionId id1, TransactionId id2)
Definition: transam.c:300
TransactionId xmax
Definition: snapbuild.c:159
#define Assert(condition)
Definition: c.h:739
#define NormalTransactionIdFollows(id1, id2)
Definition: transam.h:103
void SnapBuildSnapDecRefcount(Snapshot snap)
Definition: snapbuild.c:428
#define elog(elevel,...)
Definition: elog.h:228
#define TransactionIdIsValid(xid)
Definition: transam.h:41
static void SnapBuildSnapIncRefcount(Snapshot snap)
Definition: snapbuild.c:416
static TransactionId SnapBuildNextPhaseAt(SnapBuild *builder)
Definition: snapbuild.c:280
XLogRecPtr start_decoding_at
Definition: snapbuild.c:165

◆ SnapBuildCurrentState()

SnapBuildState SnapBuildCurrentState ( SnapBuild snapstate)

Definition at line 395 of file snapbuild.c.

References SnapBuild::state.

Referenced by DecodeHeap2Op(), DecodeHeapOp(), DecodeLogicalMsgOp(), DecodeXactOp(), and DecodingContextReady().

396 {
397  return builder->state;
398 }

◆ SnapBuildExportSnapshot()

const char* SnapBuildExportSnapshot ( SnapBuild snapstate)

Definition at line 631 of file snapbuild.c.

References CurrentResourceOwner, elog, ereport, errmsg_plural(), ERROR, ExportInProgress, ExportSnapshot(), IsTransactionOrTransactionBlock(), LOG, SnapBuildInitialSnapshot(), StartTransactionCommand(), XACT_REPEATABLE_READ, XactIsoLevel, XactReadOnly, and SnapshotData::xcnt.

Referenced by CreateReplicationSlot().

632 {
633  Snapshot snap;
634  char *snapname;
635 
637  elog(ERROR, "cannot export a snapshot from within a transaction");
638 
640  elog(ERROR, "can only export one snapshot at a time");
641 
643  ExportInProgress = true;
644 
646 
647  /* There doesn't seem to a nice API to set these */
649  XactReadOnly = true;
650 
651  snap = SnapBuildInitialSnapshot(builder);
652 
653  /*
654  * now that we've built a plain snapshot, make it active and use the
655  * normal mechanisms for exporting it
656  */
657  snapname = ExportSnapshot(snap);
658 
659  ereport(LOG,
660  (errmsg_plural("exported logical decoding snapshot: \"%s\" with %u transaction ID",
661  "exported logical decoding snapshot: \"%s\" with %u transaction IDs",
662  snap->xcnt,
663  snapname, snap->xcnt)));
664  return snapname;
665 }
int errmsg_plural(const char *fmt_singular, const char *fmt_plural, unsigned long n,...)
Definition: elog.c:932
ResourceOwner CurrentResourceOwner
Definition: resowner.c:142
#define XACT_REPEATABLE_READ
Definition: xact.h:38
bool IsTransactionOrTransactionBlock(void)
Definition: xact.c:4653
char * ExportSnapshot(Snapshot snapshot)
Definition: snapmgr.c:1191
#define LOG
Definition: elog.h:26
static ResourceOwner SavedResourceOwnerDuringExport
Definition: snapbuild.c:252
#define ERROR
Definition: elog.h:43
static bool ExportInProgress
Definition: snapbuild.c:253
#define ereport(elevel, rest)
Definition: elog.h:141
bool XactReadOnly
Definition: xact.c:77
void StartTransactionCommand(void)
Definition: xact.c:2797
int XactIsoLevel
Definition: xact.c:74
Snapshot SnapBuildInitialSnapshot(SnapBuild *builder)
Definition: snapbuild.c:539
uint32 xcnt
Definition: snapshot.h:169
#define elog(elevel,...)
Definition: elog.h:228

◆ SnapBuildGetOrBuildSnapshot()

Snapshot SnapBuildGetOrBuildSnapshot ( SnapBuild builder,
TransactionId  xid 
)

Definition at line 671 of file snapbuild.c.

References Assert, SNAPBUILD_CONSISTENT, SnapBuildBuildSnapshot(), SnapBuildSnapIncRefcount(), SnapBuild::snapshot, and SnapBuild::state.

