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Rearrange logrep worker's snapshot handling some more.

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It turns out that worker.c's code path for TRUNCATE was also
careless about establishing a snapshot while executing user-defined
code, allowing the checks added by commit 84f5c2908 to fail when
a trigger is fired in that context.

We could just wrap Push/PopActiveSnapshot around the truncate call,
but it seems better to establish a policy of holding a snapshot
throughout execution of a replication step.  To help with that and
possible future requirements, replace the previous ensure_transaction
calls with pairs of begin/end_replication_step calls.

Per report from Mark Dilger.  Back-patch to v11, like the previous
changes.

Discussion: https://postgr.es/m/B4A3AF82-79ED-4F4C-A4E5-CD2622098972@enterprisedb.com
This commit is contained in:
Tom Lane 2021-06-10 12:27:27 -04:00
parent bb4aed46a5
commit 3a09d75b4f
1 changed files with 48 additions and 37 deletions
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85
src/backend/replication/logical/worker.c
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@ -282,30 +282,41 @@ should_apply_changes_for_rel(LogicalRepRelMapEntry *rel)
}
/*
* Make sure that we started local transaction.
* Begin one step (one INSERT, UPDATE, etc) of a replication transaction.
*
* Also switches to ApplyMessageContext as necessary.
* Start a transaction, if this is the first step (else we keep using the
* existing transaction).
* Also provide a global snapshot and ensure we run in ApplyMessageContext.
*/
static bool
ensure_transaction(void)
static void
begin_replication_step(void)
{
if (IsTransactionState())
SetCurrentStatementStartTimestamp();
if (!IsTransactionState())
{
SetCurrentStatementStartTimestamp();
if (CurrentMemoryContext != ApplyMessageContext)
MemoryContextSwitchTo(ApplyMessageContext);
return false;
StartTransactionCommand();
maybe_reread_subscription();
}
SetCurrentStatementStartTimestamp();
StartTransactionCommand();
maybe_reread_subscription();
PushActiveSnapshot(GetTransactionSnapshot());
MemoryContextSwitchTo(ApplyMessageContext);
return true;
}
/*
* Finish up one step of a replication transaction.
* Callers of begin_replication_step() must also call this.
*
* We don't close out the transaction here, but we should increment
* the command counter to make the effects of this step visible.
*/
static void
end_replication_step(void)
{
PopActiveSnapshot();
CommandCounterIncrement();
}
/*
@ -359,13 +370,6 @@ create_edata_for_relation(LogicalRepRelMapEntry *rel)
RangeTblEntry *rte;
ResultRelInfo *resultRelInfo;
/*
* Input functions may need an active snapshot, as may AFTER triggers
* invoked during finish_edata. For safety, ensure an active snapshot
* exists throughout all our usage of the executor.
*/
PushActiveSnapshot(GetTransactionSnapshot());
edata = (ApplyExecutionData *) palloc0(sizeof(ApplyExecutionData));
edata->targetRel = rel;
@ -433,8 +437,6 @@ finish_edata(ApplyExecutionData *edata)
ExecResetTupleTable(estate->es_tupleTable, false);
FreeExecutorState(estate);
pfree(edata);
PopActiveSnapshot();
}
/*
@ -831,7 +833,7 @@ apply_handle_stream_start(StringInfo s)
* transaction for handling the buffile, used for serializing the
* streaming data and subxact info.
*/
ensure_transaction();
begin_replication_step();
/* notify handle methods we're processing a remote transaction */
in_streamed_transaction = true;
