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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 315 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().

319 {
320  MemoryContext context;
321  MemoryContext oldcontext;
322  SnapBuild *builder;
323 
324  /* allocate memory in own context, to have better accountability */
326  "snapshot builder context",
328  oldcontext = MemoryContextSwitchTo(context);
329 
330  builder = palloc0(sizeof(SnapBuild));
331 
332  builder->state = SNAPBUILD_START;
333  builder->context = context;
334  builder->reorder = reorder;
335  /* Other struct members initialized by zeroing via palloc0 above */
336 
337  builder->committed.xcnt = 0;
338  builder->committed.xcnt_space = 128; /* arbitrary number */
339  builder->committed.xip =
340  palloc0(builder->committed.xcnt_space * sizeof(TransactionId));
341  builder->committed.includes_all_transactions = true;
342 
343  builder->initial_xmin_horizon = xmin_horizon;
344  builder->start_decoding_at = start_lsn;
345  builder->building_full_snapshot = need_full_snapshot;
346 
347  MemoryContextSwitchTo(oldcontext);
348 
349  return builder;
350 }
#define AllocSetContextCreate
Definition: memutils.h:170
struct SnapBuild::@24 committed
uint32 TransactionId
Definition: c.h:507
bool building_full_snapshot
Definition: snapbuild.c:179
static MemoryContext MemoryContextSwitchTo(MemoryContext context)
Definition: palloc.h:109
size_t xcnt_space
Definition: snapbuild.c:226
size_t xcnt
Definition: snapbuild.c:223
SnapBuildState state
Definition: snapbuild.c:155
#define ALLOCSET_DEFAULT_SIZES
Definition: memutils.h:192
ReorderBuffer * reorder
Definition: snapbuild.c:194
TransactionId initial_xmin_horizon
Definition: snapbuild.c:176
TransactionId * xip
Definition: snapbuild.c:249
bool includes_all_transactions
Definition: snapbuild.c:233
MemoryContext CurrentMemoryContext
Definition: mcxt.c:38
void * palloc0(Size size)
Definition: mcxt.c:980
MemoryContext context
Definition: snapbuild.c:158
XLogRecPtr start_decoding_at
Definition: snapbuild.c:170

◆ CheckPointSnapBuild()

void CheckPointSnapBuild ( void  )

Definition at line 1937 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().