Referenced by DecodeLogicalMsgOp().

672 {
673  Assert(builder->state == SNAPBUILD_CONSISTENT);
674 
675  /* only build a new snapshot if we don't have a prebuilt one */
676  if (builder->snapshot == NULL)
677  {
678  builder->snapshot = SnapBuildBuildSnapshot(builder);
679  /* increase refcount for the snapshot builder */
681  }
682 
683  return builder->snapshot;
684 }
Snapshot snapshot
Definition: snapbuild.c:179
SnapBuildState state
Definition: snapbuild.c:150
static Snapshot SnapBuildBuildSnapshot(SnapBuild *builder)
Definition: snapbuild.c:460
#define Assert(condition)
Definition: c.h:739
static void SnapBuildSnapIncRefcount(Snapshot snap)
Definition: snapbuild.c:416

◆ SnapBuildInitialSnapshot()

Snapshot SnapBuildInitialSnapshot ( SnapBuild builder)

Definition at line 539 of file snapbuild.c.

References Assert, SnapBuild::committed, elog, ereport, errcode(), errmsg(), ERROR, FirstSnapshotSet, GetMaxSnapshotXidCount(), GetOldestSafeDecodingTransactionId(), SnapBuild::includes_all_transactions, LW_SHARED, LWLockAcquire(), LWLockRelease(), MyPgXact, NormalTransactionIdPrecedes, palloc(), SNAPBUILD_CONSISTENT, SnapBuildBuildSnapshot(), SNAPSHOT_MVCC, SnapshotData::snapshot_type, SnapBuild::state, test(), TransactionIdAdvance, TransactionIdIsValid, TransactionIdPrecedesOrEquals(), XACT_REPEATABLE_READ, XactIsoLevel, SnapshotData::xcnt, xidComparator(), SnapshotData::xip, SnapshotData::xmax, SnapshotData::xmin, and PGXACT::xmin.

Referenced by CreateReplicationSlot(), and SnapBuildExportSnapshot().

540 {
541  Snapshot snap;
542  TransactionId xid;
543  TransactionId *newxip;
544  int newxcnt = 0;
545 
548 
549  if (builder->state != SNAPBUILD_CONSISTENT)
550  elog(ERROR, "cannot build an initial slot snapshot before reaching a consistent state");
551 
552  if (!builder->committed.includes_all_transactions)
553  elog(ERROR, "cannot build an initial slot snapshot, not all transactions are monitored anymore");
554 
555  /* so we don't overwrite the existing value */
557  elog(ERROR, "cannot build an initial slot snapshot when MyPgXact->xmin already is valid");
558 
559  snap = SnapBuildBuildSnapshot(builder);
560 
561  /*
562  * We know that snap->xmin is alive, enforced by the logical xmin
563  * mechanism. Due to that we can do this without locks, we're only
564  * changing our own value.
565  */
566 #ifdef USE_ASSERT_CHECKING
567  {
568  TransactionId safeXid;
569 
570  LWLockAcquire(ProcArrayLock, LW_SHARED);
571  safeXid = GetOldestSafeDecodingTransactionId(false);
572  LWLockRelease(ProcArrayLock);
573 
574  Assert(TransactionIdPrecedesOrEquals(safeXid, snap->xmin));
575  }
576 #endif
577 
578  MyPgXact->xmin = snap->xmin;
579 
580  /* allocate in transaction context */
581  newxip = (TransactionId *)
583 
584  /*
585  * snapbuild.c builds transactions in an "inverted" manner, which means it
586  * stores committed transactions in ->xip, not ones in progress. Build a
587  * classical snapshot by marking all non-committed transactions as
588  * in-progress. This can be expensive.
589  */
590  for (xid = snap->xmin; NormalTransactionIdPrecedes(xid, snap->xmax);)
591  {
592  void *test;
593 
594  /*
595  * Check whether transaction committed using the decoding snapshot
596  * meaning of ->xip.
597  */
598  test = bsearch(&xid, snap->xip, snap->xcnt,
599  sizeof(TransactionId), xidComparator);
600 
601  if (test == NULL)
602  {
603  if (newxcnt >= GetMaxSnapshotXidCount())
604  ereport(ERROR,
605  (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
606  errmsg("initial slot snapshot too large")));
607 
608  newxip[newxcnt++] = xid;
609  }
610 
612  }
613 
614  /* adjust remaining snapshot fields as needed */
616  snap->xcnt = newxcnt;
617  snap->xip = newxip;
618 
619  return snap;
620 }
#define TransactionIdAdvance(dest)
Definition: transam.h:75
TransactionId GetOldestSafeDecodingTransactionId(bool catalogOnly)
Definition: procarray.c:2177
struct SnapBuild::@24 committed
static void test(void)
uint32 TransactionId
Definition: c.h:514
TransactionId xmin
Definition: proc.h:228
#define XACT_REPEATABLE_READ
Definition: xact.h:38
int errcode(int sqlerrcode)
Definition: elog.c:608
PGXACT * MyPgXact
Definition: proc.c:68
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1726
SnapBuildState state
Definition: snapbuild.c:150
bool TransactionIdPrecedesOrEquals(TransactionId id1, TransactionId id2)
Definition: transam.c:319
#define ERROR
Definition: elog.h:43
bool FirstSnapshotSet
Definition: snapmgr.c:205
static Snapshot SnapBuildBuildSnapshot(SnapBuild *builder)
Definition: snapbuild.c:460
bool includes_all_transactions
Definition: snapbuild.c:228
SnapshotType snapshot_type
Definition: snapshot.h:144
TransactionId xmax
Definition: snapshot.h:158
TransactionId xmin
Definition: snapshot.h:157
#define ereport(elevel, rest)
Definition: elog.h:141
TransactionId * xip
Definition: snapshot.h:168
int GetMaxSnapshotXidCount(void)
Definition: procarray.c:1452
#define Assert(condition)
Definition: c.h:739
int XactIsoLevel
Definition: xact.c:74
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1122
#define NormalTransactionIdPrecedes(id1, id2)
Definition: transam.h:98
uint32 xcnt
Definition: snapshot.h:169
void * palloc(Size size)
Definition: mcxt.c:949
int errmsg(const char *fmt,...)
Definition: elog.c:822
#define elog(elevel,...)
Definition: elog.h:228
#define TransactionIdIsValid(xid)
Definition: transam.h:41
int xidComparator(const void *arg1, const void *arg2)
Definition: xid.c:138

