diff options
Diffstat (limited to 'src/backend/commands/copy.c')
| -rw-r--r-- | src/backend/commands/copy.c | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c index feab7aa6e2a..ca72dd161c1 100644 --- a/src/backend/commands/copy.c +++ b/src/backend/commands/copy.c @@ -2353,13 +2353,25 @@ CopyFrom(CopyState cstate) /* * Optimize if new relfilenode was created in this subxact or one of its * committed children and we won't see those rows later as part of an - * earlier scan or command. This ensures that if this subtransaction - * aborts then the frozen rows won't be visible after xact cleanup. Note + * earlier scan or command. The subxact test ensures that if this subxact + * aborts then the frozen rows won't be visible after xact cleanup. Note * that the stronger test of exactly which subtransaction created it is - * crucial for correctness of this optimisation. + * crucial for correctness of this optimisation. The test for an earlier + * scan or command tolerates false negatives. FREEZE causes other sessions + * to see rows they would not see under MVCC, and a false negative merely + * spreads that anomaly to the current session. */ if (cstate->freeze) { + /* + * Tolerate one registration for the benefit of FirstXactSnapshot. + * Scan-bearing queries generally create at least two registrations, + * though relying on that is fragile, as is ignoring ActiveSnapshot. + * Clear CatalogSnapshot to avoid counting its registration. We'll + * still detect ongoing catalog scans, each of which separately + * registers the snapshot it uses. + */ + InvalidateCatalogSnapshot(); if (!ThereAreNoPriorRegisteredSnapshots() || !ThereAreNoReadyPortals()) ereport(ERROR, (errcode(ERRCODE_INVALID_TRANSACTION_STATE), |