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Don't propagate a null subtransaction snapshot up to parent transaction.

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This oversight could cause logical decoding to fail to decode an outer
transaction containing changes, if a subtransaction had an XID but no
actual changes.  Per bug #14279 from Marko Tiikkaja.  Patch by Marko
based on analysis by Andrew Gierth.

Discussion: <20160804191757.1430.39011@wrigleys.postgresql.org>
This commit is contained in:
Tom Lane
2016-08-07 13:15:55 -04:00
parent 3676631c68
commit bcbecbce2f
3 changed files with 40 additions and 6 deletions
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9
src/backend/replication/logical/reorderbuffer.c
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@ -807,13 +807,14 @@ ReorderBufferCommitChild(ReorderBuffer *rb, TransactionId xid,
elog(ERROR, "subxact logged without previous toplevel record");
/*
* Pass the our base snapshot to the parent transaction if it doesn't have
* Pass our base snapshot to the parent transaction if it doesn't have
* one, or ours is older. That can happen if there are no changes in the
* toplevel transaction but in one of the child transactions. This allows
* the parent to simply use it's base snapshot initially.
* the parent to simply use its base snapshot initially.
*/
if (txn->base_snapshot == NULL ||
txn->base_snapshot_lsn > subtxn->base_snapshot_lsn)
if (subtxn->base_snapshot != NULL &&
(txn->base_snapshot == NULL ||
txn->base_snapshot_lsn > subtxn->base_snapshot_lsn))
{
txn->base_snapshot = subtxn->base_snapshot;
txn->base_snapshot_lsn = subtxn->base_snapshot_lsn;