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Use full 64-bit XID for checking if a deleted GiST page is old enough.

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Otherwise, after a deleted page gets even older, it becomes unrecyclable
again. B-tree has the same problem, and has had since time immemorial,
but let's at least fix this in GiST, where this is new.

Backpatch to v12, where GiST page deletion was introduced.

Reviewed-by: Andrey Borodin
Discussion: https://www.postgresql.org/message-id/835A15A5-F1B4-4446-A711-BF48357EB602%40yandex-team.ru
This commit is contained in:
Heikki Linnakangas
2019-07-24 20:24:07 +03:00
parent 9eb5607e69
commit 6655a7299d
9 changed files with 134 additions and 28 deletions
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32
src/backend/access/gist/gistxlog.c
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@ -356,8 +356,7 @@ gistRedoPageDelete(XLogReaderState *record)
{
Page page = (Page) BufferGetPage(leafBuffer);
GistPageSetDeleteXid(page, xldata->deleteXid);
GistPageSetDeleted(page);
GistPageSetDeleted(page, xldata->deleteXid);
PageSetLSN(page, lsn);
MarkBufferDirty(leafBuffer);
@ -396,8 +395,27 @@ gistRedoPageReuse(XLogReaderState *record)
*/
if (InHotStandby)
{
ResolveRecoveryConflictWithSnapshot(xlrec->latestRemovedXid,
xlrec->node);
FullTransactionId latestRemovedFullXid = xlrec->latestRemovedFullXid;
FullTransactionId nextFullXid = ReadNextFullTransactionId();
uint64 diff;
/*
* ResolveRecoveryConflictWithSnapshot operates on 32-bit
* TransactionIds, so truncate the logged FullTransactionId. If the
* logged value is very old, so that XID wrap-around already happened
* on it, there can't be any snapshots that still see it.
*/
nextFullXid = ReadNextFullTransactionId();
diff = U64FromFullTransactionId(nextFullXid) -
U64FromFullTransactionId(latestRemovedFullXid);
if (diff < MaxTransactionId / 2)
{
TransactionId latestRemovedXid;
latestRemovedXid = XidFromFullTransactionId(latestRemovedFullXid);
ResolveRecoveryConflictWithSnapshot(latestRemovedXid,
xlrec->node);
}
}
}
@ -554,7 +572,7 @@ gistXLogSplit(bool page_is_leaf,
* downlink from the parent page.
*/
XLogRecPtr
gistXLogPageDelete(Buffer buffer, TransactionId xid,
gistXLogPageDelete(Buffer buffer, FullTransactionId xid,
Buffer parentBuffer, OffsetNumber downlinkOffset)
{
gistxlogPageDelete xlrec;
@ -578,7 +596,7 @@ gistXLogPageDelete(Buffer buffer, TransactionId xid,
* Write XLOG record about reuse of a deleted page.
*/
void
gistXLogPageReuse(Relation rel, BlockNumber blkno, TransactionId latestRemovedXid)
gistXLogPageReuse(Relation rel, BlockNumber blkno, FullTransactionId latestRemovedXid)
{
gistxlogPageReuse xlrec_reuse;
@ -591,7 +609,7 @@ gistXLogPageReuse(Relation rel, BlockNumber blkno, TransactionId latestRemovedXi
/* XLOG stuff */
xlrec_reuse.node = rel->rd_node;
xlrec_reuse.block = blkno;
xlrec_reuse.latestRemovedXid = latestRemovedXid;
xlrec_reuse.latestRemovedFullXid = latestRemovedXid;
XLogBeginInsert();
XLogRegisterData((char *) &xlrec_reuse, SizeOfGistxlogPageReuse);