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Make XLOG_FPI_FOR_HINT records honor full_page_writes setting. 

Commit 2c03216d83 changed XLOG_FPI_FOR_HINT records so that they always
included full-page images even when full_page_writes was disabled. However,
in this setting, they don't need to do that because hint bit updates don't
need to be protected from torn writes.

Therefore, this commit makes XLOG_FPI_FOR_HINT records honor full_page_writes
setting. That is, XLOG_FPI_FOR_HINT records may include no full-page images
if full_page_writes is disabled, and WAL replay of them does nothing.

Reported-by: Zhang Wenjie
Author: Kyotaro Horiguchi
Reviewed-by: Fujii Masao
Discussion: https://postgr.es/m/tencent_60F11973A111EED97A8596FFECC4A91ED405@qq.com
This commit is contained in:
Fujii Masao 2021-07-21 11:19:00 +09:00
parent d9809bf869
commit 7fcf2faf9c
2 changed files with 22 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
src/backend/access/transam/xlog.c
View File

@ -10148,7 +10148,10 @@ xlog_redo(XLogReaderState *record)
uint8 info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
XLogRecPtr lsn = record->EndRecPtr;
/* in XLOG rmgr, backup blocks are only used by XLOG_FPI records */
/*
* In XLOG rmgr, backup blocks are only used by XLOG_FPI and
* XLOG_FPI_FOR_HINT records.
*/
Assert(info == XLOG_FPI || info == XLOG_FPI_FOR_HINT ||
!XLogRecHasAnyBlockRefs(record));
@ -10356,25 +10359,32 @@ xlog_redo(XLogReaderState *record)
else if (info == XLOG_FPI || info == XLOG_FPI_FOR_HINT)
{
/*
* Full-page image (FPI) records contain nothing else but a backup
* block (or multiple backup blocks). Every block reference must
* include a full-page image - otherwise there would be no point in
* this record.
* XLOG_FPI records contain nothing else but one or more block
* references. Every block reference must include a full-page image
* even if full_page_writes was disabled when the record was generated
* - otherwise there would be no point in this record.
*
* XLOG_FPI_FOR_HINT records are generated when a page needs to be
* WAL-logged because of a hint bit update. They are only generated
* when checksums and/or wal_log_hints are enabled. They may include
* no full-page images if full_page_writes was disabled when they were
* generated. In this case there is nothing to do here.
*
* No recovery conflicts are generated by these generic records - if a
* resource manager needs to generate conflicts, it has to define a
* separate WAL record type and redo routine.
*
* XLOG_FPI_FOR_HINT records are generated when a page needs to be
* WAL- logged because of a hint bit update. They are only generated
* when checksums are enabled. There is no difference in handling
* XLOG_FPI and XLOG_FPI_FOR_HINT records, they use a different info
* code just to distinguish them for statistics purposes.
*/
for (uint8 block_id = 0; block_id <= record->max_block_id; block_id++)
{
Buffer buffer;
if (!XLogRecHasBlockImage(record, block_id))
{
if (info == XLOG_FPI)
elog(ERROR, "XLOG_FPI record did not contain a full-page image");
continue;
}
if (XLogReadBufferForRedo(record, block_id, &buffer) != BLK_RESTORED)
elog(ERROR, "unexpected XLogReadBufferForRedo result when restoring backup block");
UnlockReleaseBuffer(buffer);

5
src/backend/access/transam/xloginsert.c
View File

@ -287,8 +287,6 @@ XLogRegisterBlock(uint8 block_id, RelFileNode *rnode, ForkNumber forknum,
{
registered_buffer *regbuf;
/* This is currently only used to WAL-log a full-page image of a page */
Assert(flags & REGBUF_FORCE_IMAGE);
Assert(begininsert_called);
if (block_id >= max_registered_block_id)
@ -995,7 +993,7 @@ XLogSaveBufferForHint(Buffer buffer, bool buffer_std)
if (lsn <= RedoRecPtr)
{
int flags;
int flags = 0;
PGAlignedBlock copied_buffer;
char *origdata = (char *) BufferGetBlock(buffer);
RelFileNode rnode;
@ -1022,7 +1020,6 @@ XLogSaveBufferForHint(Buffer buffer, bool buffer_std)
XLogBeginInsert();
flags = REGBUF_FORCE_IMAGE;
if (buffer_std)
flags |= REGBUF_STANDARD;