Don't do logical replication of TRUNCATE of zero tables

When due to publication configuration, a TRUNCATE change ends up with
zero tables to be published, don't send the message out, just skip it.
It's not wrong, but obviously useless overhead.

diff --git a/src/backend/replication/pgoutput/pgoutput.c b/src/backend/replication/pgoutput/pgoutput.c
index a3e5300679f896adb05e5d518a84d6ee675c6c80..86e0951a700e1c3737c6098cc5bc5e143505db4d 100644 (file)
--- a/src/backend/replication/pgoutput/pgoutput.c
+++ b/src/backend/replication/pgoutput/pgoutput.c
@@ -407,13 +407,16 @@ pgoutput_truncate(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
                maybe_send_schema(ctx, relation, relentry);
        }
 
-       OutputPluginPrepareWrite(ctx, true);
-       logicalrep_write_truncate(ctx->out,
-                                                         nrelids,
-                                                         relids,
-                                                         change->data.truncate.cascade,
-                                                         change->data.truncate.restart_seqs);
-       OutputPluginWrite(ctx, true);
+       if (nrelids > 0)
+       {
+               OutputPluginPrepareWrite(ctx, true);
+               logicalrep_write_truncate(ctx->out,
+                                                                 nrelids,
+                                                                 relids,
+                                                                 change->data.truncate.cascade,
+                                                                 change->data.truncate.restart_seqs);
+               OutputPluginWrite(ctx, true);
+       }
 
        MemoryContextSwitchTo(old);
        MemoryContextReset(data->context);