◆ SnapBuildProcessChange()

bool SnapBuildProcessChange ( SnapBuild builder,
TransactionId  xid,
XLogRecPtr  lsn 
)

Definition at line 715 of file snapbuild.c.

References SnapBuild::reorder, ReorderBufferSetBaseSnapshot(), ReorderBufferXidHasBaseSnapshot(), SNAPBUILD_CONSISTENT, SNAPBUILD_FULL_SNAPSHOT, SnapBuildBuildSnapshot(), SnapBuildNextPhaseAt(), SnapBuildSnapIncRefcount(), SnapBuild::snapshot, SnapBuild::state, and TransactionIdPrecedes().

Referenced by DecodeHeap2Op(), DecodeHeapOp(), and DecodeLogicalMsgOp().

716 {
717  /*
718  * We can't handle data in transactions if we haven't built a snapshot
719  * yet, so don't store them.
720  */
721  if (builder->state < SNAPBUILD_FULL_SNAPSHOT)
722  return false;
723 
724  /*
725  * No point in keeping track of changes in transactions that we don't have
726  * enough information about to decode. This means that they started before
727  * we got into the SNAPBUILD_FULL_SNAPSHOT state.
728  */
729  if (builder->state < SNAPBUILD_CONSISTENT &&
731  return false;
732 
733  /*
734  * If the reorderbuffer doesn't yet have a snapshot, add one now, it will
735  * be needed to decode the change we're currently processing.
736  */
737  if (!ReorderBufferXidHasBaseSnapshot(builder->reorder, xid))
738  {
739  /* only build a new snapshot if we don't have a prebuilt one */
740  if (builder->snapshot == NULL)
741  {
742  builder->snapshot = SnapBuildBuildSnapshot(builder);
743  /* increase refcount for the snapshot builder */
745  }
746 
747  /*
748  * Increase refcount for the transaction we're handing the snapshot
749  * out to.
750  */
752  ReorderBufferSetBaseSnapshot(builder->reorder, xid, lsn,
753  builder->snapshot);
754  }
755 
756  return true;
757 }
bool ReorderBufferXidHasBaseSnapshot(ReorderBuffer *rb, TransactionId xid)
Snapshot snapshot
Definition: snapbuild.c:179
void ReorderBufferSetBaseSnapshot(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn, Snapshot snap)
SnapBuildState state
Definition: snapbuild.c:150
ReorderBuffer * reorder
Definition: snapbuild.c:189
static Snapshot SnapBuildBuildSnapshot(SnapBuild *builder)
Definition: snapbuild.c:460
bool TransactionIdPrecedes(TransactionId id1, TransactionId id2)
Definition: transam.c:300
static void SnapBuildSnapIncRefcount(Snapshot snap)
Definition: snapbuild.c:416
static TransactionId SnapBuildNextPhaseAt(SnapBuild *builder)
Definition: snapbuild.c:280

