Merge branch '6.x' into ccr-6.x

* 6.x:
  Refactor internal engine
  [Docs] Fix note in bucket_selector
  Added release notes for 6.0.0-rc2
  [Docs] Fix indentation of examples (#27168)
  [Docs] Clarify `span_not` query behavior for non-overlapping matches (#27150)
  [Docs] Remove first person "I" from getting started (#27155)

Author: jasontedor

core/src/main/java/org/elasticsearch/index/engine/Engine.java

@@ -572,7 +572,11 @@ public CommitStats commitStats() {
         return new CommitStats(getLastCommittedSegmentInfos());
     }
 
-    /** get the sequence number service */
+    /**
+     * The sequence number service for this engine.
+     *
+     * @return the sequence number service
+     */
     public abstract SequenceNumbersService seqNoService();
 
     /**

core/src/main/java/org/elasticsearch/index/engine/InternalEngine.java

@@ -66,7 +66,7 @@ public SequenceNumbersService(
      *
      * @return the next assigned sequence number
      */
-    public long generateSeqNo() {
+    public final long generateSeqNo() {
         return localCheckpointTracker.generateSeqNo();
     }
 

core/src/main/java/org/elasticsearch/index/seqno/SequenceNumbersService.java

@@ -316,7 +316,7 @@ public long addDocument(Iterable<? extends IndexableField> doc) throws IOExcepti
                             assert documentFailureMessage != null;
                             throw new IOException(documentFailureMessage);
                         }
-                    }, null, config);
+                    }, null, null, config);
         }
     }
 

core/src/test/java/org/elasticsearch/index/engine/InternalEngineTests.java

@@ -638,6 +638,7 @@ public long addDocument(final Iterable<? extends IndexableField> doc) throws IOE
                                 }
                             },
                     null,
+                    null,
                     config);
         }
 

core/src/test/java/org/elasticsearch/index/replication/IndexLevelReplicationTests.java

@@ -6,7 +6,7 @@ in the parent multi-bucket aggregation. The specified metric must be numeric and
 If the script language is `expression` then a numeric return value is permitted. In this case 0.0 will be evaluated as `false`
 and all other values will evaluate to true.
 
-Note: The bucket_selector aggregation, like all pipeline aggregations, executions after all other sibling aggregations. This means that
+NOTE: The bucket_selector aggregation, like all pipeline aggregations, executions after all other sibling aggregations. This means that
 using the bucket_selector aggregation to filter the returned buckets in the response does not save on execution time running the aggregations.
 
 ==== Syntax

core/src/test/java/org/elasticsearch/index/replication/RecoveryDuringReplicationTests.java

@@ -13,7 +13,7 @@ Here are a few sample use-cases that Elasticsearch could be used for:
 * You run a price alerting platform which allows price-savvy customers to specify a rule like "I am interested in buying a specific electronic gadget and I want to be notified if the price of gadget falls below $X from any vendor within the next month". In this case you can scrape vendor prices, push them into Elasticsearch and use its reverse-search (Percolator) capability to match price movements against customer queries and eventually push the alerts out to the customer once matches are found.
 * You have analytics/business-intelligence needs and want to quickly investigate, analyze, visualize, and ask ad-hoc questions on a lot of data (think millions or billions of records). In this case, you can use Elasticsearch to store your data and then use Kibana (part of the Elasticsearch/Logstash/Kibana stack) to build custom dashboards that can visualize aspects of your data that are important to you. Additionally, you can use the Elasticsearch aggregations functionality to perform complex business intelligence queries against your data.
 