@ -861,6 +863,8 @@ apply_handle_stream_start(StringInfo s)
subxact_info_read(MyLogicalRepWorker->subid, stream_xid);
pgstat_report_activity(STATE_RUNNING, NULL);
end_replication_step();
}
/*
@ -937,7 +941,7 @@ apply_handle_stream_abort(StringInfo s)
StreamXidHash *ent;
subidx = -1;
ensure_transaction();
begin_replication_step();
subxact_info_read(MyLogicalRepWorker->subid, xid);
for (i = subxact_data.nsubxacts; i > 0; i--)
@ -958,7 +962,7 @@ apply_handle_stream_abort(StringInfo s)
{
/* Cleanup the subxact info */
cleanup_subxact_info();
end_replication_step();
CommitTransactionCommand();
return;
}
@ -986,6 +990,7 @@ apply_handle_stream_abort(StringInfo s)
/* write the updated subxact list */
subxact_info_write(MyLogicalRepWorker->subid, xid);
end_replication_step();
CommitTransactionCommand();
}
}
@ -1013,7 +1018,8 @@ apply_handle_stream_commit(StringInfo s)
elog(DEBUG1, "received commit for streamed transaction %u", xid);
ensure_transaction();
/* Make sure we have an open transaction */
begin_replication_step();
/*
* Allocate file handle and memory required to process all the messages in
@ -1046,6 +1052,8 @@ apply_handle_stream_commit(StringInfo s)
in_remote_transaction = true;
pgstat_report_activity(STATE_RUNNING, NULL);
end_replication_step();
/*
* Read the entries one by one and pass them through the same logic as in
* apply_dispatch.
@ -1227,7 +1235,7 @@ apply_handle_insert(StringInfo s)
if (handle_streamed_transaction(LOGICAL_REP_MSG_INSERT, s))
return;
ensure_transaction();
begin_replication_step();
relid = logicalrep_read_insert(s, &newtup);
rel = logicalrep_rel_open(relid, RowExclusiveLock);
@ -1238,6 +1246,7 @@ apply_handle_insert(StringInfo s)
* transaction so it's safe to unlock it.
*/
logicalrep_rel_close(rel, RowExclusiveLock);
end_replication_step();
return;
}
@ -1266,7 +1275,7 @@ apply_handle_insert(StringInfo s)
logicalrep_rel_close(rel, NoLock);
CommandCounterIncrement();
end_replication_step();
}
/*
@ -1346,7 +1355,7 @@ apply_handle_update(StringInfo s)
if (handle_streamed_transaction(LOGICAL_REP_MSG_UPDATE, s))
return;
ensure_transaction();
begin_replication_step();
relid = logicalrep_read_update(s, &has_oldtup, &oldtup,
&newtup);
@ -1358,6 +1367,7 @@ apply_handle_update(StringInfo s)
* transaction so it's safe to unlock it.
*/
logicalrep_rel_close(rel, RowExclusiveLock);
end_replication_step();
return;
}
@ -1416,7 +1426,7 @@ apply_handle_update(StringInfo s)
logicalrep_rel_close(rel, NoLock);
CommandCounterIncrement();
end_replication_step();
}
/*
@ -1501,7 +1511,7 @@ apply_handle_delete(StringInfo s)
if (handle_streamed_transaction(LOGICAL_REP_MSG_DELETE, s))
return;
ensure_transaction();
begin_replication_step();
relid = logicalrep_read_delete(s, &oldtup);
rel = logicalrep_rel_open(relid, RowExclusiveLock);
@ -1512,6 +1522,7 @@ apply_handle_delete(StringInfo s)
* transaction so it's safe to unlock it.
*/
logicalrep_rel_close(rel, RowExclusiveLock);
end_replication_step();
return;
}
@ -1542,7 +1553,7 @@ apply_handle_delete(StringInfo s)
logicalrep_rel_close(rel, NoLock);
CommandCounterIncrement();
end_replication_step();
}
/*
@ -1867,7 +1878,7 @@ apply_handle_truncate(StringInfo s)
if (handle_streamed_transaction(LOGICAL_REP_MSG_TRUNCATE, s))
return;
ensure_transaction();
begin_replication_step();
remote_relids = logicalrep_read_truncate(s, &cascade, &restart_seqs);
@ -1958,7 +1969,7 @@ apply_handle_truncate(StringInfo s)
table_close(rel, NoLock);
}
CommandCounterIncrement();
end_replication_step();
}