Don't refres on _flush _force_merge and _upgrade

Today all these API calls have a sideeffect of making documents visible
to search requests. While this is sometimes desired it's an unnecessary sideeffect
and now that we have an internal (engine-private) index reader (elastic#26972) we artificially
add a refresh call for bwc. This change removes this sideeffect in 7.0.

core/src/main/java/org/elasticsearch/index/shard/IndexShard.java

@@ -1005,7 +1005,6 @@ public Engine.CommitId flush(FlushRequest request) {
         }
         final long time = System.nanoTime();
         final Engine.CommitId commitId = engine.flush(force, waitIfOngoing);
-        engine.refresh("flush"); // TODO this is technically wrong we should remove this in 7.0
         flushMetric.inc(System.nanoTime() - time);
         return commitId;
     }
@@ -1036,9 +1035,6 @@ public void forceMerge(ForceMergeRequest forceMerge) throws IOException {
         Engine engine = getEngine();
         engine.forceMerge(forceMerge.flush(), forceMerge.maxNumSegments(),
             forceMerge.onlyExpungeDeletes(), false, false);
-        if (forceMerge.flush()) {
-            engine.refresh("force_merge"); // TODO this is technically wrong we should remove this in 7.0
-        }
     }
 
     /**
@@ -1055,8 +1051,6 @@ public org.apache.lucene.util.Version upgrade(UpgradeRequest upgrade) throws IOE
         engine.forceMerge(true,  // we need to flush at the end to make sure the upgrade is durable
             Integer.MAX_VALUE, // we just want to upgrade the segments, not actually optimize to a single segment
             false, true, upgrade.upgradeOnlyAncientSegments());
-        engine.refresh("upgrade"); // TODO this is technically wrong we should remove this in 7.0
-
         org.apache.lucene.util.Version version = minimumCompatibleVersion();
         if (logger.isTraceEnabled()) {
             logger.trace("upgraded segments for {} from version {} to version {}", shardId, previousVersion, version);

core/src/test/java/org/elasticsearch/action/admin/indices/segments/IndicesSegmentsRequestTests.java

@@ -55,6 +55,7 @@ public void setupIndex() {
             client().prepareIndex("test", "type1", id).setSource("text", "sometext").get();
         }
         client().admin().indices().prepareFlush("test").get();
+        client().admin().indices().prepareRefresh().get();
     }
 
     public void testBasic() {

core/src/test/java/org/elasticsearch/get/GetActionIT.java

@@ -131,16 +131,17 @@ public void testSimpleGet() {
         assertThat(response.getField("field1").getValues().get(0).toString(), equalTo("value1"));
         assertThat(response.getField("field2"), nullValue());
 
-        logger.info("--> flush the index, so we load it from it");
-        flush();
 
-        logger.info("--> realtime get 1 (loaded from index)");
+        logger.info("--> realtime get 1");
         response = client().prepareGet(indexOrAlias(), "type1", "1").get();
         assertThat(response.isExists(), equalTo(true));
         assertThat(response.getIndex(), equalTo("test"));
         assertThat(response.getSourceAsMap().get("field1").toString(), equalTo("value1"));
         assertThat(response.getSourceAsMap().get("field2").toString(), equalTo("value2"));
 
+        logger.info("--> refresh the index, so we load it from it");
+        refresh();
+
         logger.info("--> non realtime get 1 (loaded from index)");
         response = client().prepareGet(indexOrAlias(), "type1", "1").setRealtime(false).get();
         assertThat(response.isExists(), equalTo(true));

core/src/test/java/org/elasticsearch/indices/stats/IndexStatsIT.java

@@ -573,6 +573,7 @@ public void testSegmentsStats() {
 
         client().admin().indices().prepareFlush().get();
         client().admin().indices().prepareForceMerge().setMaxNumSegments(1).execute().actionGet();
+        client().admin().indices().prepareRefresh().get();
         stats = client().admin().indices().prepareStats().setSegments(true).get();
 
         assertThat(stats.getTotal().getSegments(), notNullValue());

core/src/test/java/org/elasticsearch/search/nested/SimpleNestedIT.java

@@ -83,12 +83,10 @@ public void testSimpleNested() throws Exception {
                 .endObject()).execute().actionGet();
 
         waitForRelocation(ClusterHealthStatus.GREEN);
-        // flush, so we fetch it from the index (as see that we filter nested docs)
-        flush();
         GetResponse getResponse = client().prepareGet("test", "type1", "1").get();
         assertThat(getResponse.isExists(), equalTo(true));
         assertThat(getResponse.getSourceAsBytes(), notNullValue());
-
+        refresh();
         // check the numDocs
         assertDocumentCount("test", 3);
 
@@ -126,8 +124,7 @@ public void testSimpleNested() throws Exception {
                 .endArray()
                 .endObject()).execute().actionGet();
         waitForRelocation(ClusterHealthStatus.GREEN);
-        // flush, so we fetch it from the index (as see that we filter nested docs)
-        flush();
+        refresh();
         assertDocumentCount("test", 6);
 
         searchResponse = client().prepareSearch("test").setQuery(nestedQuery("nested1",
@@ -151,8 +148,7 @@ public void testSimpleNested() throws Exception {
         DeleteResponse deleteResponse = client().prepareDelete("test", "type1", "2").execute().actionGet();
         assertEquals(DocWriteResponse.Result.DELETED, deleteResponse.getResult());
 
-        // flush, so we fetch it from the index (as see that we filter nested docs)
-        flush();
+        refresh();
         assertDocumentCount("test", 3);
 
         searchResponse = client().prepareSearch("test").setQuery(nestedQuery("nested1", termQuery("nested1.n_field1", "n_value1_1"), ScoreMode.Avg)).execute().actionGet();
@@ -179,11 +175,10 @@ public void testMultiNested() throws Exception {
                 .endArray()
                 .endObject()).execute().actionGet();
 
-        // flush, so we fetch it from the index (as see that we filter nested docs)
-        flush();
         GetResponse getResponse = client().prepareGet("test", "type1", "1").execute().actionGet();
         assertThat(getResponse.isExists(), equalTo(true));
         waitForRelocation(ClusterHealthStatus.GREEN);
+        refresh();
         // check the numDocs
         assertDocumentCount("test", 7);