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Commit fc49e24fa6
added an input argument after the existing output
argument. Flip those.
Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20180708182345.imdgovmkffgtihhk@alvherre.pgsql
404 lines
11 KiB
C
404 lines
11 KiB
C
/*-------------------------------------------------------------------------
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*
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* parsexlog.c
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* Functions for reading Write-Ahead-Log
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*
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* Portions Copyright (c) 1996-2018, 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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*-------------------------------------------------------------------------
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*/
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#include "postgres_fe.h"
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#include <unistd.h>
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#include "pg_rewind.h"
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#include "filemap.h"
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#include "logging.h"
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#include "access/rmgr.h"
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#include "access/xlog_internal.h"
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#include "access/xlogreader.h"
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#include "catalog/pg_control.h"
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#include "catalog/storage_xlog.h"
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#include "commands/dbcommands_xlog.h"
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/*
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* RmgrNames is an array of resource manager names, to make error messages
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* a bit nicer.
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*/
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#define PG_RMGR(symname,name,redo,desc,identify,startup,cleanup,mask) \
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name,
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static const char *RmgrNames[RM_MAX_ID + 1] = {
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#include "access/rmgrlist.h"
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};
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static void extractPageInfo(XLogReaderState *record);
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static int xlogreadfd = -1;
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static XLogSegNo xlogreadsegno = -1;
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static char xlogfpath[MAXPGPATH];
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typedef struct XLogPageReadPrivate
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{
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const char *datadir;
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int tliIndex;
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} XLogPageReadPrivate;
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static int SimpleXLogPageRead(XLogReaderState *xlogreader,
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XLogRecPtr targetPagePtr,
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int reqLen, XLogRecPtr targetRecPtr, char *readBuf,
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TimeLineID *pageTLI);
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/*
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* Read WAL from the datadir/pg_wal, starting from 'startpoint' on timeline
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* index 'tliIndex' in target timeline history, until 'endpoint'. Make note of
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* the data blocks touched by the WAL records, and return them in a page map.
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*/
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void
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extractPageMap(const char *datadir, XLogRecPtr startpoint, int tliIndex,
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XLogRecPtr endpoint)
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{
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XLogRecord *record;
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XLogReaderState *xlogreader;
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char *errormsg;
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XLogPageReadPrivate private;
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private.datadir = datadir;
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private.tliIndex = tliIndex;
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xlogreader = XLogReaderAllocate(WalSegSz, &SimpleXLogPageRead,
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&private);
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if (xlogreader == NULL)
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pg_fatal("out of memory\n");
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do
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{
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record = XLogReadRecord(xlogreader, startpoint, &errormsg);
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if (record == NULL)
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{
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XLogRecPtr errptr;
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errptr = startpoint ? startpoint : xlogreader->EndRecPtr;
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if (errormsg)
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pg_fatal("could not read WAL record at %X/%X: %s\n",
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(uint32) (errptr >> 32), (uint32) (errptr),
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errormsg);
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else
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pg_fatal("could not read WAL record at %X/%X\n",
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(uint32) (startpoint >> 32),
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(uint32) (startpoint));
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}
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extractPageInfo(xlogreader);
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startpoint = InvalidXLogRecPtr; /* continue reading at next record */
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} while (xlogreader->ReadRecPtr != endpoint);
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XLogReaderFree(xlogreader);
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if (xlogreadfd != -1)
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{
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close(xlogreadfd);
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xlogreadfd = -1;
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}
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}
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/*
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* Reads one WAL record. Returns the end position of the record, without
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* doing anything with the record itself.
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*/
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XLogRecPtr
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readOneRecord(const char *datadir, XLogRecPtr ptr, int tliIndex)
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{
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XLogRecord *record;
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XLogReaderState *xlogreader;
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char *errormsg;
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XLogPageReadPrivate private;
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XLogRecPtr endptr;
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private.datadir = datadir;
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private.tliIndex = tliIndex;
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xlogreader = XLogReaderAllocate(WalSegSz, &SimpleXLogPageRead,
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&private);
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if (xlogreader == NULL)
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pg_fatal("out of memory\n");
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record = XLogReadRecord(xlogreader, ptr, &errormsg);
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if (record == NULL)
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{
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if (errormsg)
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pg_fatal("could not read WAL record at %X/%X: %s\n",
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(uint32) (ptr >> 32), (uint32) (ptr), errormsg);
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else
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pg_fatal("could not read WAL record at %X/%X\n",
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(uint32) (ptr >> 32), (uint32) (ptr));
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}
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endptr = xlogreader->EndRecPtr;
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XLogReaderFree(xlogreader);
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if (xlogreadfd != -1)
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{
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close(xlogreadfd);
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xlogreadfd = -1;
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}
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return endptr;
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}
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/*
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* Find the previous checkpoint preceding given WAL location.
