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Fix and improve cache invalidation logic for logical decoding.

Browse Source 
There are basically three situations in which logical decoding needs
to perform cache invalidation. During/After replaying a transaction
with catalog changes, when skipping a uninteresting transaction that
performed catalog changes and when erroring out while replaying a
transaction. Unfortunately these three cases were all done slightly
differently - partially because 8de3e410fa, which greatly simplifies
matters, got committed in the midst of the development of logical
decoding.

The actually problematic case was when logical decoding skipped
transaction commits (and thus processed invalidations). When used via
the SQL interface cache invalidation could access the catalog - bad,
because we didn't set up enough state to allow that correctly. It'd
not be hard to setup sufficient state, but the simpler solution is to
always perform cache invalidation outside a valid transaction.

Also make the different cache invalidation cases look as similar as
possible, to ease code review.

This fixes the assertion failure reported by Antonin Houska in
53EE02D9.7040702@gmail.com. The presented testcase has been expanded
into a regression test.

Backpatch to 9.4, where logical decoding was introduced.
This commit is contained in:
Andres Freund
2014-11-13 19:06:43 +01:00
parent 5a2c184058
commit 89fd41b390
4 changed files with 153 additions and 43 deletions
Download Patch File Download Diff File Expand all files Collapse all files

83
src/backend/replication/logical/reorderbuffer.c
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@ -1264,8 +1264,7 @@ ReorderBufferCommit(ReorderBuffer *rb, TransactionId xid,
volatile CommandId command_id = FirstCommandId;
volatile Snapshot snapshot_now = NULL;
volatile bool txn_started = false;
volatile bool subtxn_started = false;
volatile bool using_subtxn = false;
txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr,
false);
@ -1305,7 +1304,6 @@ ReorderBufferCommit(ReorderBuffer *rb, TransactionId xid,
PG_TRY();
{
txn_started = false;
/*
* Decoding needs access to syscaches et al., which in turn use
@ -1317,16 +1315,12 @@ ReorderBufferCommit(ReorderBuffer *rb, TransactionId xid,
* When we're called via the SQL SRF there's already a transaction
* started, so start an explicit subtransaction there.
*/
if (IsTransactionOrTransactionBlock())
{
using_subtxn = IsTransactionOrTransactionBlock();
if (using_subtxn)
BeginInternalSubTransaction("replay");
subtxn_started = true;
}
else
{
StartTransactionCommand();
txn_started = true;
}
rb->begin(rb, txn);
@ -1489,22 +1483,22 @@ ReorderBufferCommit(ReorderBuffer *rb, TransactionId xid,
elog(ERROR, "output plugin used XID %u",
GetCurrentTransactionId());
/* make sure there's no cache pollution */
ReorderBufferExecuteInvalidations(rb, txn);
/* cleanup */
TeardownHistoricSnapshot(false);
/*
* Abort subtransaction or the transaction as a whole has the right
* Aborting the current (sub-)transaction as a whole has the right
* semantics. We want all locks acquired in here to be released, not
* reassigned to the parent and we do not want any database access
* have persistent effects.
*/
if (subtxn_started)
AbortCurrentTransaction();
/* make sure there's no cache pollution */
ReorderBufferExecuteInvalidations(rb, txn);
if (using_subtxn)
RollbackAndReleaseCurrentSubTransaction();
else if (txn_started)
AbortCurrentTransaction();
if (snapshot_now->copied)
ReorderBufferFreeSnap(rb, snapshot_now);
@ -1520,20 +1514,21 @@ ReorderBufferCommit(ReorderBuffer *rb, TransactionId xid,
TeardownHistoricSnapshot(true);
/*
* Force cache invalidation to happen outside of a valid transaction
* to prevent catalog access as we just caught an error.
*/
AbortCurrentTransaction();
/* make sure there's no cache pollution */
ReorderBufferExecuteInvalidations(rb, txn);
if (using_subtxn)
RollbackAndReleaseCurrentSubTransaction();
if (snapshot_now->copied)
ReorderBufferFreeSnap(rb, snapshot_now);
if (subtxn_started)
RollbackAndReleaseCurrentSubTransaction();
else if (txn_started)
AbortCurrentTransaction();
/*
* Invalidations in an aborted transactions aren't allowed to do
* catalog access, so we don't need to still have the snapshot setup.
*/
ReorderBufferExecuteInvalidations(rb, txn);
/* remove potential on-disk data, and deallocate */
ReorderBufferCleanupTXN(rb, txn);
@ -1645,20 +1640,24 @@ ReorderBufferForget(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn)
*/
if (txn->base_snapshot != NULL && txn->ninvalidations > 0)
{
/* setup snapshot to perform the invalidations in */
SetupHistoricSnapshot(txn->base_snapshot, txn->tuplecid_hash);
PG_TRY();
{
ReorderBufferExecuteInvalidations(rb, txn);
TeardownHistoricSnapshot(false);
}
PG_CATCH();
{
/* cleanup */
TeardownHistoricSnapshot(true);
PG_RE_THROW();
}
PG_END_TRY();
bool use_subtxn = IsTransactionOrTransactionBlock();
if (use_subtxn)
BeginInternalSubTransaction("replay");
/*
* Force invalidations to happen outside of a valid transaction - that
* way entries will just be marked as invalid without accessing the
* catalog. That's advantageous because we don't need to setup the
* full state necessary for catalog access.
*/
if (use_subtxn)
AbortCurrentTransaction();
ReorderBufferExecuteInvalidations(rb, txn);
if (use_subtxn)
RollbackAndReleaseCurrentSubTransaction();
}
else
Assert(txn->ninvalidations == 0);