◆ SnapBuildProcessNewCid()

void SnapBuildProcessNewCid ( SnapBuild builder,
TransactionId  xid,
XLogRecPtr  lsn,
struct xl_heap_new_cid cid 
)

Definition at line 765 of file snapbuild.c.

References xl_heap_new_cid::cmax, xl_heap_new_cid::cmin, xl_heap_new_cid::combocid, elog, ERROR, InvalidCommandId, Max, SnapBuild::reorder, ReorderBufferAddNewCommandId(), ReorderBufferAddNewTupleCids(), ReorderBufferXidSetCatalogChanges(), xl_heap_new_cid::target_node, xl_heap_new_cid::target_tid, and xl_heap_new_cid::top_xid.

Referenced by DecodeHeap2Op().

767 {
768  CommandId cid;
769 
770  /*
771  * we only log new_cid's if a catalog tuple was modified, so mark the
772  * transaction as containing catalog modifications
773  */
774  ReorderBufferXidSetCatalogChanges(builder->reorder, xid, lsn);
775 
776  ReorderBufferAddNewTupleCids(builder->reorder, xlrec->top_xid, lsn,
777  xlrec->target_node, xlrec->target_tid,
778  xlrec->cmin, xlrec->cmax,
779  xlrec->combocid);
780 
781  /* figure out new command id */
782  if (xlrec->cmin != InvalidCommandId &&
783  xlrec->cmax != InvalidCommandId)
784  cid = Max(xlrec->cmin, xlrec->cmax);
785  else if (xlrec->cmax != InvalidCommandId)
786  cid = xlrec->cmax;
787  else if (xlrec->cmin != InvalidCommandId)
788  cid = xlrec->cmin;
789  else
790  {
791  cid = InvalidCommandId; /* silence compiler */
792  elog(ERROR, "xl_heap_new_cid record without a valid CommandId");
793  }
794 
795  ReorderBufferAddNewCommandId(builder->reorder, xid, lsn, cid + 1);
796 }
uint32 CommandId
Definition: c.h:528
void ReorderBufferAddNewTupleCids(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn, RelFileNode node, ItemPointerData tid, CommandId cmin, CommandId cmax, CommandId combocid)
#define ERROR
Definition: elog.h:43
ReorderBuffer * reorder
Definition: snapbuild.c:189
#define InvalidCommandId
Definition: c.h:531
#define Max(x, y)
Definition: c.h:905
#define elog(elevel,...)
Definition: elog.h:228
void ReorderBufferXidSetCatalogChanges(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn)
void ReorderBufferAddNewCommandId(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn, CommandId cid)

◆ SnapBuildProcessRunningXacts()

void SnapBuildProcessRunningXacts ( SnapBuild builder,
XLogRecPtr  lsn,
struct xl_running_xacts running 
)

Definition at line 1090 of file snapbuild.c.

References ReorderBuffer::current_restart_decoding_lsn, DEBUG3, elog, InvalidTransactionId, InvalidXLogRecPtr, SnapBuild::last_serialized_snapshot, LogicalIncreaseRestartDecodingForSlot(), LogicalIncreaseXminForSlot(), xl_running_xacts::oldestRunningXid, SnapBuild::reorder, ReorderBufferGetOldestTXN(), ReorderBufferGetOldestXmin(), ReorderBufferTXN::restart_decoding_lsn, SNAPBUILD_CONSISTENT, SnapBuildFindSnapshot(), SnapBuildPurgeCommittedTxn(), SnapBuildSerialize(), SnapBuild::state, SnapBuild::xmax, and SnapBuild::xmin.