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*/
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void
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findLastCheckpoint(const char *datadir, XLogRecPtr forkptr, int tliIndex,
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XLogRecPtr *lastchkptrec, TimeLineID *lastchkpttli,
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XLogRecPtr *lastchkptredo)
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{
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/* Walk backwards, starting from the given record */
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XLogRecord *record;
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XLogRecPtr searchptr;
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XLogReaderState *xlogreader;
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char *errormsg;
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XLogPageReadPrivate private;
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/*
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* The given fork pointer points to the end of the last common record,
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* which is not necessarily the beginning of the next record, if the
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* previous record happens to end at a page boundary. Skip over the page
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* header in that case to find the next record.
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*/
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if (forkptr % XLOG_BLCKSZ == 0)
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{
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if (XLogSegmentOffset(forkptr, WalSegSz) == 0)
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forkptr += SizeOfXLogLongPHD;
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else
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forkptr += SizeOfXLogShortPHD;
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}
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private.datadir = datadir;
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private.tliIndex = tliIndex;
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xlogreader = XLogReaderAllocate(WalSegSz, &SimpleXLogPageRead,
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&private);
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if (xlogreader == NULL)
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pg_fatal("out of memory\n");
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searchptr = forkptr;
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for (;;)
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{
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uint8 info;
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record = XLogReadRecord(xlogreader, searchptr, &errormsg);
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if (record == NULL)
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{
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if (errormsg)
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pg_fatal("could not find previous WAL record at %X/%X: %s\n",
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(uint32) (searchptr >> 32), (uint32) (searchptr),
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errormsg);
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else
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pg_fatal("could not find previous WAL record at %X/%X\n",
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(uint32) (searchptr >> 32), (uint32) (searchptr));
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}
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/*
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* Check if it is a checkpoint record. This checkpoint record needs to
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* be the latest checkpoint before WAL forked and not the checkpoint
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* where the master has been stopped to be rewinded.
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*/
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info = XLogRecGetInfo(xlogreader) & ~XLR_INFO_MASK;
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if (searchptr < forkptr &&
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XLogRecGetRmid(xlogreader) == RM_XLOG_ID &&
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(info == XLOG_CHECKPOINT_SHUTDOWN ||
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info == XLOG_CHECKPOINT_ONLINE))
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{
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CheckPoint checkPoint;
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memcpy(&checkPoint, XLogRecGetData(xlogreader), sizeof(CheckPoint));
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*lastchkptrec = searchptr;
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*lastchkpttli = checkPoint.ThisTimeLineID;
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*lastchkptredo = checkPoint.redo;
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break;
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}
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/* Walk backwards to previous record. */
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searchptr = record->xl_prev;
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}
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XLogReaderFree(xlogreader);
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if (xlogreadfd != -1)
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{
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close(xlogreadfd);
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xlogreadfd = -1;
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}
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}
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/* XLogreader callback function, to read a WAL page */
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static int
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SimpleXLogPageRead(XLogReaderState *xlogreader, XLogRecPtr targetPagePtr,
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int reqLen, XLogRecPtr targetRecPtr, char *readBuf,
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TimeLineID *pageTLI)
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{
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XLogPageReadPrivate *private = (XLogPageReadPrivate *) xlogreader->private_data;
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uint32 targetPageOff;
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XLogRecPtr targetSegEnd;
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XLogSegNo targetSegNo;
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XLByteToSeg(targetPagePtr, targetSegNo, WalSegSz);
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XLogSegNoOffsetToRecPtr(targetSegNo + 1, 0, WalSegSz, targetSegEnd);
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targetPageOff = XLogSegmentOffset(targetPagePtr, WalSegSz);
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/*
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* See if we need to switch to a new segment because the requested record
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* is not in the currently open one.
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*/
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if (xlogreadfd >= 0 &&
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!XLByteInSeg(targetPagePtr, xlogreadsegno, WalSegSz))
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{
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close(xlogreadfd);
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xlogreadfd = -1;
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}
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XLByteToSeg(targetPagePtr, xlogreadsegno, WalSegSz);
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if (xlogreadfd < 0)
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{
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char xlogfname[MAXFNAMELEN];
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/*
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* Since incomplete segments are copied into next timelines, switch to
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* the timeline holding the required segment. Assuming this scan can
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* be done both forward and backward, consider also switching timeline
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* accordingly.