1938 {
1939  XLogRecPtr cutoff;
1940  XLogRecPtr redo;
1941  DIR *snap_dir;
1942  struct dirent *snap_de;
1943  char path[MAXPGPATH + 21];
1944 
1945  /*
1946  * We start off with a minimum of the last redo pointer. No new
1947  * replication slot will start before that, so that's a safe upper bound
1948  * for removal.
1949  */
1950  redo = GetRedoRecPtr();
1951 
1952  /* now check for the restart ptrs from existing slots */
1954 
1955  /* don't start earlier than the restart lsn */
1956  if (redo < cutoff)
1957  cutoff = redo;
1958 
1959  snap_dir = AllocateDir("pg_logical/snapshots");
1960  while ((snap_de = ReadDir(snap_dir, "pg_logical/snapshots")) != NULL)
1961  {
1962  uint32 hi;
1963  uint32 lo;
1964  XLogRecPtr lsn;
1965  struct stat statbuf;
1966 
1967  if (strcmp(snap_de->d_name, ".") == 0 ||
1968  strcmp(snap_de->d_name, "..") == 0)
1969  continue;
1970 
1971  snprintf(path, sizeof(path), "pg_logical/snapshots/%s", snap_de->d_name);
1972 
1973  if (lstat(path, &statbuf) == 0 && !S_ISREG(statbuf.st_mode))
1974  {
1975  elog(DEBUG1, "only regular files expected: %s", path);
1976  continue;
1977  }
1978 
1979  /*
1980  * temporary filenames from SnapBuildSerialize() include the LSN and
1981  * everything but are postfixed by .$pid.tmp. We can just remove them
1982  * the same as other files because there can be none that are
1983  * currently being written that are older than cutoff.
1984  *
1985  * We just log a message if a file doesn't fit the pattern, it's
1986  * probably some editors lock/state file or similar...
1987  */
1988  if (sscanf(snap_de->d_name, "%X-%X.snap", &hi, &lo) != 2)
1989  {
1990  ereport(LOG,
1991  (errmsg("could not parse file name \"%s\"", path)));
1992  continue;
1993  }
1994 
1995  lsn = ((uint64) hi) << 32 | lo;
1996 
1997  /* check whether we still need it */
1998  if (lsn < cutoff || cutoff == InvalidXLogRecPtr)
1999  {
2000  elog(DEBUG1, "removing snapbuild snapshot %s", path);
2001 
2002  /*
2003  * It's not particularly harmful, though strange, if we can't
2004  * remove the file here. Don't prevent the checkpoint from
2005  * completing, that'd be a cure worse than the disease.
2006  */
2007  if (unlink(path) < 0)
2008  {
2009  ereport(LOG,
2011  errmsg("could not remove file \"%s\": %m",
2012  path)));
2013  continue;
2014  }
2015  }
2016  }
2017  FreeDir(snap_dir);
2018 }
#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:593
XLogRecPtr ReplicationSlotsComputeLogicalRestartLSN(void)
Definition: slot.c:791
unsigned int uint32
Definition: c.h:358
DIR * AllocateDir(const char *dirname)
Definition: fd.c:2466
#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:2532
XLogRecPtr GetRedoRecPtr(void)
Definition: xlog.c:8186
#define lstat(path, sb)
Definition: win32_port.h:244
int errmsg(const char *fmt,...)
Definition: elog.c:784
#define elog(elevel,...)
Definition: elog.h:226
char d_name[MAX_PATH]
Definition: dirent.h:14
#define snprintf
Definition: port.h:192
int FreeDir(DIR *dir)
Definition: fd.c:2584

◆ FreeSnapshotBuilder()

void FreeSnapshotBuilder ( SnapBuild cache)

Definition at line 356 of file snapbuild.c.

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

Referenced by FreeDecodingContext().

357 {
358  MemoryContext context = builder->context;
359 
360  /* free snapshot explicitly, that contains some error checking */
361  if (builder->snapshot != NULL)
362  {
363  SnapBuildSnapDecRefcount(builder->snapshot);
364  builder->snapshot = NULL;
365  }
366 
367  /* other resources are deallocated via memory context reset */
368  MemoryContextDelete(context);
369 }
void MemoryContextDelete(MemoryContext context)
Definition: mcxt.c:211
void SnapBuildSnapDecRefcount(Snapshot snap)
Definition: snapbuild.c:433

◆ SnapBuildClearExportedSnapshot()

void SnapBuildClearExportedSnapshot ( void  )

Definition at line 697 of file snapbuild.c.

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

Referenced by exec_replication_command().

698 {
699  /* nothing exported, that is the usual case */
700  if (!ExportInProgress)
701  return;
702 
703  if (!IsTransactionState())
704  elog(ERROR, "clearing exported snapshot in wrong transaction state");
705 
706  /* make sure nothing could have ever happened */
708 
711  ExportInProgress = false;
712 }
void AbortCurrentTransaction(void)
Definition: xact.c:3159
ResourceOwner CurrentResourceOwner
Definition: resowner.c:142
static ResourceOwner SavedResourceOwnerDuringExport
Definition: snapbuild.c:257
#define ERROR
Definition: elog.h:43
static bool ExportInProgress
Definition: snapbuild.c:258
bool IsTransactionState(void)
Definition: xact.c:356
#define elog(elevel,...)
Definition: elog.h:226

◆ SnapBuildCommitTxn()

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

Definition at line 928 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().

