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Commit686a719

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Protect against torn pages when deleting GIN list pages.
To-be-deleted list pages contain no useful information, as they are beingdeleted, but we must still protect the writes from being torn by a crashafter a partial write. To do that, re-initialize the pages on WAL replay.Jeff Janes caught this with a test program to test partial writes.Backpatch to all supported versions.
1 parent5c5bfc0 commit686a719

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‎src/backend/access/gin/ginxlog.c

Lines changed: 14 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -699,26 +699,26 @@ ginRedoDeleteListPages(XLogRecPtr lsn, XLogRecord *record)
699699
* cannot get past a reader that is on, or due to visit, any page we are
700700
* going to delete. New incoming readers will block behind our metapage
701701
* lock and then see a fully updated page list.
702+
*
703+
* No full-page images are taken of the deleted pages. Instead, they are
704+
* re-initialized as empty, deleted pages. Their right-links don't need to
705+
* be preserved, because no new readers can see the pages, as explained
706+
* above.
702707
*/
703708
for (i=0;i<data->ndeleted;i++)
704709
{
705-
Bufferbuffer=XLogReadBuffer(data->node,data->toDelete[i], false);
710+
Bufferbuffer;
711+
Pagepage;
706712

707-
if (BufferIsValid(buffer))
708-
{
709-
Pagepage=BufferGetPage(buffer);
710-
711-
if (!XLByteLE(lsn,PageGetLSN(page)))
712-
{
713-
GinPageGetOpaque(page)->flags=GIN_DELETED;
713+
buffer=XLogReadBuffer(data->node,data->toDelete[i], true);
714+
page=BufferGetPage(buffer);
715+
GinInitBuffer(buffer,GIN_DELETED);
714716

715-
PageSetLSN(page,lsn);
716-
PageSetTLI(page,ThisTimeLineID);
717-
MarkBufferDirty(buffer);
718-
}
717+
PageSetLSN(page,lsn);
718+
PageSetTLI(page,ThisTimeLineID);
719+
MarkBufferDirty(buffer);
719720

720-
UnlockReleaseBuffer(buffer);
721-
}
721+
UnlockReleaseBuffer(buffer);
722722
}
723723
UnlockReleaseBuffer(metabuffer);
724724
}

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