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If a user requests the commit timestamp for a transaction old enough that its data is concurrently being truncated away by vacuum at just the right time, they would receive an ugly internal file-not-found error message from slru.c rather than the expected NULL return value. In a primary server, the window for the race is very small: the lookup has to occur exactly between the two calls by vacuum, and there's not a lot that happens between them (mostly just a multixact truncate). In a standby server, however, the window is larger because the truncation is executed as soon as the WAL record for it is replayed, but the advance of the oldest-Xid is not executed until the next checkpoint record. To fix in the primary, simply reverse the order of operations in vac_truncate_clog. To fix in the standby, augment the WAL truncation record so that the standby is aware of the new oldest-XID value and can apply the update immediately. WAL version bumped because of this. No backpatch, because of the low importance of the bug and its rarity. Author: Craig Ringer Reviewed-By: Petr Jelínek, Peter Eisentraut Discussion: https://postgr.es/m/CAMsr+YFhVtRQT1VAwC+WGbbxZZRzNou=N9Ed-FrCqkwQ8H8oJQ@mail.gmail.com
77 lines
2.3 KiB
C
77 lines
2.3 KiB
C
/*
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* commit_ts.h
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*
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* PostgreSQL commit timestamp manager
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*
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* Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/access/commit_ts.h
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*/
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#ifndef COMMIT_TS_H
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#define COMMIT_TS_H
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#include "access/xlog.h"
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#include "datatype/timestamp.h"
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#include "replication/origin.h"
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#include "utils/guc.h"
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extern PGDLLIMPORT bool track_commit_timestamp;
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extern bool check_track_commit_timestamp(bool *newval, void **extra,
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GucSource source);
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extern void TransactionTreeSetCommitTsData(TransactionId xid, int nsubxids,
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TransactionId *subxids, TimestampTz timestamp,
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RepOriginId nodeid, bool write_xlog);
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extern bool TransactionIdGetCommitTsData(TransactionId xid,
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TimestampTz *ts, RepOriginId *nodeid);
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extern TransactionId GetLatestCommitTsData(TimestampTz *ts,
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RepOriginId *nodeid);
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extern Size CommitTsShmemBuffers(void);
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extern Size CommitTsShmemSize(void);
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extern void CommitTsShmemInit(void);
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extern void BootStrapCommitTs(void);
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extern void StartupCommitTs(void);
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extern void CommitTsParameterChange(bool xlrecvalue, bool pgcontrolvalue);
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extern void CompleteCommitTsInitialization(void);
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extern void ShutdownCommitTs(void);
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extern void CheckPointCommitTs(void);
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extern void ExtendCommitTs(TransactionId newestXact);
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extern void TruncateCommitTs(TransactionId oldestXact);
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extern void SetCommitTsLimit(TransactionId oldestXact,
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TransactionId newestXact);
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extern void AdvanceOldestCommitTsXid(TransactionId oldestXact);
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/* XLOG stuff */
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#define COMMIT_TS_ZEROPAGE 0x00
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#define COMMIT_TS_TRUNCATE 0x10
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#define COMMIT_TS_SETTS 0x20
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typedef struct xl_commit_ts_set
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{
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TimestampTz timestamp;
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RepOriginId nodeid;
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TransactionId mainxid;
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/* subxact Xids follow */
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} xl_commit_ts_set;
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#define SizeOfCommitTsSet (offsetof(xl_commit_ts_set, mainxid) + \
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sizeof(TransactionId))
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typedef struct xl_commit_ts_truncate
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{
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int pageno;
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TransactionId oldestXid;
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} xl_commit_ts_truncate;
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#define SizeOfCommitTsTruncate (offsetof(xl_commit_ts_truncate, oldestXid) + \
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sizeof(TransactionId))
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extern void commit_ts_redo(XLogReaderState *record);
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extern void commit_ts_desc(StringInfo buf, XLogReaderState *record);
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extern const char *commit_ts_identify(uint8 info);
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#endif /* COMMIT_TS_H */
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