Add STREAM_START/STREAM_STOP for transactional messages during decoding.

In test_decoding module, when skip_empty_xacts option was specified, add
stream_start/stop for streaming transactional messages. This makes the
handling of transactional messages stream consistent irrespective of
whether skip_empty_xacts option was specified.

Commit 26dd0284b9 made a similar change for non-streaming messages but
forgot to update the streaming cases.

Author: Peter Smith
Reviewed-by: Amit Kapila
Discussion: http://postgr.es/m/OS0PR01MB5716AEBD2988F8F5E9D5985794DFA@OS0PR01MB5716.jpnprd01.prod.outlook.com

contrib/test_decoding/expected/stream.out

@@ -29,7 +29,10 @@ COMMIT;
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
+ opening a streamed block for transaction
  streaming message: transactional: 1 prefix: test, sz: 50
+ closing a streamed block for transaction
+ aborting streamed (sub)transaction
  opening a streamed block for transaction
  streaming change for transaction
  streaming change for transaction
@@ -53,7 +56,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'incl
  streaming change for transaction
  closing a streamed block for transaction
  committing streamed transaction
-(24 rows)
+(27 rows)
 
 -- streaming test for toast changes
 ALTER TABLE stream_test ALTER COLUMN data set storage external;

contrib/test_decoding/expected/twophase_stream.out

@@ -31,7 +31,10 @@ PREPARE TRANSACTION 'test1';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
+ opening a streamed block for transaction
  streaming message: transactional: 1 prefix: test, sz: 50
+ closing a streamed block for transaction
+ aborting streamed (sub)transaction
  opening a streamed block for transaction
  streaming change for transaction
  streaming change for transaction
@@ -55,7 +58,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'incl
  streaming change for transaction
  closing a streamed block for transaction
  preparing streamed transaction 'test1'
-(24 rows)
+(27 rows)
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
@@ -84,8 +87,11 @@ PREPARE TRANSACTION 'test1_nodecode';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
+ opening a streamed block for transaction
  streaming message: transactional: 1 prefix: test, sz: 50
-(1 row)
+ closing a streamed block for transaction
+ aborting streamed (sub)transaction
+(4 rows)
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT

contrib/test_decoding/test_decoding.c

@@ -944,6 +944,19 @@ pg_decode_stream_message(LogicalDecodingContext *ctx,
 						 ReorderBufferTXN *txn, XLogRecPtr lsn, bool transactional,
 						 const char *prefix, Size sz, const char *message)
 {
+	/* Output stream start if we haven't yet for transactional messages. */
+	if (transactional)
+	{
+		TestDecodingData *data = ctx->output_plugin_private;
+		TestDecodingTxnData *txndata = txn->output_plugin_private;
+
+		if (data->skip_empty_xacts && !txndata->stream_wrote_changes)
+		{
+			pg_output_stream_start(ctx, data, txn, false);
+		}
+		txndata->xact_wrote_changes = txndata->stream_wrote_changes = true;
+	}
+
 	OutputPluginPrepareWrite(ctx, true);
 
 	if (transactional)