930 {
931  int nxact;
932 
933  bool needs_snapshot = false;
934  bool needs_timetravel = false;
935  bool sub_needs_timetravel = false;
936 
937  TransactionId xmax = xid;
938 
939  /*
940  * Transactions preceding BUILDING_SNAPSHOT will neither be decoded, nor
941  * will they be part of a snapshot. So we don't need to record anything.
942  */
943  if (builder->state == SNAPBUILD_START ||
944  (builder->state == SNAPBUILD_BUILDING_SNAPSHOT &&
946  {
947  /* ensure that only commits after this are getting replayed */
948  if (builder->start_decoding_at <= lsn)
949  builder->start_decoding_at = lsn + 1;
950  return;
951  }
952 
953  if (builder->state < SNAPBUILD_CONSISTENT)
954  {
955  /* ensure that only commits after this are getting replayed */
956  if (builder->start_decoding_at <= lsn)
957  builder->start_decoding_at = lsn + 1;
958 
959  /*
960  * If building an exportable snapshot, force xid to be tracked, even
961  * if the transaction didn't modify the catalog.
962  */
963  if (builder->building_full_snapshot)
964  {
965  needs_timetravel = true;
966  }
967  }
968 
969  for (nxact = 0; nxact < nsubxacts; nxact++)
970  {
971  TransactionId subxid = subxacts[nxact];
972 
973  /*
974  * Add subtransaction to base snapshot if catalog modifying, we don't
975  * distinguish to toplevel transactions there.
976  */
977  if (ReorderBufferXidHasCatalogChanges(builder->reorder, subxid))
978  {
979  sub_needs_timetravel = true;
980  needs_snapshot = true;
981 
982  elog(DEBUG1, "found subtransaction %u:%u with catalog changes",
983  xid, subxid);
984 
985  SnapBuildAddCommittedTxn(builder, subxid);
986 
987  if (NormalTransactionIdFollows(subxid, xmax))
988  xmax = subxid;
989  }
990 
991  /*
992  * If we're forcing timetravel we also need visibility information
993  * about subtransaction, so keep track of subtransaction's state, even
994  * if not catalog modifying. Don't need to distribute a snapshot in
995  * that case.
996  */
997  else if (needs_timetravel)
998  {
999  SnapBuildAddCommittedTxn(builder, subxid);
1000  if (NormalTransactionIdFollows(subxid, xmax))
1001  xmax = subxid;
1002  }
1003  }
1004 
1005  /* if top-level modified catalog, it'll need a snapshot */
1006  if (ReorderBufferXidHasCatalogChanges(builder->reorder, xid))
1007  {
1008  elog(DEBUG2, "found top level transaction %u, with catalog changes",
1009  xid);
1010  needs_snapshot = true;
1011  needs_timetravel = true;
1012  SnapBuildAddCommittedTxn(builder, xid);
1013  }
1014  else if (sub_needs_timetravel)
1015  {
1016  /* track toplevel txn as well, subxact alone isn't meaningful */
1017  SnapBuildAddCommittedTxn(builder, xid);
1018  }
1019  else if (needs_timetravel)
1020  {
1021  elog(DEBUG2, "forced transaction %u to do timetravel", xid);
1022 
1023  SnapBuildAddCommittedTxn(builder, xid);
1024  }
1025 
1026  if (!needs_timetravel)
1027  {
1028  /* record that we cannot export a general snapshot anymore */
1029  builder->committed.includes_all_transactions = false;
1030  }
1031 
1032  Assert(!needs_snapshot || needs_timetravel);
1033 
1034  /*
1035  * Adjust xmax of the snapshot builder, we only do that for committed,
1036  * catalog modifying, transactions, everything else isn't interesting for
1037  * us since we'll never look at the respective rows.
1038  */
1039  if (needs_timetravel &&
1040  (!TransactionIdIsValid(builder->xmax) ||
1041  TransactionIdFollowsOrEquals(xmax, builder->xmax)))
1042  {
1043  builder->xmax = xmax;
1044  TransactionIdAdvance(builder->xmax);
1045  }
1046 
1047  /* if there's any reason to build a historic snapshot, do so now */
1048  if (needs_snapshot)
1049  {
1050  /*
1051  * If we haven't built a complete snapshot yet there's no need to hand
1052  * it out, it wouldn't (and couldn't) be used anyway.
1053  */
1054  if (builder->state < SNAPBUILD_FULL_SNAPSHOT)
1055  return;
1056 
1057  /*
1058  * Decrease the snapshot builder's refcount of the old snapshot, note
1059  * that it still will be used if it has been handed out to the
1060  * reorderbuffer earlier.
1061  */
1062  if (builder->snapshot)
1064 
1065  builder->snapshot = SnapBuildBuildSnapshot(builder);
1066 
1067  /* we might need to execute invalidations, add snapshot */
1068  if (!ReorderBufferXidHasBaseSnapshot(builder->reorder, xid))
1069  {
1071  ReorderBufferSetBaseSnapshot(builder->reorder, xid, lsn,
1072  builder->snapshot);
1073  }
1074 
1075  /* refcount of the snapshot builder for the new snapshot */
1077 
1078  /* add a new catalog snapshot to all currently running transactions */
1080  }
1081 }
#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:858
uint32 TransactionId
Definition: c.h:507
Snapshot snapshot
Definition: snapbuild.c:184
bool building_full_snapshot
Definition: snapbuild.c:179
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:155
static void SnapBuildDistributeNewCatalogSnapshot(SnapBuild *builder, XLogRecPtr lsn)
Definition: snapbuild.c:812
#define DEBUG2
Definition: elog.h:24
ReorderBuffer * reorder
Definition: snapbuild.c:194
static Snapshot SnapBuildBuildSnapshot(SnapBuild *builder)
Definition: snapbuild.c:465
bool includes_all_transactions
Definition: snapbuild.c:233
bool ReorderBufferXidHasCatalogChanges(ReorderBuffer *rb, TransactionId xid)
bool TransactionIdPrecedes(TransactionId id1, TransactionId id2)
Definition: transam.c:300
TransactionId xmax
Definition: snapbuild.c:164
#define Assert(condition)
Definition: c.h:732
#define NormalTransactionIdFollows(id1, id2)
Definition: transam.h:103
void SnapBuildSnapDecRefcount(Snapshot snap)
Definition: snapbuild.c:433
#define elog(elevel,...)
Definition: elog.h:226
#define TransactionIdIsValid(xid)
Definition: transam.h:41
static void SnapBuildSnapIncRefcount(Snapshot snap)
Definition: snapbuild.c:421
static TransactionId SnapBuildNextPhaseAt(SnapBuild *builder)
Definition: snapbuild.c:285
XLogRecPtr start_decoding_at
Definition: snapbuild.c:170