-For the rest of this tutorial, I will guide you through the process of getting Elasticsearch up and running, taking a peek inside it, and performing basic operations like indexing, searching, and modifying your data. At the end of this tutorial, you should have a good idea of what Elasticsearch is, how it works, and hopefully be inspired to see how you can use it to either build sophisticated search applications or to mine intelligence from your data.
+For the rest of this tutorial, you will be guided through the process of getting Elasticsearch up and running, taking a peek inside it, and performing basic operations like indexing, searching, and modifying your data. At the end of this tutorial, you should have a good idea of what Elasticsearch is, how it works, and hopefully be inspired to see how you can use it to either build sophisticated search applications or to mine intelligence from your data.
 --
 
 == Basic Concepts
@@ -660,7 +660,7 @@ Now that we've gotten a glimpse of the basics, let's try to work on a more reali
 --------------------------------------------------
 // NOTCONSOLE
 
-For the curious, I generated this data from http://www.json-generator.com/[`www.json-generator.com/`] so please ignore the actual values and semantics of the data as these are all randomly generated.
+For the curious, this data was generated using http://www.json-generator.com/[`www.json-generator.com/`], so please ignore the actual values and semantics of the data as these are all randomly generated.
 
 [float]
 === Loading the Sample Dataset
@@ -1284,4 +1284,4 @@ There are many other aggregations capabilities that we won't go into detail here
 
 == Conclusion
 
-Elasticsearch is both a simple and complex product. We've so far learned the basics of what it is, how to look inside of it, and how to work with it using some of the REST APIs. I hope that this tutorial has given you a better understanding of what Elasticsearch is and more importantly, inspired you to further experiment with the rest of its great features!
+Elasticsearch is both a simple and complex product. We've so far learned the basics of what it is, how to look inside of it, and how to work with it using some of the REST APIs. Hopefully this tutorial has given you a better understanding of what Elasticsearch is and more importantly, inspired you to further experiment with the rest of its great features!

docs/reference/aggregations/pipeline/bucket-selector-aggregation.asciidoc

@@ -76,7 +76,7 @@ GET /_search
         "common": {
             "body": {
                 "query": "this is bonsai cool",
-                    "cutoff_frequency": 0.001
+                "cutoff_frequency": 0.001
             }
         }
     }
@@ -100,8 +100,8 @@ GET /_search
         "common": {
             "body": {
                 "query": "nelly the elephant as a cartoon",
-                    "cutoff_frequency": 0.001,
-                    "low_freq_operator": "and"
+                "cutoff_frequency": 0.001,
+                "low_freq_operator": "and"
             }
         }
     }
@@ -200,11 +200,11 @@ GET /_search
         "common": {
             "body": {
                 "query": "nelly the elephant not as a cartoon",
-                    "cutoff_frequency": 0.001,
-                    "minimum_should_match": {
-                        "low_freq" : 2,
-                        "high_freq" : 3
-                    }
+                "cutoff_frequency": 0.001,
+                "minimum_should_match": {
+                    "low_freq" : 2,
+                    "high_freq" : 3
+                }
             }
         }
     }
@@ -261,11 +261,11 @@ GET /_search
         "common": {
             "body": {
                 "query": "how not to be",
-                    "cutoff_frequency": 0.001,
-                    "minimum_should_match": {
-                        "low_freq" : 2,
-                        "high_freq" : 3
-                    }
+                "cutoff_frequency": 0.001,
+                "minimum_should_match": {
+                    "low_freq" : 2,
+                    "high_freq" : 3
+                }
             }
         }
     }

docs/reference/getting-started.asciidoc

@@ -1,7 +1,9 @@
 [[query-dsl-span-not-query]]
 === Span Not Query
 
-Removes matches which overlap with another span query. The span not
+Removes matches which overlap with another span query or which are
+within x tokens before (controlled by the parameter `pre`) or y tokens
+after (controled by the parameter `post`) another SpanQuery. The span not
 query maps to Lucene `SpanNotQuery`. Here is an example:
 
 [source,js]
@@ -39,7 +41,7 @@ In the above example all documents with the term hoya are filtered except the on
 Other top level options:
 
 [horizontal]
-`pre`::     If set the amount of tokens before the include span can't have overlap with the exclude span.
-`post`::    If set the amount of tokens after the include span can't have overlap with the exclude span.
+`pre`::     If set the amount of tokens before the include span can't have overlap with the exclude span. Defaults to 0.
+`post`::    If set the amount of tokens after the include span can't have overlap with the exclude span. Defaults to 0.
 `dist`::    If set the amount of tokens from within the include span can't have overlap with the exclude span. Equivalent
             of setting both `pre` and `post`.