>From 4f7eb5b8fdbab2539731414e81d7a7419a83e5b1 Mon Sep 17 00:00:00 2001 From: Petr Jelinek Date: Sat, 3 Jun 2017 02:06:22 +0200 Subject: [PATCH 1/2] Use virtual transaction instead of normal ones in exported snapshots --- doc/src/sgml/ref/set_transaction.sgml | 8 ++--- src/backend/storage/ipc/procarray.c | 11 +++--- src/backend/storage/lmgr/predicate.c | 22 ++++++------ src/backend/utils/time/snapmgr.c | 68 ++++++++++++++++++++++++----------- src/include/storage/predicate.h | 3 +- src/include/storage/procarray.h | 2 +- 6 files changed, 72 insertions(+), 42 deletions(-) diff --git a/doc/src/sgml/ref/set_transaction.sgml b/doc/src/sgml/ref/set_transaction.sgml index ca55a5b..116315f 100644 --- a/doc/src/sgml/ref/set_transaction.sgml +++ b/doc/src/sgml/ref/set_transaction.sgml @@ -221,9 +221,9 @@ SET SESSION CHARACTERISTICS AS TRANSACTION transa BEGIN TRANSACTION ISOLATION LEVEL REPEATABLE READ; SELECT pg_export_snapshot(); - pg_export_snapshot --------------------- - 000003A1-1 + pg_export_snapshot +--------------------- + 00000003-0000001B-1 (1 row) @@ -233,7 +233,7 @@ SELECT pg_export_snapshot(); BEGIN TRANSACTION ISOLATION LEVEL REPEATABLE READ; -SET TRANSACTION SNAPSHOT '000003A1-1'; +SET TRANSACTION SNAPSHOT '00000003-0000001B-1'; diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index 8a71536..c9ae5bf 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -1793,14 +1793,15 @@ GetSnapshotData(Snapshot snapshot) * Returns TRUE if successful, FALSE if source xact is no longer running. */ bool -ProcArrayInstallImportedXmin(TransactionId xmin, TransactionId sourcexid) +ProcArrayInstallImportedXmin(TransactionId xmin, + VirtualTransactionId *sourcevxid) { bool result = false; ProcArrayStruct *arrayP = procArray; int index; Assert(TransactionIdIsNormal(xmin)); - if (!TransactionIdIsNormal(sourcexid)) + if (!sourcevxid || !VirtualTransactionIdIsValid(*sourcevxid)) return false; /* Get lock so source xact can't end while we're doing this */ @@ -1817,8 +1818,10 @@ ProcArrayInstallImportedXmin(TransactionId xmin, TransactionId sourcexid) if (pgxact->vacuumFlags & PROC_IN_VACUUM) continue; - xid = pgxact->xid; /* fetch just once */ - if (xid != sourcexid) + /* We are only interested in the specific virtual transaction. */ + if (proc->backendId != sourcevxid->backendId) + continue; + if (proc->lxid != sourcevxid->localTransactionId) continue; /* diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c index 27c4af9..64acd6e 100644 --- a/src/backend/storage/lmgr/predicate.c +++ b/src/backend/storage/lmgr/predicate.c @@ -148,7 +148,7 @@ * predicate lock maintenance * GetSerializableTransactionSnapshot(Snapshot snapshot) * SetSerializableTransactionSnapshot(Snapshot snapshot, - * TransactionId sourcexid) + * VirtualTransactionId *sourcevxid) * RegisterPredicateLockingXid(void) * PredicateLockRelation(Relation relation, Snapshot snapshot) * PredicateLockPage(Relation relation, BlockNumber blkno, @@ -434,7 +434,7 @@ static uint32 predicatelock_hash(const void *key, Size keysize); static void SummarizeOldestCommittedSxact(void); static Snapshot GetSafeSnapshot(Snapshot snapshot); static Snapshot GetSerializableTransactionSnapshotInt(Snapshot snapshot, - TransactionId sourcexid); + VirtualTransactionId *sourcevxid); static bool PredicateLockExists(const PREDICATELOCKTARGETTAG *targettag); static bool GetParentPredicateLockTag(const PREDICATELOCKTARGETTAG *tag, PREDICATELOCKTARGETTAG *parent); @@ -1510,7 +1510,7 @@ GetSafeSnapshot(Snapshot origSnapshot) * one passed