◆ SnapBuildCurrentState()

SnapBuildState SnapBuildCurrentState ( SnapBuild snapstate)

Definition at line 400 of file snapbuild.c.

References SnapBuild::state.

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

401 {
402  return builder->state;
403 }

◆ SnapBuildExportSnapshot()

const char* SnapBuildExportSnapshot ( SnapBuild snapstate)

Definition at line 636 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().

637 {
638  Snapshot snap;
639  char *snapname;
640 
642  elog(ERROR, "cannot export a snapshot from within a transaction");
643 
645  elog(ERROR, "can only export one snapshot at a time");
646 
648  ExportInProgress = true;
649 
651 
652  /* There doesn't seem to a nice API to set these */
654  XactReadOnly = true;
655 
656  snap = SnapBuildInitialSnapshot(builder);
657 
658  /*
659  * now that we've built a plain snapshot, make it active and use the
660  * normal mechanisms for exporting it
661  */
662  snapname = ExportSnapshot(snap);
663 
664  ereport(LOG,
665  (errmsg_plural("exported logical decoding snapshot: \"%s\" with %u transaction ID",
666  "exported logical decoding snapshot: \"%s\" with %u transaction IDs",
667  snap->xcnt,
668  snapname, snap->xcnt)));
669  return snapname;
670 }
int errmsg_plural(const char *fmt_singular, const char *fmt_plural, unsigned long n,...)
Definition: elog.c:837
ResourceOwner CurrentResourceOwner
Definition: resowner.c:142
#define XACT_REPEATABLE_READ
Definition: xact.h:38
bool IsTransactionOrTransactionBlock(void)
Definition: xact.c:4651
char * ExportSnapshot(Snapshot snapshot)
Definition: snapmgr.c:1191
#define LOG
Definition: elog.h:26
static ResourceOwner SavedResourceOwnerDuringExport
Definition: snapbuild.c:257
#define ERROR
Definition: elog.h:43
static bool ExportInProgress
Definition: snapbuild.c:258
#define ereport(elevel, rest)
Definition: elog.h:141
bool XactReadOnly
Definition: xact.c:78
void StartTransactionCommand(void)
Definition: xact.c:2794
int XactIsoLevel
Definition: xact.c:75
Snapshot SnapBuildInitialSnapshot(SnapBuild *builder)
Definition: snapbuild.c:544
uint32 xcnt
Definition: snapshot.h:169
#define elog(elevel,...)
Definition: elog.h:226

