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Commit2776922

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Assert in init_toast_snapshot() that some snapshot registered or active.
Commit <FIXME> fixed the bug that RemoveTempRelationsCallback() did notpush/register a snapshot. That only went unnoticed because often a validcatalog snapshot exists and is returned by GetOldestSnapshot(). But due toinvalidation processing that is not reliable.Thus assert in init_toast_snapshot() that there is a registered or activesnapshot, using the new HaveRegisteredOrActiveSnapshot().Author: Andres FreundDiscussion:https://postgr.es/m/20220219180002.6tubjq7iw7m52bgd@alap3.anarazel.de
1 parent7c38ef2 commit2776922

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3 files changed

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‎src/backend/access/common/toast_internals.c

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@@ -660,5 +660,14 @@ init_toast_snapshot(Snapshot toast_snapshot)
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if (snapshot==NULL)
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elog(ERROR,"cannot fetch toast data without an active snapshot");
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/*
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* Catalog snapshots can be returned by GetOldestSnapshot() even if not
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* registered or active. That easily hides bugs around not having a
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* snapshot set up - most of the time there is a valid catalog
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* snapshot. So additionally insist that the current snapshot is
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* registered or active.
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*/
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Assert(HaveRegisteredOrActiveSnapshot());
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InitToastSnapshot(*toast_snapshot,snapshot->lsn,snapshot->whenTaken);
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}

‎src/backend/utils/time/snapmgr.c

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@@ -1625,6 +1625,32 @@ ThereAreNoPriorRegisteredSnapshots(void)
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return false;
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}
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/*
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* HaveRegisteredOrActiveSnapshots
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*Is there any registered or active snapshot?
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*
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* NB: Unless pushed or active, the cached catalog snapshot will not cause
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* this function to return true. That allows this function to be used in
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* checks enforcing a longer-lived snapshot.
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*/
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bool
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HaveRegisteredOrActiveSnapshot(void)
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{
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if (ActiveSnapshot!=NULL)
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return true;
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/*
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* The catalog snapshot is in RegisteredSnapshots when valid, but can be
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* removed at any time due to invalidation processing. If explicitly
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* registered more than one snapshot has to be in RegisteredSnapshots.
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*/
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if (pairingheap_is_empty(&RegisteredSnapshots)||
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!pairingheap_is_singular(&RegisteredSnapshots))
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return false;
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returnCatalogSnapshot==NULL;
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}
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/*
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* Return a timestamp that is exactly on a minute boundary.

‎src/include/utils/snapmgr.h

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@@ -135,6 +135,7 @@ extern bool XactHasExportedSnapshots(void);
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externvoidDeleteAllExportedSnapshotFiles(void);
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externvoidWaitForOlderSnapshots(TransactionIdlimitXmin,boolprogress);
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externboolThereAreNoPriorRegisteredSnapshots(void);
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externboolHaveRegisteredOrActiveSnapshot(void);
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externboolTransactionIdLimitedForOldSnapshots(TransactionIdrecentXmin,
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Relationrelation,
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TransactionId*limit_xid,

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