to it, but we avoid assuming that here. */ snapshot = GetSerializableTransactionSnapshotInt(origSnapshot, - InvalidTransactionId); + NULL); if (MySerializableXact == InvalidSerializableXact) return snapshot; /* no concurrent r/w xacts; it's safe */ @@ -1643,7 +1643,7 @@ GetSerializableTransactionSnapshot(Snapshot snapshot) return GetSafeSnapshot(snapshot); return GetSerializableTransactionSnapshotInt(snapshot, - InvalidTransactionId); + NULL); } /* @@ -1658,7 +1658,7 @@ GetSerializableTransactionSnapshot(Snapshot snapshot) */ void SetSerializableTransactionSnapshot(Snapshot snapshot, - TransactionId sourcexid) + VirtualTransactionId *sourcevxid) { Assert(IsolationIsSerializable()); @@ -1673,7 +1673,7 @@ SetSerializableTransactionSnapshot(Snapshot snapshot, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("a snapshot-importing transaction must not be READ ONLY DEFERRABLE"))); - (void) GetSerializableTransactionSnapshotInt(snapshot, sourcexid); + (void) GetSerializableTransactionSnapshotInt(snapshot, sourcevxid); } /* @@ -1687,7 +1687,7 @@ SetSerializableTransactionSnapshot(Snapshot snapshot, */ static Snapshot GetSerializableTransactionSnapshotInt(Snapshot snapshot, - TransactionId sourcexid) + VirtualTransactionId *sourcevxid) { PGPROC *proc; VirtualTransactionId vxid; @@ -1741,17 +1741,17 @@ GetSerializableTransactionSnapshotInt(Snapshot snapshot, } while (!sxact); /* Get the snapshot, or check that it's safe to use */ - if (!TransactionIdIsValid(sourcexid)) + if (!sourcevxid) snapshot = GetSnapshotData(snapshot); - else if (!ProcArrayInstallImportedXmin(snapshot->xmin, sourcexid)) + else if (!ProcArrayInstallImportedXmin(snapshot->xmin, sourcevxid)) { ReleasePredXact(sxact); LWLockRelease(SerializableXactHashLock); ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("could not import the requested snapshot"), - errdetail("The source transaction %u is not running anymore.", - sourcexid))); + errdetail("The source virtual transaction %d/%u is not running anymore.", + sourcevxid->backendId, sourcevxid->localTransactionId))); } /* diff --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr.c index b3d4fe3..b8e1933 100644 --- a/src/backend/utils/time/snapmgr.c +++ b/src/backend/utils/time/snapmgr.c @@ -211,9 +211,9 @@ static Snapshot FirstXactSnapshot = NULL; /* Define pathname of exported-snapshot files */ #define SNAPSHOT_EXPORT_DIR "pg_snapshots" -#define XactExportFilePath(path, xid, num, suffix) \ - snprintf(path, sizeof(path), SNAPSHOT_EXPORT_DIR "/%08X-%d%s", \ - xid, num, suffix) +#define XactExportFilePath(path, backenId, lxid, num, suffix) \ + snprintf(path, sizeof(path), SNAPSHOT_EXPORT_DIR "/%08X-%08X-%d%s", \ + backenId, lxid, num, suffix) /* Current xact's exported snapshots (a list of Snapshot structs) */ static List *exportedSnapshots = NIL; @@ -558,7 +558,7 @@ SnapshotSetCommandId(CommandId curcid) * in GetTransactionSnapshot. */ static void -SetTransactionSnapshot(Snapshot sourcesnap, TransactionId sourcexid, +SetTransactionSnapshot(Snapshot sourcesnap, VirtualTransactionId *sourcevxid, PGPROC *sourceproc) { /* Caller should have checked this already */ @@ -617,12 +617,12 @@ SetTransactionSnapshot(Snapshot sourcesnap, TransactionId sourcexid, errmsg("could not import the requested snapshot"), errdetail("The source transaction is not running anymore."))); } - else if (!ProcArrayInstallImportedXmin(CurrentSnapshot->xmin, sourcexid)) + else if (!ProcArrayInstallImportedXmin(CurrentSnapshot->xmin, sourcevxid)) ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("could not import the requested snapshot"), - errdetail("The source transaction %u is not running anymore.", - sourcexid))); + errdetail("The source virtual transaction %d/%u is not running anymore.", + sourcevxid->backendId, sourcevxid->localTransactionId))); /* * In transaction-snapshot mode, the first snapshot must live until end of @@ -632,7 +632,7 @@ SetTransactionSnapshot(Snapshot sourcesnap, TransactionId sourcexid, if (IsolationUsesXactSnapshot()) { if (IsolationIsSerializable()) - SetSerializableTransactionSnapshot(CurrentSnapshot, sourcexid); + SetSerializableTransactionSnapshot(CurrentSnapshot, sourcevxid); /* Make a saved copy */ CurrentSnapshot = CopySnapshot(CurrentSnapshot); FirstXactSnapshot = CurrentSnapshot; @@ -1075,7 +1075,6 @@ AtEOXact_Snapshot(bool isCommit, bool resetXmin) */ if (exportedSnapshots != NIL) { - TransactionId myxid = GetTopTransactionId(); int i; char buf[MAXPGPATH]; ListCell *lc; @@ -1087,7 +1086,7 @@ AtEOXact_Snapshot(bool isCommit, bool resetXmin) */ for (i = 1; i <= list_length(exportedSnapshots); i++) { - XactExportFilePath(buf, myxid, i, ""); + XactExportFilePath(buf, MyProc->backendId, MyProc->lxid, i, ""); if (unlink(buf)) elog(WARNING, "could not unlink file \"%s\": %m", buf); } @@ -1183,9 +1182,9 @@ ExportSnapshot(Snapshot snapshot) */ /* - * This will assign a transaction ID if we do not yet have one. + * Get our transaction ID if there is one, to include in the snapshot. */ - topXid = GetTopTransactionId(); + topXid = GetTopTransactionIdIfAny(); /* * We cannot export a snapshot from a subtransaction because there's no @@ -1226,7 +1225,7 @@ ExportSnapshot(Snapshot snapshot) */ initStringInfo(&buf); - appendStringInfo(&buf, "xid:%u\n", topXid); + appendStringInfo(&buf, "vxid:%d/%u\n", MyProc->backendId, MyProc->lxid); appendStringInfo(&buf, "dbid:%u\n", MyDatabaseId); appendStringInfo(&buf, "iso:%d\n", XactIsoLevel); appendStringInfo(&buf, "ro:%d\n", XactReadOnly); @@ -1245,7 +1244,8 @@ ExportSnapshot(Snapshot snapshot) * xmax. (We need not make the same check for subxip[] members, see * snapshot.h.) */ - addTopXid = TransactionIdPrecedes(topXid, snapshot->xmax) ? 1 : 0; + addTopXid = (TransactionIdIsValid(topXid) && + TransactionIdPrecedes(topXid, snapshot->xmax)) ? 1 : 0; appendStringInfo(&buf, "xcnt:%d\n", snapshot->xcnt + addTopXid); for (i = 0; i < snapshot->xcnt; i++) appendStringInfo(&buf, "xip:%u\n", snapshot->xip[i]); @@ -1276,7 +1276,8 @@ ExportSnapshot(Snapshot snapshot) * ensures that no other backend can read an incomplete file * (ImportSnapshot won't allow it because of its valid-characters check). */ - XactExportFilePath(pathtmp, topXid, list_length(exportedSnapshots), ".tmp"); + XactExportFilePath(pathtmp, MyProc->backendId, MyProc->lxid, + list_length(exportedSnapshots), ".tmp"); if (!(f = AllocateFile(pathtmp, PG_BINARY_W))) ereport(ERROR, (errcode_for_file_access(), @@ -1298,7 +1299,8 @@ ExportSnapshot(Snapshot snapshot) * Now that we have written everything into a .tmp file, rename the file * to remove the .tmp suffix. */ - XactExportFilePath(path, topXid, list_length(exportedSnapshots), ""); + XactExportFilePath(path, MyProc->backendId, MyProc->lxid, + list_length(exportedSnapshots), ""); if (rename(pathtmp, path) < 0) ereport(ERROR, @@ -1384,6 +1386,30 @@ parseXidFromText(const char *prefix, char **s, const char *filename) return val; } +static void +parseVxidFromText(const char *prefix, char **s, const char *filename, + VirtualTransactionId *vxid) +{ + char *ptr = *s; + int prefixlen = strlen(prefix); + + if (strncmp(ptr, prefix, prefixlen) != 0) + ereport(ERROR, + (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION), + errmsg("invalid snapshot data in file \"%s\"", filename))); + ptr += prefixlen; + if (sscanf(ptr, "%d/%u", &vxid->backendId, &vxid->localTransactionId) != 2) + ereport(ERROR, + (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION), + errmsg("invalid snapshot data in file \"%s\"", filename))); + ptr = strchr(ptr, '\n'); + if (!ptr) + ereport(ERROR, + (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION), + errmsg("invalid snapshot data in file \"%s\"", filename))); + *s = ptr + 1; +} + /* * ImportSnapshot * Import a previously exported snapshot. The argument should be a @@ -1399,7 +1425,7 @@ ImportSnapshot(const char *idstr) char *filebuf; int xcnt; int i; - TransactionId src_xid; + VirtualTransactionId src_vxid; Oid src_dbid; int src_isolevel; bool src_readonly; @@ -1463,7 +1489,7 @@ ImportSnapshot(const char *idstr) */ memset(&snapshot, 0, sizeof(snapshot)); - src_xid = parseXidFromText("xid:", &filebuf, path); + parseVxidFromText("vxid:", &filebuf, path, &src_vxid); /* we abuse parseXidFromText a bit here ... */ src_dbid = parseXidFromText("dbid:", &filebuf, path); src_isolevel = parseIntFromText("iso:", &filebuf, path); @@ -1513,7 +1539,7 @@ ImportSnapshot(const char *idstr) * don't trouble to check the array elements, just the most critical * fields. */ - if (!TransactionIdIsNormal(src_xid) || + if (!VirtualTransactionIdIsValid(src_vxid) || !OidIsValid(src_dbid) || !TransactionIdIsNormal(snapshot.xmin) || !TransactionIdIsNormal(snapshot.xmax)) @@ -1554,7 +1580,7 @@ ImportSnapshot(const char *idstr) errmsg("cannot import a snapshot from a different database"))); /* OK, install the snapshot */ - SetTransactionSnapshot(&snapshot, src_xid, NULL); + SetTransactionSnapshot(&snapshot, &src_vxid, NULL); } /* @@ -2141,5 +2167,5 @@ RestoreSnapshot(char *start_address) void RestoreTransactionSnapshot(Snapshot snapshot, void *master_pgproc) { - SetTransactionSnapshot(snapshot, InvalidTransactionId, master_pgproc); + SetTransactionSnapshot(snapshot, NULL, master_pgproc); } diff --git a/src/include/storage/predicate.h b/src/include/storage/predicate.h index 8f9ea29..671d953 100644 --- a/src/include/storage/predicate.h +++ b/src/include/storage/predicate.h @@ -14,6 +14,7 @@ #ifndef PREDICATE_H #define PREDICATE_H +#include "storage/lock.h" #include "utils/relcache.h" #include "utils/snapshot.h" @@ -46,7 +47,7 @@ extern bool PageIsPredicateLocked(Relation relation, BlockNumber blkno); /* predicate lock maintenance */ extern Snapshot GetSerializableTransactionSnapshot(Snapshot snapshot); extern void SetSerializableTransactionSnapshot(Snapshot snapshot, - TransactionId sourcexid); + VirtualTransactionId *sourcevxid); extern void RegisterPredicateLockingXid(TransactionId xid); extern void PredicateLockRelation(Relation relation, Snapshot snapshot); extern void PredicateLockPage(Relation relation, BlockNumber blkno, Snapshot snapshot); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index 22955a7..5cf8ff7 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -82,7 +82,7 @@ extern int GetMaxSnapshotSubxidCount(void); extern Snapshot GetSnapshotData(Snapshot snapshot); extern bool ProcArrayInstallImportedXmin(TransactionId xmin, - TransactionId sourcexid); + VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); extern RunningTransactions GetRunningTransactionData(void); -- 2.7.4