◆ SnapBuildGetOrBuildSnapshot()

Snapshot SnapBuildGetOrBuildSnapshot ( SnapBuild builder,
TransactionId  xid 
)

Definition at line 676 of file snapbuild.c.

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

Referenced by DecodeLogicalMsgOp().

677 {
678  Assert(builder->state == SNAPBUILD_CONSISTENT);
679 
680  /* only build a new snapshot if we don't have a prebuilt one */
681  if (builder->snapshot == NULL)
682  {
683  builder->snapshot = SnapBuildBuildSnapshot(builder);
684  /* increase refcount for the snapshot builder */
686  }
687 
688  return builder->snapshot;
689 }
Snapshot snapshot
Definition: snapbuild.c:184
SnapBuildState state
Definition: snapbuild.c:155
static Snapshot SnapBuildBuildSnapshot(SnapBuild *builder)
Definition: snapbuild.c:465
#define Assert(condition)
Definition: c.h:732
static void SnapBuildSnapIncRefcount(Snapshot snap)
Definition: snapbuild.c:421

◆ SnapBuildInitialSnapshot()

Snapshot SnapBuildInitialSnapshot ( SnapBuild builder)

Definition at line 544 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().

545 {
546  Snapshot snap;
547  TransactionId xid;
548  TransactionId *newxip;
549  int newxcnt = 0;
550 
553 
554  if (builder->state != SNAPBUILD_CONSISTENT)
555  elog(ERROR, "cannot build an initial slot snapshot before reaching a consistent state");
556 
557  if (!builder->committed.includes_all_transactions)
558  elog(ERROR, "cannot build an initial slot snapshot, not all transactions are monitored anymore");
559 
560  /* so we don't overwrite the existing value */
562  elog(ERROR, "cannot build an initial slot snapshot when MyPgXact->xmin already is valid");
563 
564  snap = SnapBuildBuildSnapshot(builder);
565 
566  /*
567  * We know that snap->xmin is alive, enforced by the logical xmin
568  * mechanism. Due to that we can do this without locks, we're only
569  * changing our own value.
570  */
571 #ifdef USE_ASSERT_CHECKING
572  {
573  TransactionId safeXid;
574 
575  LWLockAcquire(ProcArrayLock, LW_SHARED);
576  safeXid = GetOldestSafeDecodingTransactionId(false);
577  LWLockRelease(ProcArrayLock);
578 
579  Assert(TransactionIdPrecedesOrEquals(safeXid, snap->xmin));
580  }
581 #endif
582 
583  MyPgXact->xmin = snap->xmin;
584 
585  /* allocate in transaction context */
586  newxip = (TransactionId *)
588 
589  /*
590  * snapbuild.c builds transactions in an "inverted" manner, which means it
591  * stores committed transactions in ->xip, not ones in progress. Build a
592  * classical snapshot by marking all non-committed transactions as
593  * in-progress. This can be expensive.
594  */
595  for (xid = snap->xmin; NormalTransactionIdPrecedes(xid, snap->xmax);)
596  {
597  void *test;
598 
599  /*
600  * Check whether transaction committed using the decoding snapshot
601  * meaning of ->xip.
602  */
603  test = bsearch(&xid, snap->xip, snap->xcnt,
604  sizeof(TransactionId), xidComparator);
605 
606  if (test == NULL)
607  {
608  if (newxcnt >= GetMaxSnapshotXidCount())
609  ereport(ERROR,
610  (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
611  errmsg("initial slot snapshot too large")));
612 
613  newxip[newxcnt++] = xid;
614  }
615 
617  }
618 
619  /* adjust remaining snapshot fields as needed */
621  snap->xcnt = newxcnt;
622  snap->xip = newxip;
623 
624  return snap;
625 }
#define TransactionIdAdvance(dest)
Definition: transam.h:75
TransactionId GetOldestSafeDecodingTransactionId(bool catalogOnly)
Definition: procarray.c:2175
struct SnapBuild::@24 committed
static void test(void)
uint32 TransactionId
Definition: c.h:507
TransactionId xmin
Definition: proc.h:228
#define XACT_REPEATABLE_READ
Definition: xact.h:38
int errcode(int sqlerrcode)
Definition: elog.c:570
PGXACT * MyPgXact
Definition: proc.c:69
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1726
SnapBuildState state
Definition: snapbuild.c:155
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:465
bool includes_all_transactions
Definition: snapbuild.c:233
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:1450
#define Assert(condition)
Definition: c.h:732
int XactIsoLevel
Definition: xact.c:75
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:784
#define elog(elevel,...)
Definition: elog.h:226
#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 720 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().

