AsterixDB changes for fixing issue873.

For example, in the following query plan, the change lets the optimizer recognize that $12 and $20 are equivalent.
Therefore, HASH_PARTITION_EXCHANGE [$$12] can be replaced by ONE_TO_ONE_EXCHANGE.

-- COMMIT  |PARTITIONED|
  project ([$$12])
  -- STREAM_PROJECT  |PARTITIONED|
    exchange
    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
      delete from TinySocial:TweetMessages from %0->$$4 partitioned by [%0->$$12]
      -- INSERT_DELETE  |PARTITIONED|
        exchange
        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
          materialize
          -- MATERIALIZE  |PARTITIONED|
            exchange
            -- HASH_PARTITION_EXCHANGE [$$12]  |PARTITIONED|
              assign [$$12] <- [function-call: asterix:field-access-by-index, Args:[%0->$$4, AInt32: {0}]]
              -- ASSIGN  |PARTITIONED|
                project ([$$4])
                -- STREAM_PROJECT  |PARTITIONED|
                  assign [$$4] <- [function-call: asterix:open-record-constructor, Args:[AString: {tweetid}, %0->$$14, AString: {user}, function-call: asterix:field-access-by-index, Args:[%0->$$0, AInt32: {1}], AString: {sender-location}, function-call: asterix:field-access-by-index, Args:[%0->$$0, AInt32: {2}], AString: {send-time}, function-call: asterix:field-access-by-index, Args:[%0->$$0, AInt32: {3}], AString: {referred-topics}, function-call: asterix:field-access-by-index, Args:[%0->$$0, AInt32: {4}], AString: {message-text}, function-call: asterix:field-access-by-index, Args:[%0->$$0, AInt32: {5}]]]
                  -- ASSIGN  |PARTITIONED|
                    exchange
                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                      unnest-map [$$14, $$0] <- function-call: asterix:index-search, Args:[AString: {TweetMessages}, AInt32: {0}, AString: {TinySocial}, AString: {TweetMessages}, ABoolean: {false}, ABoolean: {false}, ABoolean: {false}, AInt32: {1}, %0->$$20, AInt32: {1}, %0->$$21, TRUE, TRUE, TRUE]
                      -- BTREE_SEARCH  |PARTITIONED|
                        exchange
                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                          assign [$$20, $$21] <- [AString: {15}, AString: {15}]
                          -- ASSIGN  |PARTITIONED|
                            empty-tuple-source
                            -- EMPTY_TUPLE_SOURCE  |PARTITIONED|

Change-Id: Ife8c378a62cdbbcd8c19b521de246162f1f3d6ec
Reviewed-on: https://asterix-gerrit.ics.uci.edu/267
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Wenhai Li <lwhaymail@yahoo.com>
Reviewed-by: Ildar Absalyamov <ildar.absalyamov@gmail.com>
diff --git a/asterix-app/src/test/resources/optimizerts/results/skip-index/dont-skip-primary-index-search-in-delete.plan b/asterix-app/src/test/resources/optimizerts/results/skip-index/dont-skip-primary-index-search-in-delete.plan
index 0a66ccb..e2e6dff 100644
--- a/asterix-app/src/test/resources/optimizerts/results/skip-index/dont-skip-primary-index-search-in-delete.plan
+++ b/asterix-app/src/test/resources/optimizerts/results/skip-index/dont-skip-primary-index-search-in-delete.plan
@@ -4,7 +4,7 @@
       -- INSERT_DELETE  |PARTITIONED|
         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
           -- MATERIALIZE  |PARTITIONED|
-            -- HASH_PARTITION_EXCHANGE [$$12]  |PARTITIONED|
+            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
               -- ASSIGN  |PARTITIONED|
                 -- STREAM_PROJECT  |PARTITIONED|
                   -- ASSIGN  |PARTITIONED|
diff --git a/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-ngram-index-search-in-delete.plan b/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-ngram-index-search-in-delete.plan
index 37c6587..c882d81 100644
--- a/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-ngram-index-search-in-delete.plan
+++ b/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-ngram-index-search-in-delete.plan
@@ -9,7 +9,7 @@
                 -- INSERT_DELETE  |PARTITIONED|
                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                     -- MATERIALIZE  |PARTITIONED|
-                      -- HASH_PARTITION_EXCHANGE [$$11]  |PARTITIONED|
+                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                         -- ASSIGN  |PARTITIONED|
                           -- STREAM_PROJECT  |PARTITIONED|
                             -- ASSIGN  |PARTITIONED|
diff --git a/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-rtree-index-search-in-delete.plan b/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-rtree-index-search-in-delete.plan
index cf609cb..b69dfa3 100644
--- a/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-rtree-index-search-in-delete.plan
+++ b/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-rtree-index-search-in-delete.plan
@@ -11,7 +11,7 @@
                     -- INSERT_DELETE  |PARTITIONED|
                       -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                         -- MATERIALIZE  |PARTITIONED|
-                          -- HASH_PARTITION_EXCHANGE [$$17]  |PARTITIONED|
+                          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                             -- ASSIGN  |PARTITIONED|
                               -- STREAM_PROJECT  |PARTITIONED|
                                 -- ASSIGN  |PARTITIONED|
diff --git a/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-secondary-btree-index-search-in-delete.plan b/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-secondary-btree-index-search-in-delete.plan
index 67ec849..c882d81 100644
--- a/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-secondary-btree-index-search-in-delete.plan
+++ b/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-secondary-btree-index-search-in-delete.plan
@@ -9,7 +9,7 @@
                 -- INSERT_DELETE  |PARTITIONED|
                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                     -- MATERIALIZE  |PARTITIONED|
-                      -- HASH_PARTITION_EXCHANGE [$$12]  |PARTITIONED|
+                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                         -- ASSIGN  |PARTITIONED|
                           -- STREAM_PROJECT  |PARTITIONED|
                             -- ASSIGN  |PARTITIONED|
diff --git a/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-word-index-search-in-delete.plan b/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-word-index-search-in-delete.plan
index c3b9264..c882d81 100644
--- a/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-word-index-search-in-delete.plan
+++ b/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-word-index-search-in-delete.plan
@@ -9,7 +9,7 @@
                 -- INSERT_DELETE  |PARTITIONED|
                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                     -- MATERIALIZE  |PARTITIONED|
-                      -- HASH_PARTITION_EXCHANGE [$$14]  |PARTITIONED|
+                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                         -- ASSIGN  |PARTITIONED|
                           -- STREAM_PROJECT  |PARTITIONED|
                             -- ASSIGN  |PARTITIONED|