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Minimize hot standby feedback xmins to next_xid.

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Hot standby feedback xmins can be greater than next_xid due to sparse update of
nextXid on pageserver (to do less writes it advances next xid on
1024). ProcessStandbyHSFeedback ignores such xids from the future; to fix,
minimize received xmin to next_xid.

Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
This commit is contained in:
Arseny Sher
2024-05-20 18:41:39 +03:00
committed by Arseny Sher
parent f2771a99b7
commit d43dcceef9
1 changed files with 17 additions and 4 deletions
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21
pgxn/neon/walproposer_pg.c
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@@ -1944,13 +1944,26 @@ walprop_pg_process_safekeeper_feedback(WalProposer *wp, Safekeeper *sk)
CombineHotStanbyFeedbacks(&hsFeedback, wp);
if (memcmp(&hsFeedback, &agg_hs_feedback, sizeof hsFeedback) != 0)
{
FullTransactionId xmin = hsFeedback.xmin;
FullTransactionId catalog_xmin = hsFeedback.catalog_xmin;
FullTransactionId next_xid = ReadNextFullTransactionId();
/*
* Page server is updating nextXid in checkpoint each 1024 transactions,
* so feedback xmin can be actually larger then nextXid and
* function TransactionIdInRecentPast return false in this case,
* preventing update of slot's xmin.
*/
if (FullTransactionIdPrecedes(next_xid, xmin))
xmin = next_xid;
if (FullTransactionIdPrecedes(next_xid, catalog_xmin))
catalog_xmin = next_xid;
agg_hs_feedback = hsFeedback;
elog(DEBUG2, "ProcessStandbyHSFeedback(xmin=%d, catalog_xmin=%d", XidFromFullTransactionId(hsFeedback.xmin), XidFromFullTransactionId(hsFeedback.catalog_xmin));
ProcessStandbyHSFeedback(hsFeedback.ts,
XidFromFullTransactionId(hsFeedback.xmin),
EpochFromFullTransactionId(hsFeedback.xmin),
XidFromFullTransactionId(hsFeedback.catalog_xmin),
EpochFromFullTransactionId(hsFeedback.catalog_xmin));
XidFromFullTransactionId(xmin),
EpochFromFullTransactionId(xmin),
XidFromFullTransactionId(catalog_xmin),
EpochFromFullTransactionId(catalog_xmin));
}
CheckGracefulShutdown(wp);