721 {
722  /*
723  * We can't handle data in transactions if we haven't built a snapshot
724  * yet, so don't store them.
725  */
726  if (builder->state < SNAPBUILD_FULL_SNAPSHOT)
727  return false;
728 
729  /*
730  * No point in keeping track of changes in transactions that we don't have
731  * enough information about to decode. This means that they started before
732  * we got into the SNAPBUILD_FULL_SNAPSHOT state.
733  */
734  if (builder->state < SNAPBUILD_CONSISTENT &&
736  return false;
737 
738  /*
739  * If the reorderbuffer doesn't yet have a snapshot, add one now, it will
740  * be needed to decode the change we're currently processing.
741  */
742  if (!ReorderBufferXidHasBaseSnapshot(builder->reorder, xid))
743  {
744  /* only build a new snapshot if we don't have a prebuilt one */
745  if (builder->snapshot == NULL)
746  {
747  builder->snapshot = SnapBuildBuildSnapshot(builder);
748  /* increase refcount for the snapshot builder */
750  }
751 
752  /*
753  * Increase refcount for the transaction we're handing the snapshot
754  * out to.
755  */
757  ReorderBufferSetBaseSnapshot(builder->reorder, xid, lsn,
758  builder->snapshot);
759  }
760 
761  return true;
762 }
bool ReorderBufferXidHasBaseSnapshot(ReorderBuffer *rb, TransactionId xid)
Snapshot snapshot
Definition: snapbuild.c:184
void ReorderBufferSetBaseSnapshot(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn, Snapshot snap)
SnapBuildState state
Definition: snapbuild.c:155
ReorderBuffer * reorder
Definition: snapbuild.c:194
static Snapshot SnapBuildBuildSnapshot(SnapBuild *builder)
Definition: snapbuild.c:465
bool TransactionIdPrecedes(TransactionId id1, TransactionId id2)
Definition: transam.c:300
static void SnapBuildSnapIncRefcount(Snapshot snap)
Definition: snapbuild.c:421
static TransactionId SnapBuildNextPhaseAt(SnapBuild *builder)
Definition: snapbuild.c:285

◆ SnapBuildProcessNewCid()

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

Definition at line 770 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().

772 {
773  CommandId cid;
774 
775  /*
776  * we only log new_cid's if a catalog tuple was modified, so mark the
777  * transaction as containing catalog modifications
778  */
779  ReorderBufferXidSetCatalogChanges(builder->reorder, xid, lsn);
780 
781  ReorderBufferAddNewTupleCids(builder->reorder, xlrec->top_xid, lsn,
782  xlrec->target_node, xlrec->target_tid,
783  xlrec->cmin, xlrec->cmax,
784  xlrec->combocid);
785 
786  /* figure out new command id */
787  if (xlrec->cmin != InvalidCommandId &&
788  xlrec->cmax != InvalidCommandId)
789  cid = Max(xlrec->cmin, xlrec->cmax);
790  else if (xlrec->cmax != InvalidCommandId)
791  cid = xlrec->cmax;
792  else if (xlrec->cmin != InvalidCommandId)
793  cid = xlrec->cmin;
794  else
795  {
796  cid = InvalidCommandId; /* silence compiler */
797  elog(ERROR, "xl_heap_new_cid record without a valid CommandId");
798  }
799 
800  ReorderBufferAddNewCommandId(builder->reorder, xid, lsn, cid + 1);
801 }
uint32 CommandId
Definition: c.h:521
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:194
#define InvalidCommandId
Definition: c.h:524
#define Max(x, y)
Definition: c.h:898
#define elog(elevel,...)
Definition: elog.h:226
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 1095 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().