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*/
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while (private->tliIndex < targetNentries - 1 &&
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targetHistory[private->tliIndex].end < targetSegEnd)
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private->tliIndex++;
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while (private->tliIndex > 0 &&
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targetHistory[private->tliIndex].begin >= targetSegEnd)
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private->tliIndex--;
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XLogFileName(xlogfname, targetHistory[private->tliIndex].tli,
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xlogreadsegno, WalSegSz);
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snprintf(xlogfpath, MAXPGPATH, "%s/" XLOGDIR "/%s", private->datadir, xlogfname);
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xlogreadfd = open(xlogfpath, O_RDONLY | PG_BINARY, 0);
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if (xlogreadfd < 0)
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{
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printf(_("could not open file \"%s\": %s\n"), xlogfpath,
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strerror(errno));
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return -1;
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}
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}
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/*
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* At this point, we have the right segment open.
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*/
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Assert(xlogreadfd != -1);
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/* Read the requested page */
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if (lseek(xlogreadfd, (off_t) targetPageOff, SEEK_SET) < 0)
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{
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printf(_("could not seek in file \"%s\": %s\n"), xlogfpath,
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strerror(errno));
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return -1;
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}
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if (read(xlogreadfd, readBuf, XLOG_BLCKSZ) != XLOG_BLCKSZ)
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{
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printf(_("could not read from file \"%s\": %s\n"), xlogfpath,
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strerror(errno));
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return -1;
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}
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Assert(targetSegNo == xlogreadsegno);
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*pageTLI = targetHistory[private->tliIndex].tli;
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return XLOG_BLCKSZ;
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}
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/*
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* Extract information on which blocks the current record modifies.
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*/
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static void
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extractPageInfo(XLogReaderState *record)
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{
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int block_id;
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RmgrId rmid = XLogRecGetRmid(record);
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uint8 info = XLogRecGetInfo(record);
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uint8 rminfo = info & ~XLR_INFO_MASK;
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/* Is this a special record type that I recognize? */
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if (rmid == RM_DBASE_ID && rminfo == XLOG_DBASE_CREATE)
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{
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/*
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* New databases can be safely ignored. It won't be present in the
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* source system, so it will be deleted. There's one corner-case,
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* though: if a new, different, database is also created in the source
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* system, we'll see that the files already exist and not copy them.
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* That's OK, though; WAL replay of creating the new database, from
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* the source systems's WAL, will re-copy the new database,
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* overwriting the database created in the target system.
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*/
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}
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else if (rmid == RM_DBASE_ID && rminfo == XLOG_DBASE_DROP)
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{
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/*
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* An existing database was dropped. We'll see that the files don't
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* exist in the target data dir, and copy them in toto from the source
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* system. No need to do anything special here.
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*/
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}
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else if (rmid == RM_SMGR_ID && rminfo == XLOG_SMGR_CREATE)
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{
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/*
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* We can safely ignore these. The file will be removed from the
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* target, if it doesn't exist in source system. If a file with same
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* name is created in source system, too, there will be WAL records
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* for all the blocks in it.
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*/
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}
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else if (rmid == RM_SMGR_ID && rminfo == XLOG_SMGR_TRUNCATE)
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{
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/*
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* We can safely ignore these. When we compare the sizes later on,
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* we'll notice that they differ, and copy the missing tail from
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* source system.
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*/
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}
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else if (info & XLR_SPECIAL_REL_UPDATE)
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{
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/*
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* This record type modifies a relation file in some special way, but
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* we don't recognize the type. That's bad - we don't know how to
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* track that change.
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*/
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pg_fatal("WAL record modifies a relation, but record type is not recognized\n"
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"lsn: %X/%X, rmgr: %s, info: %02X\n",
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(uint32) (record->ReadRecPtr >> 32), (uint32) (record->ReadRecPtr),
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RmgrNames[rmid], info);
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}
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for (block_id = 0; block_id <= record->max_block_id; block_id++)
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{
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RelFileNode rnode;
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ForkNumber forknum;
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BlockNumber blkno;
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if (!XLogRecGetBlockTag(record, block_id, &rnode, &forknum, &blkno))
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continue;
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/* We only care about the main fork; others are copied in toto */
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if (forknum != MAIN_FORKNUM)
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continue;
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process_block_change(forknum, rnode, blkno);
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}
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}
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