> On 20 Aug 2016, at 15:59, Craig Ringer <cr...@2ndquadrant.com> wrote:
> 
> I'll wait for a test case or some more detail.

Thanks for clarification about how restart_lsn is working.

Digging slightly deeper into this topic revealed that problem was in two phase 
decoding, not it logical decoding itself.
While I was writing DecodePrepare() I've and copied call to 
SnapBuildCommitTxn() function from DecodeCommit()
which was removing current transaction from running list and that’s obviously 
wrong thing to do for a prepared tx.

So I end up with following workaround:

--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -950,7 +950,7 @@ SnapBuildAbortTxn(SnapBuild *builder, XLogRecPtr lsn,
  */
 void
 SnapBuildCommitTxn(SnapBuild *builder, XLogRecPtr lsn, TransactionId xid,
-                                  int nsubxacts, TransactionId *subxacts)
+                                  int nsubxacts, TransactionId *subxacts, bool 
isCommit)
 {
        int                     nxact;
 
@@ -1026,7 +1026,8 @@ SnapBuildCommitTxn(SnapBuild *builder, XLogRecPtr lsn, 
TransactionId xid,
         * Make sure toplevel txn is not tracked in running txn's anymore, 
switch
         * state to consistent if possible.
         */
-       SnapBuildEndTxn(builder, lsn, xid);
+       if (isCommit)
+               SnapBuildEndTxn(builder, lsn, xid);


Calling SnapBuildCommitTxn with isCommit=true from commit and false from 
Prepare. However while I’m not
observing partially decoded transactions anymore, I’m not sure that this is 
right way to build proper snapshot and
something else isn’t broken.

Also while I was playing psycopg2 logical decoding client I do see empty 
transaction containing only
BEGIN/COMMIT (with test_decoding output plugin, and current postgres master).


-- 
Stas Kelvich
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company



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