1096 {
1097  ReorderBufferTXN *txn;
1098  TransactionId xmin;
1099 
1100  /*
1101  * If we're not consistent yet, inspect the record to see whether it
1102  * allows to get closer to being consistent. If we are consistent, dump
1103  * our snapshot so others or we, after a restart, can use it.
1104  */
1105  if (builder->state < SNAPBUILD_CONSISTENT)
1106  {
1107  /* returns false if there's no point in performing cleanup just yet */
1108  if (!SnapBuildFindSnapshot(builder, lsn, running))
1109  return;
1110  }
1111  else
1112  SnapBuildSerialize(builder, lsn);
1113 
1114  /*
1115  * Update range of interesting xids based on the running xacts
1116  * information. We don't increase ->xmax using it, because once we are in
1117  * a consistent state we can do that ourselves and much more efficiently
1118  * so, because we only need to do it for catalog transactions since we
1119  * only ever look at those.
1120  *
1121  * NB: We only increase xmax when a catalog modifying transaction commits
1122  * (see SnapBuildCommitTxn). Because of this, xmax can be lower than
1123  * xmin, which looks odd but is correct and actually more efficient, since
1124  * we hit fast paths in heapam_visibility.c.
1125  */
1126  builder->xmin = running->oldestRunningXid;
1127 
1128  /* Remove transactions we don't need to keep track off anymore */
1129  SnapBuildPurgeCommittedTxn(builder);
1130 
1131  /*
1132  * Advance the xmin limit for the current replication slot, to allow
1133  * vacuum to clean up the tuples this slot has been protecting.
1134  *
1135  * The reorderbuffer might have an xmin among the currently running
1136  * snapshots; use it if so. If not, we need only consider the snapshots
1137  * we'll produce later, which can't be less than the oldest running xid in
1138  * the record we're reading now.
1139  */
1140  xmin = ReorderBufferGetOldestXmin(builder->reorder);
1141  if (xmin == InvalidTransactionId)
1142  xmin = running->oldestRunningXid;
1143  elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u",
1144  builder->xmin, builder->xmax, running->oldestRunningXid, xmin);
1145  LogicalIncreaseXminForSlot(lsn, xmin);
1146 
1147  /*
1148  * Also tell the slot where we can restart decoding from. We don't want to
1149  * do that after every commit because changing that implies an fsync of
1150  * the logical slot's state file, so we only do it every time we see a
1151  * running xacts record.
1152  *
1153  * Do so by looking for the oldest in progress transaction (determined by
1154  * the first LSN of any of its relevant records). Every transaction
1155  * remembers the last location we stored the snapshot to disk before its
1156  * beginning. That point is where we can restart from.
1157  */
1158 
1159  /*
1160  * Can't know about a serialized snapshot's location if we're not
1161  * consistent.
1162  */
1163  if (builder->state < SNAPBUILD_CONSISTENT)
1164  return;
1165 
1166  txn = ReorderBufferGetOldestTXN(builder->reorder);
1167 
1168  /*
1169  * oldest ongoing txn might have started when we didn't yet serialize
1170  * anything because we hadn't reached a consistent state yet.
1171  */
1172  if (txn != NULL && txn->restart_decoding_lsn != InvalidXLogRecPtr)
1174 
1175  /*
1176  * No in-progress transaction, can reuse the last serialized snapshot if
1177  * we have one.
1178  */
1179  else if (txn == NULL &&
1183  builder->last_serialized_snapshot);
1184 }
#define InvalidXLogRecPtr
Definition: xlogdefs.h:28
uint32 TransactionId
Definition: c.h:507
#define DEBUG3
Definition: elog.h:23
void LogicalIncreaseRestartDecodingForSlot(XLogRecPtr current_lsn, XLogRecPtr restart_lsn)
Definition: logical.c:936
XLogRecPtr current_restart_decoding_lsn
static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running)
Definition: snapbuild.c:1197
SnapBuildState state
Definition: snapbuild.c:155
static void SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
Definition: snapbuild.c:1485
ReorderBuffer * reorder
Definition: snapbuild.c:194
#define InvalidTransactionId
Definition: transam.h:31
XLogRecPtr last_serialized_snapshot
Definition: snapbuild.c:189
TransactionId xmax
Definition: snapbuild.c:164
TransactionId ReorderBufferGetOldestXmin(ReorderBuffer *rb)
ReorderBufferTXN * ReorderBufferGetOldestTXN(ReorderBuffer *rb)
void LogicalIncreaseXminForSlot(XLogRecPtr current_lsn, TransactionId xmin)
Definition: logical.c:879
TransactionId xmin
Definition: snapbuild.c:161
#define elog(elevel,...)
Definition: elog.h:226
XLogRecPtr restart_decoding_lsn
TransactionId oldestRunningXid
Definition: standbydefs.h:53
static void SnapBuildPurgeCommittedTxn(SnapBuild *builder)
Definition: snapbuild.c:887

