Add push-based channels and improve broker notifications

Change-Id: Ie3c7cae0f015d6bc01dd912499565bb12c15abc3
diff --git a/asterix-bad/src/test/resources/optimizerts/results/channel/channel-push.plan b/asterix-bad/src/test/resources/optimizerts/results/channel/channel-push.plan
new file mode 100644
index 0000000..770617f
--- /dev/null
+++ b/asterix-bad/src/test/resources/optimizerts/results/channel/channel-push.plan
@@ -0,0 +1,64 @@
+-- NOTIFY_BROKERS  |PARTITIONED|
+  -- STREAM_PROJECT  |PARTITIONED|
+    -- STREAM_PROJECT  |PARTITIONED|
+      -- ASSIGN  |PARTITIONED|
+        -- STREAM_PROJECT  |PARTITIONED|
+          -- STREAM_SELECT  |PARTITIONED|
+            -- STREAM_PROJECT  |PARTITIONED|
+              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                -- HYBRID_HASH_JOIN [$$128][$$135]  |PARTITIONED|
+                  -- HASH_PARTITION_EXCHANGE [$$128]  |PARTITIONED|
+                    -- STREAM_PROJECT  |PARTITIONED|
+                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                        -- HYBRID_HASH_JOIN [$$126, $$124][$$117, $$118]  |PARTITIONED|
+                          -- HASH_PARTITION_EXCHANGE [$$126, $$124]  |PARTITIONED|
+                            -- STREAM_PROJECT  |PARTITIONED|
+                              -- ASSIGN  |PARTITIONED|
+                                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                  -- DATASOURCE_SCAN  |PARTITIONED|
+                                    -- BROADCAST_EXCHANGE  |PARTITIONED|
+                                      -- ASSIGN  |UNPARTITIONED|
+                                        -- EMPTY_TUPLE_SOURCE  |UNPARTITIONED|
+                          -- HASH_PARTITION_EXCHANGE [$$117, $$118]  |PARTITIONED|
+                            -- STREAM_PROJECT  |PARTITIONED|
+                              -- ASSIGN  |PARTITIONED|
+                                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                  -- DATASOURCE_SCAN  |PARTITIONED|
+                                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                      -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                  -- HASH_PARTITION_EXCHANGE [$$135]  |PARTITIONED|
+                    -- NESTED_LOOP  |PARTITIONED|
+                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                        -- STREAM_SELECT  |PARTITIONED|
+                          -- ASSIGN  |PARTITIONED|
+                            -- STREAM_PROJECT  |PARTITIONED|
+                              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                -- DATASOURCE_SCAN  |PARTITIONED|
+                                  -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                    -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                      -- BROADCAST_EXCHANGE  |PARTITIONED|
+                        -- PRE_CLUSTERED_GROUP_BY[$$120]  |PARTITIONED|
+                                {
+                                  -- AGGREGATE  |LOCAL|
+                                    -- STREAM_SELECT  |LOCAL|
+                                      -- NESTED_TUPLE_SOURCE  |LOCAL|
+                                }
+                          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                            -- STABLE_SORT [$$120(ASC)]  |PARTITIONED|
+                              -- HASH_PARTITION_EXCHANGE [$$120]  |PARTITIONED|
+                                -- NESTED_LOOP  |PARTITIONED|
+                                  -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                    -- STREAM_PROJECT  |PARTITIONED|
+                                      -- ASSIGN  |PARTITIONED|
+                                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                          -- DATASOURCE_SCAN  |PARTITIONED|
+                                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                              -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                  -- BROADCAST_EXCHANGE  |PARTITIONED|
+                                    -- STREAM_PROJECT  |PARTITIONED|
+                                      -- ASSIGN  |PARTITIONED|
+                                        -- STREAM_PROJECT  |PARTITIONED|
+                                          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                            -- DATASOURCE_SCAN  |PARTITIONED|
+                                              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
\ No newline at end of file