Referenced by DecodeStandbyOp().

1091 {
1092  ReorderBufferTXN *txn;
1093  TransactionId xmin;
1094 
1095  /*
1096  * If we're not consistent yet, inspect the record to see whether it
1097  * allows to get closer to being consistent. If we are consistent, dump
1098  * our snapshot so others or we, after a restart, can use it.
1099  */
1100  if (builder->state < SNAPBUILD_CONSISTENT)
1101  {
1102  /* returns false if there's no point in performing cleanup just yet */
1103  if (!SnapBuildFindSnapshot(builder, lsn, running))
1104  return;
1105  }
1106  else
1107  SnapBuildSerialize(builder, lsn);
1108 
1109  /*
1110  * Update range of interesting xids based on the running xacts
1111  * information. We don't increase ->xmax using it, because once we are in
1112  * a consistent state we can do that ourselves and much more efficiently
1113  * so, because we only need to do it for catalog transactions since we
1114  * only ever look at those.
1115  *
1116  * NB: We only increase xmax when a catalog modifying transaction commits
1117  * (see SnapBuildCommitTxn). Because of this, xmax can be lower than
1118  * xmin, which looks odd but is correct and actually more efficient, since
1119  * we hit fast paths in heapam_visibility.c.
1120  */
1121  builder->xmin = running->oldestRunningXid;
1122 
1123  /* Remove transactions we don't need to keep track off anymore */
1124  SnapBuildPurgeCommittedTxn(builder);
1125 
1126  /*
1127  * Advance the xmin limit for the current replication slot, to allow
1128  * vacuum to clean up the tuples this slot has been protecting.
1129  *
1130  * The reorderbuffer might have an xmin among the currently running
1131  * snapshots; use it if so. If not, we need only consider the snapshots
1132  * we'll produce later, which can't be less than the oldest running xid in
1133  * the record we're reading now.
1134  */
1135  xmin = ReorderBufferGetOldestXmin(builder->reorder);
1136  if (xmin == InvalidTransactionId)
1137  xmin = running->oldestRunningXid;
1138  elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u",
1139  builder->xmin, builder->xmax, running->oldestRunningXid, xmin);
1140  LogicalIncreaseXminForSlot(lsn, xmin);
1141 
1142  /*
1143  * Also tell the slot where we can restart decoding from. We don't want to
1144  * do that after every commit because changing that implies an fsync of
1145  * the logical slot's state file, so we only do it every time we see a
1146  * running xacts record.
1147  *
1148  * Do so by looking for the oldest in progress transaction (determined by
1149  * the first LSN of any of its relevant records). Every transaction
1150  * remembers the last location we stored the snapshot to disk before its
1151  * beginning. That point is where we can restart from.
1152  */
1153 
1154  /*
1155  * Can't know about a serialized snapshot's location if we're not
1156  * consistent.
1157  */
1158  if (builder->state < SNAPBUILD_CONSISTENT)
1159  return;
1160 
1161  txn = ReorderBufferGetOldestTXN(builder->reorder);
1162 
1163  /*
1164  * oldest ongoing txn might have started when we didn't yet serialize
1165  * anything because we hadn't reached a consistent state yet.
1166  */
1167  if (txn != NULL && txn->restart_decoding_lsn != InvalidXLogRecPtr)
1169 
1170  /*
1171  * No in-progress transaction, can reuse the last serialized snapshot if
1172  * we have one.
1173  */
1174  else if (txn == NULL &&
1178  builder->last_serialized_snapshot);
1179 }
#define InvalidXLogRecPtr
Definition: xlogdefs.h:28
uint32 TransactionId
Definition: c.h:514
#define DEBUG3
Definition: elog.h:23
void LogicalIncreaseRestartDecodingForSlot(XLogRecPtr current_lsn, XLogRecPtr restart_lsn)
Definition: logical.c:932
XLogRecPtr current_restart_decoding_lsn
static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running)
Definition: snapbuild.c:1192
SnapBuildState state
Definition: snapbuild.c:150
static void SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
Definition: snapbuild.c:1480
ReorderBuffer * reorder
Definition: snapbuild.c:189
#define InvalidTransactionId
Definition: transam.h:31
XLogRecPtr last_serialized_snapshot
Definition: snapbuild.c:184
TransactionId xmax
Definition: snapbuild.c:159
TransactionId ReorderBufferGetOldestXmin(ReorderBuffer *rb)
ReorderBufferTXN * ReorderBufferGetOldestTXN(ReorderBuffer *rb)
void LogicalIncreaseXminForSlot(XLogRecPtr current_lsn, TransactionId xmin)
Definition: logical.c:875
TransactionId xmin
Definition: snapbuild.c:156
#define elog(elevel,...)
Definition: elog.h:228
XLogRecPtr restart_decoding_lsn
TransactionId oldestRunningXid
Definition: standbydefs.h:53
static void SnapBuildPurgeCommittedTxn(SnapBuild *builder)
Definition: snapbuild.c:882