◆ SnapBuildSerializationPoint()

void SnapBuildSerializationPoint ( SnapBuild builder,
XLogRecPtr  lsn 
)

Definition at line 1472 of file snapbuild.c.

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

Referenced by DecodeXLogOp().

1473 {
1474  if (builder->state < SNAPBUILD_CONSISTENT)
1475  SnapBuildRestore(builder, lsn);
1476  else
1477  SnapBuildSerialize(builder, lsn);
1478 }
static bool SnapBuildRestore(SnapBuild *builder, XLogRecPtr lsn)
Definition: snapbuild.c:1694
SnapBuildState state
Definition: snapbuild.c:155
static void SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
Definition: snapbuild.c:1485

◆ SnapBuildSnapDecRefcount()

void SnapBuildSnapDecRefcount ( Snapshot  snap)

Definition at line 433 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().

434 {
435  /* make sure we don't get passed an external snapshot */
437 
438  /* make sure nobody modified our snapshot */
439  Assert(snap->curcid == FirstCommandId);
440  Assert(!snap->suboverflowed);
441  Assert(!snap->takenDuringRecovery);
442 
443  Assert(snap->regd_count == 0);
444 
445  Assert(snap->active_count > 0);
446 
447  /* slightly more likely, so it's checked even without casserts */
448  if (snap->copied)
449  elog(ERROR, "cannot free a copied snapshot");
450 
451  snap->active_count--;
452  if (snap->active_count == 0)
453  SnapBuildFreeSnapshot(snap);
454 }
bool copied
Definition: snapshot.h:185
bool suboverflowed
Definition: snapshot.h:182
uint32 regd_count
Definition: snapshot.h:199
#define FirstCommandId
Definition: c.h:523
#define ERROR
Definition: elog.h:43
static void SnapBuildFreeSnapshot(Snapshot snap)
Definition: snapbuild.c:375
SnapshotType snapshot_type
Definition: snapshot.h:144
CommandId curcid
Definition: snapshot.h:187
#define Assert(condition)
Definition: c.h:732
bool takenDuringRecovery
Definition: snapshot.h:184
#define elog(elevel,...)
Definition: elog.h:226
uint32 active_count
Definition: snapshot.h:198

◆ SnapBuildXactNeedsSkip()

bool SnapBuildXactNeedsSkip ( SnapBuild snapstate,
XLogRecPtr  ptr 
)

Definition at line 409 of file snapbuild.c.

References SnapBuild::start_decoding_at.

Referenced by DecodeCommit(), and DecodeLogicalMsgOp().

410 {
411  return ptr < builder->start_decoding_at;
412 }