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Protect against torn pages when deleting GIN list pages.

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To-be-deleted list pages contain no useful information, as they are being
deleted, but we must still protect the writes from being torn by a crash
after 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.
This commit is contained in:
Heikki Linnakangas 2014-05-08 14:43:04 +03:00
parent 02c9a93805
commit 4f7bb4b2a3
1 changed files with 13 additions and 13 deletions
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26
src/backend/access/gin/ginxlog.c
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@ -884,25 +884,25 @@ ginRedoDeleteListPages(XLogRecPtr lsn, XLogRecord *record)
* cannot get past a reader that is on, or due to visit, any page we are * cannot get past a reader that is on, or due to visit, any page we are
* going to delete. New incoming readers will block behind our metapage * going to delete. New incoming readers will block behind our metapage
* lock and then see a fully updated page list. * lock and then see a fully updated page list.
*
* No full-page images are taken of the deleted pages. Instead, they are
* re-initialized as empty, deleted pages. Their right-links don't need to
* be preserved, because no new readers can see the pages, as explained
* above.
*/ */
for (i = 0; i < data->ndeleted; i++) for (i = 0; i < data->ndeleted; i++)
{ {
Buffer buffer = XLogReadBuffer(data->node, data->toDelete[i], false); Buffer buffer;
Page page;
if (BufferIsValid(buffer)) buffer = XLogReadBuffer(data->node, data->toDelete[i], true);
{ page = BufferGetPage(buffer);
Page page = BufferGetPage(buffer); GinInitBuffer(buffer, GIN_DELETED);
if (lsn > PageGetLSN(page)) PageSetLSN(page, lsn);
{ MarkBufferDirty(buffer);
GinPageGetOpaque(page)->flags = GIN_DELETED;
PageSetLSN(page, lsn); UnlockReleaseBuffer(buffer);
MarkBufferDirty(buffer);
}
UnlockReleaseBuffer(buffer);
}
} }
UnlockReleaseBuffer(metabuffer); UnlockReleaseBuffer(metabuffer);
} }