◆ SnapBuildSerializationPoint()

void SnapBuildSerializationPoint ( SnapBuild builder,
XLogRecPtr  lsn 
)

Definition at line 1467 of file snapbuild.c.

References SNAPBUILD_CONSISTENT, SnapBuildRestore(), SnapBuildSerialize(), and SnapBuild::state.

Referenced by DecodeXLogOp().

1468 {
1469  if (builder->state < SNAPBUILD_CONSISTENT)
1470  SnapBuildRestore(builder, lsn);
1471  else
1472  SnapBuildSerialize(builder, lsn);
1473 }
static bool SnapBuildRestore(SnapBuild *builder, XLogRecPtr lsn)
Definition: snapbuild.c:1689
SnapBuildState state
Definition: snapbuild.c:150
static void SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
Definition: snapbuild.c:1480

◆ SnapBuildSnapDecRefcount()

void SnapBuildSnapDecRefcount ( Snapshot  snap)

Definition at line 428 of file snapbuild.c.

References SnapshotData::active_count, Assert, SnapshotData::copied, SnapshotData::curcid, elog, ERROR, FirstCommandId, SnapshotData::regd_count, SnapBuildFreeSnapshot(), SNAPSHOT_HISTORIC_MVCC, SnapshotData::snapshot_type, SnapshotData::suboverflowed, and SnapshotData::takenDuringRecovery.

Referenced by FreeSnapshotBuilder(), ReorderBufferCleanupTXN(), ReorderBufferFreeSnap(), ReorderBufferTransferSnapToParent(), SnapBuildCommitTxn(), and SnapBuildRestore().

429 {
430  /* make sure we don't get passed an external snapshot */
432 
433  /* make sure nobody modified our snapshot */
434  Assert(snap->curcid == FirstCommandId);
435  Assert(!snap->suboverflowed);
436  Assert(!snap->takenDuringRecovery);
437 
438  Assert(snap->regd_count == 0);
439 
440  Assert(snap->active_count > 0);
441 
442  /* slightly more likely, so it's checked even without casserts */
443  if (snap->copied)
444  elog(ERROR, "cannot free a copied snapshot");
445 
446  snap->active_count--;
447  if (snap->active_count == 0)
448  SnapBuildFreeSnapshot(snap);
449 }
bool copied
Definition: snapshot.h:185
bool suboverflowed
Definition: snapshot.h:182
uint32 regd_count
Definition: snapshot.h:199
#define FirstCommandId
Definition: c.h:530
#define ERROR
Definition: elog.h:43
static void SnapBuildFreeSnapshot(Snapshot snap)
Definition: snapbuild.c:370
SnapshotType snapshot_type
Definition: snapshot.h:144
CommandId curcid
Definition: snapshot.h:187
#define Assert(condition)
Definition: c.h:739
bool takenDuringRecovery
Definition: snapshot.h:184
#define elog(elevel,...)
Definition: elog.h:228
uint32 active_count
Definition: snapshot.h:198

◆ SnapBuildXactNeedsSkip()

bool SnapBuildXactNeedsSkip ( SnapBuild snapstate,
XLogRecPtr  ptr 
)

Definition at line 404 of file snapbuild.c.

References SnapBuild::start_decoding_at.

Referenced by DecodeCommit(), and DecodeLogicalMsgOp().

405 {
406  return ptr < builder->start_decoding_at;
407 }