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/*-------------------------------------------------------------------------
*
* sequence.c
* RMGR WAL routines for sequences.
*
* Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/commands/sequence_xlog.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/bufmask.h"
#include "access/xlogutils.h"
#include "commands/sequence_xlog.h"
#include "storage/bufmgr.h"
void
seq_redo(XLogReaderState *record)
{
XLogRecPtr lsn = record->EndRecPtr;
uint8 info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
Buffer buffer;
Page page;
Page localpage;
char *item;
Size itemsz;
xl_seq_rec *xlrec = (xl_seq_rec *) XLogRecGetData(record);
sequence_magic *sm;
if (info != XLOG_SEQ_LOG)
elog(PANIC, "seq_redo: unknown op code %u", info);
buffer = XLogInitBufferForRedo(record, 0);
page = BufferGetPage(buffer);
/*
* We always reinit the page. However, since this WAL record type is also
* used for updating sequences, it's possible that a hot-standby backend
* is examining the page concurrently; so we mustn't transiently trash the
* buffer. The solution is to build the correct new page contents in
* local workspace and then memcpy into the buffer. Then only bytes that
* are supposed to change will change, even transiently. We must palloc
* the local page for alignment reasons.
*/
localpage = (Page) palloc(BufferGetPageSize(buffer));
PageInit(localpage, BufferGetPageSize(buffer), sizeof(sequence_magic));
sm = (sequence_magic *) PageGetSpecialPointer(localpage);
sm->magic = SEQ_MAGIC;
item = (char *) xlrec + sizeof(xl_seq_rec);
itemsz = XLogRecGetDataLen(record) - sizeof(xl_seq_rec);
if (PageAddItem(localpage, item, itemsz, FirstOffsetNumber, false, false) == InvalidOffsetNumber)
elog(PANIC, "seq_redo: failed to add item to page");
PageSetLSN(localpage, lsn);
memcpy(page, localpage, BufferGetPageSize(buffer));
MarkBufferDirty(buffer);
UnlockReleaseBuffer(buffer);
pfree(localpage);
}
/*
* Mask a Sequence page before performing consistency checks on it.
*/
void
seq_mask(char *page, BlockNumber blkno)
{
mask_page_lsn_and_checksum(page);
mask_unused_space(page);
}
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